This SOLAR PLAN MUST be Possible>>

ggunn

Re: This SOLAR PLAN MUST be Possible>>

Mangas wrote: »

I have an off grid system that runs two 2 1/2 ton central A/C units. They are set up up in two zones to provide redundancy.

The four SW 5500 watt inverters easily start and handle the compressor surge helped in part by highly energy effficient variable speed air handlers and dual stage compressors. With the compressors running on the high stage, I've never seen the inverters operating above 16 amps with about 11 amps the norm for lower stage.

Second, on overcast humid days lasting more than a week the back up generator might run about a couple hours in the morning as storage declines over a few days but I've never seen it run more than 20 hours or so the entire summer.

Key point here is you have to have an adequately sized battery bank to run the A/C overnight. If you don't balance the panel array and battery bank size efficiently you'll either run the generator too long and/or you won't have enough starting power to run the compressors.

A/C is not a problem if you size your system properly.

OK, but you are not claiming that your A/C costs less to run off grid than it would if power from the grid were available a 9-10 cents a kWh, are you? That's what the OP wants to do; run his A/C off grid to save money.

Treblig

Re: This SOLAR PLAN MUST be Possible>>

Mangas,
That is some good solid information, nothing like real life examples to pull you back into reality!! All you need to add is "how much wattage DC are you getting from your solar panels" and "are the AC units the only things you have running on solar"? I'm trying to isolate the power needed to run the AC units (only).

ggun,
When I said that I wouldn't need as many panels or as many batteries I wasn't implying that I would use less energy (power). What I meant was that by deceasing the start-up amperage (which is something that "The Coot" said would require more batteries and/or panels for the initial surge) I could lower my initial costs. I understand the law of physics, whether the AC motors start slow or fast basically consumes the same amount of energy....but it requires LESS standy amperage (initial start-up power). Or am I way off base here??

Gil in Tex

Cariboocoot

Re: This SOLAR PLAN MUST be Possible>>

Mangas wrote: »

I have an off grid system that runs two 2 1/2 ton central A/C units. They are set up up in two zones to provide redundancy.

The four SW 5500 watt inverters easily start and handle the compressor surge helped in part by highly energy effficient variable speed air handlers and dual stage compressors. With the compressors running on the high stage, I've never seen the inverters operating above 16 amps with about 11 amps the norm for lower stage.

Second, on overcast humid days lasting more than a week the back up generator might run about a couple hours in the morning as storage declines over a few days but I've never seen it run more than 20 hours or so the entire summer.

Key point here is you have to have an adequately sized battery bank to run the A/C overnight. If you don't balance the panel array and battery bank size efficiently you'll either run the generator too long and/or you won't have enough starting power to run the compressors.

A/C is not a problem if you size your system properly.

I am not at all surprised that 22 kW of inverter can run your A/C. :roll:
I hope the OP will read that post and see what he's up against.
You can size an off-grid system to run a whole town if you want. But it won't be cheap and it won't be practical.

Treblig

Re: This SOLAR PLAN MUST be Possible>>

I want to run one small AC unit during the hottest part of the day (10AM- 5Pm) on solar to keep my 4ton home unit from running so much during the day. That's when it's the hottest and when the sun shines on my house (relentlessly) all day. It's always cooler at night and the 4ton has an easy time at night.

Gil in Tex

Cariboocoot

Re: This SOLAR PLAN MUST be Possible>>

Treblig wrote: »

Mangas,
That is some good solid information, nothing like real life examples to pull you back into reality!! All you need to add is "how much wattage DC are you getting from your solar panels" and "are the AC units the only things you have running on solar"? I'm trying to isolate the power needed to run the AC units (only).

ggun,
When I said that I wouldn't need as many panels or as many batteries I wasn't implying that I would use less energy (power). What I meant was that by deceasing the start-up amperage (which is something that "The Coot" said would require more batteries and/or panels for the initial surge) I could lower my initial costs. I understand the law of physics, whether the AC motors start slow or fast basically consumes the same amount of energy....but it requires LESS standy amperage (initial start-up power). Or am I way off base here??

Gil in Tex

Start-up surges are tough to understand. Motors get designed to be connected to grid power, which has the ability to supply huge amounts of current all at once. This means the motor makers take advantage of this and build their stuff to spin up to full speed at a rate we mere humans would consider to be "instantaneous". It uses a lot of power to overcome the inertia, and it uses it "all at once". This results in a sudden, sharp Amperage spike. Fine for the grid, but batteries and inverter are a different scenario. Their power capacity is much closer in size to the load demands: the average house is wired for 48 kW of power - far more than you're likely to use. It is, in essence, over-sized. So for the grid to supply this spike is easy. For the off-grid to do it is not easy; you either demand it supply everything it's got right now, or you over-size it so the demand is not as close to peak power.

