Thermostatic Mixing Valve

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ajohansson

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whats the scoop on a thermostatic mixing valve at the hotwater outlet? set it at 120 and forget it?

Reading stuff about allowing hotwater in tank to be hot enough to kill bacteria without the risk of scaulding at the point of use. seems most washing machine detergents and dishwashers are ok at 120 degrees.

just would like opinions on this forum as I seem to get the best knowledge on here. If was building a new house seems like a straight run to the washing machine and dishwasher would be best if you wanted full hot hot water and plumb the rest with a TMV but this an existing home,

Any help would be appreciated.

AJ
 

Terry

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For clothes I wash with cold and it's fine. My dishwasher has a built in hi-temp wash. A must for anybody. Without the hi-temp option, most loads wind up with cold or luke warm water. You would have to run the kitchen faucet to drain the hot line and then start the dishwasher right away. Almost nobody does that.
 

Jadnashua

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Not sure exactly what you are asking...except for possible creep as things age, yes, you set the mixing valve for your desired output temperature and it just does its thing, mixing in enough cold water to lower it, until, once the incoming water doesn't need it, running the hot straight through. It isn't magic, and won't 'make' hot water, but it will keep a fairly constant output temp.
 

Reach4

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If was building a new house seems like a straight run to the washing machine and dishwasher would be best if you wanted full hot hot water and plumb the rest with a TMV
Much better IMO. Best, I think, would be to have the mixing valve(s), for those things that need the mixing valve, to be closer to the point of use.
 
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Jadnashua

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Thermostatic mixing valves are moderately expensive and do require access since they do fail eventually. If full temp hot water is important, much less expensive to run those lines before the valve. Generally, in a home, it's dangerous to have the hot water higher than 120-degrees F, but if you want higher in the WH for various reasons, it's not safe, and some places would not pass code inspection. Where I live, all of the hot water is required to come after the mixer (there may be an exception for the DW). As Terry mentions, though, if you want good performance from your DW, buy one with the ability to heat it up internally. Between cycles, and the fact most DW don't use a huge amount of water, that extra heat may still not provide the best performance unless it is heated in the thing. FWIW, my WM can heat the water, if I ask it to, so hot is not required.
 

ajohansson

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thanks everyone.

Ok I just put in a new DW and it does have a "hi-temp" wash and I will start using it. I do run the hotwater at kitchen sink so its hot when I start but
I do plan on putting in a Redytemp circulator so I can stop waisting the cold water in the hot water line. Nice thing is the end of the line fixture in the house is the Kitchen so I have power under the sink. I plan to use the Leviton LevNet Rf self powered switches and one of their low voltage relays to trigger the system to come on. I can put Levnet RF switches in all the bathrooms and laundry. CLick the switch wait 30 seconds and you got hot water.

Since the house is 15 years old not new construction I will install a TMV at the hotwater output so I can have 120 and keep the WH at say 140 or so to keep it more sanitary and to reduce the risk of bacteria infection.

Thanks all for your help.

AJ
 

ajohansson

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Also can I get an accurate temperature from the water out of the TPR discharge line?

I have two water heaters in series so I need to measure the temp of each. The last one in series I can test at a sink easily but I need to test the first one someway and was thinking releasing water out of the TPR into a cup and then measuring the temp of that water. Would that work?
 

Jadnashua

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It should as that outlet comes off the top of the tank, or near it. But, once the tank has finished heating the water, before it has a chance to cool off, just draining some out the bottom drain valve since you'll not need much, should provide the same results. T&P valves are best left alone, but a test like that shouldn't hurt anything. They do recommend you test it once a year to verify it is not stuck closed, but they don't always reseal well once they get older.
 
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