Solar system design for home radon fan remediation system (off-grid)

Rezolution

I'm sorry if I'm posting this in the wrong section but I wasn't sure where this should go...

I have a 75W 120VAC radon fan that runs 24/7/365. I want the fan to run 100% of the time off of solar power (with battery system). I'm trying to spec out a system that would be roof mountable (panels on roof, electronics and batteries in basement) and would always produce enough energy to keep the fan running, even with the worst solar months of winter. I'm based in PA where we get something like 3.9 usable solar charging hours a day "on average" based on the charts I see online. I'm not sure what the numbers equate to but in PA it's probably half of what it is in AZ.

The idea is to have this system set up solely for the radon fan. That way, if we're without power for a week (rare but not outside the realm of possibilities), the fan will stay running and we don't have a toxic build up in the house. The house will revert to 50 pCi/L 12 hours after the fan turns off (not good). So far, I've been thinking this setup would be adequate but the only knowledge I really have is what I've read and watched on the internet...

I'm thinking I would need 4 panels (100W, 160W, or 185W) hooked up in series, totaling at least 400W. This series setup would make the system charge in lower light days, rather than waiting till it gets bright enough for the cells to produce enough voltage in parallel to start charging allowing the system to get the most of the PA daylight. I've been reading all the reviews for all of the panels on Amazon but I can't tell by the Amazon reviews if the 185W panels are actually 185W or not though since everyone complains that their maximum output is 111W, even in Florida.

I don't think the charge controller really matters that much but I'll include what I'm considering below.

The inverter... I really only need it to be 100W since the fan is roughly 75W. I'm considering getting 1000W or 2000W because for the additional cost, I could always use it to run a space heater or something else that uses a lot of power if I ever really needed to use it for anything else besides the radon fan in an extreme emergency. I honestly have no idea if a 1000W or 2000W inverter will "waste" energy if I'm only using it to power a 100W fan though... Someone would have to explain to me if it's better to have a smaller inverter of if it doesn't make any difference besides the price.

Batteries... I know that sealed lead acid is out because all of this is going to be mounted in my basement (not the panels LOL, they'll be on the roof). I have to choose between AGM and Li-Ion. I'm probably going to go with AGM since they're cheaper. I'm guessing I'll need either 2,3, or 4 of the 100Ah batteries. I'm not sure how many to buy because I'm not sure how much extra juice there will be to charge the batteries while the panels are trying to run the 75W radon fan. I realize that all the numbers calculate much lower in real life because of the inefficiencies of all the separate parts and length of wire runs, etc.

I guess I need someone to help with suggestions or just do a sanity check on what I'm trying to plan out here. Thanks in advance for any helpful comments or suggestions. I'm trying to keep the total cost of the system under $2500.

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These are the three different brand panels I'm considering getting 4 of (not sure which is the best/most reliable):

www.amazon.com/Newpowa-Moncrystalline-Solar-Efficiency-Module/dp/B0772PD96K/ref=sr_1_4?s=lawn-

www.amazon.com/Renogy-Watts-Volts-Monocrystalline-

www.amazon.com/dp/B079DJBJVL/ref=psdc_2236628011_t1_B0772PD96K

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The charge controllers are rated for 100V open panel voltage and will work with 4 of any of the panels above. None of the panels above exceed 23V open. I'm not sure it matters which charge controller I get but here are the two I'm looking at:

www.amazon.com/dp/B01GMUPGZA/ref=as_li_ss_tl?ie=UTF8&linkCode=sl1&tag=desrtprep-

www.amazon.com/Controller-Negative-Battery-LiFePO4-

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These are the batteries I'm considering buying, of course I'm open to suggestions of buying them locally if they are available cheaper at battery stores, marine stores, or auto parts stores. I'm near a tractor supply, many boat stores, and many autoparts stores... I'm not sure if it would be to my benefit to buy 2, 3, or 4 of the 12V AGM 100AH batteries.

www.amazon.com/dp/B072QTMVRT/ref=as_li_ss_tl?ie=UTF8&linkCode=sl1&tag=waypoianalyt-

www.amazon.com/Renogy-Battery-Marine-Off-grid-

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As far as inverters go, I would really like one that has an adjustable shutoff voltage so I can select at what battery voltage it would shut down. Then I have the option to figure out what percentage I'm willing to drag my batteries down to before the inverter turns off. I'm also not sure if having an inverter that's rated much higher than I need (but would be nice to have just in case) will have any efficiency issues. IE, will having a 2000W inverter that I'm using for a 75W fan waste any of my power. All I know for sure is It has to be a pure sine wave inverter since it's running a fan.

2000W: www.amazon.com/dp/B01E3V66QS/ref=twister_B07M98W429?_encoding=UTF8&psc=1

1500W: www.amazon.com/dp/B07JNCD6VZ/ref=twister_B07M98W429?_encoding=UTF8&th=1

1000W: www.amazon.com/dp/B000C73A3K/ref=twister_B07M98W429?_encoding=UTF8&th=1

180W: www.amazon.com/dp/B002AMPHHC/ref=twister_B07M98W429?th=1

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Sorry for the long post but any help is appreciated since I'm flying blind here...

Estragon

Any chance of using a DC fan? This would eliminate inverter cost and losses, and simplify overally design.

Oversizing an inverter is generally a bad idea, especially for a relatively constant load application like this.

mike95490

75w 24/7/365 = 1800 daily consumed. Add in inverter losses, an easy 2000wh daily. 2Kwh daily

How many days backup do you need ? 3 days ? 5 days ?

