Air volume flow rate per watt of rated total cooling capacity is out of range at 6.741E-005 m3/s/W

The Coil Final Gross Total Capacity is 25799.329 Watts. And the Coil Final Reference Air Volume Flow Rate is 1.038939 m3/s. Dividing 1.038939 by 25799.329 gives 4.02700008E-5. But why does the warning in energyplus say "Air volume flow rate per watt of rated total cooling capacity is out of range at 6.741E-005 m3/s/W"

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653

Siv

asked 2018-09-17 03:30:54 -0500

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__AmirRoth__

updated 2018-09-17 07:14:46 -0500

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Is this a sizing warning, or a warning during the simulation which has a timestamp? If so, look at the timestep output for flow rate and coil load.

MJWitte (2018-09-18 16:33:25 -0500) edit

Lets say, this is a recurring warning during simulation, I was able to divide the flow rate by capacity and equate it. However, could you please tell me how to overcome this issue ? What is the solution to this problem ?

Siv (2018-09-18 22:54:33 -0500) edit

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I was able to resolve this error by using the setpoint manager "Setpoint Manager Single Zone One Stage Cooling" previously I was using "Setpoint Manager Single Zone Cooling" Could someone explain why this is happening ?

653

Siv

answered 2018-09-19 05:56:11 -0500

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We need to know more about the rest of the HVAC system in order to help. What kind of air terminal units, airloohvac components, etc. Or just post the full idf.

MJWitte (2018-09-19 10:09:16 -0500) edit

I have used "Setpoint Manager Single Zone Cooling" for Thermal Zone 1 and "Setpoint Manager Single Zone One Stage Cooling" for Thermal Zones 2, 3 and 4. The Warning regarding "Air volume flow rate per watt of rated total cooling capacity"occurs only for the COIL COOLING DX SINGLE SPEED 1 which serves Thermal Zone 1. Kindly help me why this occurs and I have added a link to my model as well as the climate file.

https://drive.google.com/open?id=1x9r...

Siv (2018-09-19 23:20:21 -0500) edit

These warnings can be overly protective at times. The warnings use the System Node Current Density Volume Flow rate divided by the rated capacity. So, the value will vary as the inlet conditions change. This model has just a few warnings and the max value is only slightly above the range. I would just ignore the warnings

MJWitte (2018-09-25 13:54:47 -0500) edit

I understand, however how does the warning not appear when I change the setpoint manager to "Setpoint Manager Single Zone One Stage Cooling" ?? this is what is confounding me

Siv (2018-09-27 04:51:26 -0500) edit

That's a difficult question to answer without running both cases in debug mode to check values. Based on a check of the source code, the air volume flow rate for this warning is calculated from the mass flow rate using the density at coil entering conditions. These conditions will change with the two different setpoint managers. I wouldn't be concerned about these warnings.

MJWitte (2018-10-04 14:42:43 -0500) edit

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Air volume flow rate per watt of rated total cooling capacity is out of range at 6.741E-005 m3/s/W

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Air volume flow rate per watt of rated total cooling capacity is out of range at 6.741E-005 m3/s/W