New to me (Gooseberry) water heater.......

[boywonder]

...I'm still confused about flat plate style heaters......

If the engine coolant is at say 240 deg F (pretty typical) what's to keep the hot potable water on the other side of the exchanger from getting this hot? Some type of thermostatic valve?.....I cannot imagine that to be very safe......gotta be some other way......

[haywoodphotomaccom]

Info from my dad a few minutes ago...

Parts purchased from
Rixen Enterprises
Sandy Oregon
Rixens.com
1-800-925-6260
Owner is Jim Rixen


Rixens’ specializes in RV heating utilizing Espar Hydronic units, but also sells individual components.

I have a Winnebago View RV on a 2006 Sprinter chassis. It is seriously modified with the ultimate goal of completely eliminating propane. I have 400Ah of LiFePO4 batteries, 400w solar, 240 amp alternator with a Sterling Alternator to Battery charge controller and a Magnum 2000w sine wave inverter/100A charger, so power is not a problem.

My first project was to eliminate the stock water heater by using a few of Rixen’s components to heat the water using the 1500w, 120vac heating element, and later plumb in the hot engine/ Espar coolant .

Main component is a tank that Rixen calls the Comfort Hot. It is a 2 gallon aluminum tank with a standard 7# radiator cap on the top. On the end is a gray box that houses a 1500w 120vac heating element, thermal protection and wiring. On the bottom are 3 1/2” threaded pipe openings, (coolant input, output and drain).

Other 2 components are a small heat exchanger and a small 12vdc circulation pump that circulates the hot coolant from the Comfort Hot through one side of the heat exchanger.

On the output side of the heat exchanger I simply plumbed my cold water into one side and and used a Honeywell AM1 thermostatic valve on the output side to set water temperature to 105 degrees, this removes the need to fiddle with the hot/cold to get uniform water temperature for a shower!.

This closed system will heat the coolant to 170 degrees in the Comfort Hot tank in about 15 minutes. The Comfort Hot heating element will cycle on/off to keep the tank temperature between 150 and 170. With the small circulation pump running I can get approximately 3 gallons of continuous hot water at 105 degrees for a shower before the coolant temperature drops. Of course, using hot water at the sink in the usual intermittent way while washing dishes, etc, the system will keep up with your use.

When fully plumbed into the Espar or just engine hot water lines the hot water supply will be virtually continuous as long as you have engine heat. When using engine heat you will have hot water as fast as you engine heats up, probably faster than the 1500w heating element, which is actually meant to be a backup system or used when shore power is available.

These 3 components, Comfort Hot, heat exchanger, circulation pump and Temperature control valve cost a bit over $1000 total, and I also needed a few fittings, 3/4” heater hose and clamps.

Next step - Plumb into the engine coolant lines. My Sprinter already has a stock Espar diesel engine preheating unit. It pre-heats the coolant by firing up a small diesel furnace in the engine compartment and circulating the hot coolant through the engine block. As many others have done, I plan on tapping into that hot coolant hose and have it heat my hot water with a heat exchanger and cabin with a small radiator and fan. Modification to the Espar unit and engine plumbing are required to use it as a stand alone heat system independent of the engine . These components are all available on the Rixen website.

John Haywood

[daveb]

Originally Posted by boywonder

...I'm still confused about flat plate style heaters......

If the engine coolant is at say 240 deg F (pretty typical) what's to keep the hot potable water on the other side of the exchanger from getting this hot? Some type of thermostatic valve?.....I cannot imagine that to be very safe......gotta be some other way......

Well it don't come out as steam but the first time I used mine w/o the tempering valve, I almost burned off my scalp Mine was one of the first installs of the Espar flat plate's SMB did. But I actually used it for several years before I had the valve installed. I don't know if I yelled more from the shots of hot water or the burst of cold water after adjusting the hot/cold controls.

[Gooseberry]

Ok I'm used to the insta hots we install at bathrooms and they do take 20 amps to work so I could be wrong and yes I have been wrong on many times.

[daveb]

I'd guess your still correct about running a 1500 watt heater element. That's big amps at 12v...about twice as much as my microwave. But I'm thinking that if the system has a tank, the flat plate will heat the water via the engine coolant. The AC element wouldn't have to do much to keep the water warm for a short period of time if it cycles and the tank is well insulated. It would only pull a lot if starting with a dead cold engine and at that I'd think you would be on shore power. For a thousand bucks I doubt there is a hydronic unit in the mix, just a flat plate.
On my build I can take a few showers without having to run the espar provided the engine had been running at full temps prior to using the shower.



In a sense, the engine block and radiator are the water tank. But the pump that circulates the coolant pulls about 7 (DC)amps plus the fresh water pump pull a few amps as well. At least it doesn't take too long to shower. When I run the Espar by itself I don't have to run the circulation pump cause the Espar has a small pump inside the unit itself. When that's running I'm only pulling a couple of amps.

[i3enhamin]

I am trying to ascertain if this small 10-plate heat exchanger can supply shower heat with the stock Espar D5 2 gpm pump or is this to be used w/ a larger, more capable pump?