A pair of 6V 325ah floor scrubber L-16 batteries will give 12V 325ah or 4560wh of storage, 48 hours till 100% dead.

here's another way to look at this

Bad weather to knock down the power lines, will also mess up your solar PV harvest, so I'll twist this another way.

Why not keep the batteries on a nice float charger, and use a generator to recharge them if your power is off more than 24 hours.

And is there any way to can install a vapor barrier to keep the basement fumes from leaking into the conditioned envelop of the house

Rezolution

I use a radonaway RP145 fan. I have a few spare RP145 units as well. As far as I know there are no DC radon fans. I think converting the piping and the system over to a new unit would be out of the question at this point.

If using a larger inverter is generally a bad idea (I assume there is a good reason), then I can simply buy the 100W unit and the 2000W unit. I will test the 2000W unit and then keep it in a box, just in case I never need it. It would just be as simple as connecting it if I ever needed it. Optionally, I could also hook them both up side by side and have then both connected with circuit breakers. Then I could turn them on or off as needed. Then the unit could be there if needed, just by throwing the breaker for it.

Estragon

The main reason to avoid oversizing inverter is self-consumption losses. Big inverters have higher losses, possibly on the order of 1/2 or more of your 75w load. 75w might really be 120 or so out of the battery, so 120*24=2,880wh/day.

I like Mike's thought on using a generator for standby charging. I could charge the batteries, and run the loads you'd use the 2000w inverter for as well.

Rezolution

https://forum.solar-electric.com/discussion/comment/395352#Comment_395352

I'm not sure how many days backup I would need since I hadn't thought of just running it off a UPS. I hadn't considered just running the fan off of a UPS because I was looking for a more permanent (solar) solution that I didn't have to worry about charging or messing with in the event that the house lost commercial power. I thought if I had a strong enough solar system I wouldn't have to worry about the fan any more besides changing the batteries out every few years.

If I run the fan off of a UPS type system as you suggest, I'd just need the float charger, the batteries, and the 100W inverter. That would buy me a few days of UPS if the grid went down but doesn't offer a long term type of solution. I do have a 9200W portable generator that I can connect to the house via a 40A cable. I have one of those mechanical lockouts in my breaker panel to switch over to generator from grid power to keep everything safe and the generator has a floating ground. I have about 30 gallons of gas on hand. I suppose I could hook the generator up to house in the event of an outage and use a few of my 6A chargers to get the batteries up to full charge but I'm thinking that would take a while.

While I do agree that it's a much cheaper solution, using generators and and having the radon fan on "UPS" sort of defeat what I'm trying to accomplish though, making the fan and power system self contained and not requiring any outside intervention, other than brushing the snow off the panels in winter. I'm also not thrilled at the ideal of using lead acid batteries since they off-gas hydrogen and I have a finished basement. If I were to go that route, I'd probably also buy one of those little honda generators and just run the fan (or UPS) off of the tiny generator 24/7 until the power came back.

When you ask about the fumes, I'm not sure if you mean radon fumes, exhaust fumes (from a generator), or hydrogen fumes from lead acid batteries. There is no way to seal off the basement area (it's a walk out basement that's finished) because of the HVAC system. It has intakes and exhausts in the basement plus radon sort of creeps wherever it wants when the fan is off. I have no way of reliably blocking off the upper sections of the house with any vapor barrier.

These are great ideas though, I appreciate them.

Estragon

In normal operation AGM (or more generally VRLA - still lead acid, but not flooded liquid electrolyte)) batteries have essentially no off-gassing. Although I lean toward flooded in many applications, AGM is well suited to this one. They have low self-discharge as well, and can handle float service or periodic top-up better than flooded.

In an outage, would it really be necessary to run 24/7, or could just exhausting for say a few hours daily keep earth gasses at bay well enough?

The way I would do it is run the genny to charge batteries and any "big" loads for a few hours/day, and on battery power for critical loads overnight. Did that at the cabin for a few years before I got the solar system.

mike95490

The idea of your HVAC return in the basement with contaminated air, is abhorrent !! No way that should be legal. I would rig up a return plenum in the main floor and isolate the basement.

But back to solar. How many days do you want it to run ? 1 day, 5 days, 3 weeks ? The more days you want, the more batteries you need. 2 big floor scrubber batteries for every 2 days you want to run. And the batteries start aging to death the day they are made. Do you want the batteries to charge in cloudy weather ? That's a LOT more pv panels. Only in the sun, when you are not likely to loose power, 3 panels would do it.

Estragon

My understanding of a radon remediation system is it creates negative pressure under a basement slab, thereby evacuating air contaminated by earth gasses to atmosphere.

The basement is likely to have return air in any case. You could block HVAC return, but supply air would just pressurize a stairwell or whatever to return air anyway.

softdown

Thinking a vapor barrier is the way to go. Have you measured your radon levels?

jonr

A tall vertical exhaust stack from the basement to above the roof will, in Winter, use stack effect to create some level of under-slab depressurization. Quite possibly no fan is needed. In summer - open the windows.

Rezolution

For the questions about the radon, remediation, and HVAC:

The house has 3 floors (basement, 1st and 2nd). Every room in the house has a supply and a return (except the bathrooms, there is no return in the bathrooms). The basement has 4 supplies and one return. The basement is finished. The basement cracks were "sealed up" when radon was discovered and a sub slab pump was installed. Most houses in PA have radon, some are higher, some are lower. There is nothing you can do other than install a fan, or ignore. We chose to install a fan. When the fan is running, the levels are 0.4 pCi/L in summer and 0.8 pCi/L in winter. If the sub slab fan is turned of, gets broken, or is without power for 24 hours, the basement levels will return to anywhere between 25 pCi/L or 50pCi/L.

