Why the metered energy consumption is two times higher than the energy consumption reported by PS-H

3 posts / 0 new
Last post

Yongquing,

I confirm that I am seeing the doubling of the CH-1-HEATING input electricity in the PS-F compared with PS-H when I run your file. I have seen this doubling of the input electricity to a loop-to-loop heat pump chiller before.

In the scenario where I previously saw the doubling of the chiller input energy, I had done as you appear to have - created a dummy chilled water loop. In the scenario I had, the heat pump chillers did not generate hot water and chilled water simultaneously as the Loop-to-loop heat pump element in eQUEST does. So I created a no load dummy cooling loop which seemed to cause the doubling of input electricity.

I resolved the error by removing the dummy loop. This was done by having the heating chillers and the cooling loop-to-loop chillers on the same chilled water and hot water loops but staged them with equipment controls. In reality, I had 4 chillers that either produced hot water or chilled water simultaneously. I modelled it as 8 chillers - 4 that provided heating only and 4 that provided cooling only - but all were on the HW loop and all on the CHW loop. The heating equipment control only called on the heating chillers, the cooling equipment control only called on the cooling chillers. Then I tested to make sure they were not operating simultaneously (they weren't). This worked for me. In your scenario you may bump up against the limit of 10 pieces of equipment per primary loop so may have to combine some of your chillers.

Hoping this helps.

Brian

PS - I appreciate the reminder as this issue may be cropping up on a current project and I had forgotten about the prior problem/solution.

Footprint

Brian Fountain
Associate
d 416 572 8501 m 416 562 6831

Brian Fountain's picture
Offline
Joined: 2019-05-02
Reputation: 0

There is indeed a bug that causes the input electricity for loop-to-loop heat pumps in heating only mode to be doubled. The PS-C/PS-H reports show the correct electrical energy but that value is doubled in the BEPU/PS-F/ES-D reports. It is only the heating energy (cooling reports correctly) and only occurs when the loop-to-loop heat pump is in heating only mode with no assigned cooling load.

The problem can be avoided by setting the chilled water loop control option keyword to "standby" rather than "demand".

Interestingly, adding a process load to the cooling loop does not resolve the issue but instead causes the heating only load to be reported twice - once under heating end use and a second time under miscellaneous.

Compliments to Eric Rubli of our office for identifying the loop control solution.

B

Footprint

Brian Fountain
Associate
d 416 572 8501 m 416 562 6831

Brian Fountain's picture
Offline
Joined: 2019-05-02
Reputation: 0

Hi,Brian

I revised the model to set the chilled water loop control option to "standby".But in my current model,the problem still existed.

If I remove the heat storage, hourly report indicates that heating of the loop to loop heat pump was doubled in very few time steps.

Howerver,more strangely,if the heating storage system was modeled,at some time step,even if the Elctricity use for heat pump is 0,the ELEC-METER also reported heating energy use.

There is indeed a bug that causes the input electricity for loop-to-loop heat pumps in heating only mode to be doubled. The PS-C/PS-H reports show the correct electrical energy but that value is doubled in the BEPU/PS-F/ES-D reports. It is only the heating energy (cooling reports correctly) and only occurs when the loop-to-loop heat pump is in heating only mode with no assigned cooling load.

The problem can be avoided by setting the chilled water loop control option keyword to ?standby? rather than ?demand?.

Interestingly, adding a process load to the cooling loop does not resolve the issue but instead causes the heating only load to be reported twice ? once under heating end use and a second time under miscellaneous.

Compliments to Eric Rubli of our office for identifying the loop control solution.

B

Footprint

Brian Fountain
Associate
d 416 572 8501 m 416 562 6831

zhayongqing's picture
Offline
Joined: 2012-08-03
Reputation: 0