Would like info on using tempering valves

I would like to know if anyone uses tempering valves for domestic hot water. With an instant hot water coil in a coal boiler I run into situations where boiler temps can range between 140 and 180 in the span of under an hour. It is just the nature of the beast because with coal stokers off is not really off, it is kind of “high/low” versus “on/off” for oil and gas. To kind of even the feel of the hot water at all faucets I thought about using a tempering valve set to about 130 degrees. It may save a pound or two of coal along the way but my main object is to even out the feel of the hot water.

I have seen half and three quarter inch tempering valves from Watts, Taco and others for under $40 to more than $300
The questions are; do they work very well? How reliable is the mechanism? Most state that the thermostat can be replaced but how often do they usually need to be replaced? If I go this route do you think I’ll be satisfied or will I feel I wasted my time and money?

Any experiences or information would be appreciated. Thanks.

I have used tempering valves on my current coal setup and on the old gas boiler both with Hot water coil.

They work very well. I have had fairly good luck with the Honeywell / Sparkomatic type valve. I believe they are required by code now for antiscald protection. The first one lasted about 10 years or so, but my water is somewhat corrosive.

I keep the coal boiler set to about 150 and the tap water never gets too hot to touch.

They are not cheap, typically around $100 or so.

Here is a link to an online vendor and all the valves they carry.

http://www.houseneeds.com/shop/HeatingP ... vesbuy.asp

I had a Watts 70A-F on my previous oil boiler domestic coil. It never really worked well. I replaced it with a manual valve to meter the mix of cold water and boiler domestic hot water. Valve setting was determined experimentally. A less than satisfactory fix but no worse than the tempering valve. Unlikely my fix would work on a coal boiler. When I went to a indirect hot water heater because I needed a stainless steel tank the temperature variation was also solved.

Ive used the Watts valves before also. They are currently about $40 or so, you get what you pay for.

The prices on the referenced link are fair prices. Here's what my wholesaler lists for the same or similar items.

Watts:

70A 1/2" Solder $38.70
70AT 1/2" FPT $77.24
70A 3/4" Solder $46.75
70AT 3/4" FPT $95.00

70ARK Replacement Thermostat all models $22.22

SPARCOMIX:

AM-100-US-1 1/2" Sweat Union 100-145°F $64.02
AM101-US-1 3/4" Sweat Union 100-145°F $77.74
AM100-1 1/2" NPT 100-145°F $62.92
AM101-1 3/4" NPT 100-145°F $66.96
AM102-1 1" NPT 100-145°F $109.48
AM100C-1 1/2" NPT 80-120°F $75.30
AM101C-1 3/4" NPT 80-120°F $75.62
AM101R-US-1 3/4" Sweat Union 80-180°F $71.54
AM102R-US-1 1" Sweat Union 80-180°F $83.51
AMX101-US-1 3/4" Sweat Union 90-130°F $82.98
AMX102-US-1 1" Sweat Union 90-130°F $94.05

These valves don't survive very long with hard water, so be advised. In soft water they will perform well.

Gary, the most important reason for using a mixing or tempering valve is to prevent scalding you or your family. 150* can cause 1st degree burns, 180* can cause 2nd degree burns.

I have a mixing valve on the output of my domestic water heater, when the coal boiler is in operation, the water in the tank is about 150*, so the output is mixed with some cold water to temper it. So far it is working pretty well, I do soften this water, so I hope it will last a long time.

For safety-sake, I'd install one, take a look on Ebay, you may find a good deal, I did.

Greg L.

Thanks for the replies. I think I will give one a try. Thanks for bringing up the soft water business too. I have been installing a water softener for two years and all that good intention still did not get it done, I guess I had better move that to my short list.

When they fail do you lose all water down line or just the temperature control? Would it be a good idea to plumb it in such a way that it can be bypassed and isolated in the event of failure?

Follow the installation instructions for piping carefully. I didn't the first time I installed it and I had direct conducted heat from the boiler coil to the thermostatic element. Obviously it always thought the water was too hot. You want the piping such that there is no heat conducted to element when the water is not flowing. Should be easier to do today with CPVC pipe which will conduct heat much less that the copper pipe I used.

I'd add valves so I could easily take it apart and get to the thermostatic element. As I recall I had to clean mine occasionally to keep it operational.

gaw wrote:When they fail do you lose all water down line or just the temperature control? Would it be a good idea to plumb it in such a way that it can be bypassed and isolated in the event of failure?

It usually starts by having trouble maintaining a fixed temperature and then they stop adjusting. The water will continue to flow. It is salts that build up and stick the mechanism. I would put a unions on to make servicing it easier. Shutoff valves are nice too.