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Tempering/Mixing valve for DHW

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by arngnick, Apr 15, 2013.

  1. arngnick

    arngnick Member

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    I thought I could control my domestic hot water temperature without overheating my hot water tank but it seems as though I cannot...

    I have decided to add a tempering valve to regulate the output temperature to about 130* easy right!? I got the valve in the mail today (Watts 70A) and in the directions it says an incoming temperature differential will cause problems. Since my tank fluctuates temperatures depending on how hot the water being used to heat the DHW is from my storage and how long it has been since the tank has been heated the water in the DHW tank can fluctuate between 120* and 160*. The whole purpose of the tempering valve is to regulate my water to a consistent temperature. Will this valve work or do I need something different?

    Any recommendations for valves?

    (I need tp add a tempering valve for my radiant zone too so maybe this valve will work there.)

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  2. BadgerBoilerMN

    BadgerBoilerMN New Member

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  3. arngnick

    arngnick Member

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    The cold water will be coming from the well but the hot water coming from the tank will vary.
  4. BoilerMan

    BoilerMan Minister of Fire

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    I had the Watts 70A on my Toyotomi (On at 130 off at 180) and it did ok at temperature regulation............... I use the Honeywell AM series and the water is PERFECT all the time as long as the inlet (H port) is above the setpoint. Proper heat trapping the valve will make it last much longer. I pipe the cold (C) inlet into the same inlet as the water heater for a balanced pressure from hot to cold inlet ports.

    TS
  5. tom in maine

    tom in maine Minister of Fire

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    Use something that is spec'd as an antiscald valve. Honeywell AM series or similar.
    The standard cheap Watts or Taco mixing valves are not safe for the temps that wood devices can generate.

    Many years ago, we found that valves like the Watts 70a will work sometimes but can offer a spike of hot water before they start to regulate. Their performance can be erratic. Antiscald is the important nomenclature when looking for them.
    Many companies now make them. We have used Honeywell/sparco for many years. Zurn, Watts, Caleffi and many other companies now also make antiscald valves.
    It is important to use the right type of valve.
    ewdudley likes this.
  6. arngnick

    arngnick Member

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    This is good info I will have to do some research and see what kind of deals I can find. I will use the Watts for my heat zone tempering I am not to worried about that getting a little hot now and then.

    On a side note do I temper the heating zone with return water?
  7. ewdudley

    ewdudley Minister of Fire

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    You've got it, and of course the circulator needs to pull the mixed water out of the mixed port.
  8. nate379

    nate379 Guest

    I have a Honeywell valve, I'd let it go for pretty cheap if you are interested? 3 way, hot, cold and mix. 1.25" lines, was used on my boiler for a few years, I've replaced it with an electric Taco outdoor reset one. Worked just fine taking 200* water and mixing it to 130* for the floor heat.

    I dunno your setup, but mine I have a pump that comes on when the tank temp is below 120* and it shuts off at 135*. Tank stays at that temp.
  9. maple1

    maple1 Minister of Fire

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    I think with the Watts, if you've got ups & downs on the hot temps in, you'll get corresponding ups & downs on the mixed temps out. I'm using one now, but my DHW temps don't get up there real high - so it serves to 'take the edge off' at the tap when it does. So mine works OK, but it's one of my system components that I have in my head for a possible upgrade - say if I get to getting my DHW temps up once it's all up to speed (I still have some control type things to do to get it to work 'right' when there are no space heating draws and just using storage).

    My old unit with tankless coil also had a Watts installed when the system was originally put in, but it stopped working all together (I think it was mixing too cold all the time). So I took it out and used the gate valves & T that were there to either choke the cold mix into the T off in non-heating season (so I could turn my boiler temp down), or let it in during heating season. Crude but again took the edge of the hot at the tap.
  10. arngnick

    arngnick Member

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    Thanks for the offer I sent you a message.
  11. maple1

    maple1 Minister of Fire

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    More input on the 'cheap' way out (Watts).

    I've had my electric tank shut off for a little while, so it wouldn't cut in during those momentary low temps the bottom element might see between fires. My Watts will keep mixing during those times - so while you might have water coming out the top of the hot water tank that should be more than hot enough, it will mix down enough so that by the time it gets to the tap, it's not hot enough. So it really gives some wild swings in tap temperature, with swings in tank temps. I assume the Honeywell will give more even temps? Does it get to a point where it stops mixing all together if the hot in gets cool enough (say 120) ?
  12. BoilerMan

    BoilerMan Minister of Fire

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    Short answer: Yes

    Anything rated to ASSE 1017 is for DHW distribution and will give you an even water temp. I let my indirect get up to 160 usually and mix to 120. The temp in very consistent until the tank gets below 120 then the cold port does not flow and it's as if the mixing velve is not there and water comes straight from the tank to the faucet. The ASSE 1017 standard is not, however and anti-scald certification so it's onlt intended for installation at the water heater which is what you want. I actually have a Watts not a Honeywell as I thought. It's the Watts 1170 in 1/2" whatever you use make sure it's properly heat trapped so it'll last and not waste heat by keeping more pipe hot than necessary. Notice the hot (lest side) pipe is insulated (cheapo foam) which comes down into the valve from the tho of the indirect. Hot water won't convect down to the valve so it's only hot when there is a draw of hot water. BTW the blue tank is not my indirect, it's the well tank so to allivate confusion. The indirect is 6' tall and just to the left out of the pic with the two 1" copper lines feeding the coil from the Oil Miser.

    TS

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