Issue overview

When you have a zone multiplier, all internal gains from e.g. Equipment objects are multiplied before the load is calculated for the HVAC system. Good.

However, water heater tank losses are calling the same zone internal gain method (SetupZoneInternalGain method for the mixed tank water heater, for example), so the zone multiplier is being applied here as well. The tank losses should not be multiplied by the zone multiplier because, if you are actually trying to model a thermal zone that represents X units, each with its own water heater, you still have to either model 1 water heater with 4x the tank losses or model 4 water heaters -- so the zone multiplier ends up double counted.

A solution could be to update the WaterThermalTankData::setupZoneInternalGains method and pass the tank losses divided by the zone multiplier to the SetupZoneInternalGain method to counteract that the zone multiplier will be applied. That said, there are probably other objects that have this issue too, so perhaps the SetupZoneInternalGain method needs to be updated instead.

cc @mjwitte

Details

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• Platform (Operating system, version)
• Version of EnergyPlus (if using an intermediate build, include SHA)
• Unmethours link or helpdesk ticket number

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