Furnace fan never turns off

asked 2016-09-29 10:02:02 -0600

EnergyNerd
51 ●3

updated 2017-09-09 13:26:28 -0600

__AmirRoth__

4436 ●5 ●17 http://bleedinggreenna...

OK, I have the furnace template (with A/C) running a one zone/one space model. The electrical use chart shows the same amount of fan energy consumption each month, meaning it is on all the time, correct? The fan should receive information about the operation of the gas burner and turn off when the heating demand is satisfied. I am also getting large (most days of the year) unmet hours which may be affecting this situation. Any ideas on how to correct this issue? Thanks.

Comments

Did you check to see if you fan has an "always on discrete" schedule?

mdahlhausen ( 2016-09-29 10:39:57 -0600 )edit

I had it on a schedule that matched the HtgSetp for my building type - MidriseApartment. I switched the schedule to always on discreet. When I reran the model, this did not appear to change anything. Thanks, Matt

EnergyNerd ( 2016-09-29 12:16:18 -0600 )edit

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answered 2016-09-29 12:58:07 -0600

rraustad

13804 ●79 ●12 http://www.fsec.ucf.edu/

The setup you are using now is a gas heating coil and a fan sitting independently on an air loop. The fan knows nothing about how the coil is operating. You would need to incorporate a cycling fan system in your model (i.e., 'AirloopHVAC:Unitary:Furnace:HeatOnly'). With this system type you can choose to run the fan continuously or cycle the fan with the coil operation.

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Thanks Richard. That's what I was thinking, but there is no such component in OpenStudio that I can find. There was just the one furnace template. Anyone else know about this?

EnergyNerd ( 2016-09-29 13:43:39 -0600 )edit

OpenStudio chose to use the AirLoopHVAC:UnitarySystem object, which can be configured with many different types of coil/fan combinations. Go to HVAC tab > Library > AirLoopHVAC Unitary System and you should see one called Unitary - Gas heat - Cycling. I think this is what you want. If the system isn't cycling, check out the Supply Air Fan Operating Schedule field, as this schedule controls whether the fan cycles or runs constantly.