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Modeling a split heatpump water heater

asked 2016-07-20 14:41:47 -0600

jugonzal07 gravatar image

updated 2016-08-02 10:27:12 -0600

HI all,

I'm new to both OS and unmet hours so my apologies if I'm posting in the wrong place.

When trying to model a HPWH, I have no issues running a simulation when the HPWH is cooling a zone. This is my current setup:

image description

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I place the HPWH in the zone I want to cool and leave the AIr Inlet Configuration to ZoneAirOnly.

However, what I'm not sure of is how to model a HPWH with it's evaporator outdoors. I receive the following errors when I try to change the Air Inlet Configuration to "OutdoorAirOnly":

Inlet Air Configuration must be Zone Air Only or Zone And * ~~~ * Outdoor Air when compressor location equals ZONE.

Parasitic Heat Rejection Location must be ZoneAirOnly or ZoneAndOutdoorAir * ~~~ * when parasitic heat rejection location equals Zone.

Given that my compressor is located within the zone in an integral split system, how would I want to change the settings in OS to correctly model this? Am I misunderstanding the inputs in OS or something about HPWH configuration?

Thanks!

Update

By changing the compressor location and parasitic heat rejection location to the outdoors, I was able to run a simulation and the results look good. That said, I received a few errors that had me worried that just because the results look reasonable, that the simulation was ran incorrectly. The new severe, but not simulation ending errors I received were:

* Severe * Node Connection Error, Node="NODE 71", ZoneInlet node did not find an outlet node.

* ~~~ * Reference Object=ZONEHVAC:EQUIPMENTCONNECTIONS, Name=BLOCKS-427_OFFICE_1_CORE

* Severe * Node Connection Error, Node="NODE 70", ZoneExhaust node did not find a matching inlet node.

* ~~~ * Reference Object=ZONEHVAC:EQUIPMENTCONNECTIONS, Name=BLOCKS-427_OFFICE_1_CORE *** There were 2 node connection errors noted.

Results looked reasonable in that the backup heat did not come on during the summer months and were more dominant during the winter months. That said, why are there these missing node connections?

EDIT (8/2/2016) RESOLUTION:

So after taking the workshop with the bigladder folks, I've come to understand the underlying E+ structure and was able to deduce what's going on. Here are the settings for packaged and split systems respectively:

Package System (uses zone cooling capabilities):

  • Inlet Air Configuration: ZoneAirOnly
  • Compressor Location: Zone
  • Parasitic Heat Rejection Location: Zone

Split System (does not use zone cooling capabilities):

  • Inlet Air Configuration: OutoorAirOnly
  • Compressor Location: Outdoors
  • Parasitic Heat Rejection Location: Outdoors

As of 8/2/2016, it appears that setting HPWH to use outdoor air still creates inlet and outlet nodes for the zone equipment even though it no longer requires them. I would presume this is a bug. Anyhow, going into the OS text file and removing the extra inlet and exhaust nodes should cause the OSM to stop throwing the severe errors and produce a correct simulation.

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answered 2016-08-02 10:27:53 -0600

jugonzal07 gravatar image

updated 2016-08-02 10:28:47 -0600

SOLVED:

So after taking the workshop with the bigladder folks, I've come to understand the underlying E+ structure and was able to deduce what's going on. Here are the settings for packaged and split systems respectively:

Package System (uses zone cooling capabilities):

  • Inlet Air Configuration: ZoneAirOnly
  • Compressor Location: Zone
  • Parasitic Heat Rejection Location: Zone

Split System (does not use zone cooling capabilities):

  • Inlet Air Configuration: OutoorAirOnly
  • Compressor Location: Outdoors
  • Parasitic Heat Rejection Location: Outdoors

As of 8/2/2016, it appears that setting HPWH to use outdoor air still creates inlet and outlet nodes for the zone equipment even though it no longer requires them. I would presume this is a bug. Anyhow, going into the OS text file and removing the extra inlet and exhaust nodes should cause the OSM to stop throwing the severe errors and produce a correct simulation.

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Asked: 2016-07-20 14:41:47 -0600

Seen: 189 times

Last updated: Aug 02 '16