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Indirect Heater and Mixing Valve

Depending on the logistics, an express DWH line at high temperature to laundry and dishwasher is a nice touch. I first saw it on a house using an immersion coil, oil fired HW boiler kept at 180F (in the 'good old days').

But today with consciousness at an all time high regarding Legionella, energy use, scalding hazards, I think a savvy homeowner would appreciate the suggestion at least.

Comments

  • pennron
    pennron Member Posts: 48
    Indirect Water Heater and Mixing Valve

    I have an 40 gallon indirect water heater working off a Burnham Revolution boiler utilizing a Taco 007, priority. I have the heater's aquastat set to 115 degrees which we find works well for my household. ie: we can't scald ourselves, dishes and clothes are getting cleaned etc. I set it at 115 for the reasons listed and to also save on fuel.

    The one "small" problem (more of a nuisance) is when we fill our Jucuzzi she'll run out of hot water before the water level gets above the jets. We have to wait 10 minutes and then we can get the level over the jets.

    I was told by a tech that some agency (i forget who) recommends that the minimum setting should be 120 and they have now changed that to be 130 degrees so that there is no chance of germs, legionaires disease and other problems like that arising.

    His advice was to install a mixing valve and expansion tank on the water heater and then set it to 160 degrees. He said then there is no germ problem and the whirlpool should fill in one shot. He also said even though you are keeping the heater at 160 I'll most likely use the same amt. of gas or possibly very very little more. I think my heater drops 1/2 degree /hr according to the Alliance specs.

    More info: My HVAC co. came up with a 48,000 heat loss for my home. I used HVAC-CALC and measured every nook and cranny, took 5 hrs to do it and came up with a 30,000 heat/loss. The program also called for a 1 1/2 ton A/C and I have a 4 ton unit and my home cools beautifully so I don't know why such a difference in the heat/loss calc.

    Do you think the mixing valve (160 set temp) is worth doing and will it work? He also said that a separate expansion tank should also be installed. Something to do with the house water pressure and water meter. I have a water regulator installed on the main that he was not aware of which we keep at 60. thank you...

  • pennron
    pennron Member Posts: 48
    Indirect Water Heater and Mixing Valve

    I have an 40 gallon indirect water heater working off a Burnham Revolution boiler utilizing a Taco 007, priority. I have the heater's aquastat set to 115 degrees which we find works well for our household. ie: we can't scald ourselves, dishes and clothes are getting cleaned etc. I set it at 115 degrees for the reasons listed and to also save on fuel.

    The one "small" problem (more of a nuisance) is when we fill our Jucuzzi she'll run out of hot water before the water level gets above the jets. We have to wait 10 minutes and then we can get the level over the jets.

    I was told by a tech that some agency (i forget who) recommends that the minimum setting should be 120 and they have now changed that to be 130 degrees so that there is no chance of germs, legionaires disease and other problems like that arising.

    His advice was to install a mixing valve and expansion tank on the water heater and then set the heater's aquastat to 160 degrees. He said then there is no germ problem and the whirlpool should fill in one shot. He also said even though you are keeping the heater at 160 I'll most likely use the same amt. of gas or possibly very very little more. It will probably be a wash. I think my heater drops 1/2 degree /hr according to the Alliance specs.

    More info: My HVAC co. came up with a 48,000 heat loss for my home. I used HVAC-CALC and measured every nook and cranny, took 5 hrs to do it and came up with a 30,000 heat/loss. The program also called for a 1 1/2 ton A/C and I have a 4 ton unit and my home cools beautifully so I don't know why such a difference in the heat/loss calc.

    Do you think the mixing valve (160 set temp) is worth doing and will it work? He also said that a separate expansion tank should also be installed. Something to do with the house water pressure and water meter. I have a water regulator installed on the main that he was not aware of which we keep at 60. thank you...
  • Al Corelli
    Al Corelli Member Posts: 454
    We set up systems differently.

    We do it just like it is being recommended to you.

    Many houses around here are getting new water meters with built in checks. It only makes sense to install a domestic water expansion tank.

