Tankless Hot Water Heaters

fooddiva
fooddiva Registered Users Posts: 15 ✭
in General Solar Power Topics #1
We have been off grid for 23 years now. We have just upgraded and added panels. And now we have to replace our hot water heater. We have always used a tankless hot water heater/propane. Never had a problem with it. We are trying to decide on the best off grid heater to replace our old one. Does anyone have knowledge or experience with either the Rinnai R75LS or Bosch 425HNL? Or can you recommend another one? We'd like to vent it outside and hang it on the cellar wall if possible. Would love some feedback and suggestions.
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  • SCharles
    SCharles Solar Expert Posts: 123 ✭✭
    #2
    Re: Tankless Hot Water Heaters

    I looked into tankless a while back and decided against it only because we live at high altitude and they would not be good for here. But during my discussions with the various companies making and selling them [trying to find one that would work up here at nearly 9,000 ft] the Rinnai people warned me that their product is only sold to installers and they do not sell to DIYers. Don't know if that is the same everywhere [this is in Colorado] but that was a no-deal for me as I do everything myself and getting an installer up here in the sticks would cost a ton of money.

    If you are replacing one, it obviously works at your location. So that part is ok. If you want to do the install yourself, make sure Rinnai will allow it if you choose them. I have heard good reports about Paloma, Bosch, and Rinnai but those are anecdotal. For what it's worth.
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  • petertearai
    petertearai Solar Expert Posts: 471 ✭✭✭✭
    #3
    Re: Tankless Hot Water Heaters

    I have had a Bosh hydro 16 l per minuite .Dont know what model number. It has been in for coming on 8 years. Weekend use. Has never been looked at,just keeps on working.
    2225 wattts pv . Outback 2kw  fxr pure sine inverter . fm80 charge controller . Mate 3. victron battery monitor . 24 volts  in 2 volt Shoto lead carbon extreme batterys. off grid  holiday home 
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #4
    Re: Tankless Hot Water Heaters

    I have installed dozens over the years. I personally would shy away from Bosches, as I have had trouble with them in the past. I would install a Rinnai or a Takagi in a heart beat. both will direct vent out a side wall.

    I. Have done a number of old standing pilot Paloma's over the years, but they are sort of old technology nowadays. I have never installed a electronic Paloma.

    My favorite of late is the Takagi TKJr. It does ~4 gallons a minute at ~60 degree F rise.

    Tony
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  • Grandpaclark61
    Grandpaclark61 Registered Users Posts: 5 ✭
    #5
    Re: Tankless Hot Water Heaters

    I am sure this is old news, but my son just installed tank-less water heaters in a laundry mat he owns, working great for him! I actually just recently found about it! Seems like it's been around for awhile. Does anyone know if a washington dc water heater installer would be able to put one of these in my home? Thanks for the advice!
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  • pabloesguapo
    pabloesguapo Solar Expert Posts: 116 ✭✭
    #6
    Re: Tankless Hot Water Heaters

    I am building a home in the spring, and will be equipping it with an off-grid solar PV system. (We're in the middle of nowhere, there's no chance of having any utility lines of any kind run to our house) I've been wondering about how to get hot water. The posts here have given me a starting point for my research into the matter. Thanks much.

    One question though. If I went with a whiole house tankless system, should I go strictly electric or should I go with a propane powered unit? How much electricity do these things eat up? How much propane do they use per month, or per year, for a 4 bedroom, 2 1/2 bath house?
    27 Kyocera panels, 6,500w
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: Tankless Hot Water Heaters
    pabloesguapo wrote: »
    I am building a home in the spring, and will be equipping it with an off-grid solar PV system. (We're in the middle of nowhere, there's no chance of having any utility lines of any kind run to our house) I've been wondering about how to get hot water. The posts here have given me a starting point for my research into the matter. Thanks much.

    One question though. If I went with a whiole house tankless system, should I go strictly electric or should I go with a propane powered unit? How much electricity do these things eat up? How much propane do they use per month, or per year, for a 4 bedroom, 2 1/2 bath house?

    Go propane or natural gas if available. How much they will use depends on how much hot water you use and how hot you want it. For two people it is quite a savings. If it is a family (with children) and lots of hot water is used you are probably better off with a tank-type heater. The savings of the tankless depend on using less hot water, as they don't heat water not used (unlike the tank-type which keeps the water heated whether you need it or not).

    Never, ever install an electric tankless water heater anywhere under any circumstances. It is more horrible than you can ever imagine. You certainly can't support one off-grid: they use massive amounts of power.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #8
    Re: Tankless Hot Water Heaters

    An electric demand water heater is a huge load,, 5-15 kw!

    If you have enough solar to power a demand electric,, you really have to consider solar hot water first, as it comes at ~1/10 the cost per BTU!

