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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