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WSHP Air to Water - how to insert into plant or air loop?

asked 2017-07-20 13:24:22 -0500

Matt Koch gravatar image

So, I am trying to insert a "Wtr-to-Air HP Elec Backup" into my model, either a plant loop or an air loop, but neither will accept it when dragging it over. Both pop up the error "The selected component is not allowed at this location."

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I have looked at the WSHP measures, and at least one of them seems to work, though it makes little sense to me. So I was just wanting to see if I can create such a system from scratch. Any clues would be appreciated.

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answered 2017-07-21 10:07:37 -0500

Matt Koch gravatar image

updated 2017-07-26 08:36:40 -0500

Wow, this is rather fascinating! Thank you, Julien Marrec and TomB, for this insight. I followed your advice exactly, and it seemed to work. Sorry for being so dense about this in the first place.

Interestingly, on the Thermal Zones tab, when I click on the (now present) entry under Zone Equipment, I can apparently edit some air-side parameters, including fan data and at what temperature to kick on/off supplemental heating. And on the HVAC Systems tab, when I select the plant loop and click on the Cooling or Heating Coil and select the Edit/Settings view, I can set things like cooling or heating capacities and COPs.

More importantly, the whole "WSHP and DOAS" discussion sent me off on the wrong track. As it turns out, it seems one does not need to specify an air loop at all to make this work. And, in the "WSHP and DOAS" discussion, the air loop only shows up to enable DOAS, which, in my opinion, is wholly unconnected to any WSHP aspects.

However, I don't think I saw a way to set the type or capacity of supplemental heating itself?

EDIT to add multiple zones per WSHP, following Julien Marrec's recommendations <<<

This is really cool. It works exactly as Juilen Marec describes. I have set up a CW plant loop and two WSHP air loops, the first of which serves two zones and the second of which serves three zones. Using the various "links" in the various Edit panels is key to connecting everything up. But when one does, the following pictures emerge.

Plant Loop: Condenser Water Loop (with boiler set to 36 oF and cooling tower set to 86 oF and condenser water set to 85 oF)

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For the Air Loops, I inserted an "AirLoopHVAC Unitary System" - "Unitary - WaterToAir Heat Pump - Cycling - Elec reheat" into each of two loops. Make sure to link both heating and cooling coil of this heat pump to the Condenser Water Loop for each air loop.

Water Source Heat Pump 1 (with deck set to 55 oF)

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Water Source Heat Pump 2 (with deck set to 55 oF)

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Zone Configuration (using VAV driven by air provided bu WSHP)

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Note that the "Controlling Zone or Thermostat Location" field in WSHP-1 or WSHP-2 needs to be set to to an actual zone. I used Zone 101 for WSHP-1 and Zone 103 for WSHP-2.

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Matt, this is not an answer, rather a comment (or at least an edit to the original question, though that ship has sailed a bit...). I'll edit my answer though... (EDIT: now this is an answer:) )

Julien Marrec gravatar image Julien Marrec  ( 2017-07-22 08:04:16 -0500 )edit

Please mark one of the answer as accepted, thanks!

Julien Marrec gravatar image Julien Marrec  ( 2017-07-26 15:14:22 -0500 )edit

answered 2017-07-21 04:11:52 -0500

updated 2017-07-22 08:06:28 -0500

You have to drag these into your Thermal Zones (on the Thermal Zone tab) and connect them to to plant Loop. Then you'll be able to see it under the plant Loop.

Drag it to the zone, and click on "Edit"

Thermal Zone Tab

Link both coils to the plant loop

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Now you can see it under the Plant Loop:

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Under the Thermal Zone tab, if you click on the WSHP, you'll see all the components, including the coils. If you have selected a WSHP with Elec Backup, you'll see the OS:ZoneHVAC:WaterToAirHeatPumpas well as the heating/cooling coils (OS:Coil:Heating:WaterToAirHeatPump:EquationFit and OS:Coil:Cooling:WaterToAirHeatPump:EquationFit) and you'll see the OS:Coil:Heating:Electric that is the backup elec coil. You cannot change the backup coil type after the fact, that's why you have 3 different WSHP in the hvac library.

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Yes, thanks for confirming that. I had also stumbled upon that coil upon closer inspection, but after I had already posed the question. Anyway, glad this is so comprehensive. It leaves me with one last question. As discussed thus far, these are meant to be zone level equipment. However, some manufacturers make WSHP units large enough to be system level equipment (e.g. Trane Axiom @ 25 ton, AAON SA @ 70 ton), where they may then serve multiple zones, e.g. via VAV or FPB. I suppose OpenStudio cannot currently handle these? Or is there a way to package "slave" zones into "master" zones?

Matt Koch gravatar image Matt Koch  ( 2017-07-24 07:11:20 -0500 )edit

You would use an AirLoopHVAC for these, and need to use an AirLoopHVAC:UnitarySystem in which you'll wrap the Coil:Cooling:WaterToAirHeatPump:EquationFit and Coil:Heating:WaterToAirHeatPump:EquationFit

Julien Marrec gravatar image Julien Marrec  ( 2017-07-25 10:36:08 -0500 )edit

That way you produce an AirLoopHVAC that uses WaterToAir coils as central coil, and you can serve multiple zones like any typical AirLoopHVAC. You can choose whatever air terminal you like (VAV, PFB, get crazy).

Julien Marrec gravatar image Julien Marrec  ( 2017-07-25 10:37:12 -0500 )edit

I've asked and answered several question on this site regarding this subject, including a problem with simulation times that explodes. I suggest you look for that. (Basically use one UnitarySystem for each water to air Coil, and control these on setpoint... that'll help a lot...)

Julien Marrec gravatar image Julien Marrec  ( 2017-07-25 10:38:05 -0500 )edit

answered 2017-07-21 04:10:13 -0500

TomB gravatar image

Try adding the component on the Thermal Zones tab. You'll need to take note of the link (chain icon) next to the settings (cog) icon which allows you to connect the component to a plant loop.

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Asked: 2017-07-20 13:24:22 -0500

Seen: 975 times

Last updated: Jul 26 '17