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airflow sizing problem in Equest

asked 2015-07-21 11:31:30 -0500

kaczjer's avatar

updated 2020-03-07 22:02:51 -0500


I am modeling in eQuest 7-floor office building in Poland. This will be used for LEED certification.

I have a big problem with air flow sizing for each zone.

Most rooms are provided with CAV (constant air volume) with heating and cooling coils prowered by hot/chilled water loop and there are

4-pipe fancoils which helps with conditioning. Chilled water is produced in chilers and hot water is produced in heat exchanger which gets heat from municipal heating grid.

For proposed building I have modeled one big (for few floors) and few small ( per one floor) fancoils system (with heating/cooling coils)

which get Outside Air from "Constant Volume Single zone with Reheat" system. Each CAVs powers one Dummy zone.I set termostat schedules, so they equals to temperatures which CAVs supplies in cooling and heating mode.

I set air flow volume (CFM) and kW/cfm for CAV, defatul values for fans in fan coil systems and loads for both.

I set fan (0/1) schedule for systems, termostat and design T cool/heat schedules for all zones.

At first I started in DD wizzard but mainly work was done in Detailed Mode.

In results I got lots of unmet hours and the energy consumption (gas) is overkilling. The problem I think, is connected with adjusting properly airflow to each zone. For some zones I have 0 unmets but an overkilling airflow.

For the rest zones factor of cfm/sf is 0.1 and there I have lots of unmets. I saw in project that before calculations airflow is already assigned for each zone. I supposed that Wizzard did it for me, but these are bad sized values.

After deleting it I got ennormous flow for each zone and lots of cooling unmets(all year for each zone). The same problem is in Baseline model. I have no idea how to deal with this problem.

Thanks in advance

Przemysław Rejczak

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answered 2018-04-25 17:25:31 -0500

Cox311's avatar

It sounds like you haven't set the airflow rates for each of the fan coil units. For a proposed LEED model the flow rates need to match the design. I think if you set the flow rates for each fan coil, including the ventilation air rates that should help a lot with your unmet hours in the proposed case.

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Asked: 2015-07-21 11:31:30 -0500

Seen: 467 times

Last updated: Apr 25 '18