Measuring for an Office Building with 92 Heat Pumps

Projects that have a dedicated outside air system that supplies ventilation to distributed heat pumps and/or fan coil units it would be necessary to perform the calculations and measurements at each distributed system.

I believe measurements at each heat pump are outside the scope of the balloted rating system. The rating system states, "measurements taken at the system level...Each air-handler must be measured."
However, the calculations to find minimum OA flow would need to account for the critical zone, and associated occupant density and total airflow.

I asked this same question to the GBCI, there response was what I have posted previously. Perhaps submit with an OA measurement at the supply fan but understand they may require OA tests at all 92 heat pumps.

good luck!

I would agree that measuring the outside air at each heat pump is not required and rather that the 'system level' in this case is the dedicated outside air unit. It would be different if the dedicated OA unit supplied OA to floor by floor AHUs. In that case, each AHU would need to be tested.

Why wouldn't the heat pumps be considered as AHUs? In the Q&A above, the example is pretty clear that a DOAS providing ducted airflow to other fan systems (in this case the heat pumps) would be measured at each AHU.

If each heat pump wasn't measured, how would you know how much OA was coming to each heat pump? The system could be out of balance, but this wouldn't be detected by measuring the DOAS only.

I could see a more practical approach if the DOAS total airflow was much higher than the minimum and if the design airflows of the heat pumps corroborated an ample airflow, and a few were sampled and showed compliance.

Although personally I'd advocate for a more practical approach, and which might be approved by the reviewer on a case-by-case basis...the OA quantity might be cross-checked if the heat pumps have any digital temperature sensors for instance without airflow measurement, or CO2 measurements could be taken as a reference...I think David Hubka is correct according to the stated requirements.

I think LEED v 4 allows sampling. Maybe submitting this credit under LEED v4 is a good way to go?