Groundwater Source Heat Pumps

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Dear All,

ASHRAE 90.1-2007 minimum EER and COP ratings for heat pumps in Table
6.8.1B. The referenced testing is ISO 13256-1 and the rating condition
is 59F entering water for cooling and 50F entering water for heating.
What is the exact definition of "entering water"? Shouldn't both
entering water and leaving water temperatures be specified (in other
words delta T) for a meaningful efficiency requirement?

Thanks

?mer Moltay

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?Entering Water? refers to the condenser loop water temperature as it enters
the condenser (e.g. 59F or 50F). I believe ISO leaves the delta-T ?as
specified by the mfgr.? The older ARI ratings specified this value at 10F
for cooling mode. You should be able to back it out if you know the heat of
rejection (or extraction) and the condenser flow rate.

Anthony Hardman, PE, LEED AP BD&C

Anthony Hardman, PE

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Omer,

Entering water is the ground loop temperature as it enters the condenser. Delta T is needed to calculate the efficiency of a specific condenser/heat exchanger, but it is not directly relevant to defining an overall system efficiency because EER/SEER/COP do not refer to the condenser alone. They quantify the total cooling/heating effect relative to compressor and fan input electrical power. Two different units may have the same EER but differing condenser delta T's at the same entering water temperature.

Thanks,
Dakota

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DAKOTA KELLEY

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Thanks for the information. Apart from the condenser side, shouldn't the
COP be dependant on the leaving water and return water temperatures? How
are they specified in Table 6.8.1B?

Thanks,

Omer Moltay

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