Enter the start capacitor. With that addition instead of the current going high for a fraction of a second the power charges the capacitor over time and the electromagnetic field of the motor builds "slowly" thus the motor speeds up "slowly". In our human sense it is still instantaneous, but to the power system it is lengthy. If you expand this thought to more manageable terms it is the same as using "X" Watt hours: you can use 1/2X over two hours or X over one hour: same amount of power (mostly - must include disclaimer for nit-pickers ).

I hope that helps.

Cariboocoot

Re: This SOLAR PLAN MUST be Possible>>

Treblig wrote: »

I want to run one small AC unit during the hottest part of the day (10AM- 5Pm) on solar to keep my 4ton home unit from running so much during the day. That's when it's the hottest and when the sun shines on my house (relentlessly) all day. It's always cooler at night and the 4ton has an easy time at night.

Gil in Tex

I, at least, understand this.
That doesn't change the fact that the power from the panels will be inconsistent during that time period and needs to be stored/regulated/smoothed-out by batteries. Nor does it change the fact that solar power equipment is an expensive way to make electricity compared to grid power. On average, an off-grid set-up runs at a cost of $1 per kW hour over the life of the equipment. The smaller the system, the more expensive it becomes due to the standard economic functions of economy of scale. Grid-tie can be cheaper, especially with utility and government incentives to help alleviate the capital investment costs. Furthermore the grid-tie would provide maximum value for the solar panels, as everything they are capable of harvesting would be used (A/C running or not). Perhaps not by you, but by the utility (which should pay you something for your surplus power).

It still won't be cheap, and may not be as cheap as simply running a small mini-split unit off the grid in rooms you want to keep extra cool.

I've always wondered why they don't make A/C thermostats that measure outside air temp and adjust the inside setting to be "X" degrees below, rather than a fixed figure. Maybe they do. Up here we open a window and let the breeze blow in off the glacier. Mind you, keeping the polar bears away can be a nuisance.

BB.

Re: This SOLAR PLAN MUST be Possible>>

A standard load can take surge current to upwards of 5x rated power.

The typical "good" inverter can supply upwards of 2x rated power for several seconds.

The numbers I use for flooded cell batteries--is they can run about 13% of their 20 hour AH rating (will drain battery flat in about 8 hours). And they can run around 40% of their 20 Hour Rating for surge current/power.

There are AGM batteries that can supply upwards of 400% of their rating as surge current. But that would take a battery dead in 15 minutes.

So--Frequently the thing to first look at is your loads--can you 1) get more efficient loads and 2) can you get loads that behave nicely on inverters...

That answer is the Sanyo (and other) Mini-Split AC systems... They tend to be quite a bit more efficient than the older/window units and do not take surge current much in excess of their max power ratings. Also, when not on maximum cooling, they can run down towards 300 watts all day long without surge current.

But--to use such a small/efficient A/C system--you have to review your insulation and sealing around your rooms/home... If you don't have R40+ of attic insulation and have heaps of insulation around your A/C ducting--you may want to review adding insulation. For my old homes (no A/C), I found adding double pane vinyl windows with low E glass kept my rooms much cooler too.

-Bill

Treblig

Re: This SOLAR PLAN MUST be Possible>>

cariboocoot,
Yes, it explains it very clearly. But does it mean that you are saying (don't want to put words in your mouth) that a lower start-up amperage allows you to require fewer batteries and/or fewer panels because the initial demand of start-up is mitigated by the slow start cap?? I understand the need to "overpower" the system but the goal is to minimize initial "solar" start-up cost. The amount you have to "overpower" is controlled, to some degree, by the start-up amperage because the "run" amperage is pretty constant. I had read many posts before I started this one and the motor home guys talked alot about the start-up problems and slow start caps..so it MUST require less initial power or they wouldn't be making these changes to their systems.

Gil in Tex

ggunn

Re: This SOLAR PLAN MUST be Possible>>

Treblig wrote: »

I want to run one small AC unit during the hottest part of the day (10AM- 5Pm) on solar to keep my 4ton home unit from running so much during the day. That's when it's the hottest and when the sun shines on my house (relentlessly) all day. It's always cooler at night and the 4ton has an easy time at night.

