Water heater size with and without tempering valve

Discussion in 'Water Heater Forum, Tanks' started by queen50, Jul 12, 2014.

  1. queen50

    queen50 Member

    Messages:
    40
    Location:
    Washington state
    I want to install an acrylic tub with a 60 gallon capacity. The current 40 gallon electric WH is not going to cut it; it supports 7 people, 3 baths, washing machine, and dishwasher now but we occasionally run short of hot water.

    I'm thinking of replacing it with either a 70 gallon HWH or a 60 gallon with a tempering valve. Would either of these provide adequate hot water?

    What about cost? I think the 60 gal option would actually cost more to install, since there would be added plumbing; I suspect the 70 gal with no tempering valve would be more efficient. What do you think?
  2. Terry

    Terry Administrator Staff Member

    Messages:
    15,050
    Location:
    Bothell, Washington
    I would go with the tempering valve, and set the tank thermostats high, blending the water down to 120 degrees.
    [​IMG]

    Honeywell AMX300

    [​IMG]

    Installed on a 50 gallon gas water heater here.

    A 50 gallon at 120 with the tempering valve could put out 75 gallons at 120 it the water heater is set to 180.
  3. queen50

    queen50 Member

    Messages:
    40
    Location:
    Washington state
    Thank you so much!
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,684
    Location:
    Cave Creek, Arizona
    I doubt that any residential heater will have a thermostat that will go to 180 degrees. But, if it did, the manufacturer had better have a massive liability insurance policy because they will be the first one any customer will sue if there is an injury.
  5. Terry

    Terry Administrator Staff Member

    Messages:
    15,050
    Location:
    Bothell, Washington
    It's funny you say that. I read the instructions that come with the heaters and this is what it says. We install a lot of water heaters in the greater Seattle area.

    [​IMG]


    [​IMG]


    [​IMG]

    [​IMG]

    And that's why I like tempering valves. My mother is 97, and with her tempering valve, I don't have to wonder if any of 65 relatives dropping by her home will change her thermostat setting on her.
    Last edited: Jul 14, 2014
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,055
    Location:
    New England
    In the small city where I live, all new/replacement WH installations (at least those that get a permit and inspection!) are required to also have a tempering valve AND an expansion tank.
  7. JerryR

    JerryR Member

    Messages:
    246
    Location:
    Florida
    Here's a picture of my Honeywell AMX300 installed on my 50 gallon WH. Prior to installing it the jetted large Ronan tub would run out of hot water while filling. Now it's not a problem at all. I've set the WH thermostat temps to 150dF and adjusted the AMX300 to deliver 120dF water.

    The only thing I noticed is with the AMX300 the hot water flow to the tub is slightly reduced. This is only noticeable when filling the tub, not at any sinks or showers.

    [​IMG]
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,684
    Location:
    Cave Creek, Arizona
    Mot residential water heater thermostats will only go to 160 degrees maximum. And that is too hot unless there is a thermostatic valve on the outlet. Bradford White "high efficiency" gas heaters run at 160 with a factory installed mixing valve to control the user temperature.
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