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Discussion Starter #1 (Edited)
Have some questions about experience with an electric water heater. As we were talking about hot showers in another thread, I had a thought about using something made for this vs my current method of using the electric kettle.

Eccotemp makes a nice small portable 2.5 gallon electric water heater. It has a 1400 Watt heating element and according to them, it takes ~13 mins to heat up 2.5 gallons from 60 degrees to 125 degrees, which seems perfect for a shower, or using it to wash your hands/face with warm water. It would be really easy to plumb it up. I've got the space for it behind my water tank, and I could run the hot water to the faucet as well as the outdoor shower.

I've got 400Ah of batteries, so I should be able to handle this no problem, and technically it shouldn't take THAT much more power than my 1200 Watt electric kettle takes to heat up 1/2 gallon of water to 220 degrees. I think my normal use case for this would be to run this water heater while I'm driving and while the alternator is supplying 20Ah+ to my batteries. Maybe even insulate it further than it currently is, so it can hold the 125 degree water for quite a few hours.

Link: https://www.eccotemp.com/eccotemp-em-2-5-electric-mini-tank-water-heater/

Anyone used something like this?

edit: Also a possible option is this $400 12V DC unit. With a 300w heater element, but powered by DC, this would be a LOT more efficient. Also states that it will hold the hot water for 10 hours. Add a layer of insulation over the top and I bet that would be even longer: http://www.defender.com/product.jsp...-gallon&path=-1|51|2234308|2234310&id=2785571

edit2: MOAR googling and I did find a reasonably priced engine coolant driven unit with 4 gallon capacity. While that's bigger than I wanted, it seems this would be the ultimate way to go. As this would be heat the water while driving, for free, and it's reported that it stays warm for 12-15 hours: http://www.isotherm-parts.com/index.php?main_page=product_info&cPath=4_34_107&products_id=1986. Guess this could get mounted somewhere underneath the van maybe vs running engine coolant lines inside.....

edit3: Another 12V unit here. This one is like $500, but seems definitely targeted for campers/vans: https://www.truma.com/int/en/products/truma-water-systems/truma-electric-water-heater-boiler.html Here is an install in a camper van: https://campervanconverts.com/tag/truma-electric-boiler/
 

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If you are going to be charging while running the AC heater, that might work okay. Remember your 1200w electric kettle probably only runs for 1-2 minutes before bringing the small amount of water to temp. Bringing 2.5 gallons to temp will take longer. If your batteries aren't fully charged it might trip the inverter if the voltage drops too much.

As for the DC unit at 300w, that's going to take a long time to heat up the water.

The coolant mixture typically requires another fuel source (not familiar with this specific unit). It may only work while driving, which wouldn't be idle for all scenarios.

The Truma isn't for the US market as it runs on 230V.
 

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The Isotemp unit also has a 750 watt 115 VAC heater, so it's a bit both worlds.

I'm considering hooking one up to a solar water heater panel instead of engine heat. Hadn't considered mounting it below deck, might free up some space for me it that works and gives me a better route to hook up to engine heat if I decide otherwise.

Last I researched it, I believe Truma was only selling to OEMs in the US.
 

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edit2: MOAR googling and I did find a reasonably priced engine coolant driven unit with 4 gallon capacity. While that's bigger than I wanted, it seems this would be the ultimate way to go. As this would be heat the water while driving, for free, and it's reported that it stays warm for 12-15 hours: http://www.isotherm-parts.com/index.php?main_page=product_info&cPath=4_34_107&products_id=1986. Guess this could get mounted somewhere underneath the van maybe vs running engine coolant lines inside.....
We have the 4 gallon in our promaster connected to the engine cooling system. We've used a similar system in 2 previous RV's since 1993. This is the way most live aboard boaters heat hot water.

Because the water is stored at near engine temperature it's mixed with cooler water from your fresh water tank with a thermostatic mixing valve that comes with the Isotherm and then with more cold water at your sink or shower faucet, so the 4 gallons lasts a long time.

We take our showers at night but there's still hot water for washing and dishes the next day. If we don't drive the next day, idling the engine for 15 or 20 minutes heats it back up.