Gil in Tex

I understand. Do you understand that no matter how you slice and dice it it's going to be far cheaper for you to run that A/C from the grid than to build an off grid PV system to run it?

Treblig

Re: This SOLAR PLAN MUST be Possible>>

BB,
I installed "double pane vinyl windows with low E glass" two years ago. I appreciate all the comments but everyone must realize that I spend 4 days drilling 75- 3" holes in my eaves just to let the attic "breath" after I installed a high volume attic fan (in the roof)....those static vents are of no use at all. Yes I have plenty of insulation, I plan to put more in next winter (Dec 26 -Jan 3)...YES, thats how long winter last here and by winter I mean temperatures as low and 50 degrees (actually high 30's for one or two days) but not very often. I've had two techs come and check the temps of my attic, my walls and had tests run on "whole house" leakage. AC vents have been sealed...I'm doing all I can, I'm just looking to take advantage of all this feakin' sunlight!!

Gil in Tex

Cariboocoot

Re: This SOLAR PLAN MUST be Possible>>

Gil;

There's a cause-and-effect relationship interconnecting it all. Deep cycle batteries that are suitable for prolonged discharge over time aren't good at delivering sudden burst of heavy current. "Automotive" batteries are, but won't take the prolonged discharge rates that are required to keep an inverter functioning. So the trick is having to size up the battery bank to where it will be able to supply the sudden peak demand, and that results in a need for a larger array to properly recharge it. There is also a need for a larger inverter capable of supply that current to the load. A lot of extra cost to provide a moment's power demands. Adding a soft start device mitigates the sudden power need, but does not eliminate it. The mini-split units are designed from scratch to deal with this problem, and as such they function more efficiently than merely adding a capacitor to an existing unit will.

One of the other problems with sudden-start is that it does use slightly more power because any time current draw goes up some more power goes to heat and not to actually doing work. This is a bigger problem on 12 Volt systems than 24 or 48 Volts because of the greater amount of current needed to affect an increase in Watts.

And we haven't even mentioned the evil Power Factor Monster that's lurking in the dark corner of the discussion.

ggunn

Re: This SOLAR PLAN MUST be Possible>>

Treblig wrote: »

cariboocoot,
Yes, it explains it very clearly. But does it mean that you are saying (don't want to put words in your mouth) that a lower start-up amperage allows you to require fewer batteries and/or fewer panels because the initial demand of start-up is mitigated by the slow start cap??

Fewer batteries, maybe, since the more batteries you have in parallel, the more instantaneous current you can draw. Fewer modules, no, because the amount of energy (kWh) you need to produce is the same, or maybe even a little more.

ggunn

Re: This SOLAR PLAN MUST be Possible>>

Treblig wrote: »

BB,
I'm doing all I can, I'm just looking to take advantage of all this feakin' sunlight!!

Gil in Tex

Your best option to do that, IMO, is to install a grid tied system to offset your overall electric bill. You'll get far more kWh/$ with a grid tied system than with an off grid system, and your A/C cares not where the electrons come from. Sometimes you just gotta recognize when it's time to let go of a bad idea.

Treblig

Re: This SOLAR PLAN MUST be Possible>>

ggun,

I do not disagree. I read and "take it to heart" everything you guys (gals) write. I looked up the mini-splits (cariboocoot's idea) ...16-20 seer!!! Whoa!! I would have bought one of those for my bedroom had I known about them except for the fact that the smallest on is 9000BTU (a bit much for my bedroom). But for an alternate as a back-up on the 4ton...maybe. I would wonder what percentage it would save me relative to 13.5 SEER 4ton...no way to know. "COOT", I'm listening!! It must all make sense though. I'm not unreasonable..just stubborn.
don't get angry at me...educate me!!

And yes, hooking to the grid with solar does seem to make more sense, I think...

Gil in Tex

ggunn

Re: This SOLAR PLAN MUST be Possible>>

Treblig wrote: »

ggun,

I do not disagree. I read and "take it to heart" everything you guys (gals) write. I looked up the mini-splits (cariboocoot's idea) ...16-20 seer!!! Whoa!! I would have bought one of those for my bedroom had I known about them except for the fact that the smallest on is 9000BTU (a bit much for my bedroom). But for an alternate as a back-up on the 4ton...maybe. I would wonder what percentage it would save me relative to 13.5 SEER 4ton...no way to know. "COOT", I'm listening!! It must all make sense though. I'm not unreasonable..just stubborn.
don't get angry at me...educate me!!

And yes, hooking to the grid with solar does seem to make more sense, I think...

