Hard Sizing the HVAC - Energyplus

asked 2021-12-16 09:12:04 -0500

Adharsh's avatar

updated 2022-02-06 12:06:06 -0500

Hi Iam trying to see the change in consumption due to the Weatherization(Energyplus). ( variation in R value and the infiltration variation is bit higher). I used the PNNL model for Single Family. The Heating and cooling coil capacity is "autosize ". Hence iam seeing a change in both the pre and post models capacity and so the the change in energy consumption is higher. To get the change in consumption for the Weatherization alone Iam planning to hard size the post IDF with the values from the pre run EIO values. is the approach correct? if i want to make the HVAC setting same in pre and post then need to change the "autosize" to values from Pre run So which are fields to be changed?

  1. Sizing system :- I changed the cooling and heating design capacity
  2. cooling coil DX single speed :- I changed the Cooling capacity
  3. Coil Heating Fule :- I changed the Nominal Capacity
  4. AirloopHVAC:UnitaryHeatCool :- Changed the cooling and heating supply air flow rate all these fields from "autosize" to value got from the EIO of the pre run.

Is the changes correct so that both the system is identical ? Should I change anything other fields?

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Yes, your approach is correct for a retrofit measure. In general, you can search the IDF for "autosize" and replace that with the capacity/flow value that's listed in the output of your sizing run.

ericmartinpe's avatar ericmartinpe  ( 2021-12-16 10:12:32 -0500 )edit

Thanks eric. !!
Is it ok to leave the Fan settings in Autosize?

Adharsh's avatar Adharsh  ( 2021-12-16 10:31:17 -0500 )edit

Why would you leave the fan to autosize but hardsize everything else? Are you planning to replace the fan as part of weatherization?

ericmartinpe's avatar ericmartinpe  ( 2021-12-16 10:45:45 -0500 )edit

No Eric. Iam just capturing the Gas consumption alone.

Adharsh's avatar Adharsh  ( 2021-12-16 11:53:21 -0500 )edit