Adding a passive pipe has no effect at this house, that's the first thing they try. If the passive pipes dont work, they cut them and then add a fan inline. Nothing can be added to the house at this point to change the dymanics of air flow, seal anything any differently, or change any designs of anything. I'm stuck with keeping the fan running. We have an electronic Radon detector on each floor and I monitor them every day. They also have an audible alarm when the level goes above 4.0 pCi/L (the action level recommended by the EPA).

Worst case, if we lose power (and we're home), it's possible to open all the windows and the sliding glass door in the basement. Since the HVAC wouldn't be running, theoretically we'd be fine. The way that works is, air must come into the basement and pressruize the slab enough so radon can't come in. You would think you'd want to suck the air OUT through the windows but that actually makes it worse. You want the outside air to creep in and pressurize things. This is obvlisluy unsafe for many reasons and not a good solution. It's not something I'm willing to test for 2 days though.

If I hook the generator up, it's appx 9000W and will literally run everything in my house, including the heating system in winter (natural gas and forced air) and the A/C in summertime. That also runs the radon fan. The problem is, this is not a 'long term' solution.

The goal of my project is not to keep the fan running until power returns. My goal is to have a solar/battery system that always keeps the fan running and is totally separate from the grid. For me, this is the best solution, one I should only have to check on once a week or so to make sure that I'm not in danger of killing my batteries. I really want to avoid running a UPS type of system that needs to constantly be checked/maintained and would die after a certain amount of days if not charged back up by generator.

The goal of this project is to find out how much overhead I need to build in to run a 75 Watt Radon fan and a 5W Radon detector 24/7/365. I'm guessing checking the batteries once a week and brushing snow off would be my two biggest maintenances.

If I need to buy 6 panels (100W or 150W each) then I'm willing to do that. If I need to buy 4 100Ah batteries, then I'm willing to do that. I'm thinking if buy 6 panels and run them in two rows of 3, that's two legs that top out at 75V open and the rows can be put in parallel. I'm not sure if that would be enough, I don't have any real world experience with solar so I don't know how to size it correctly. Whatever it takes so that I always have enough power to run the fan all of the time with as little intervention as possible, regardless of a few days of bad weather. I could always put some type of low voltage alarm on the system so that I have an indication that we've had too many days of bad weather to maintain without battery damage if needed. Then I could put a charger on it get the system back up to speed. The goal though would be not to have to worry about that.

BB.

A 75 Watt load 24x7 is just about the same as running a refrigerator full time--Not a small load.

Normally, for a lead acid off grid power system, we start with 2 days of storage... You can run 3 days all right, but when you get more, it becomes pretty costly. The larger the battery bank, the larger the solar array/charging source needed to keep the batteries properly charged. 5% to 13% rate of charge is what is recommended, 5% for a summer/weekend system and 10%+ for full time off grid. If you had a radically large system, say 5 days of storage (and 50% maximum discharge for long battery life), perhaps just 5% rate of charge would be enough (battery self discharge would be more of a "load" than your 75 Watt load itself).

Flooded cell batteries are relatively cheap and rugged. AGM batteries are roughly 2x the cost. Li Ion can be even more expensive. "Cheaper" FLA batteries such as Golf Cart batteries can last 3-5 years (keeping batteries cold, i.e., 10C/18F less than 25C/75C, will double the aging life of the bank). High end FLA Forklift/traction batteries can last 15-20 years.

Anyway, let's start with 2 days and 50% discharge using our basic rules of thumbs.

• 75 Watts * 24 hours per day = 1,800 WH per day = 1.8 kWH per day
• 1,800 WH * 1/0.85 AC inverter eff * 2 days storage * 1/0.50 max discharge * 1/12 volt battery bank = 706 AH @ 12 volt battery bank

Normally, I would be suggesting a small ~300 Watt AC inverter as it would be more efficient than a 2,000 Watt inverter @ 48 volts (larger inverters are not very efficient with smaller AC loads). However, around 800 AH @ 12 volt battery bank, if you wanted (for example 4 days of storage), then I would be suggesting going to an ~706 AH @ 24 volt battery bank (or 353 AH @ 48 volt battery bank). Remember Power=Voltage*Current ... So if we double the voltage and 1/2 the current, we get the same amount of power (or storage if talking about Amp*Hours and Voltage = Watt*Hours).

It looks like there are more options these days for small 48 VDC inverters. Here are a couple to look at:

COTEK SE400-148 400 Watt 48 Volt Pure Sine Wave Inverter

$213.34

Samlex PST-600-48 600W 48VDC Pure Sine Wave Inverter

$250.31

Compared with 12 VDC input AC sine wave inverters:

https://www.solar-electric.com/morningstar-si-300-115v-ul-inverter.html

https://www.solar-electric.com/sa300wa12vos.html

I looked around for some 48 VDC fans... There may be something out there that would work, at about 1/2 the energy usage. But I don't really know anything about your needs and fan design used--So, for now, I will not go down that road (no inverter, lower power usage, usually a good thing for solar power systems).

Using our 2dx50% max discharge, we have two solar panel calculations to make. One is based on size of battery bank (5-13% rate of charge), and the other based on hours of sun you get:

• 706 AH * 14.5 volts charging * 1/0.77 panel+controller deratigs * 0.05 rate of charge = 665 Watt array minimum
• 706 AH * 14.5 volts charging * 1/0.77 panel+controller deratigs * 0.10 rate of charge = 1,329 Watt array nominal
• 706 AH * 14.5 volts charging * 1/0.77 panel+controller deratigs * 0.13 rate of charge = 1,728 Watt array "cost effective" maximum

And then based on hours of sun for your location and your loads. Fixed array, facing south, tilted for best winter production:

http://www.solarelectricityhandbook.com/solar-irradiance.html

Hmm... The new forum editor hates tables. Not good, use the above link and pick your country/state/nearest city. I used Wilkes-Barre, 34 degrees from vertical, and got December as 2.62 hours of sun (long term daily average).

