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Add Setpoint Manager to Cooling Coil Air Node of Unitary System

asked 2015-05-11 00:49:45 -0500

pflaumingo gravatar image

updated 2015-07-12 12:10:26 -0500

I am trying to model a self-contained VAV using the AirLoopHVAC:UnitarySystem component, but with the API I can't figure out how to put a setpoint manager on the cooling coil air outlet node of the Coil:Cooling:WaterToAirHeatPump:EquationFit component within the unitary system, or any component within the unitary system for that matter. The problem is that the air inlet and outlet nodes for components within the unitary system don't seem to get initialized until the IDF gets written. I could probably write an EnergyPlus measure to add a setpoint manager to the outlet node, but it's not quite the solution I am looking for. Alternatively, I could also just use the unitary system to house the cooling coil and place the setpoint manager on the outlet of the unitary system because this will be the same node as the air outlet of the cooling coil. However, if I had a unitary system with multiple components (i.e cooling coil, heating coil and fan) is there a way I can force the nodes to initialize or somehow apply a setpoint manager to each of the individual component outlet nodes?

This question is sort of a follow up from a previous post and it gives a bit more information about the type of system I am refering to.

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answered 2015-05-13 09:37:00 -0500

You have assessed what OpenStudio is doing correctly. Those inner nodes of the unitary system do not get created until the idf file is created. If you really want to know, that point is right here in the osm->idf translator. You could use this information to predict the names of the generated nodes so that you can add a setpoint manager later, perhaps with an IDF Measure.

I suggest instead that if you are using the setpoint mode of AirLoopHVACUnitarySystem, just wrap a single component in each unitary. If you have a heating coil and a cooling coil, use one unitary for each. I have done this myself in the CBECC-COM -> OS Translator. E+ will have no issue with multiple unitary systems on a single AirLoopHVAC. You are just using the unitary as a coil wrapper in this case to allow the component you want on the air loop.

One of the main value propositions of OpenStudio when it comes to HVAC is that it manages the (complicated) connectivity of things for you. Unfortunately the fancy mechanisms OS uses to connect HVAC components to each other do not extend to the inside of compound HVAC components. Hopefully we will have time to improve this in the future. When that happens the inner nodes will be instantiated and connected together in the osm so that you can reference them and attach things to them.

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Thanks for the help. I'll probably use one unitary system as a wrapper for each component that I need as you suggested because this seems the most practical method.

pflaumingo gravatar image pflaumingo  ( 2015-05-13 13:58:59 -0500 )edit

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Asked: 2015-05-11 00:49:45 -0500

Seen: 676 times

Last updated: May 13 '15