Gil in Tex

No one here is angry at you. What you are going through is a learning curve, and we have all been there.

Cariboocoot

Re: This SOLAR PLAN MUST be Possible>>

Treblig wrote: »

"COOT", I'm listening!! It must all make sense though.

Oh, well ... if you go around expecting it to make sense you'll never get anywhere.

It all works by magic. And if you do something wrong the magic smoke comes out and it stops working.

Now isn't that easier on the brain?

Treblig

Re: This SOLAR PLAN MUST be Possible>>

Does anyone know where all the water (condensate) goes in a mini-split system. I've been reading the info on these units....there's an outside unit and an inside unit with cables and lines in between. Where I live the AC units extract gallons of water out of the houses because of the 90% plus humidity.

Gil in Tex

solar_dave

Re: This SOLAR PLAN MUST be Possible>>

Treblig wrote: »

ggun,

I do not disagree. I read and "take it to heart" everything you guys (gals) write. I looked up the mini-splits (cariboocoot's idea) ...16-20 seer!!! Whoa!! I would have bought one of those for my bedroom had I known about them except for the fact that the smallest on is 9000BTU (a bit much for my bedroom). But for an alternate as a back-up on the 4ton...maybe. I would wonder what percentage it would save me relative to 13.5 SEER 4ton...no way to know. "COOT", I'm listening!! It must all make sense though. I'm not unreasonable..just stubborn.
don't get angry at me...educate me!!

And yes, hooking to the grid with solar does seem to make more sense, I think...

Gil in Tex

There are lots of different brand names on the mini splits, some go up to 26 seer. I am using a 33KBtu Friedrich Inverter type base unit with 3 9000 Btu wall units. Other manufacturers abound.

http://www.friedrich.com/products/commercial/ductless-split-systems

I have 2 9000 BTU wall units operational now on super quiet mode and the Ted tells me that the whole thing is only drawing 475 watts with 2 mac mini's, a mac laptop and a shelf Stereo in operation. Comfortable here with outside temps now pushing 107F inside set to 76F and holding OK. May have to bump it to low mode later today. Of course this building has 2X6 walls stuffed with batts with 2 inches of exterior foam board all taped with stucco over that, good attic ventilation with a about R45 blown in fiberglass. It is tight as a drum as well with no south or west facing windows to impact heat gain. The North and East facing windows have insulating cellular shades on them.

I heartily recommend considering Coot's suggestions about mini splits.

Please to read some more about Grid tie, research your utility's policy and programs, and consider the big benefit of offsetting some or all your usage, including winter time usage.

Treblig

Re: This SOLAR PLAN MUST be Possible>>

solar dave,

Do you know where all the water (humidity) goes. In my house 4ton AC it drains from the coil plenum box out into the sewer line (waste water). The small window unit drains out the window on the outside of the AC unit.

Gil in Tex

Vic

Re: This SOLAR PLAN MUST be Possible>>

Treblig,

Mangas has a quite large system for off-grid. The way I calc it, those 44ea 185 watt STC panels equal about 8.14 Kw. Each those 5500 Watt inverters can surge 4X that amount for some number of seconds, if one has the battery to support that.

His large PV system easily represents an investment of $60-70 THOUSAND. Those 185 watt panels may have cost around $4/watt when they were purchased. I know nothing specific about MG's system, other than from his signature. You would not need nearly this much of a system, but off-grid power is very expensive, and only makes any econimic sense at all when there is absolutely NO ALTERNATIVE (like the Grid).

As all others have said, The gird is the world's best and least expensive battery.

CONSERVE, INSULATE, then CONSERVE AND INSULATE some more. My lil window A/C 13 EER (IIRC) units run at about 500 watts each. That would require about 800ish STC watts of panels, and cannot cool a very large space when outside temps are high. At high temps, PV put out less power.

There is a drain for the indoor parts of the MiniSplit A/C units, as I recall EDIT (OOPS forgot to finish the post), have a drain port, which would normally drain outside, Recall seeing a pump kit, perhaps for a below-grade install.

Keep cool, Happy Fourth, Vic

Mangas

Re: This SOLAR PLAN MUST be Possible>>

Vic, Cariboocoot and Bill pretty much summed it up.

We have a real world system operating in a hostile remote desert mountain environment. As background, we built it 5 years ago as a challenge to see what we could with then exisiting technology to meet our lifestyle objectives. We chose not to bring the grid to us because the ranch is in conservation and borders National Forest. The cost to bring out the grid was about the same as our "all in" off grid system investment $90K.

