Overly Hot Water from Heater

woodster · Jul 28, 2011

if i am not mistaken there is a mixing valve that will keep you from getting scalded...i think its called a tempering valve???...what it does is mixes cold water with the out comming hot water and can be set to a safe temp for your use as hot water.....some one chime in here and correct me if i am wrong....

regards

woody

jsalley · Jul 28, 2011

Agree, my hot water is also scalding-temp when the engine has heated it, although the pressure relief valve doesn't open. As Woody described, many home and marine water heaters incorporate a mixing valve to prevent overheating the water, but mine doesn't have one. Not sure if any aftermarket solutions are available, but if your boat has been modified with a heater bypass to help with winterization, you might be able to use the crossover valve to mix some cold water with the hot.

Siamese · Jul 28, 2011

According to the gauge, my engine operates at about 150 degrees. Using 150 degree coolant to heat water results in some very hot water. I haven't measured the temperature of the water in my water heater, but I'm guessing it has to be 150 degrees or less.

I know for sure that the water coming from the faucet is dangerously hot, and wouldn't be tolerated in a home. We're just darned careful to make sure we use the mixing valve mounted on the sink.

I'm at a loss to see how to reduce the temperature of the water in the tank. When there's no water running, the water remains in the water heater, and is heated by the 150 degree water flowing through it. I see no way to lower the temperature of the water from the engine. T

I suppose it wouldn't be all that difficult to route the hose from the water heater, and a cold water hose to an old fashioned two handled mixing valve (like from a laundry tub), and preset the handles to a safe temperature. The hot water for the shower, galley, and head would all run off that mixing valve. There's plenty of room in the area where the water heater sits to fit a valve. If I had kids on board I'd probably try it (so they wouldn't hear the adult language when I scald myself).

Stu Jackson · Jul 28, 2011

Do a search on "tempering valve" by Maine Sail. He's discussed this in great detail.

If your prv is popping, it's time to get a new one. Once they pop they are notorious for staying open. ACE hardware.

While the dhw is too hot for legal home use, Maine Sail's been working with ABYC to do something about it, 'cuz it's dangerous, 'specially for little kids.

But if you're running with a 180F thermostat, it ain't gonna get any hotter than that. You could change down to a 160F thermostat, but a tempering valve is a much better solution.

Siamese · Jul 28, 2011

Nice post from Stu Jackson....here's the quote from "Maine Sail" that he referenced:

"Tell me about it. I am in the loop on the issue discussing engine heated water heaters with the ABYC right now. Please send John Adey, he's the ABYC technical director, jadey@abycinc.org any cases or reports of scalding or burns that you have or know about so we can build a good evidence case for changing the requirement for regulating the temperature on engine heated water heaters...

I have been fighting for well over a year to get this into PTC committee and get the standard to require tempering valves on heaters that are directly connected to an engine added. Iso-Temp for example ships tempering valves as standard equipment as should EVERY manufacturer. It should be illegal, not just an ABYC suggested requirement, to sell ANY heater than can be heated off engine coolant that could get to 130 degrees or more. This would NEVER be allowed in residential and commercial plumbing codes and is not.

The U.S. Consumer Product Safety Commission (CPSC) suggests users set their water heaters to 120 degrees F or less.
Keep in mind that adults can sustain third-degree burns if exposed to just 150 degree water for only 2 seconds! At 160 degrees you are down to less than half a second to sustain a second or third degree burn! Even a six-second exposure to just 140 degree water can scald or burn.

Please support this important SAFETY change to the ABYC standards by emailing John Adey your concerns and asking for temperature REGULATED hot water heaters when intended to be heated off engines. The ABYC is evidence based and most folks don't have a clue as to why they got burned or scalded and just accept it rather than report it. My nephew was badly scalded on our 2005 Catalina 310 and I now take this quite seriously..."

I sure like the looks of that tempering valve. Think I'll take a look at what it'll take to add one.

Maine Sail · Jul 28, 2011

David21717 said:
My 2008 Catalina 309 seems to have a water heater problem. When the engine has been running a while, my hot water from the water heater becomes overly hot--in fact, scalding. (I do not turn on the "water heater" fuse switch in the electrical panel, so the heat is from the engine heat exchanger, so I believe). To keep the water heater relief valve from sending hot water into the bilge area, I have to drain the water heater into the galley sink by running the hot water through the faucet for several minutes.

Has anybody else had this problem? Do you have suggestions? I have flushed my engine coolant system--this did not change the problem. My engine is not overheating according to my instrument gage on the binnacle.

David

This is not a "problem" it is just how your boat was built. It is simple cost cutting allowed by the lack of any standards to regulate this...

PLEASE email your concerns to the ABYC. You can email the technical director at: jadey@abycinc.org

What you need is a thermostatic tempering valve on your hot water heater and you can easily install one. Your situation is not uncommon and the ABYC is looking into this but they do need to hear from boaters who have this dangerous problem in order to get any safety issues like this through the PTC.

Stu Jackson · Jul 28, 2011

PLEASE email your concerns to the ABYC. You can email the technical director at:...

Done. Thanks for spreading the word.