• 1,800 WH * 1/0.52 off grid AC system eff * 1/2.62 hours of sun per day (Dec avg) = 1,321 Watt array "break even" Dec avg.

For a full time base load, I would be suggesting almost a 2x larger array (weather, etc.). Or ~2,642 Watt array. Which if you were going to use AGM and 5% rate of charge, would support a much larger battery bank:

• 2,642 Watt array * 0.77 panel+controller losses * 1/14.5 volts charging = 2,896 AH @ 12 volts
• 2,642 Watt array * 0.77 panel+controller losses * 1/58. volts charging = 701 AH @ 48 volts

If you are looking to use a large AH battery bank, you should look at lower voltage batteries (6/4/2 volt) and much larger AH capacity... Just to give you an idea:

https://www.solar-electric.com/residential/batteries-battery-storage/deep-cycle-batteries.html?nav_battery_type=443&nav_battery_voltage=387

I will stop here... There are just so many ways to go. Solar power is expensive. Batteries last 3-15 years (AGM typically last a couple years less vs FLA), chargers/inverters last 10+ years, etc.

Normally, I would be (at best) setting up a smaller system (2 days storage, 50% discharge) maximum, and then using your AC genset for power when needed during winter/bad weather. A smaller system is just going to be more cost effective for 80% of your outages.

Also, using a Kill-a-Watt type power meter to measure your actual fan draw... You may find it uses 1/2 the rated power (and can build a 1/2 size solar system).

A DC fan would be neat (save energy, no inverter, etc.)... But that is something that you don't want to play with (family health).

Set up a simple 120 VAC relay to switch between Utility/genset power and battery power (UPS like setup). This one is "way overkill", but an example of simple/cheap transfer switch

https://www.solar-electric.com/pomaxpmautrs.html

Sorry for the word salad post. This is not a standard off grid setup, and there are as many questions about your loads and needs (size of battery bank, etc.) and load questions, as there is straight off grid solar math...

-Bill

Rezolution

Thanks for the write up Bill. I've read the post a few times and what I'm getting from this is that to meet the bare minimum of:

"1,800 WH * 1/0.52 off grid AC system eff * 1/2.62 hours of sun per day (Dec avg) = 1,321 Watt array "break even" Dec avg."

I would need at least thirteen 100 watt panels and seven or eight (12V) 100Ah batteries. If I wanted to make the system so that it never needed attention, regardless of bad weather, I'd need to roughly double that to twenty six panels 100W panels and fourteen to sixteen 100Ah batteries.

I think basically what you're telling me is that to meet the bare minimum, I'm looking at about $3300. If I want to make it maintenance free (no generator charging) and weatherproof (a run of shady weather), I'd need to spend about $7000. Also, I'll never make the investment back for the amount of electricity generated under any circumstance. Finally, In 3-7 years I'll have to replace the batteries, and in about 10 years I'll need to replace the charge controller and the inverter.

The fan is hard wired into the basement "lighting" breaker. I don't think I could get an accurate reading with my clamp meter. I have a kill-a-watt meter but I'd have to cut the wire that feeds the fan, put a plug on one end and an outlet on the other to read the consumption. It's entirely possible that the fan only uses 45 to 50 watts of energy, it depends what fan has to pull to get the correct sub slab vacuum. I tried to get them to put in the RP140 unit which only uses about 25W of electricity but they said they don't use that unit because it has a lower CFM and the wattage difference is "nominal" on people electric bill.

I suppose the first thing I have to do is figure out EXACTLY how much power the fan is using to figure out if it's going to be worth the investment or not.

At this point it would probably be cheaper just to buy the most gasoline efficient tiny honda generator made (perhaps 1000W) and figure out what's the best or cheapest way to make a UPS for the fan to run on off of grid power. But then I'm back to square one of manual intervention.

This is kind of bumming me out...

BB.

Yes, you pretty much have it...

I would suggest staying at 2 days and 50% discharge (4x daily loads). That will carry you through 2-3 days (after 3 days, you really need to start up the genset/charge some other way quickly).

And 2x the solar array. It probably would carry you through all but the darkest multi-day storm (every dark days, you can get down to 1% of sunny day harvest--i.e., solar on very dark/stormy days are pretty much useless).

Lead acid and their variants (FLA, AGM, GEL, VRLA, etc.) all pretty much do not like being stored at less than 75% state of charge.

Li Ion batteries love being "stored" between 20-90% SoC. And can supply very high amounts of short term current (surge current, large motors, etc.).

But for pure cost of stored energy, it is difficult to beat FLA (or AGM if you don't want to service the cells).

At ~1,800 WH or 1.8 kWH per day, you probably paying around $0.20 or so per kWH, or ~$0.36 per day (or 365 days per year ~ $131.40 per year). Off grid (battery backed, 120 VAC) is never going to compare with that. At best, most people get around $1-$2 per kWH (10x your utility rate). And if you want more storage/more panels, the cost is going to be higher (for excess energy you may only use 1 week out of the year).

I use 10+ years for electronics... It is highly variable (quality of design/mfg., external damage, dust, lightning, hot climate, bad luck) all play together in equipment life. Most solar electronics are not repairable (for smaller units), or at best, board swap level for larger units (and past 5-10 years, getting parts can be difficult to impossible).

