dual tankless water heaters

Home Support Forum Lowrise Residential Software & Compliance dual tankless water heaters

This topic contains 1 reply, has 1 voice, and was last updated by  Pat Splitt 11 months, 3 weeks ago.

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  • #5917

    lynnibob
    Participant

    We sized a house for instantaneous gas water heaters.  Due to the whirlpool bath and multiple bathrooms, it needs two 180kbtuh tankless.  When we model one tankless of any size, the house passes. When we model two tankless of the proper size, the house no longer passes. The difference is about 10%.

    Does anyone know why or how to get around it? These are being modeled at 95% efficiency, and we did try “insulate all pipes” and all the other good ways to get some credits.

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  • #5920

    Pat Splitt
    Participant

    This result is total B.S. Assuming the residential demand is the same for both options, the energy use for one or two tank-less systems should be identical. However, two tank water heaters would use more energy, due to additional standby losses.

    While still not correct, try modeling one each domestic water heater 1, plus one each domestic water heater 2. This seems to provide a better result.

    Pat Splitt

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