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Air to water heat pump with boiler backup in OpenStudio

asked 2017-10-08 22:43:53 -0500

VickyZhou's avatar

updated 2017-10-16 18:53:48 -0500

I'm modeling a system with a heat pump for heating and a boiler as the backup. Saying that if the heat pump is unable to satisfy the heating requirements of the heating loop, the heating water boiler is enabled. Upon setpoint being achieved the boiler is disabled first and then the heat pump. I was trying to use the tempering valve but after reading the instruction in Energyplus I noticed that tempering valve is not the correct choice in this case.

Do you have any recommendations on how to do it in Openstudio?

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Hi, welcome to unmethours. We have a convention to not include greetings here ("Hi", "thanks", etc), and it's always a good idea to tag your question appropriately using existing tags, especially if you are referring to a specific software (openstudio here)

Julien Marrec's avatar Julien Marrec  ( 2017-10-11 02:34:26 -0500 )edit

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answered 2017-10-11 03:02:28 -0500

You want to place both the heat pump and the boiler on the supply side of the plant loop, on parallel branches is fine. You want your  PlantLoop Load Distribution Scheme to be SequentialLoad, and you want a PlantEquipmentOperation:HeatingLoad attached to the PlantLoop that references a PlantEquipmentList that has the heat pump first, then the boiler. This will ensure the heat pump gets loaded first, then the boiler.

You can either rely on OpenStudio inner workings, and connect the Heat Pump first to the PlantLoop, then the Boiler:HotWater and this should produce what you want, and you should check the resulting E+ IDF file to make sure.

Or you can use the Ruby bindings (API) to create your own custom PlantEquipmentOperationHeatingLoad, it's maybe more complicated but you're sure to produce the right one...

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Thank you, Julien, Sorry I have to add a supplement to my question. The heated water always passes through the heat pump first. If the leaving water temperature is lower than the setpoint temp, then the boiler will start to work. Otherwise, the heated water will not pass through the boiler. So do I still use the parallel branches in this case?

VickyZhou's avatar VickyZhou  ( 2017-10-11 13:50:43 -0500 )edit

This is not similar. Put them in series (HP first, then boiler), and add a SetpointManager:Scheduled on the outlet of the HP and the boiler, OpenStudio will create a PlantEquipmentOperation:ComponentSetpoint for you that should work.

Julien Marrec's avatar Julien Marrec  ( 2017-10-13 05:34:00 -0500 )edit

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Asked: 2017-10-08 21:29:59 -0500

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Last updated: Oct 11 '17