Previous camper had a 6 gallon version that would last 2 days.

They make a cylindrical unit as well as a rectangular unit. We have the cylindrical unit mounted inside with the coolant hoses running underneath the van until the enter just below the heater. The heater is very well insulated and we insulated the coolant hoses where they enter and we don't notice any heat coming from the installation.

Free hot water while you drive is definitely the ultimate way to go.
 

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We have the 4 gallon in our promaster connected to the engine cooling system. We've used a similar system in 2 previous RV's since 1993. This is the way most live aboard boaters heat hot water.

Because the water is stored at near engine temperature it's mixed with cooler water from your fresh water tank with a thermostatic mixing valve that comes with the Isotherm and then with more cold water at your sink or shower faucet, so the 4 gallons lasts a long time.
I like this heating system very much BUT am concerned that a heat exchanger leak will contaminate shower and worse dish washing water. I realize it's a remote occurrence but internally tube brazing, plate seals and metallurgy failures (pin hole) will cross contaminate.

I don't know enough about the van's "safe & friendly" coolant to be comfortable enough to heat water this way even though I think its a great water heating way to go. Engine coolant has a tough job keeping the cooling system working that is the engine coolant's number one job as it should be.

I know its a remote possibility but am not ready to always wonder if my hot water has been compromised long before it becomes apparent. Life is full of risks. It's all around and starts when you get out of bed - but why add to the list.
 

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Discussion Starter #6
We have the 4 gallon in our promaster connected to the engine cooling system. We've used a similar system in 2 previous RV's since 1993. This is the way most live aboard boaters heat hot water.

Because the water is stored at near engine temperature it's mixed with cooler water from your fresh water tank with a thermostatic mixing valve that comes with the Isotherm and then with more cold water at your sink or shower faucet, so the 4 gallons lasts a long time.

We take our showers at night but there's still hot water for washing and dishes the next day. If we don't drive the next day, idling the engine for 15 or 20 minutes heats it back up.

Previous camper had a 6 gallon version that would last 2 days.

They make a cylindrical unit as well as a rectangular unit. We have the cylindrical unit mounted inside with the coolant hoses running underneath the van until the enter just below the heater. The heater is very well insulated and we insulated the coolant hoses where they enter and we don't notice any heat coming from the installation.

Free hot water while you drive is definitely the ultimate way to go.
That does sound like the ultimate setup and even though it's, let's say $500-600 more than something simple, it's just worth it.

Do you have pics of your install at all? Where did you end up putting the cylindrical unit? I ask because my water system/pump/etc is ALL the way in the back of the van. This is what I was thinking of mounting the unit halfway or something rather than running coolant lines the entire length of the van.
 

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I like this heating system very much BUT am concerned that a heat exchanger leak will contaminate shower and worse dish washing water. .... I don't know enough about the van's "safe & friendly" coolant to be comfortable enough to heat water this way even though I think its a great water heating way to go.
We had the same thoughts but still went with the Isotherm given its marine/RV track record. We'll be installing backflow preventers to at least keep the hot out of the cold side and fresh tank. We can rinse dishes with cold water and not drink in the shower. ;)

We did confirm the factory coolant (FCA spec MS-12106) is definitely the deadly ethylene glycol stuff (95%); it's just its OAT rust inhibitors that are "safe & friendly" (whoopee). We can switch to non-toxic propylene glycol antifreeze (Amsoil) once the engine warranty expires. Sadly, the Amsoil stuff would meet factory specs if it was 10-yr rated, but it's only 5.

EDIT: trhoppe, we are mounting a 6.5-gal unit in the back under the bed. Like tgregg, we'll run insulated coolant lines underneath. Even thinking about running them alongside the grey tank for a little freeze protection.
 

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We had the same thoughts but still went with the Isotherm given its marine/RV track record. We'll be installing backflow preventers to at least keep the hot out of the cold side and fresh tank. We can rinse dishes with cold water and not drink in the shower. ;)
I badly want to use engine coolant to heat our water. You make excellent points on minimizing potential problem (unseen ones at that) using solid plumbing design and practices such cold water dishes rinse can help with. Knowing myself I would take this further if I switch to coolant for heat. I thank you for this.