    Fearing legionella, we keep all indirects at or above 160 degrees, and use a tempering (mixing) valve to get the water down to safe levels. I find that it increases the perceived capacity of the unit, Sort of a win-win situation.

    The mixing valves are also required by code around here.
  • pennron
    pennron Member Posts: 48


    hi:

    Is there much difference in fuel usage???

    When I thought about it I figured that yes we will be using less hot water because we wont turn that hot water faucet dial on as much. More cold faucet and less hot faucet. But appliances like washing machines and DW don't know that and will pour 160 water in. Is this correct?
  • Brad White_150
    Brad White_150 Member Posts: 29
    That is about right...

    With modern tanks that have good insulation, the biggest heat loss is cold water going in.

    Setting the tank higher does mean more hot water at the faucet because it is mixed down to suit.

    If your tank were to be set at 115F, a 3.0 GPM showerhead would use 2.5 gallons of tank water to get you to 104 degrees at the shower head when blended with 50 degree cold water.

    Raise that tank to 140 and you only need 1.8 GPM of the hot with the remainder at 50 degrees to get you to 104 degrees at the showerhead.

    Standby/storage losses are higher but in the end you spend not a whole lot more in energy. Setting your indirect on a timer so it is not kept hot all the time is a good idea so long as you have a boost to 140F-plus for Legionella protection.

    As you said, laundry and dishwasher usage will be higher because they are net volume based loads. But your dishes come out sparkling clean and your whites their whitest :)

    A good front-loading Staber washer helps on the laundry side at least.
  • Al Corelli
    Al Corelli Member Posts: 454


    Rarely see the DHW system split up for high and low temp loads like that. Not residential anyway. I really cannot think of the last time I saw a HOUSE set up that way.

    The dishwasher, normally being piped from the kitchen sink, would have the same tempered water as the rest of the system. The clothes washer, if it is near the boiler (Equipment)room, could be piped in from the hot side of the tempering valve if necessary. I have never been asked to provide such piping, nor has the need arisen for me to offer it. I'm sure, this coming week, I will have cause to offer same!
  • kevin coppinger_4
    kevin coppinger_4 Member Posts: 2,124
    I agree w/...

    the general idea of the mixing valve....Just not cranking up the tank temperatures so high...By putting the temps to 160 in most cases you now cut the warranty period to 5 yrs in most cases. If you read the fine print that happens if it goes higher that 150F. In my own home I put a sparco mixing valve on and only put the tank temp up to 145F.
    The other thing is that you have a 007 for the indirect...depending on the water heater that might not be enough flow for quick recovery...a Grundfos 15-58 on high speed or a taco 0010 might be a better match...What is the brand of indirect? kpc

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  • Scott04
    Scott04 Member Posts: 69


    Pennron,

    With the mixing valve, you will not get 160* water at the faucets, dishwasher, etc.. The Indirect will be set for 160* (or as was mentioned, closer to 140*-150*) but the mixing valve will mix cold water with it, in the pipe, so you will have 110*-120* water at the fixtures.

    All the advantages mentioned will be there, without the disadvantages of scalding, and the automatic appliances using hotter water!

    Hope this helps,

    Scott
  • Dave Belisle
    Dave Belisle Member Posts: 68


    We do it for filling the big tubs when people don't want to change the tank. We raise the tempature of the tank and install a tempering valve.

    It works well.........

    This is code in Vermont. The tank is required to be at a minumum of 140 and a tempering valve installed to bring the tempature back down at the fixtures .

    NH looked at doing this but hasn't yet...

    The reason , Legionella is killed at 140 degrees..... A nice side effect , lots of hot water....


    Dave in NH
  • pennron
    pennron Member Posts: 48
    mixing valve questions

    hey thanks everyone for all the info. KPC, to answer your question I'm using a Burnham Alliance 40 gal. indirect. Its 3 yrs old.

    So it seems I should keep the tank at say 150 degrees and then this tempering or mixing valve will "blend" the water down to 120 degrees. So its always 150 in the tank and 120 at faucets, appliances etc. ok I got it.

    lastly how do you regulate the temp. to the faucets, appliances to a specific temp like 120 degrees? Thanks.
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