Support commercial water heaters

[shorowit]

In HPXML v3.1, a new StandbyLoss element was added for WaterHeatingSystem. It has units of F/hr, which is what AHRI collects for indirect water heaters. However, commercial water heaters have units of %/hr and Btu/hr. The best approach would be to add Units and Value children, though this would be a breaking change.

<WaterHeatingSystem>
    ....
    <StandbyLoss>
        <Units>XXXX</Units>
        <Value>XXXX</Value>
    </StandbyLoss>
</WaterHeatingSystem>

(Note: The thermal efficiency metric for commercial water heaters already exists.)

[shorowit]

For commercial heat pump water heaters, we should ask for COP. See https://www.energystar.gov/products/commercial_water_heaters/partners for example.

[RockyMtnBrian]

The breaking change matches what I assumed would be needed to feed commercial water heater data into OS-ERI. I'm glad to know that Thermal Efficiency already has an input ready!
Regarding COP - That data is not presently available for commercial water heaters in AHRI; in fact, I cannot find commercial HP water heaters in AHRI. Given this, I think making it a required input is not viable for ERI ratings.

[shorowit]

@RockyMtnBrian For what it's worth, ENERGY STAR requires COPs for commercial water heaters, see here for example products. We need to collect some kind of efficiency value for a commercial HPWH, and in the absence of AHRI data, it's the only data I've seen.

[RockyMtnBrian]

@shorowit If it's only required for commercial HPWH, and not other commercial water heaters, then I think it is viable. I think the initial proposed inputs need to remain available and sufficient for most commercial water heaters.