Hot Water Engine Heat Exchanger

No valves on the coolant lines to/from water heater.

You could add one on coolant line to water heater and shut the flow off.

Just valve it in when you want to take advantage of that free heat

AND remember that both lines would still have coolant in them IF you did any work on water heater that required disconnecting them at the heat exchanger tube.

No idea what engine or even the year of your RV since it's not in your sig or profile so just throwing this out there...with diesel pushers, they always put gate valves on the engine to shut off the coolant that goes to the dash heater. Develop a leak in that heater system and it's a simple matter of shutting off two gate valves, top and bottom of the engine. That way you're not dead on the road. Makes sense, doesn't it? It's happened to me, puked antifreeze for 3 miles until I could pull off the freeway and shut them off.

OK, so now with your system, it seems logical to me that they'd put a couple gate valves on that system too, near the engine. So maybe climb under there and follow the hoses back to the engine and check that.

Sorry, finally took the time to update my profile to reflect equipment. I posted earlier rather quickly and didn't think to put down rig type, but made a bad assumption that posting under Class C said enough. Thanks for the responses so far.

I have to run up to the truck service center where I get the chassis taken care of and I'll have them look at it as well to see if a bypass could be added if there isn't one. I looked around where it appeared the lines are being routed and couldn't find any type of valves associated.

Coolant lines to water heater heat exchange tubes do not have shutoff valves.
You always have to pinch coolant lines closed when disconnecting from the water heater.

Logic and RVs do not coincide.

Winnebago has been using that "Motor-Aid" water heater system for quite a while. Haven't seen any with valves but would be a good idea in your case.

Don’t forget to add a bypass not just shut off valves. If you merely deadhead the supply line you can create problems. The coolant system is designed to have a certain amount of circulation even when the heaters are in the ‘cold’ position. Bypass ALL of the remote heat, especially the dash heater.

You need 2 T-fittings, 2 ball valves and a bit of hose. Put a T fitting in the supply line with a ball valve just downstream of the T fitting. Then connect the 2 T fittings with some hose with a ball valve in the middle.

Summer time the ball valve in the bypass line is opened and the one in the supply line is closed. In cool weather the positions are reversed.

A bypass setup will also keep the dash A/C working FAR better.

Thanks! I think that would be doable even for me. Only other option is to try and insulate the compartment. May end up doing both.

More than likely your motor aid (and also your coach heater driven by the engine) are teed off the main heater core circuit for the cab. If so, you don't need a bypass circuit for the 2 lines going back to the house.

Steve

Hey
My old hot water heater is AC and heat exchanger. I run AC when it's available, which makes it easier for the engine to maintain temp rather than heating cold water.
Jon

JohnyWalter wrote:
Hey
My old hot water heater is AC and heat exchanger. I run AC when it's available, which makes it easier for the engine to maintain temp rather than heating cold water.
Jon

RV Water heater with 'motoraid' heats the water WHENEVER engine is running........coolant flows thru heat exchanger when engine is ON