The warning is telling you that the PTAC is operating in cooling mode when it is -3C outside. Creating a different performance curve will not eliminate the warning (although we should make this a recurring instead of printing thousands of them). What is means by special performance curves is that manufacturers do not provide cooling performance data at these cold temperatures, you need to assure yourself that the curves you are using are accurate at the cold outdoors temps.
DX equipment can have difficulty circulating oil at these temp's which can cause the compressor to fail. It won't fail in the simulation, but it might in a real building.
Although it is possible to need cooling during cold winters, it seems unlikely. For example, an economizer could be used instead. Or if cooling is required, a water-cooled condenser could be used.
You need to determine what in your simulation causes the zone(s) to request cooling. Equipment/lighting loads, ground temperature in contact with the slab, etc.
On 5/8/2013 11:06 PM, Sankey, Maxim L
wrote:
Hello,
I keep getting this error for each zone thousands of times per simulation. I'm using the HVAC PTAC Template. Is there a solution besides creating a performance curve? In the same building I'm getting unrealistic heating energy demand (almost zero). Could these warnings be the source of my low heating loads?
** Warning ** CalcDoe2DXCoil: Coil:Cooling:DX:SingleSpeed "FLOOR 5 CORRIDOR PTAC COOLING COIL" - Air-cooled condenser inlet dry-bulb temperature below 0 C. Outdoor dry-bulb temperature = -3.35
** ~~~ ** ... Occurrence info = RUN PERIOD 1, 01/01 00:00 - 00:10
** ~~~ ** ... Operation at low ambient temperatures may require special performance curves.
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