Electric Water Heater?

NFRicaS · 01-08-2019, 02:30 AM

I never have liked/used the propane in my RV...thought I read somewhere about a way to replace the tank with an (on-demand?) electric hot water heater..I have measured the space, have a picture of current hot water tank (can’t figure out how to attach

.would love to just take out/off the propane tank..Welcoming ideas..thoughts..

GeorgeRa · 01-08-2019, 02:37 AM

A good concept, but from where will you draw required energy would be a key question.

NFRicaS · 01-08-2019, 01:45 PM

From campground/shore power...I am not a boondocker...does anyone remember where the old thread was/is that had some discussion on this?? Thanks in advance!!

SteveJ · 01-08-2019, 02:34 PM

Quote:

Originally Posted by NFRicaS

From campground/shore power...I am not a boondocker...does anyone remember where the old thread was/is that had some discussion on this?? Thanks in advance!!

Not near enough power available on 30 amp, and really not enough if you were to fab up some sort of 50 amp service. Photo is from Home Depot online.

mloganusda · 01-08-2019, 02:39 PM

You could replace your hot water tank with a marine water tank that is heated by the engine and 110v heating element. This is what is standard in the Rialta MH. It is now being used in some class A MH.

SteveJ · 01-08-2019, 09:00 PM

A number of years ago I made my own heat exchanger for the standard water tank on our '78 class A Georgie Boy. I made a U loop from 1/2" copper tubing and used a thermally conductive paste to attach it. As we lived up in Minnesnowta at the time I procured a rear school bus heater and installed it under a dining seat. I then plumbed up a coolant run that hit both. It all worked a treat.

A person could add an electric element to a standard Suburban tank, I believe.

Having typed all of that, it is a lot of work to effect these changes and unless you use a tremendously inordinate amount of hot water I don't really see the upside for the small amount of propane usage that heating water entails. If it's about a "feel good feeling" about not using propane then that is a factor in the decision. Converting the current tank would leave the propane option in place if things changed, i.e. selling to a boon-docker or ??

avanti · 01-08-2019, 09:17 PM

There is no great difficulty using shore power to heat your water. Lots of propane water heaters have an electric coil built in. Get one of those and simply don't fill your propane tank (or pull it out).

The difficulty comes from the stipulation the you want an on-demand unit and no a storage tank. That may prove to be difficult, since you need a lot of power to heat the water fast enough. It isn't a great idea anyway, since that style of heater has a minimum flow requirement, and they thus are hard on tank space. A hydronic system with a flash-plate instant heater is more practical, but more complex.

GeorgeRa · 01-08-2019, 09:49 PM

I agree, to limit electrical power requirements for water heating buffering water is the best way. With an LPG or a marine 4-6 gal. water heater with 750-1500W electric heater rod 8-10 gal. shower temperature water can be obtain every 15-30 min. In my marine water heater, I have a 750W rod electric heating element it is plenty for our light hot water users when on shore power. But I do enjoy speeding my water heating with the roaring 5kW diesel heater.

Hatteras Jim · 01-08-2019, 10:10 PM

I use a 4 gallon electric heater (120V) in my class B. It was purchased from Lowes. A Bosch Tronic 3000. Maximum current draw is 12 amps.

When I built the van, I wired it for 50 amp 120V service, which actually supplies 100 amps to 2 banks of breakers at 120V each. I also have a 2 burner electric glass cook top, also 120V and 15 amps per burner on high.

If I have to use a 30 amp service, I'll heat the water without the AC on, then turn the heater off to use the AC. Water stays hot for quite a while. Only use the hot water for washing hands, dishes and cleaning. Do not have a bath or shower. Same when using the cook top on a 30 amp service (only use 1 burner). You just have to be aware of "current" events (bad pun). Try to get 50 amp service when I can; but, can make do with 30 or without if need be.

When all else fails, we fall back to the coleman gas stove outside or the small BBQ grill. Mainly use the cook top for rainy days.

Also did not want to deal with propane, especially since my wife and I were home brewing our own sprinter.

Nice thing about a small tank heater, is that you have warm-hot water during your trip and upon arrival at the next site.

In my opinion, the smallest tankless heater at 29 amps would be OK for 50 amp (actually 100A) service; but, not for 30. Good luck.

Boxster1971 · 01-09-2019, 01:39 AM

Quote:

Originally Posted by Hatteras Jim

I use a 4 gallon electric heater (120V) in my class B. It was purchased from Lowes. A Bosch Tronic 3000. Maximum current draw is 12 amps. ...

... In my opinion, the smallest tankless heater at 29 amps would be OK for 50 amp (actually 100A) service; but, not for 30. Good luck.

That is a very nice water heater. I had to dig a bit to find it as the basic Bosch Tronic 3000 is a tankless water heater. You are using a Bosch Tronic 3000T Mini-Tank Series ES4.

https://www.homedepot.com/p/Bosch-4-...ES-4/206393135

About half the cost of a typical RV water heater.

tgregg · 01-09-2019, 02:12 AM

Quote:

Originally Posted by GeorgeRa

I agree, to limit electrical power requirements for water heating buffering water is the best way. With an LPG or a marine 4-6 gal. water heater with 750-1500W electric heater rod 8-10 gal. shower temperature water can be obtain every 15-30 min. In my marine water heater, I have a 750W rod electric heating element it is plenty for our light hot water users when on shore power. But I do enjoy speeding my water heating with the roaring 5kW diesel heater.