    That said, a gas unit big enough for a tub or two showers, ~ 5 gpm flow at 60f rise will burn ~ 140,000 BTUs an hour going full bore. That is 2 gallons of propane per hour. Consider however, that a 6 minute shower, might only use 2 gpm, or about 1/2 the BTUs. That same shower .1 hour at 2.5 gpm might burn 7500 BTUs,, or about 1/10 of a gallon.

    The bottom line, with the exception of solar hot water, and possibly heat pump recapture, there is no other way that is more efficient than a good demand water heater.

    Tony
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
    Re: Tankless Hot Water Heaters

    Tony;

    It's even worse than you thought: the Bosch RP27 uses 27 kW and can only manage 45F rise @ 4 GPM. It's wired with 2 AWG. Really horrible things.
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  • Fe-Wood
    Fe-Wood Solar Expert Posts: 96 ✭✭
    #10
    Re: Tankless Hot Water Heaters

    Some other points to consider with a tankless water heaters is relative efficiency. I installed a Navien brand last year that was 92% efficient, it direct vented with PVC and didn't have the dreaded cold water sandwich. This brand also has a hot water re-circulation option. Runs on Propane or NG. My clients love it!
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #11
    Re: Tankless Hot Water Heaters

    The Navien looks to be a nice unit,, I have never heard of them. The fact that it can vent through a PVC vent is and advantage,, although it is a special PVC vent.

    It comes at a significant premium over a similar Takagi however. A similar Takagi is ~$600, while the Navien is ~$1200.

    The Takagi has an energy factor of .83, the Navien a bit higher, .95 or so. $600 will buy a lot of gas in a demand water heater.

    Tony
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  • solarvic
    solarvic Solar Expert Posts: 1,071 ✭✭✭✭
    #12
    Re: Tankless Hot Water Heaters

    The GE GEO SPRING electric heat pump waterheater is doable on offgrid also. Mine used just less than 500 kwh for a year. I just got my MS 4024 magnum inverter working today and am tyring to learn its capacity to power different items. The water heater draws about 28 amp at 24 volt which should be about 670 watts 220 AC. Also could run the washer and 220 vac waterpump off a fork truck battery. Got a crown 12-85-13 battery and wish I would have got the next size bigger. :Dsolarvic:D
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  • pabloesguapo
    pabloesguapo Solar Expert Posts: 116 ✭✭
    #13
    Re: Tankless Hot Water Heaters

    I do have a family, wife, 3 kids, plus grandma. I like the Rheem unit (model #?) That can pump out 9.5 gpm. Home Depot sells it for $899. If our hot water demands outpace the unit, I can always buy another, and connect it in series.

    Although I have seen some passive solar units with 100 gal tank for the same price as two tankless Rheems...
    27 Kyocera panels, 6,500w
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #14
    Re: Tankless Hot Water Heaters
    pabloesguapo wrote: »
    I do have a family, wife, 3 kids, plus grandma. I like the Rheem unit (model #?) That can pump out 9.5 gpm. Home Depot sells it for $899. If our hot water demands outpace the unit, I can always buy another, and connect it in series.

    Although I have seen some passive solar units with 100 gal tank for the same price as two tankless Rheems...

    The problem is the tankless units use more gas to heat the same over-all volume of water because they are doing in quickly. That means there needs to be higher flame temp to transfer more heat to the water in a shorter period of time, and that means more btu's which means more fuel.

    Just my opinion, but with six people in the house all using hot water (probably 50 gallons of water a day each, about 50% of that hot for a total of 150 gallons of hot water per day) you're better off with a gas-fired tank-type heater.

    We used to figure on 100 gallons of water per person per day, but that was a pretty sloppy calculation and doesn't apply in this day of low-use faucets, showers, and toilets. It also turns out that a house has a sort of minimum "base" number, and the per-person rate goes down as the number of people in the household goes up.

    Even so, a 10 minute shower @ 3 gpm = 30 gallons. If 50% hot that's 15 gallons per person right there. Multiply by 6 and you're already at 90 gallons of hot water.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #15
    Re: Tankless Hot Water Heaters

    I believe that Rheem is the North American version of Paloma,, made in Japan. The older standing pilot Paloma's were great units, don't know much about the new electronic versions.

    I actually dis agree with 'coot in a general sense. Stand by loses are considerble in any tank type heater, and unless they are going all the time and or the standby lose is able to be used as space heat year round, the annual fuel cost is likely to always be less with a demand.

    The 85-95 ef modern units capture so much of the heat, sealed combustion, and no stand by loses make them winners in my world. It really doesn't matter if you put 100k BTUs over an hour, or 12 hours, if the same percentage is going into the water net/net.


    Additionally, most tanks have an internal flue that draws air through the tank 24/7 (to some limited extent) which has the effect of cooling down the tank faster. The same is true of a demand, but only a few liters of water are cooled, while the entire tank is cooled in a tank system.

