SHW Loop Causing WSHP Loop Errors?

asked 2017-02-03 16:27:19 -0600

Tim Johnson gravatar image

updated 2017-08-15 13:46:16 -0600

I have a 70,000 sf university building with a water source heat pump loop. The loop is running as expected, going from 60-90°F on the supply side and unmet hours are at a reasonable level. After some checking, I was satisfied with the operation and moved to the SHW loop. I added a loop with the AEDG Secondary School script and got a fatal error telling me that my Heat Pump Loop temperature is out of range. It seems unable to calculate adequate flow across the heat pumps in heating mode and ends up with a -577°C loop temperature. Deleting the SHW loop fixes the problem. I get the same result when I create a SHW loop by hand.

Why would the SHW systems impact the heat pump loop operation? Any ideas for me?

C:\fakepath\Heat Pump Loop Temp.JPG

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What are the two Nodes on your graph? Are the SHW and Heat Pump Loop interconnected in any way? If so how?

What's your water heating equipment used for SHW? Is it a WaterHeater:HeatPump of some kind? If so, what's its inlet/outlet air configuration?

Julien Marrec gravatar image Julien Marrec  ( 2017-02-04 09:15:19 -0600 )edit

The nodes in the plot are the supply side inlet and outlet nodes on my water source heat pump loop before the SHW loop is added to show that it operates roughly as expected. The upper and lower temperatures are holding and the zone level heat pumps are changing the loop temp. The SHW loop consists of one WaterHeater:Mixed with natural gas heat. I tried using the "AedgK12Swh" script and it generates several water use connections. I also tried making my own with just one scheduled usage. If there is any connection between the HP and SHW loops, it is not my intention.

Tim Johnson gravatar image Tim Johnson  ( 2017-02-06 09:28:42 -0600 )edit