Can I adjust fan CFM on a schedule in eQuest?

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I'm preparing an energy model in eQuest for a multifamily apartment building and have run into an issue with the DOAS system.

The building has (2) AHU units supplying 100% outside air which is conditioned by a CHW and HW Loop. There is one larger unit at an estimated 18,000 cfm and a smaller unit at 12,000 cfm. Currently, they are modeled together as one 30,000 cfm VAV (with the OA and fan max and min ratios both set to 1 in order to accurately represent the operating conditions of the actual equipment).

I was informed by the facility manager today that the larger AHU was actually not working for 6 months out of the year. This explains why my calibration was off during those months. Anyway, is there a way to mimic this in eQuest?

A way to assign a single zone to (2) DOAS systems and then kill the fan power to one of them with a schedule
Drop the CFM for the combined DOAS at a certain month during the year with a schedule?
Any other method you guys might have?

Thanks for the help!

amitpaul527

asked 2014-12-12 10:27:02 -0500

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Neal Kruis

updated 2015-01-09 12:00:58 -0500

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I don't think this is possible as you can't have 2 systems serving 1 space in eQUEST.

I think you'd need to run the simulation twice, once with both fans combined, and once with just the smaller system. Then you'll need to piece the data together.

Or you could generate a custom fan curve that mimics the performance of the system, but this might cause problems in low flow conditions for the 6 months of the year where both fans are running.

Good luck with this challenging problem.

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301_Hours

answered 2015-03-29 13:52:21 -0500

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Found this post while perusing eQUEST/doe2 related queries some time later... surely too late to help with this project directly but I can answer for the record if anyone else has a similar query:

The 'easy' response to achieve the intended effect for the purposes of calibration would be to (A) not combine the two existing DOAS systems (so split them up, permitting the assignment of unique FAN-SCHEDULEs), then (B) creating a "broken" FAN-SCHEDULE forcing non-operation for the requisite 6 months out of the year (using days with all zeroes for the hourly ON/OFF/FLAG input).

An ECM to resolve that issue, thus providing the amount of OA intended by the design, could then simply swap in the "normal" fan schedule that's assigned to the other DOAS for each run.

Hope that helps someone moving forward!

~Nick

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Nick Caton

answered 2016-09-21 04:30:22 -0500

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I'm not aware of a schedule for this. You could create two versions of the model and run each version for a different period of time. It Detailed Edit mode go to the "Project and Site" tab, and look for Simulation Options -> Entire Year. You can specify the parts of the year that you want the model to run for. E.g. you can run the model with both systems from Jan-March and then from Oct-Dec and run the model with only one system from Apr-Sept.