Empty water heater...

NYSail

.
Jan 6, 2006
3,048
Beneteau 423 Mt. Sinai, NY
With a hot water heater that has a/c as well as an engine fed heat exchanger, I know not to run a/c element when empty but what about when just engine is running. I have never given this much thought but it seems I would have no issues.

Opinions please....

Thanks
Greg
 
Feb 10, 2004
3,919
Hunter 40.5 Warwick, RI
I opinion (and worth every penny you are paying for it) is that it is a non-issue. I see no difference between hot engine water running through the heating coil in the heater vs hot water running through baseboard heaters in your home. Unlike an electric element, there is nothing to burn out from over-heating.
I think you are good to go.
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
This is not a big issue. The heat exchanger in the tank simply heats air. A couple of years ago my tank started leaking, so I took it out of the water system but left the heat exchanger connected. Never overheated.

Some setups have a valve on the coolant supply side. That could get shut to keep the engine water from circulating. This will be OK so long as the coolant can still get to the expansion tank. The valve is on the right side in this photo (obviously not yet connected to the engine cooling system).

Edit found a better photo.

IMG_1436.jpg
 
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Gunni

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Mar 16, 2010
5,937
Beneteau 411 Oceanis Annapolis
Had the same concern because I winterize my potable water and drain the H/W heater prior to motoring to my winter haul. The coolant circuit is maybe 180d, well below the T/P release valve, but why take a chance on pressurizing your tank. I leave my H/W drain valve open, so any heated vapor will discharge. But you could do the same by leaving your hot faucet tap open.
 
Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
If the water tank has been winterized by bypassing the HW tank and connecting the cold supply to hot water plumbing it won't be necessary to leave a valve open. The outlet will let air enter and leave preventing any pressure build up.