AGM batteries, I would plan on a 7 year life if you get high quality batteries, and perhaps a bit more if you get float service telecom batteries (more expensive, and you generally do not daily cycle them).

Cost wise, I would get a pair of Honda eu2000i (one for backup) or possibly a pair of the eu1000i, and use gasoline (possibly propane conversions which are available for the eu2000i for sure). Gasoline, 2-3 gallons per day (eu2000i with light loads), and store it with fuel preservative (recycle once a year at least).

Note that Honda eu2000i (and possibly eu1000i) have an internal fuel pump. You can fill the genset, and put an aftermarket screw cap + hose, and draw from a 5 gallon fuel jug (or other source) so you don't have to refill the genset every 4-10 hours or so). You can also buy the cap and stuff on Amazon, eBay, etc....

http://www.camperpartsworld.com/Dual-Honda-Eu2000i-Generator-Feed-Tank-_p_18697.html

You could go with AC battery charger and AC inverter + "1-2 day battery bank"--Lets you run the system on "full auto" for short power outages, and you can run the genset during the day to power fan and recharge battery bank (use the battery bank to power emergency home LED lightning, cell phone charging, etc. as desired). Cycle out the AGM every 3-5+ years (depending on quality of battery).

Connect a simple relay/AC transfer switch to the inverter/utility power, set the inverter for "standby mode" (sleeps if no AC load, turns on if >6 Watt AC load). AC mains fail, relay transfers over to AC inverter and your system starts up.

If you want a larger "standby" power system, you can get a larger AC inverter-charger with internal transfer switch (and battery bank), and power your fan, LED lighting, and refrigerator overnight, and use the genset (and/or solar array if wanted) during the day and to recharge the battery bank.

Emergency standby power--Difficult to make "cheap" and reliable. Starting with load conservation (most efficient loads, turn stuff off when not used, running just what you need during outage--more like camping) helps keeps the emergency power system small(er), less expensive, and easier to maintain.

-Bill

Rezolution

I am considering buying this generator: https://www.homedepot.com/p/Westinghouse-1-200-Watt-Gasoline-Powered-Portable-Inverter-Generator-iGen1200/301466638

It's comparable in wattage to the 1000W Honda, has the same noise rating (around 55dB), uses 0.8 gallons per 9 hours for the load I'd be running it at, and is about 1/2 the price. It also has higher ratings than the Honda on both the Home Depot and Amazon sites. That just may be because people like that it's cheaper though and really aren't comparing apples:apples...I have a Champion 9KW whole home generator so I doubt I'd buy a backup 1000W generator.

I have tried every fuel stabilizer and the one that I've found works best is PRI-G. That's what I use in all of my stored fuel. I always keep a minimum of 30 Gallons in cans. Propane is out because of the cold temps in PA, it doesn't flow when it's cold out and it's not my favorite thing to store. We have 3 of the BBQ grill size cans of it (one in our grill, one in our fire pit, one extra we keep to swap out when one gets empty).

What would you recommend then for the battery/charger/inverter/transfer switch setup? I'd want to use a 100W inverter. I'd want to use AGM batteries (they will always be sitting at roughly 60 degrees F). I'd want it to be a "2 day" system dedicated for just the Radon fan (75W worst case) and one Radon meter (5W). I'm not sure what charger to use, perhaps they make a charger that's both a quick charger and a float charger? It would always stay connected to grid power until the grid power drops. Then I'd have to move the charger over from grid to 1000W generator via an extension cord (most likely a 75 or 100 foot cord), or I supposed I could have something wired up in advance so I dont have to leave the door or window cracked open with a cord running through it. Ideally then, it would be best if there was some combination of equipment I could buy that would function as follows:

1. Radon fan (and Radon meter) is always connected to the 12V Inverter (I'd have to purchase a spare inverter so figuring on 2x of that unit)
2. Inverter is connected to 12V AGM battery bank (not sure how many batteries or what Ah)
3. AGM Charger (possibly quick charge and float charge) hooked up to both "grid" and "outlet for generator on outside of house" via some type of transfer switch that falls over to generator when generator is hooked up and doesn't back feed into house breaker (downstairs lighting breaker)

Or you were also suggesting a different setup that would always be running the fan from grid power but switches over to the inverter when the grid goes away so that the batteries aren't constantly being discharged/charged...

1. Radon fan (and Radon meter) is always connected to a transfer switch, that is then connected to both the inverter and to grid power
2. Inverter is connected to 12V AGM battery bank (not sure how many batteries or what Ah)
3. AGM Charger (possibly quick charge and float charge) hooked up to both "grid" and "outlet for generator on outside of house" via a second transfer switch that falls over to generator when generator is hooked up to the outside outlet and doesn't back feed into the house (downstairs lighting breaker)

So the inverter probably doesn't matter too much as long as it's 100W, but if you have a recommendation on the 12V AGM fast/float chargers (if that exists), 12V AGM batteries (both rating and total amount of batteries), or transfer switches (or a different combination of things that are combined into one unit), I'm interested to see what you'd recommend.

BB.

I will make some comments about your questions. Please be very aware, I am not in the solar or genset business (just a retired/aka unemployed systems engineer). I am giving personal opinions that may be right or wrong in the "big picture" and other people will have their experiences and opinions too (and please feel free to comment/correct me here).

1) Westinghouse genset. No experience with them, have not read anything about them.

In general, I am very careful about "brand names" that are purchased/rented and slapped on a product. Honeywell was/is widely known for renting their name to other products. There was a Honeywell 2kWatt inverter genset (same product family as the Honda eu2000i) a few years ago. Out of the box, it seemed to run fine... But get some hours on it, parts failed, difficult/failed to start, etc.

