WATER HEATER THERMOSTAT

[Nancy]

That's some good info that some units have the technology to regulate the temperature when running off of the engine coolant loop as a heat exchanger. That would be nice to temper things. What manufacturer did you see that has this?

Assuming that I'm understanding the article correctly, I read about the technology here: http://stevedmarineconsulting.com/water-heater-primer/. Coincidentally, the device is offered as an option on Kuuma water heaters.

Not sure if your loop has ball or butterfly valves, but I'm sure that if you closed these down equally the water would heat up more gradually and not transfer heat as quickly with the limitation of the closed valves letting less coolant pass. If your engine run time is short it may accomplish a cooler temp in the tank, but if you run for awhile the exchange of temp will eventually catch up to your engine coolant temp.

After thinking about it for a while, I came to the same conclusion.

Even though the engine-heated hot water is extremely hot, we can manage to mix with cold at the faucet to cool it off. We were just thinking it would be less strain on the T&P valve if the water didn't get so hot to begin with. If you've read my recent thread, you know that we weren't having any luck removing the failed T&P valve from our HW tank. We had resigned ourselves to replacing the hot water heater, but access is miserable - almost everything on the shelf needs to get removed or disassembled. Our mechanic looked at all that and figured he had nothing to lose. He moved the batteries a little, which allowed him to get a 4' pipe wrench on the valve. And voila! It came off! And nothing broke! New valve is in place, but it's dripping when the engine gets up to temp. I guess it's defective.

[catalina_mike]

You can add a thermostatic mixing valve to the system but you are introducing more failure points. Your PTV should be of a high enough range not to start leaking while the engine is doing its thing.

http://www.watts.com/pages/learnAbout/t ... asp?catId=

[Nancy]

Thanks, Mike!

[Pitou]

Our mechanic looked at all that and figured he had nothing to lose. He moved the batteries a little, which allowed him to get a 4' pipe wrench on the valve. And voila! It came off! And nothing broke! New valve is in place, but it's dripping when the engine gets up to temp. I guess it's defective.

Yikes .. a 4 ft. pipe wrench! That'll give some leverage.

Glad that you got it off, but it's got to be frustrating to have that drip. Is it dripping out of the relief or from the threads? From all of the reading provided by you and Mike the relief valve shouldn't engage until 210 degrees. If your dripping from the relief valve, I'm sure it is defective. If it's the threads a little more rector seal.

Thanks for all the links and especially the article on Water Heater Primer. That was a great article on understanding how to add mixing valves or a control valve to regulate the heat exchanger loop.

[catalina_mike]

It is a closed system and as it warms up with no room for expanshion the pressure goes up. Could be working fine.. To test just crack a HW facuet after up to temp to relieve the pressure and see if it stops. Then get a higher pressure rated one.

[Nancy]

Yikes .. a 4 ft. pipe wrench! That'll give some leverage.

My husband tried an 18" pipe wrench with a 2' piece of pipe on it - no go!

Glad that you got it off, but it's got to be frustrating to have that drip. Is it dripping out of the relief or from the threads? From all of the reading provided by you and Mike the relief valve shouldn't engage until 210 degrees. If your dripping from the relief valve, I'm sure it is defective. If it's the threads a little more rector seal.

It's dripping from the valve, not the threads. I've emailed our mechanic. I'm sure he'll take care of it.

[Nancy]

It is a closed system and as it warms up with no room for expanshion the pressure goes up. Could be working fine.. To test just crack a HW facuet after up to temp to relieve the pressure and see if it stops. Then get a higher pressure rated one.

Great suggestion. Thanks, Mike!