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Need some help with WaterHeater:HeatPump [closed]

asked 2016-03-30 09:23:11 -0600

Urado gravatar image

I am trying to model a heating system based on an air-to-water heat pump. For this, I use the zonal object Heat Pump Water Heater and add the HPW Tank in my hot water loop. First I want to try with autosize, so I also add design days and allow sizing calculation in simulation control, as usual.

Since my heat pump works with outdoor air, I changed the following parameters :

OS:WaterHeater:HeatPump :

  • Inlet Air Configuration : OutdoorAirOnly
  • Compressor Location : Outdoor

OS:WaterHeater:Mixed :

  • Ambient Temperature Indicator : Outdoors
  • Ambient Temperature Outdoor Air Node Name : Out air node

When I run the simulation I get the following error :

* Severe * WaterHeater:Mixed = HPWH TANK: Outdoor Air Node not on OutdoorAir:NodeList or OutdoorAir:Node * ~~~ * ...Referenced Node Name=OUT AIR NODE

So, first question : How can I add this node to the list in OpenStudio ? This error is fixed if I export my model in .idf and add the node manually in EnergyPlus but then I cannot come back to OpenStudio. Do I need to write a measure ?

I also get a new error when running my simulation with EnergyPlus :

* Severe * AirLoopHVAC AIR LOOP HVAC 1 has no air flow * ~~~ * Check flow rate inputs for components in this air loop and, * ~~~ * if autosized, check Sizing:Zone and Sizing:System objects and related inputs.

This seems to be because I set the Outdoor Air Flow to 0 in DesignSpecification:OutdoorAir. If I add a value, this error disappears. However, I want the airflow rate to be autosized and I think it is possible this way (see

For example, it works when I use a packaged rooftop VAV so I don't understand why there is problem with this specific case. Any suggestions ?

ps : I'm using OS 1.10 and EP 8.4.

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Closed for the following reason the question is answered, right answer was accepted by Urado
close date 2016-04-01 03:50:17.993812

1 Answer

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answered 2016-03-30 13:45:33 -0600

I think these are two independent issues. For the HPWH I think you have found a bug, because I don't think we have a test for the HPWH located outside, only inside the zone. I have filed a bug here.

For the no air flow issue, if you don't have an oa requirement then you are going to need a zone load to request flow and get things moving. Do you have a thermostat in your zone? Is there load on the zone?

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Example file HeatPumpWaterHeater

  OutdoorHeatPumpWaterHeater,  !- Name
  OutdoorAirOnly,          !- Inlet Air Configuration
rraustad gravatar image rraustad  ( 2016-03-30 14:08:46 -0600 )edit

Thanks for your answer. Yes, obviously the two issues are independent. Usually I use EnergyPlus after creating my geometry in OS plugin for SketchUp, so I think my second problem is due to an error in my OpenSutdio model which I don't handle very well.

When exporting to idf, I see that my Heating Thermostat set in my Thermal Zone (in the HVAC Systems tab) is not translated so I probably missed something. First I have to look how to properly create a Thermostat in OS.

Urado gravatar image Urado  ( 2016-03-31 04:13:02 -0600 )edit

Ok, this post could explain my problem. That should be why my thermostat is not translated when I set only heating, quite disturbing though !

Urado gravatar image Urado  ( 2016-03-31 06:23:09 -0600 )edit


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Asked: 2016-03-30 09:23:11 -0600

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Last updated: Mar 30 '16