The Honda eu2000i has been known for long/reliable life. 2,000 hours to even as long as 6,000 hours (starting to use oil/smoke) with nothing more than clean fuel and scheduled oil changes. You can get a heated breather tube kit/option if running in sub freezing conditions (breather tube tended to ice up).

Propane--Yea, cold weather is a problem. Gasoline seems to work very well for most people (starting/running) in cold weather.

I like the internal fuel pump in the Honda eu2000i--drawing fuel from a larger tank makes 24 runtimes easy (monitor oil level/consumption).

I simply no nothing about the Westinghouse.

2) It is hard to find "full function" AC inverter-chargers in smaller capacities. The MorningStar has been around a long time and was about as nice as you could get for a 300 Watt TSW AC inverter with 12 VDC input. 6 Watt consumption when "ON" (Tare) and a 0.6 Watt "standby" mode ("standby" mode until AC load >8 Watts). Also has a remote on/off input (12 volt DC switch). Also a 10.8 or 11.5 LVD (low voltage disconnect).

https://www.solar-electric.com/lib/wind-sun/SureSine.pdf

https://www.solar-electric.com/morningstar-si-300-115v-ul-inverter.html

There are less expensive inverter such as from Cotek and Samlex (same family of companies) that are pretty good for medium quality inverters. Some have remote metering/controls.

https://www.solar-electric.com/samlex-pst-15s-12a-inverter.html

This Samlex RC-300 may, or may not, work with the above unit (mixed information on subject):

https://www.solar-electric.com/samlex-rc-300-remote-control-monitor.html

One thing to watch with battery banks and DC inverters... 1/2 of the inverters out there have a 15.0 volt high battery cutoff voltage. The model I pointed here to Samlex cuts out at 16.5 VDC. For Flooded Cell Lead Acid batteries, the "equalize" voltage is ~15.0 to 15.5+ volts, and, especially for cold battery banks, can be 16+ volts. For our friends in Canada, they would charge their FLA battery banks and the inverters could shut down.

For AGM batteries, they charge at lower voltages (typically 14.4 volt max at 75F). So, less of an issue (high charging voltages) for AGM.

3) For battery chargers, I really like the TC2 family. Seem to be reliable (from comments here) and has very good specifications for running on small gensets (PFC--Power Factor Correction for AC input) and has a remote battery temperature sensor (not cheap). Lots of functions you don't see on a typical consumer battery charger:

https://www.solar-electric.com/xantrex-804-1220-02-truecharge2-20-amp-battery-charger.html

I don't know anything about this (relatively new?) Cotex charger and much less expensive--Worth looking at:

https://www.solar-electric.com/cotek-cx1225-12-volt-25-amp-advance-battery-charger.html

The actual size of battery charger does both depend on your battery bank voltage and capacity, and the watt rating of your genset. A small genset can push 600 Watts AC or less than 40 amps @ 12 VDC (800 AH battery bank @ 12 volts 5% rate of charge is 40 amps).

4) Using a relay as your auto power transfer switch is pretty quick and easy (or the black box I linked to in the earlier post). For example, relay energized by AC mains, pass through to 120 VAC outlet. AC mains fail, failover from AC mains to AC inverter. You can even install a second upstream relay--AC mains vs Genset AC... That way, you leave everything plugged in, and just power up the genset to power the AC battery charger and Radon Fan (if you wish). Then when genset down (fueling, overnight, etc.), then the Radon fan pulls power from inverter.

Not pretty, and you can buy AC-inverter-chargers that do that stuff for you--But generally several kWatt rated inverters--Not 300 Watt rated.

5) Alternatives--You can wire up transfer relays to make things easier (your one trip, spouse/kids need to start/run genset without having to worry they fired up the genset, and forget to plug in the cord to the Radon Fan, etc.).

Generally, you don't need to fast charge UPS systems--But if you do, there are larger chargers that will do it for not that much money--But less sophisitcated charging/foat/bulk/absorb. And you may wish to use your larger genset for fast charging:

• 706 AH * 14.5 volts charging * 0.25 fast charge * 1/0.85 charger eff = 3,011 VA (sort of Watts rating) for genset @ ~175 Amp fast charge @ 12 volts

You can bulk charge your battery bank (50-~90% SoC) in 2-3 hours... But is it worth it to you? Vs running the little genset for ~8 hours to do similar with 5% rate of charge:

• 706 AH * 14.5 volts * 0.05 slow charge * 1/0.85 charge eff = 602 VA (~Watts) @ ~35 amp charge @ 12 volts

And this ~602 VA (~Watts) + 75 Watt fan + 5 Watt alrm = 682 VA (~Watt) load (off of your small genset... +/- depending on actual DC charger specifications.

I would go with the smaller / lower power hardware (pumping 175 Amps @ 12 volts uses a lot of heavy/short copper cable on the DC side).

I highly suggest your do a paper design (and compare prices/options/etc. for chargers, battery bank, genset, inverters, etc.) first. Then start spec'ing actual hardware and confirm it meets your needs. Before buying anything.

Also, think about what level of spares/backup you want. Is two gensets (your 9 kw, and a 900 w, and an inverter+battery bank) enough of a spare... Or do you want to have a second 900 watt gesent (pickled/long term storage) and 300 Watt inverter on the shelf, and second battery charger as spares for the spares (the old saying, 3 is 2, 2 is 1 , 1 is none).

You really even have the choice of transfer between mains and 9 kW genset too.

Those are things only you can answer.

