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190 Degree Domestic Hot Water

DonDon Member Posts: 12
I recently got involved in a job where a Slant Fin Boiler and a Turbomax indirect waterheater were specified and installed in a convent. The problem came when we had to supply 180 degrees to a commercial dishwasher. The rep said to let the Turbomax produce 180 degree water for the dishwasher and temper down the water to the rest of the domestic system consisting of showers and sinks with a mixing valve.

I have a concern with keeping 180 degree water in a system that if the mixing valve fails could migrate into the rest of the domestic system and seriously hurt someone. After speaking to the contractor we decided the best method may be to put in a second Turbomax dedicated for the dishwasher to meet the code of having 180 degree water to a dishwasher in a commercial establishment and run the original Turbomax at a lower temperature for the rest of the domestic system.

Do you feel this is overkill to have the two indirects in this system? I think it is the safest thing to do but I am not sure if we are being too cautious.


  • DavidDavid Member Posts: 250
    This might be stupid

    Why not use two tempering valves?

  • DonDon Member Posts: 12

    The goal we had was to totally isolate the high temperature domestic to avoid possible injuries. If we feed the dishwasher with the high temp Turbomax we do not have to worry about possible injuries due to a failed mixing valve. By adding a separate Turbomax operating at a lower temperature we can completely isolate the two temperatures and we do not have to worry about a failed mixing device. If the dishwasher only needed 140 degree water it would be another issue, the fact that the code requires 180 degree water for the dishwasher we were not comfortable using a single water heating device.
  • DaveGatewayDaveGateway Member Posts: 568
    Same heat source?

    But what's heating the 2nd TurboMax? If it's the same boiler, don't you have both on a primary loop or is the 2nd tank piped off the first. Aren't you adding alot of water volume to the heating system: each small tank holds over 20 gal of boiler water.
  • Mark HuntMark Hunt Member Posts: 4,909
    Doesn't the dishwasher

    have a booster heater on it? Most of the ones I have worked on do.

    What about a solenoid valve set to close when water temps get above a max set point?

    Mark H

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  • Dan PeelDan Peel Member Posts: 431
    Devoted Tank

    Keeping just enough volume at 180 in a second tank sure makes more sense to me than trying to maintain a large tank at higher temps. Another option is a demand booster to top up the temperature from 140 to 180 as required to feed the dishwasher. Enjoy.....Dan

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  • Larry (from OSHA)Larry (from OSHA) Member Posts: 677
    I'm wondering

    if perhaps point of use tempering devices might be just what you need. It would depend on how many devices you would need to protect for the correct temperature. What is the cost of the second tank verses the cost of point of use devices? And, the idea of a second mixing valve at the tank makes sense to me too. ( this from a guy not in your profession, by the way) But, the redundancy of the second mixing valve is very consistant with the concept of control reliability that is required when dealing with machne guarding. Just a thought.

    Larry (from OSHA)
  • BillyBilly Member Posts: 18

    We are making the two Turbomax units separate zones with flo-valves and pumps for each. This way we can control temperature in each area. As for the volume, we are heating a rather large building so the extra 20 gallons or so is not going to effect the system.
  • BillyBilly Member Posts: 18
    Tempering valves

    I am not sure how you would pipe two tempering valves in series if that is what you are suggesting. What we are looking to do is eliminate the tempering valves so we have a truly safe system with no chance of the 180 degree water migrating to the other side of the system.
  • BillyBilly Member Posts: 18
    No booster

    I was hoping the dishwasher would have a booster, it did not. It was less expensive to add the second Turbomax than to get a booster.

    We did think about using a normally open solenoid with an aquastat to close the valve on temperature rise but we found out in New York you must be licensed to do that and meet code.
  • Kal RowKal Row Member Posts: 1,518
    go to

    they have tons of docs on line
  • EinsiedlerEinsiedler Member Posts: 93
    Tempering Valve Code

    I'm hearing rumors of a code that will require a tempering device on all std. nat gas water heater installs. (in Alberta Canada).
    Anyone know anything about this?

    sorry for high-jacking this thread...

  • Dan PeelDan Peel Member Posts: 431
    Word is

    This has become part of the Canada wide code as of Sept. 1st. Domestic water tanks - regardless of fuel - on building permits issued after Sept. 1/04 must be set to operate at 140 F and must not deliver the water to any fixture (dishwasher and laundry are OK) above 120 F. This means a tempering valve at each water heater. I'm not sure whether this will change the requirement for pressure balance or other anti-scald devices. Check the CIPH website for code details and scope. Enjoy....Dan

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