Interpreting low pumps consumption/demand and heat rejection

asked 2021-08-23 13:30:10 -0500

Ahmad's avatar

updated 2022-02-06 12:03:22 -0500

Hi all,

In my building model, I have a boiler hot water loop and an absorption chiller cold water loop. Cooling is switched off during winter months (JAN-MAR and OCT-DEC) and heating is switched off during summer months (APR-SEP).

How would you interpret low pumps consumption and demand during heating for the months of Jan till Mar and Oct till Dec as per the openstudio results below ? Do they seem logical ?

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Also what is heat rejection here referring to ?


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Pumps consumption mainly depends on Pump Head[Pa]. What is the Pump Head of your hot water pump and chilled water pump? The type of pumps such as Constant / Variable, Primary / Primary+Secondary, etc. also affects pumps consumption.

Heat Rejection is the fan power consumption of cooling tower.

Keigo's avatar Keigo  ( 2021-08-24 03:08:32 -0500 )edit

Thanks Keigo ! Both pumps are variable speed pumps. The hot water pump head is 198043 Pa and the chilled water pump head is 239221 Pa.

Ahmad's avatar Ahmad  ( 2021-08-24 03:50:39 -0500 )edit

Not so much difference. The cause seems to be somewhere else. Did you check the result to see if the chilled water pump was running for 24hours?

Keigo's avatar Keigo  ( 2021-08-24 04:00:01 -0500 )edit

What is the best way to check if it is running for 24 hours ? Also considering the pumps results like this, can they be interpreted as logical somehow ? Or this jump from high consumption in the summer to very low in the winter seem to show inconsistency ?

Ahmad's avatar Ahmad  ( 2021-08-24 04:12:02 -0500 )edit

I'm not familiar with Openstudio, but maybe turn on Pump Electric Power in Output Variables, select Hourly output, and run the simulation. I don't even know the building type and the weather of your model, but to me, the breakdown of the energy consumption appears to be very unbalanced. Either Interior Lighting and Interior Equipment are too high, or Cooling is too low. I feel like the latter. How about Unmet Hour? Are cooling load and heating load adequately handled?

Keigo's avatar Keigo  ( 2021-08-24 04:32:32 -0500 )edit