Re: [EnergyPlus_Support] Warning Message: air volume flow per cooling capacity out of range

Hi, Brendan.

I don't have a specific answer that solves your issue.

I don't know either what to do when you get this error message when your capacities and airflows have already been sized. I hope some of this additional information helps and I wish you the best:

Error Message:

"rated air volume flow rate, total cooling capacity and sensible heat ratio yields coil exiting air conditions above the saturation curve. Possible fixes are to reduce the rated total cooling capacity, increase the rated air volume flow rate, or reduce the rated sensible heat ratio for this coil. If autosizing, it is recommended that all three of these values be autosized."

Design Builder Help:

- HVAC Sizing : Compact

"Tip: If you are using the Manual sizing option together with Compact HVAC and wish to use different cooling sizes to those obtained from looking at the output of previous EnergyPlus autosizing calculations (e.g . from eplusout.eio) you will need to ensure that the maximum supply flow is changed accordingly. If you increase the maximum cooling capacity but don't increase the Maximum supply flow rate (or even leave it as Auto) you will get "Rated air volume flow rate per watt of rated total cooling capacity is out of range" errors in the EnergyPlus simulation because the cooling capacity requested cannot be achieved with the specified air flow rate. Also due to a quirk in EnergyPlus, the Auto Maximum supply flow rate option does not work well with Manual sizing option and automatically calculated Maximum supply flow rates do not account for the 'higher than autosized' cooling capacity requested."

You might want to check these related previous E+ Yahoo Entries:

http://tech.groups.yahoo.com/group/EnergyPlus_Support/msearch?query=air+volume+flow+rate+per+watt+of+rated+total+cooling+capacity+is+out+of+range&submit=Search&charset=UTF-8

Francisco Minoyetti: Sustainability Assistant - Energy Simulation: Bovis Lend Lease S.A.
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2011/2/9 bcmcgr <bcmcgr@xxxxxxxxx>

"Rated air volume flow rate per watt of rated total cooling capacity is out of range."

I'm working on a LEED project using Design Builder and my Proposed model gets the above "Severe Error" when the model is run in E+. I can get around this by having Design Builder "autosize" my HVAC system but then when I check the HVAC system sizing output from E+ my sizes (capacities) are much less than the actual design.

It's important to note here that I'm modeling the minimum ventilation (outside air) per ASHRAE 62.1 (ie per person and per area) which is much smaller than the capabilities of the system.

Has anyone encountered this in the past? Should I just submit the model as if it's autosized?

And, of course, I'm being rushed to submit by Friday. Any help on this is much appreciated.

Thanks in advance.

Brendan