DOAS input Problem
I have started my simulation and It shows the following warning and I am not sure what is it and what to do about it. I have trying to set up a DOAS System
First of all, I am not very sure what are these errors come from and how can I solve it?
** Warning ** SimHVAC: Maximum iterations (20) exceeded for all HVAC loops, at HONG KONG SAR CHN CityUHK-45007 WMO#=450070, 01/01 03:15 - 03:30
** ~~~ ** The solution for one or more of the Air Loop HVAC systems did not appear to converge
** ~~~ ** Air System Named = DOAS did not converge for mass flow rate
** ~~~ ** Check values should be zero. Most Recent values listed first.
** ~~~ ** Demand-to-Supply interface mass flow rate check value iteration history trace:
0.421904,0.571668,0.774595,1.049554,1.422117,4.239839,0.421904,0.571668,0.774595,1.049554,
** ~~~ ** Supply-to-demand interface deck 1 mass flow rate check value iteration history trace:
0.421904,0.571668,0.774595,1.049554,1.422117,0.311375,0.421904,0.571668,0.774595,1.049554,
** ~~~ ** Air System Named = DOAS did not converge for temperature
** ~~~ ** Check values should be zero. Most Recent values listed first.
** ~~~ ** Demand-to-Supply interface temperature check value iteration history trace:
3.462632E-002,2.555499E-002,1.886016E-002,1.391922E-002,1.027269E-002,0.103233,3.462632E-002,2.555499E-002,1.886016E-002,1.391922E-002,
** ~~~ ** Supply-to-demand interface deck 1 temperature check value iteration history trace:
2.555499E-002,1.886016E-002,1.391922E-002,1.027269E-002,0.103233,3.462632E-002,2.555499E-002,1.886016E-002,1.391922E-002,1.027269E-002,
** ~~~ ** Air System Named = DOAS did not converge for energy
** ~~~ ** Check values should be zero. Most Recent values listed first.
** ~~~ ** Demand-to-Supply interface energy check value iteration history trace: 9612.881052,13025.189533,17648.773708,23913.603146,32402.274792,96602.722233,9612.881052,13025.189533,17648.773708,23913.603146,
** ~~~ ** Supply-to-demand interface deck 1 energy check value iteration history trace: -9612.881052,-13025.189533,-17648.773708,-23913.603146,-33006.735202,-7094.521112,-9612.881052,-13025.189533,-17648.773708,-23913.603146,
My next warnings are the following. As This is a DOAS System I am not sure how to adjust the input to Energyplus
Yes, !- Use Outdoor Air DX Cooling Coil
7.2; !- Outdoor Air DX Cooling Coil Leaving Minimum Air Temperature {C}
The maximum Outdoor Air DX Cooling Coil Leaving Minimum Air Temperature is 7.2C But What If my leaving air temperature is larger than 7.2? Can it still be a DOAS Coil?
** Warning ** CalcDoe2DXCoil: Coil:Cooling:DX:SingleSpeed "DOAS COOLING COIL 1" - Full load outlet air dry-bulb temperature < 2C. This indicates the possibility of coil frost/freeze. Outlet temperature = -1.12 C.
** ~~~ ** ...Occurrence info = HONG KONG SAR CHN CityUHK-45007 WMO#=450070, 01/02 08:00 - 08:04
** ~~~ ** ... Possible reasons for low outlet air dry-bulb temperatures are: This DX coil
** ~~~ ** 1) may have a low inlet air dry-bulb temperature. Inlet air temperature = 16.701 C.
** ~~~ ** 2) may have a low air flow rate per watt of cooling capacity. Check inputs.
** ~~~ ** 3) is used as part of ...
I don't have an answer, but just wanted to point out that this is occurring during your design day sizing, rather than during the actual RUN PERIOD. You may be able to safely ignore this warning.
Is it just me or the two drawings you inserted don't match? (on the second one, the area around the heat pipe doesn't make much sense: missing supply air, outdoor air not labeled right and not in correct location and exhaust air arrow is in the wrong direction)
(Also, I've never seen such a system with -4°C outlet conditions after DX coils. I'm curious, what application is that?)
Anyway, can you post the full idf or at least the sections where you defined your coils and heat pipe?