Your point on a "safer" coolant I had forgotten about is propylene glycol (Amsoil). It's lower lifespan ( 5 vs 10 years ) means nothing as I would gladly replace it more often. Warranty is another issue to be dealt with.

Thank you again Steve.
 

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That does sound like the ultimate setup and even though it's, let's say $500-600 more than something simple, it's just worth it.

Do you have pics of your install at all? Where did you end up putting the cylindrical unit? I ask because my water system/pump/etc is ALL the way in the back of the van. This is what I was thinking of mounting the unit halfway or something rather than running coolant lines the entire length of the van.
I'll look for a picture, but I'm not sure I took any of the hot water heater.

I bought the Isotherm SPA model with the composite outside shell. It's cheaper than the one with the stainless steel outside shell, which is better suited to the marine environment. They both have the same stainless steel internal tank and the same insulation.

I mounted mine just about even with the front edge of the rear wheel wells. I ran 3/8 inch coolant hoses from where the van heater hoses come out of the firewall in the engine compartment under the van just inboard the drivers side edge of van and brought them up through floor just in front of the rear axle.

I installed valves on my coolant hose so I could isolate the system for any reason.

I bought the Tees to connect to the engine heater hoses at NAPA. You want the glass fiber reinforced ones the sell, not the cheap plastic ones they also carry. Don't ask how I know this.

Another member wbullivant installed the same unit and he has a thread with some pictures and more discussion of installation considerations. You should be able to find searching for his threads / posts. He used tees he purchased as an option from RAM, but they weren't available any longer when I tried to purchase them.

Hein, another member here and on the sprinter forum installed one in a sprinter as well.
 

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I like this heating system very much. BUT am concerned that a heat exchanger leak will contaminate shower and worse dish washing water. I realize it's a remote occurrence but internally tube brazing, plate seals and metallurgy failures (pin hole) will cross contaminate.
.
I can't tell you not to be concerned about safety, but I can tell between 2 sailboats and 3 RVs, we've been heating hot water with engine coolant nearly 40 years without contanmination.

The boating industry has been using similar units for much longer and the European RV market has been as least as long. Sometimes they're called calorifiers overseas.

Certainly makes sense to buy a quality unit to ensure your safety.
 

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The boating industry has been using similar units for much longer and the European RV market has been as least as long. Sometimes they're called calorifiers overseas.

Certainly makes sense to buy a quality unit to ensure your safety.
From what I read on the marine forums, people have nothing but trouble with aluminum tank units even with proper maintenance of anodes and such. Stainless steel tanks like Isotemp's are the way to go.
 

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Having been involved with marine systems for half a century I fully agree with post 11 above. Isotemp's are the way to go for quality and safety. I have never heard of a failure of the engine coolant coil within an Isotemp so as to contaminate the domestic hot water.
 

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Im trying to figure out what to use for a hot water heater for my van and could use some help. I want hot water solely for showers and the van will be used in dead of winter so my water system must be freeze-proof. I plan on using a 5 gallon water jug with an immersion pump for my kitchen water. When freezing is possible I just remove the pump from the jug. Im trying to decide if an isotemp spa is a good choice for me and have a few questions for those of you using an isotemp spa heater or familiar with them:

-Do you use it in freezing cold temperatures? I read the instruction/install manual and it says you need to drain it in freezing temps, is this easy to do? Practical to do this daily or after short weekend trips?
-Does the unit need to be always full of water? Will it heat if the isotemp water tank is not full?
-Do the units that include a thermostat mixing valve on the tank need to be used with a another mixing valve at the shower? Can you just use the mixing valve on the tank to adjust water temp?
 

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afox, Isotherms require a pressurized water system to maintain flow in and out. In that sense, they function just like a residential hotwater tank. To a certain extent, you can accommodate outside freezing temps by installing fresh water plumbing and tank(s) inside the van along with supplemental heat. Of course, if the van is going to sit vacant for extended periods in sub-freezing weather, winterizing/draining the plumbing would be necessary. Given your simple kitchen water plans, an Isotherm doesn't really fit the same KISS principle. A portable camp hotwater heater/shower might be a better option for you.
 

