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I'm sorry in advance if this has been discussed before but..............

I'm at the stage where I have to buy a hot water heater. I'm leaning towards a conventional 6 gallon propane water heater but I keep hearing people talk about 110v tank-less on demand water heaters.

I don't plan on running my vehicle or my generator to make hot water. I do plan on having 2 x 150amp house batteries with a 3000w inverter. Ive called RV repair shops and even a couple manufacturers of the tank-less electrical heater manufacturers and they advise on using a generator or shore power and not house batteries through an inverter.

Any input would be appreciated.
 

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I'm sorry in advance if this has been discussed before but..............

I'm at the stage where I have to buy a hot water heater. I'm leaning towards a conventional 6 gallon propane water heater but I keep hearing people talk about 110v tank-less on demand water heaters.

I don't plan on running my vehicle or my generator to make hot water. I do plan on having 2 x 150amp house batteries with a 3000w inverter. Ive called RV repair shops and even a couple manufacturers of the tank-less electrical heater manufacturers and they advise on using a generator or shore power and not house batteries through an inverter.

Any input would be appreciated.
Hi,
Tankless electric water heaters pull a lot of power.

If you look at this small one from Rheem: http://www.tanklessking.com/media/uploads/Rheem-RTE-Spec-Sheet.pdf

The smallest model (RTE-3) requires 3200 watts and works on 110VAC -- so it might work with an inverter just a bit larger than you are thinking of. But, it only provides 0.44 gal per min with a 50F temp rise. If the water in your water storage tank is (say) 60F, than this would give you 0.44 gpm of 110F water. Might be OK for some things, but a typical shower is more like 1.5 gpm.

If you figure 90% inverter efficiency, then the batteries are going to see 3200/0.9 = 3600 watts drain when heater is on, which is 3600/12 = 300 amps going into your inverter from your 12 volt batteries. That's a lot of juice -- if you allow the heater to take your batteries down to 50% depth of charge, the RTE-3 heater would take them from fully charged to 50% charge in half an hour of run time.

The next model up (RTE-7) which would give you 0.8 gpm with a 60F temp rise (enough for a frugal shower) requires 7000 watts and 240VAC service -- so, its way over the kind of electrical system you are talking about.

The compactness of these heaters is really nice, but it seems like they take a larger electrical system than most of us are putting in our small conversions.

If you are planning to have propane anyway, there are some small tankless propane heaters (maybe Atwood?) that might work well and be compact.
Heating up 15 gallons of water from 60F to 120F with an 80% efficient propane heater would use about 0.1 gallons of propane -- so, if your hot water needs are modest, you probably would not really need a larger propane tank.


Gary
 

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GaryBIS Thanks for all your info, much more than I expected and very informative. I think I will go with a regular old RV 6 gallon propane water heater. I have a toy hauler trailer that has a 6 gallon water heater and it works just fine. If a second person has to shower right after the 1st the only thing we do is wait for 10-15 mins for the water to heat up again. Ive lived in my toy hauler for almost a year in an RV park and it was fine. Me and my girl go to Burningman www.Burningman.com each year for the last 5 and we each take 3 showers a day and it works just fine.

Thanks again
 

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Hi sdharlie,

I swear I'm not following you around this forum specifically but it seems we are doing some things pretty similarly. I went the tankless with propane route with this...

http://www.precisiontemp.com/rv-and-trailer/rv-550-nsp-floor-vented-tankless-water-heater-for-rv-and-trailers/

Can't say how well it works yet as I have yet to hook up the propane and water to it but I have the perfect mounting place for it if you're interested. It's pricey but I like the theory behind it. I didn't want to cut a hole in the exterior wall and I wanted as much hot water as I could get for when I'm hooked up to a supply and I didn't want to always be heating the 6 gallons of water. I only have the 5.7gallon propane tank, a little smaller than yours, but for any extended camping I'll be using an extend-a-stay so I'll have an extra 20lb tank hooked in. The freeze protection circuit for colder temps seems like a great idea. I also have an electric tank heater for freshwater so that I can keep it's temp a little more regulated.

Seems everything has it's goods and bads though.

Good Luck.
 

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I'm going through the same process and am so happy I found this forum. I haven't even bought a Promaster yet but I'm trying to get all my ducks in a row before I do and this helps answer one of my questions. I'm sure I'll be following you too.

thanks
 

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I love the idea of a floor vented water heater. I am going for the stealth look as much as possible. I have read the tankless water heaters are not the best for navy style showers, so my plan is to have a sink near the shower head. The sink will have a way to divert water back into the water tank, this way I can let the water run non stop at continuous temperature. I will have a separate water tank for drinking water and one for everything else.
 
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