We work hard and afterwards staying cool in Arizona and living comfortably is our lifestyle. We're not ashamed nor apologize for it.

That said, off grid solar running two central A/C systems in a 4,000 square foot house equipped like any other in town is not cheap. But, when you factor in our grid's poor "reliability", committment to maintain the larger landscape free of development, privacy and so on costs take on a different meaning.

After 5 years, we replaced the 64 Trojans a couple years early to take advantage of the waning solar credit. Glad we did. Second, we decided to replace our unreliable Generac 15 kw 1800 rpm propane generator with a new Onan Cummins 20 kw 1800 rpm brushless unit for peace of mind.

There are many trade offs to all of this and not all of them involve cost. Energy conservation is the first and most important consideration in designing an efficient system. Grid utility costs will continue to rise in our area of the country rationalizing somewhat our alternative energy investment.

And, we don't have a utility bill which would probably run about $8k a year.

solar_dave

Re: This SOLAR PLAN MUST be Possible>>

Treblig wrote: »

solar dave,

Do you know where all the water (humidity) goes. In my house 4ton AC it drains from the coil plenum box out into the sewer line (waste water). The small window unit drains out the window on the outside of the AC unit.

Gil in Tex

Just like any AC unit, it drain someplace, in my case it is ouside the mounting point.via PVC pipe.

wild01

Re: This SOLAR PLAN MUST be Possible>>

check with your electric company about what is required for the $2.00 a watt rebate.

I will wager you are looking at several costly requirements.

1. must be grid tied
2. must be installed by a licensed contractor approved by the elec company$$$$
3. must have a bizarre arcane outdated and costly anti-islanding feature built in (keeps the system from electrocuting utility workers who are working on lines they think have been turned off. $$$$$$$$$$$
4. may require a separate meter setup for net metering. $$$$$$$$$$


if you can find a way to do all this for practically nothing you may be able to get into a system at little cost.

I'm thinking of a certain florida based business in the "sun" that specializes in "elec"tronics

their systems also do not come with mounting hardware which can be quite costly when code following is required, but they do have amorphous grid tied systems for less than $2.00 a watt

amorphous is lower quality, but does work (it also requires more sq footage and thus more mounting hardware)

before going through all that I would suggest just replacing your a/c with a mini split style http://www.thisoldhouse.com/toh/video/0,,1630888,00.html should answer your condensate questions also keep in mind that you can both zone cool your house and eliminate the energy loss associated with your central ductwork. (usually about 30%) there are also usually incentives from your elec company for appliance upgrades. there is also a $300 tax credit available in 2011

solar tax credit of 30% of installed cost of a solar system runs through 2016

bmet

Re: This SOLAR PLAN MUST be Possible>>

At the ranch, we gravity-feed it to supplement flowerbeds around the sides of the house.

solar_dave wrote: »

Just like any AC unit, it drain someplace, in my case it is ouside the mounting point.via PVC pipe.

Frxddy

Re: This SOLAR PLAN MUST be Possible>>

From a whole different viewpoint..... have you called your power company and asked about the $2 a watt rebate? Many rebates are only for "professionally installed" systems. I am building a PV gird ties system right now. Just this week I have verified that I will not be getting any rebates other than the federal one as the master electrician I have helping me "is not NABCEP certified".

Second.... 1,000 watts of panels do not make 1,000 watts of power.

Third: Non grid tied systems are way more complicated than one might think. Listen to the advice the experts on this forum are giving.

Treblig

Re: This SOLAR PLAN MUST be Possible>>

Thanks to everyone. You guys hit me with so manys "rights" I was actually looking forward to getting hit with a "left"!!
All kidding aside, I appreciate the input. As it turns out the mini-splits really sound great. I've googled many mini-spit sites (saved them to my "favorites") and was trying to figure how much I could save by installing a 9000 to 16000 BTU (24-26 SEER) unit to run in the living room and TV room area during the hottest parts of the day (this is where I was thinking about putting the window unit on solar). My 4ton is only 13 SEER so would that should cut the daytime bill in half?? Well not really because the rest of the house still has to stay at around 78 degrees to remain comfortable. So I figure if the mini-split can cool 1/3 of the house (with good air circulation, fans, which I already have) when the 4ton come on it wouldn't run very long because it would quickly start pushing the cooler air from the living room/TV room areas to the central themostat. The central thermostat would cool down quicker thereby shutting the 4ton off sooner than normal. Conservatively, I would guess that my bill should drop about 20%. If I let the mini-split run at night as well (when it's cooler) it should also keep the 4ton from running as often and as long. That should give me another 20%???
The other big difference (this holds true in very hot climates) is that the fewer times the 4ton comes on the fewer times the whole house will get "pumped" full of very hot attic air which "bakes" the ducting in the attic when the AC is not running. This happens when the 4ton initially turns on and pushes all the hot air out of the ducts, you feel it everytime it comes on. Not sure how much saving that would give me but I know that cooling down a house that just had 30/40 cubic feet of 90 degree air pumped into it can't be the smartest way to live!!!
I wish my main unit (4ton) was a mini-split but we had a ours replaced new about 10 years ago so it should last another 5 years at least. Would the mini-split also make our 4ton last longer since it won't come on as often and shouldn't run as long when it does come on??
I think $1300 to $1800 for a mini-split is cheap if it cuts even $50 off my AC bill (that's $1200 in just two years). I honestly think it would save more.
What say yee, "COOT"????