    Personally, my favorite system is a solar preheat into a well insulted tank, feeding into a electronic demand heater. The electronic units will only heat the water to the pre set temp regardless of the inlet temp, so it uses proportionally less fuel as the water gets warmer from the sun.


    Tony
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  • pabloesguapo
    pabloesguapo Solar Expert Posts: 116 ✭✭
    #16
    Re: Tankless Hot Water Heaters

    Hmmm... Thanks for the thoughts. I think I might be able to attain a balanced solution to my own personal puzzle here. The issues I have to deal with are:

    1) Installation cost. We are building an entire 40 acre homestead (just outside of Kirkland, AZ). We begin land clearing, well digging, fence building, etc. in the spring, and begin house construction this summer, with the whole family living in trailers while we DIY. (Yes, call us crazy...) We are already hemorrhaging money with this project, so I have to be very mindful of what we spend to "get us there".

    2) Future costs and sustainability. Once we're settled in, we want to be as self-sufficient and sustainable as possible. Our water will be from our well, our electricity will be from solar, so there are two monthly utility bills eliminated right there. We WILL have a big underground propane tank, with regular deliveries of it for cooking and some water heating, but it makes sense for us to curb the usage as much as possible. From the sound of your comments, if we just use an instant tankless LP heater system, we might be looking at a monthly propane bill upwards of $200. That completely defeats our goals of "living off-grid". Apparently, water heating can account for about 70% of our LP gas bill, it makes sense to heat it some other way.

    3) Time and resource management. I have more than one cabin to build (Other in-laws are soon moving there too) and limited access to funds at any given time. We're kind of building in stages, and paying cash as we go. (Debt control is part of our sustainability plan) I'd like to build a "whole-hog" system from the very start, but won't be able to afford it in terms of both time or money. I can make do with one LP unit for a while, until I have time and money to devote to further improvements, like a solar powered heater addition.

    I read this article from Mother Earth News. It gave me the idea of building my own sun heated assistant to a Rheem unit. If I can keep 50-ish gallons of at least lukewarm water around to pump into the LP instant heater, I can save a bundle of $$$. I also found this SITE that has oodles and oodles of plans, ideas and tips on integrating a passive solar water heating system into my soon-to-be existing LP powered instant heater.
    27 Kyocera panels, 6,500w
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    Midnite Classic 150 & Classic 150 Lite in "follow me" mode
    (2) Outback fx3648 inverters
    Generac ecogen 6kw backup generator
    Mate3s
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  • solar_dave
    solar_dave Solar Expert Posts: 2,397 ✭✭✭✭
    #17
    Re: Tankless Hot Water Heaters

    Oh in Kirkland off AZ89 off the Bagdad Highway ! You need a like a 4X10 solar hot water panel and an 80 gallon tank. 10 months out of the year I have my hot water heater set to 110F and only use 3 therms of nat gas a month. Even today the 80 gallon tank is showing 110F and is used to preheat my Sears high efficient DWH. Most of the year the storage tank is 145F+.

    Solar hot water is a great DIY project, an 80 gallon hot water heater makes a great tank for storage. Ours is a Rheem Electric model not wired up. Are you high up enough that freezing is an issue? Look at drain down systems then. Mine is fully pressurized system in town, no real risk of freezing and I think the controller comes on and pumps warm water out of the storage through the collector if it gets real cold..

    You can easily get 80-90% of your needs from the sun in that location. Add a second Panel and I bet you can get almost all your needs met. There are a couple of Thermal panel makers in Phoenix.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #18
    Re: Tankless Hot Water Heaters

    I suggest you " do the math". Do a calc. On your hot wate use, and base your decisions on real world numbers, not some speculation! For example, In my world, $200 will buy ~66 gallons of propane, or ~ 5.3 million BTUs. At 85% ef, how many gallons of water can you heat with what temp rise?

    In my case, a 6 minute shower might use - max of 10-15,000 BTUs. That would be ~500 showers! (or combinations of showers/dishes/laundry etc) We use 12 gallons of propane every 6 weeks, for cooking, hot water and fridge.

    A simple flat plate solar collector can be built for under $1000, and in your climate might contribute upwards of 80% of your hot water on an annual basis. A simple controller will have a freeze protection setting to circ water when OAT is near freezing. The ones that I have built, stay thawed down to near 0f. If you have solar exposure for PV it is a no brainier to install solar hot water.

    Tony
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  • michael k
    michael k Registered Users Posts: 6 ✭
    #19
    Re: Tankless Hot Water Heaters

    Fooddiva just installed this Ecotemp - works great for small houses No TAX No SHIPPING!

