Night Cycle - minimum flow rate in EPlus

asked 2016-06-09 13:12:40 -0600

Annie Marston
4357 ●6 ●32 http://www.resustain.com

I have been trying to control the Night Cycle Availability Manager recently and I noticed that when the night cycle controls the fans to cycle on it ignores the minimum flow rate input in the fan object and will cycle on to as low a flow rate as it feels is necessary to condition the space. My fans however, in the design can not cycle that low and have a minimum flow rate. Is there a way to ensure the night cycle availability schedule also obeys the inputs into the fan object? or am I not programming the night cycle availability schedule correctly?

As always many thanks to everyone in advance for their help.

Annie

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answered 2016-06-09 22:19:57 -0600

Chandan Sharma

2442 ●1 ●2 ●9

Night cycle manager only overrides the fan schedule value (only if that is Off) to On when zone conditions are favorable. It doesn't determine air flow rates. Timestep or Hourly reporting produce average output values which can easily be misleading and Detailed frequency reporting is the best way to review outputs here. For example, when the fan is made available by night cycle manager, it remains on for entire "Cycling Run Time", then the fan is off for entire zone time step (15 min if Timestep input is 4 and 10 min if Timestep input is 6 etc.). So hourly reporting in this case could easily be misleading. Another way to verify whether night cycle is performing as expected is to report output variable, Availability Manager Night Cycle Control Status along with controlled zone mean air/thermostat temperatures at detailed frequency. If the outputs are not looking as expected, will need to take a closer look at the inputs/results if you can send the idf or attach it here.

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Thanks Chandan, I will look at detailed reporting, I was reporting timestep (15 minutes) and my night cycle was on a 900 second cycle time but I found a few other weird results as well so I will try detailed reporting and to report out night cycle control status.

Annie Marston ( 2016-06-10 08:13:19 -0600 )edit

Number of Timesteps per Hour specified in the Timestep object should also be kept in mind when reviewing the outputs in detailed frequency. Once 900s (15 min) of cycling run time is over, the fan may remain off for (60/Number of Timesteps per Hour) minutes. After that if night cycle manager determines that controlled zone temperature requires the fan to be On again, the above cycle continues. All of this can be seen in output csv file using appropriate report variables. Night cycle can only make the fan to be on, it can not make it off if the zone temperatures.are beyond limits.