Gil in Tex

BB.

Re: This SOLAR PLAN MUST be Possible>>

The Cariboocoot is located in the "Great White North"--While Marc is one smart guy--His A/C experiences may be limited vs the Texas and Florida questions we have here (and I too, do not have AC at my home).

Solar Guppy is the Florida guy that has done lots of solar design (professional) and A/C system work (hobby/good Samaritan?) on his and helping others with their home installs.

Adding insulation to >R40 in the attic and heaping it over the ducts are the first things he usually recommends.

Yes, going from 13 SEER to 26 SEER should save about 1/2 the electricity for cooling the zone(s) that the new A/C would be responsible for.

You are probably paying around $0.10 per kWH right now... In California and other left/right coast states, we can pay upwards of $0.40 per kWH--So doing these conservation efforts are almost a matter of economic survival out here (or simply doing without).

Yes, this is a solar forum, but it is probably one of the few that is going to tell you to be very aware of the total costs of solar (initial, on-going, and limitations) before spending your hard earned money.

Conservation will always offer the best return on your investment.

If you eventually install mini-split A/C systems in your home--they are also very generator friendly--Many times, an emergency genset is a good investment when power is needed only a few days or week or so of the year and the expense of a full up GT/Off-Grid (Hybrid) system is just too much or not possible.

-Bill

Cariboocoot

Re: This SOLAR PLAN MUST be Possible>>

Bill;

I think you already sold him on conservation, and apparently he's done everything short of ripping the roof off and adding some extra space to pile more insulation in!

So it's a question of spending $2,000 on a new mini-split or $8,000 on solar to run the ol' window unit. Hmm. Tough one. I may not be smart enough to figure that out. After all, the solar plan has the additional "fun to do" factor. How do you put a price on that?

Treblig

Re: This SOLAR PLAN MUST be Possible>>

Oh I forgot...What would happen if I ran the central unit fan full time (not on auto). This would circulate the mini-split air all around the house and keep the ducts cool, I know the heat will still sink into the ducts to some degree, but will there be any gain?? Of course it would also make the mini-split run all the time, but better the mini-splt than the 4ton...RIGHT??? Squirrel cages are cheap so replacing the main blower motor (every 8 years or so) is way cheaper than running the 4ton all the time. The only problem is that the mini-split doesn't have the capability to suck enough humidity out of the air as the 4ton. So the 4ton does need to come on every now and then anyway.

Gil in Tex....where the sun (almost) never sets.

Cariboocoot

Re: This SOLAR PLAN MUST be Possible>>

Treblig wrote: »

Oh I forgot...What would happen if I ran the central unit fan full time (not on auto). This would circulate the mini-split air all around the house and keep the ducts cool, I know the heat will still sink into the ducts to some degree, but will there be any gain?? Of course it would also make the mini-split run all the time, but better the mini-splt than the 4ton...RIGHT??? Squirrel cages are cheap so replacing the main blower motor (every 8 years or so) is way cheaper than running the 4ton all the time. The only problem is that the mini-split doesn't have the capability to suck enough humidity out of the air as the 4ton. So the 4ton does need to come on every now and then anyway.

Gil in Tex....where the sun (almost) never sets.

You'd essentially be asking a tiny little air conditioner to do the job of a 4 ton unit. What do you think the result would be? If you answered "the house wouldn't be cool and the mini-split will give up sooner rather than later" you get an 'A'. "Can't carry a 4 ton load in a quarter-ton truck."

Turn the thermostat up on the 4 ton to the maximum you can stand to live in. Use the mini-split to cool down the bedroom for sleeping.