Personally, I would go with two (or three) level AC transfer relays. AC mains + Genset transfer switch-> + AC inverter transfer -> Radon Fan + Battery charger.

You could hardwire all the connections, and include a "test switch" (turn off AC mains, make sure inverter picks up the Radon Fan load).

Include some simple meters or indicator lights (show AC mains power, AC genset(s) power, AC inverter output and / or AC input voltage/frequency to Radon Fan. And, at least, a voltmeter on the battery bank. A battery monitoring system would be nice for the battery bank, not cheap, and even BMS systems can get "confused".

Or you could even have plugs -> transfer switch -> AC outlet... Now you have a plug board to configure (AC mains, two AC genset inputs, and three outputs available to the Radon/protected output (i.e., you can bypass failed power sources, relays, etc.).

And the test switch where you probably want to run your Radon Fan for 12-24 hours once per month (or once per year) to ensure everything is working well.

And do you want simple panel/idiot lights to indicate AC mains, Genset power, Radon Fan power upstairs where the family is (buzzer if no AC power to fan?).

If others will be running the system (starting gensets, etc.) when you are gone--Too complex can cause operator errors.

Your thoughts?

Note, I have a bunch of links to our host (NAWS pays for the forum, I am a volunteer). They have lots of other equipment and are there to work with customers to help configure their systems. But you are welcome to go to other places too. Links are just starting points for your research/suggestions.

-Bill

softdown

https://forum.solar-electric.com/discussion/comment/395459#Comment_395459

https://www.amazon.com/gp/offer-listing/B01N2AKRTT/ref=dp_olp_all_mbc?ie=UTF8&condition=all

I would jump all over the $324 one with "small cosmetic imperfections" from Amazon Fulfillment.

Rezolution

I believe you've covered all of my questions and given me enough tools to make a decision about what road I want to travel down.

I don't think I have any other options about Radon proofing the house. Even if I completely tore up the basement and have it completely resealed, you never know when a new crack will develop and put me back to square one. Perhaps I could have someone come in with real-time metering equipment and let me know if it's leaking 'everywhere' or just in one specific spot that isn't obvious since it's colorless and odorless. Perhaps there is some kind of sub-slab sealent or something I could have pumped under the house. I'll have to investigate this as well. If it's going to cost $4000 or $5000, it would be worth having that done instead since I wouldn't have to worry about replacing batteries every 5 or 10 years.

I've read through the whole post again several times. It looks like for a solar option, I'm between $3500 and $7000 for cheapest option and 'worst case weather' option. For the battery backup option (UPS) mixed with small/large genset charging (small to do only the 'battery bank and fan' or large to run 'the whole house' for 8 hours during the daytime) I'm looking at between $2850 and $4450 depending on whether I buy 1 or 2 generators and if it's Westinghouse or Honda ($1000 Generator [if only buy one honda] or $400 Generator [if only buy one Westinghouse], $1600 batteries [if only buy 8 100Ah], $300 Inverter, $300 charger, $150 transfer switches, $100 misc).

Honestly, looking at the two choices, their complexity - intervention required from children and spouse if I'm not home... The best route for me might be to pursue the solar route since the cost difference is minimal at this point (if there is no other option to have the sub slab sealed in some way).

Rezolution

https://forum.solar-electric.com/discussion/comment/395481#Comment_395481

I've had bad experiences with Amazon warehouse items. I think a lot of times they're returns that Amazon just assumes are fine and stuffs back into a box. I have no way of knowing if the last person that had it started it up with no oil in it and sent it back because it "had scratches on it". I do appreciate you trying to help out with pricing though! This whole situation is a bit of a bummer.

Estragon

If someone offered to fix a radon problem with a $4-5,000 sealing job, I'd be pretty skeptical. That's probably pretty close to the incremental cost to do radon prevention in a new build (proper concrete curing conditions, surface prep, sealing, etc.). Seems to me someone pumping snake oil under an existing slab might be making the problem worse.

Getting to 12x "safe" levels in 12hrs absent a running sub-slab fan strikes me as pretty extreme. Any chance there's a contributing problem (eg. unbalanced HRV, blocked combustion supply air, etc)?

If you do go the solar route, I wouldn't entirely rule out looking at a DC fan. A "radon" fan is really just a fan moving 'X' cfm in a 4" pipe.

Rezolution

https://forum.solar-electric.com/discussion/comment/395486#Comment_395486

No one has suggested being able to seal up the basement with anything for any amount of money, I was just hoping there was some new type of sealing that I hadn't heard of yet. I'd be happy to pay to get it fixed permanently instead of stacking up methods of remediation and ways to power them. These solutions of constantly running a fan and then powering the fan with batteries and solar power are all less than ideal.

For the area I live in, almost every house on the street is between 4 pCi/L and 8 pCi/L. Some houses are 25, some are 50, and some are as high as 200. It's just a roll of the dice. Some houses that pass retest later on and they are high because something cracked under the house. Some people don't care about it at all and don't bother retesting every year or so. I worry about it so I installed real time detectors in the house. They'd help to let me know if the fan unexpectedly failed. I'm just very paranoid about it. I realize if the SHTF one day, Radon probably won't matter anyway, but it's something I don't want my children getting sick from in the long term. Some people are of the opinion that we'll never lose power in our development because we've only lost power 2 times in 15 years. Once for 12 hours with Hurricane Sandy and once in the summer for 2 hours when a fuse feeding the development blew.

