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Thread: not enough hot water

  1. #16
    Water system engineer riverside67's Avatar
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    Mar 2009
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    Riverside California
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    186

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    Have you looked into the Bradford White GX155S6BN high recovery model?

    - 200 gal 1st hr delivery

  2. #17
    Homeowner Thatguy's Avatar
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    Aug 2008
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    Proportion of hot and cold water
    HG = gals of hot water
    HWT = temp of hot water
    CWT = temp of cold water
    ST = shower/bath water temp

    The gallons of cold water taken to be 1.
    {HG(HWT) + 1(CWT)}/(HG + 1) = ST
    and
    HG = (ST-CWT)/(HWT-ST)

    With 2 gpm showers for 10 min. ea. you need 15 gals. of 120F and 5 gal of 40F water to give you 20 gals. of 100F water.
    Last edited by Thatguy; 12-04-2009 at 01:54 PM.

  3. #18
    Plumber @ Mechanical Contractor MechGuy's Avatar
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    Nov 2009
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    Iliinois
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    9

    Default Production rate

    Quote Originally Posted by jakeru View Post
    FYI - my *current* incoming water temp, (as showing on my TM-RE30 remote temperature controller - very convenient to monitor I might add!), is 48F. I'll bet it drops more as the cold winter sets in! For reasons unknown to me, the incoming water temps where I'm living right now seem to vary a wide amount from summer to winter.

    If i sized my tankless to what the groundwater temp chart says I'd have needed, I'd have an undersized unit. I'm thankful for every single one of my 200k BTU/h's!

    I've been able to max out my 200k BTU/h's tankless power output in the wintertime *just* by running one bathtub, at 122F output.
    Have you ever measured the GPM of that tub faucet? @ 48F inlet and 122F setpoint (74F Rise) that T-K3 should produce 4.3 GPM. And for you exact freaks the T-K3 is 199,000 Inside and the O/S model is 190,000.
    Curious if you have any water towers in your area? We've started seeing increased inlet temps due to solar gain by end of Summer and also chilling of inlet water in Winter that none of these towns anticipated. Luckily this is only in a 1-1.5 Mile radius of the towers.

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