    Pricewise not bad and responds well to watersaver heads . . .
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  • Fe-Wood
    Fe-Wood Solar Expert Posts: 96 ✭✭
    #20
    Re: Tankless Hot Water Heaters

    Ya, your $200 a month estimate for propane is off. In my old house I had one of the first generation Bosch tankless water heaters. In the summer my bill for 2 people showing at least once a day and using the bath tub often, our bill was around $30 to $45 a month. That included about $25 for electric too.

    I just installed a ecotemp unit for my new place. Haven't used it enough to give a good opinion yet. I have a Poloma that I installed about 10 years ago in a small cabin. It gets used everyday and has even had mice nest on the heat exchanger. Still going strong. If you go with a stand alone small heaters on each dwelling look into what it takes pressure wise to activate the heater. The Poloma will activate with about 20PSI but the Ecotemp needs about 45PSI. I don't know if Poloma has a standing pilot light or has gone to the Piezo type lighter. The old ones are pilot light the ecotemp I have has an igniter.

    You might also want to consider a centrally located bath house for laundry and bathing.
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  • pabloesguapo
    pabloesguapo Solar Expert Posts: 116 ✭✭
    #21
    Re: Tankless Hot Water Heaters

    @solar Dave; yeah, just off the junction. I can see the lights of the steakhouse from my property at night. If memory serves, my elevation is 3282, so I don't know about freezing possibilities. As of yesterday, my latest idea is a LP instant heater with a "breadbox" on the south wall.

    @Icarus: Yeah, $200 a month is a complete guesstimate. I know its apples and oranges, but I'm basing it off of what we pay for NG right now in our woodframe, chicken wire and stucco houses we live in now. Anything less than we collectively pay now is a bonus.

    BTW..I forgot to mention properly earlier, we're actually going to gave 10 people living off this system the first year (5 grown ups, 5 kids, until the 2nd house is built. Can you tell we're all itching to get out of the big city?:cool:). 500 showers? We'll blast through that in 6 weeks or less. That's assuming I can train everybody on hot water conservation: a grandma, a wife, her sister, my two soon to be teenage girls among the gang. 6 minute showers? No offense, but LOL!

    @Fe Wood: I'd like to get my "utility" bills as close to zero as I can. 25-50 bucks a month is nice, but 0-10 is even nicer. As close to zero and 100% sustainability as possible! :)
    A central bathing area? Fat chance, unfortunately. Thanks for the link on the ecotemp. That's another option now.

    @Everyone, thanks for offering all your advice and ideas. This forum is a wonderful resource. I can't wait to get started with actual construction and MOVE down there!

    I just got word, they're digging our well this week. Once I get depth and flow info, I can start making more accurate calculations and decisions.
    27 Kyocera panels, 6,500w
    24 CG2 6v batteries, 48v, 630Ah
    Midnite Classic 150 & Classic 150 Lite in "follow me" mode
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    Generac ecogen 6kw backup generator
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #22
    Re: Tankless Hot Water Heaters

    Look into simple solar. It should be your cheapest alternative by fr,, and is especially well suited for DIY.

    Tony
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  • monoloco
    monoloco Solar Expert Posts: 103 ✭✭
    #23
    Re: Tankless Hot Water Heaters

    I don't know why the tankless heaters sold in the states are so expensive. I have a Bosch that they sell at Home Depot and Costco here in Mexico that works well and costs less than $200.
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  • Fe-Wood
    Fe-Wood Solar Expert Posts: 96 ✭✭
    #24
    Re: Tankless Hot Water Heaters
    monoloco wrote: »
    I don't know why the tankless heaters sold in the states are so expensive. I have a Bosch that they sell at Home Depot and here in Mexico that works well and costs less than $200.

    Liability!:cry::cry:
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  • miscrms
    miscrms Registered Users Posts: 15 ✭✭
    #25
    Re: Tankless Hot Water Heaters

    FWIW we have had a small Bosch tankless (equiv of current 1600H) on our small 2 bed 1 bath historic home for ~5 years and have been very happy with it. We've had a few issues but nothing major.

    Phoenix has very hard water which caused our main control valve to need a rebuild after a few years, but there is a rebuild kit. We also installed an indoor unit outside (pretty common in phoenix) but our open cover was not sufficient to keep the rain out of it when it really poured so it would fail to light when really soaked.

    For our family of 4 the NG usage was almost in the noise compared to the gas furnace, and it was very nice to have as much HW as we needed without needing a big tank. This house is a rental now, and our new 4 BR 2 BTH home has an old tank heater. We really miss the tankless, and have been looking at the bigger Rheem unit at HD.

    Solar pre-heat with propane on-demand sounds like a great choice for your situation! Just make sure you research it, as I'm not sure all tankless can deal with pre-heated water. Bosch used to make one specifically for this purpose, but maybe the need for that has gone away with the newer electronically controlled models.

    Rob
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