It's very hard to say what the problem is. The house has been like that since it was built. The only test I've done recently is to turn the radon fan off and see what happens. The problem with that test was, all the windows are closed but the HVAC is still running (draws in air from the outside via a pipe with the furnace which shouldn't matter too much) and the water heater runs intermittently (power vent model). The water heater (power vent) basically sucks air in the basement into it and blows it outside the house. This is a possible source of the problem. I'd assume that it puts a bit of a negative pressure inside the basement when it's venting. The radon fan must be strong enough to make up for it though.

The only other tests I could run would be to shut off the breaker for the whole house, which would simulate a power outage. Then I could see how fast the radon levels rise with no power, no fans, not extra air draw on anything. Then I could also run the same test, but with just one window open in the basement and all other windows in the house closed. Then I'd have to repeat the test in the summertime with one open window in the basement and multiple open windows on the top floor. I'd have to see what each test results in after 24 hours.

The only way I'd be able to do that would be to send my family on a vacation somewhere for a week without me. I doubt that would go over well.

I'm sure most people don't understand why this is bothering me so much but I'm just trying to figure out the best solution. I've talked about this with multiple people and I just get "open your windows, you'll be fine" or "don't worry about it, it won't make you sick for 20 or 30 years anyway".

jonr

I think you will find it impossible to find any credible medical data showing that 50 pCi/L for an occasional week causes any health issues. Even 4.0 pCi/L continuously is mostly a guess (ie, very sketchy data behind it). If you don't smoke, then your risk is already low. I believe in radon mitigation, but personally, I think there are much more cost effective ways to improve health than worrying about an unlikely week at 50 pCi/L.

Estragon

I m no kind of expert, but I do know radon is a real problem. It has no "safe" level (like pretty much any carcinogen), but is less of a problem at reduced concentration and exposure time. Maybe ask the "open your window" folks if they've ever watched someone die of lung cancer.

Apart from radon, you may want to check into the furnace, water heater, etc. anyway. They really should be drawing combustion air from outside, not using inside air and causing reduced pressure when exhausting. With multiple such appliances running (plus kitchen/bath exhausts), there's a risk of backdrafting combustion products, which can kill you much faster than radon.

It sounds like the furnace is a condensing type, with pvc pipes for outside combustion supply & exhaust? If so, it should have a safety so a blocked inlet will shut it down. A leak may not though. Likewise, a double walled vent pipe like what might be used for a power vented heater could have a leak in the outer wall.

You might be able to get a rough idea if this is an issue by running the appliances on a still day, and doing a simple smoke test.

Rezolution

https://forum.solar-electric.com/discussion/comment/395492#Comment_395492

You are correct, I have no credible evidence other than all of the charts I can look at online and what the EPA says. I'm not sure who generates the charts or where they come up with the risk factors. They say things like a level of 50 is equivalent to 20,000 chest x-rays a year or smoking 3 packs of cigarettes a day. Maybe all of it is a scam, who knows. All i know is, according to the EPA, Radon is the second leading cause of lung cancer. 1. Smoking, 2. Radon, 3. Second hand smoke.

Here is what the EPA has to say about it if you're interested in looking at their numbers. https://www.epa.gov/radon/health-risk-radon#head

At the end of the day, I'd rather not have Radon in the house if it's something I can prevent.

BB.

I understand the idea of reducing things like radioactivity that are under your control (or at least try). And how the "models" for health issues caused by low levels of radioactivity may not be very accurate (make damage to our bodies much worse under statistical models than what has been gleaned from real life exposure over the decades).

And there are always more things that journalists can find that make good headlines:

https://www.geek.com/news/study-indoor-air-quality-levels-on-par-with-polluted-major-city-1775015/

💣️💥

-Bill

jonr

Say that 50 pCi/L for 1 week a year is equivalent to 1 pCi/L for 50 weeks. One could crank up their existing fan to drop radon levels by 1 additional  pCi/L, live with the very unlikely 1 week/year of higher radon level and be healthier!! - for very little cost.

Rezolution

https://forum.solar-electric.com/discussion/comment/395498#Comment_395498

That's correct, there is no safe level of Radon.

The furnace is operating correctly, it draws in a massive amount of air from outside. There is a fan that feeds the furnace combustion system and a second fan that moves air throughout the house. The 'fire' fan has both and intake and exhaust pipe with many safety features. It's made by a company called Heil and it's bundled as both furnace in winter and air conditioning (with outside unit) in the summer.

Similar to this model: https://www.homedepot.com/p/ROYALTON-44-000-BTU-95-AFUE-2-Stage-Downflow-Forced-Air-Natural-Gas-Furnace-with-Variable-Speed-Motor-95G2DF045BV12/307689738

The water heater is a goofy design but it's what most builders in PA use because it has a cheaper 'installation cost'. it pulls in air from the top of the water heater with a large fan and then pumps all of that air outside via a pvc pipe. All the combustion air is pulled into the unit from inside the room it's in.

Similar to this model: https://www.homedepot.com/p/Rheem-Performance-50-gal-Tall-6-Year-38-000-BTU-Ultra-Low-NOx-ULN-Natural-Gas-Power-Vent-Tank-Water-Heater-XG50T06PN38U0/300676632

There is a CO detector and explosive gas detector in the water heater room, the furnace room, and on each floor of our house (basement area/1st floor/2nd floor).

Rezolution

https://forum.solar-electric.com/discussion/comment/395500#Comment_395500

The media... yes, everything will kill you, especially water.

BB.

It's water folks:

http://www.dhmo.org/facts.html

Yes, it is water written up as one of the most dangerous things out there (which it is).

-Bill

Rezolution

https://forum.solar-electric.com/discussion/comment/395501#Comment_395501

If you stubbed your toe once a day for 50 days - or 50 times in 1 day, which do you think would do more damage?