Hot Water Temp Control

I'm in the process of doing a total re-plumb of the boat, including relocating the hot water heater. As I'm setting up the hot water heater, I would like to put some type of control into the system so that when the water is heated via the engine coolant, tap hot water does not come out at 190 degrees (ouch! - major scalding possibility) like it did before. I had just planned on putting a thermostatic control valve (which mixes cold water with hot to get a set temperature) at the heater outlet, but as I research plumbing systems on boats, I see no reference to using these valves. I have seen recommendations to install a gate valve shunting the input/output hoses from the engine to control flow volume through the heater, but that only makes it longer for the water to reach 190 degrees and there is still no way to control outlet temperature. Any reason I shouldn't put in a thermostatic control valve and skip the gate valve?

BTW, I am planning on installing ball valves on the engine take-off/return lines so that whole loop can be shut off.

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Thanks,

dvd

Maybe one of these could be installed on your heater.

http://isotherm-parts.com/thermostatic-mixing-valve-p-1462.html?zenid=23a6bc5159bcfe4bf43865c06e61ca9d

That's the current plan -- I just haven't seen these products recommended for marine installation anywhere.

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dvd

dvd wrote:


That's the current plan -- I just haven't seen these products recommended for marine installation anywhere.

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dvd

Click to expand...

Marine plumbing is not different from house plumbing for this type of application. A buddy of mine installed a thermostatic valve for his deck shower and it works fine.

I remember seeing at least one marine hot water tank that comes from the factory with a mixing valve, I try to get a link when I get time.* If you install one, make sure you exercise it a couple times a year or it will freeze up and not function.

For our boat:
A temperature mixing valve (Honeywell 2006) is plumbed between the HW tank and the HW distribution system.* This valve adjusts the temperature of HW from the HW tank (Set on 2 for 130 degree water). **Maintenance every 6 months:**(Assume HW tank heated to max heat setting, set mixing valve at 4 and run water for 3 minutes, then set valve at 0 and run water for 3 minutes, rest water pump for 3 minutes, repeat, then set valve at normal 2)


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Anti-scaled shower or faucet sets are at your local box store.

They are required for many handicapped style homes.

Kuma hot water heaters sell as an option, a temperature control valve that regulates the engine coolant through the hot water heater at 140 degrees.

Larry M wrote:
Kuma hot water heaters

Click to expand...

* *Why heat the hot water.

SD

Because of the cold*dock or RO*water in the PNW I*like the 150 to 160 degree water from our tank, it makes the hot water*last longer when showering, and washing clothes and dishes. If I were in Fl where the dock water is 30 or so degrees above the PNW I'd maybe rethink it. I have never found a temp mixing valve that works very well as compared to my ability to increase or decrease cold water tap flow.

Now if I had a big tub and were bathing babies or drunks who I did not want*scalding themselves, I'd stay ashore

In theory, the mixing valve is doing the same thing for you -- it doesn't change the temp of the hot water source, it just mixes some cold water with the hot water outflow based on the differential expansion of metals, therefore it is pressure-insensitive and does not depend on the temperature of the water source. My water heater is only set to 125 degrees when it is on 120V AC and, as mentioned above, it gets up to 180-190 degrees while underway and heated by the engine. I just don't want ANYONE - me, my wife, my kids or a guest - to open a shower tap and get 180 degree water coming out. That could ruin your whole day.

dvd


-- Edited by dvd on Monday 20th of February 2012 04:49:08 PM

For the anchor out set , the 190deg water stays useable as hot water longer than 140 water.

Also many limiting devices to control the water temp in the tank do not by pass the tank input , the simply throttle it.

Bad news if you plumb a heater anywhere in the same circuit.

Little water flow=little heat.

We just installed an isotherm mixing valve on our Prairie 29. It's great. We can adhjust the amount of cold water mixing with the very hot water in the heater and thus use very little hot volume, and save ourselves from scalding. We highly recommend this.

Greetings,
On other VERY good reason to temper your hot water is small children. Your kids may know the water is scalding and adjust accordingly but guest children can do themselves a very serious injury from hot water. Just sayin'

Or you could just keep the little rodents off the boat.