George, you and I have the same Isotherm 4 gallon water heater with the 750w electric element. The only difference is yours is also heated by your Espar D5 and mine is heated by my engine cooling system.

I wonder how much battery power it would take to maintain the temperature once the water was heated by my engine or your D5?

First, mine would have to cool down to below 160F from 200F+ before even needing any additional heating. What temperature do you heat yours to with the D5? Doesn't the D5 have a thermostat that heats the coolant to 180F?

Without knowing the surface area of the tank and the R factor of the insulation it's hard to calculate the BTU loss. I could try to measure the watts used to maintain the temperature with a Kill A Watt meter once it's heated with engine.

My tank is mounted inside and I believe yours is mounted outside under the vehicle, so you might experience a little more btu/hr loss on a cold day. It might be similar to the energy used by a compressor refrigerator.

avanti · 01-09-2019, 02:27 AM

Quote:

Originally Posted by tgregg

George, you and I have the same Isotherm 4 gallon water heater with the 750w electric element. The only difference is yours is also heated by your Espar D5 and mine is heated by my engine cooling system.

I wonder how much battery power it would take to maintain the temperature once the water was heated by my engine or your D5?

It takes less net energy to reheat the water than to keep it hot. So, the only real question is "how well insulated is your tank".

GeorgeRa · 01-09-2019, 03:07 AM

I never measured how often electric heater cycles when on shore, I just keep it on. D5 keeps coolant between about 160 and 180F when running which for us is once or twice a day.

The simplest way to answer your question would be to measure energy consumed.

My tank is mounted outside in a driver side in under the floor cavity, definitely higher heat losses than from an inside mounted heater.

The recently added EasyStart Timer gives me much easier access from inside to turn D5 on, so my heating system is finished, no more checking or tuning.

magicbus · 01-09-2019, 03:05 PM

If you have space for a Truma Combi you might look at that as it also provides nice hot air heat eliminating a separate furnace. The hot water tank is just over 2.5 gallons.

NFRicaS · 01-10-2019, 01:28 PM

Quote:

Originally Posted by avanti

There is no great difficulty using shore power to heat your water. Lots of propane water heaters have an electric coil built in. Get one of those and simply don't fill your propane tank (or pull it out).

The difficulty comes from the stipulation the you want an on-demand unit and no a storage tank. That may prove to be difficult, since you need a lot of power to heat the water fast enough. It isn't a great idea anyway, since that style of heater has a minimum flow requirement, and they thus are hard on tank space. A hydronic system with a flash-plate instant heater is more practical, but more complex.

Thanks...doesn’t have to be on-demand, just don’t like propane..

kite_rider · 01-10-2019, 06:21 PM

Quote:

Originally Posted by avanti

It takes less net energy to reheat the water than to keep it hot. So, the only real question is "how well insulated is your tank".

I ran into a guy using the Bosch mini-tank electric water heater. He had a very basic build (small AGM battery) but said it all worked out OK since he would heat the water while driving the van (with his inverter) and just maintain it with battery when camping. So my guess is that these units are well insulated.

It's not like this thing was heating a lot of water anyway since boondockers are generally stingy with water.

NFRicaS · 01-12-2019, 12:55 AM

Thanks, G, you always give great info...I can wait a bit for the hot water, now I just need help figuring it all out!!

israndy · 01-13-2019, 05:38 PM

I used to have a Gulfstream Class B Sprinter RV, that had an on-demand water heater, cannot remember the manufacturer. The only "warm" shower I ever took was in an RV park in summer. The temp of the water in the tank has a BIG impact. Actually thought about putting a solar heater on the roof and cycling the tank water thru. That would also keep the cabin warm at night with that big thermal mass. The other issue was the rate of flow. If it was too low the heater kept turning off and back on, if it was too high the heater didn't have enough time to heat the water. Best I ever measured from it was 92°

There is a product on the market now that uses an Omic Array to heat the water, I like to think of it like microwaving the water to heat it more efficiently than a resistive coil. Check out HeatWorks, the Model 1 that they used to make may be perfect for an RV. Still, if you want a realistic shower on-demand you may wanna look into putting a second power plug on the outside of the RV for 220V so you can run a dedicated wire from the park pedestal 50 amp plug to the water heater. Use the 30 amp plug for everything else. Most places offer both.

-Randy

avanti · 01-13-2019, 06:07 PM

Quote:

Originally Posted by israndy

There is a product on the market now that uses an Omic Array to heat the water, I like to think of it like microwaving the water to heat it more efficiently than a resistive coil.

Well, there may be advantages to this technology, but I don't see how efficiency can be one of them (nor do they seem to claim so). Resistive heaters are, I believe, 100% efficient. Where else would the energy go?

GeorgeRa · 01-13-2019, 06:13 PM

Quote:

Originally Posted by avanti

Well, there may be advantages to this technology, but I don't see how efficiency can be one of them (nor do they seem to claim so). Resistive heaters are, I believe, 100% efficient. Where else would the energy go?

The graphite heater is an array so convection heat transfer within a, no flow, tank could be improved / faster but efficiency gain will likely be undetectable, heating water with an ohmic element is 100% efficient indeed.

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