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VRF with AHU in Design Builder. Replacing DX Coil curves with VRF.

asked 2019-03-14 05:32:04 -0600

Maaz Akbar's avatar

updated 2019-03-14 23:34:49 -0600

I have to model VRF outdoor unit with Treated Fresh Air units(TFAs) in Design builder. At present we cant connect VRF ODU to external fresh air supply equipment. Can we model this scheme in e+ after exporting idf. Further,if we replace the performance curves of the DX cooling coil on Air Handling Unit with the proposed VRF system, will this approximation provide accurate results.?

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answered 2019-03-14 07:39:40 -0600

VRF terminal units can be connected to a DOAS using the AirTerminal:SingleDuct:Mixer object. See the EnergyPlus example file DOAToVRF.idf. When modeling any HVAC system it is recommended that the manufacturers data be used to create inputs, including the performance curves when used. If unsure of how to create VRF performance curves see Creating Performance Curves for VRF Heat Pumps in Energyplus.

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Dear rraustad,thanks for the help.I think i could not make my question clear. I have a DOAS with DX coil connected to VRF Outdoor unit. The example file referred here is supplying fresh air via DOAS through heat exchanger to VRF zone terminal units. In my scenario i have to connect both the terminal units as well as DOAS coils to respective VRF ODUs. Hope i made it clear this time.

Maaz Akbar's avatar Maaz Akbar  ( 2019-03-15 01:30:12 -0600 )edit

The VRF terminal units in EnergyPlus are controlled by zone load. I don't think you can put a VRF TU in an outdoor unit since it would need to be controlled using a temperature set point. Do you have engineering documentation on the VRF outdoor unit?

rraustad's avatar rraustad  ( 2019-03-19 09:13:50 -0600 )edit

So in Design Builder it's impossible to connect the VRF outdoor unit to both the DOAS coils and terminal units? If possible, how?

miguelvargues's avatar miguelvargues  ( 2021-10-07 04:54:23 -0600 )edit

You can connect the VRF condenser to zone terminal units or a central air loop terminal unit but will have to use other coil types for the OA system.

rraustad's avatar rraustad  ( 2022-02-04 13:14:42 -0600 )edit

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Asked: 2019-03-14 05:32:04 -0600

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Last updated: Mar 14 '19