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Adding airloop to Rooftop VAV with Reheat system

asked 2015-12-10 02:48:34 -0500

PBrain's avatar

updated 2015-12-10 15:25:55 -0500

Similar question to Packaged Rooftop VAV w/Reheat

I am trying to add an additional airloop to a packaged VAV with Reheat system.

My intention is to add another AHU and connect it to the chilled water loop and also the hot water loop.

New airloop setup is no worries until I add an AirTerminal Single Duct VAV Reheat object. This AirTerminal object references a hot water coil by name. The name of that coil is the one and same making its self well known in the .err That hot water coil is not visible under My Model and Library lists, which stymies my intuition to drop it on the Hot Water Loop

I've tried a few things

  1. add a hot water coil to the Hot Water Loop by drag n drop from Library and then reference that coil in the AirTerminal object defintion. No joy there.
  2. Navigate away and come back to the HVAC Systems page, hoping a refresh might show up the missing hot water coil object
    1. Turned my computer off and on again

Question time. Is the basic idea sound ? i.e if you wanted to have a few AHUs on a chilled water and hot water loop, is this a reasonable approach ? Why is the hot water coil referenced by the AirTerminal not visible, drag and droppable ? Is there a measure for that ?

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answered 2015-12-10 18:26:00 -0500

Or in pictures:

Drag in a VAV HW Rht (VAV Terminal with Hot Water Reheat)

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The terminal comes with a hot water coil inside it

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Connect the hot water coil in the terminal to the hot water loop

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Now connect to many zones. Every zone you connect will get a copy of the first terminal, so set up the terminal inputs the way you want them for all zones and connect it to the hot water loop before connecting zones.

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Step 3 was the missing link. Thanks to all for the excellent help and answers.

PBrain's avatar PBrain  ( 2015-12-10 21:53:19 -0500 )edit

answered 2015-12-10 14:30:21 -0500

Adding reheat coils to an air terminal is one of the processes that IS NOT "drag and drop" in OpenStudio. You'll need to:

  • Create a heating coil in your existing hot water loop to serve as your new terminal's reheat coil
  • Create a new air loop containing a terminal with reheat capability
  • Click on the new terminal to start editing. Click on the chain link button near the top right and select the name of your hot water loop. This connects the terminal unit to your hot water loop.
  • Scroll down until you see input fields for the OS:Coil:Heating:Water object, and make sure the name matches the heating coil you created in your hot water loop.

That should set you up to have hot water reheat in your terminals. If you want to connect central heating coils in AHUs to your hot water loop, you should see node icons above and below the coil image. This indicates that the coil is connected to another loop in your model. Also, central coils that are connected to two loops are visible in the "My Model" drop down list for drag-and-drop capability.

It sounds like you're on the right track, but I would double-check these:

  • Make sure the names match between HW coil in your plant loop and in your reheat air terminal
  • Make sure your reheat air terminal you created uses HW reheat, not electric or gas
  • Make sure that the "Hot Water Loop" box is checked under the chain link icon when you edit the reheat air terminal
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@Aaron Boranian, you don't need to create a HW coil in the plant loop manually before adding a reheat terminal. Adding the HW reheat terminal to the air loop and linking it to the HW loop will create the HW coil on the plant loop automatically.

ericringold's avatar ericringold  ( 2015-12-10 14:38:38 -0500 )edit

Clicking on the chain and ticking the box for Hot Water Loop was the missing link for me. Pardon the pun.

PBrain's avatar PBrain  ( 2015-12-11 00:58:15 -0500 )edit

@Eric Ringold good point, thanks for clarifying

Aaron Boranian's avatar Aaron Boranian  ( 2015-12-11 08:52:33 -0500 )edit

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Asked: 2015-12-10 02:48:34 -0500

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Last updated: Dec 10 '15