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-Do you use it in freezing cold temperatures? I read the instruction/install manual and it says you need to drain it in freezing temps, is this easy to do? Practical to do this daily or after short weekend trips?
I have an Isotemp hot water heater and if I use it in freezing weather my van is heated either because I'm driving or because the furnace is keeping the van above freezing. If not, you have to drain it.

Draining is easy if you installed the drain / overflow hose as indicated in the manual. I don't know how easy it is to protect the rest of your system from freezing.

-Does the unit need to be always full of water? Will it heat if the isotemp water tank is not full?
How are you going to heat the Isotemp?

If you're using the electric element, the tank has to be filled enough to cover the element.

If you're using engine coolant to heat with the heat exchanger, it won't be a problem if it's not full, but it won't heat any water if the heat exchanger isn't submerged in water.

The real problem is I don't think any water will come out of the Isotemp until you push enough water into it to force water out the hot water outlet.

-Do the units that include a thermostat mixing valve on the tank need to be used with a another mixing valve at the shower? Can you just use the mixing valve on the tank to adjust water temp?
I think you need a mixing valve at the shower. If you are heating the unit with engine coolant, the water is hotter than a household hot water heater and the mixing valve will keep it from being scalding hot, but it's still hotter than shower temperature. A single handle shower valve is going to be best for adjusting the temperature.

The advantage of heating the water to near engine temperature is it makes the 4 or 6 gallons of hot water go a long way once you mix it with cold water.
 

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Thanks very much for the isotemp info. I would install the isotemp to heat via coolant and via ac with hookups (not often).

Sounds like the isotemp has to be used with a pressurized water system. I am assuming rv valves with a built in pump switch will work?

Please help me understand how the isotemp works. If cool water enters the tank at the same rate that hot water is used doesn't that result in substantial cooling of the water in the tank? I assume that tall narrow home use hot water heaters rely on stratification of the water to deal with this. Cool water must enter at the bottom of the tank and hot water must be drawn off the top of the tank. With the small isotemp tank and horizontal mounting of the cylinder I would imagine that adding 2 gallons of cold water to a 4 gallon tank would result in cool water. Since the heating is sporadic (when the engine runs) seems it would be better if the tank did not refill at the same rate of discharge. .
 

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Yep, a pump provides the pressure. The key difference between an Isotherm and your home hotwater tank is temperature. Engine coolant will heat it to around 200dF, which means you'll use way less hotwater for a shower, especially if you take a ship shower to conserve your fresh water supply. That also means less "cold" water feeding into the tank. The AC thermostat is preset to 167dF, but you can take a shower before that.
 

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Now I just had a harebrained idea. Is there any place under the hood one could place a ~one-two-gallon water container near the engine so that it would be heated without plumbing connections? I assume this would be a easily removed metal container. Even if it only got to 100°, that's a quick shower or two.
 

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I wasnt even going to bother with a shower originally. But always having to shower at a gym sounds like even more of a bother.

I have looked at electric units just like the original post. Bosch makes one in a few sizes with a 1400w element that heats the water in 30 minutes or less.

The only unit ive seen that has a 750w element is the Isotherm. That seems to be the holy grail if hooked up to the engine. But Id really prefer not to mess with the cab. Can the isotherm be used in electric mode only?

Would a 2000w inverter with a 220AH battery bank be able to handle a 1400w water heater? Would it be wise to only heat the water with the engine running?
 

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The inverter can handle it but the load on the batteries will be nearly 200 amps. That will take a really big battery set or Lithium to support. The power used will also be 60 amp-hours for a half hour of heating. That too is a lot from normal sized battery sets. I’d heat off the engine as it’s what that device is made for and it is not rocket science to connect! Let the electric be a back up solution only and you can get by with real savings on the batteries and the solar to charge them, that will more than pay for the isotherm and connecting it, and still give you a proven system we know works.
 
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