IES-VE User Forum

Hi everydoby,
I have two questions related to ApacheHVAC:

1. What would be the best way to model a heating or cooling controller that adjusts the water flow rate on the coil depending on the room air temperature? I see there is not such a "variablew being controlled". I also read on the manual that for coils controller it is suggested to not control the heat transfer and that the controlled variable should be the off-coil temperature. What is exaclty meant by "off-coil temperature"? Why do the heating and cooling coils controllers used in the FanCoil HVAC scheme template have the same minimum and maximum values?

2. I tried run a simulation and I got the following error message: "Error: Invalid node ID in the controllers to network map (ccn file). Node '0/' is not present in the HVAC network"..any idea what this could be? I checked the network before trying to run the simulation: it didn't flag any error and there was no node 0.

Thank you in advance for any advise you could give me.

Bets

#1.a What would be the best way to model a heating or cooling controller that adjusts the water flow rate on the coil depending on the room air temperature? I see there is not such a "variablew being controlled".
#1.b I also read on the manual that for coils controller it is suggested to not control the heat transfer and that the controlled variable should be the off-coil temperature. What is exaclty meant by "off-coil temperature"?
#1.c Why do the heating and cooling coils controllers used in the FanCoil HVAC scheme template have the same minimum and maximum values?

#2 I tried run a simulation and I got the following error message: "Error: Invalid node ID in the controllers to network map (ccn file). Node '0/' is not present in the HVAC network"..any idea what this could be? I checked the network before trying to run the simulation: it didn't flag any error and there was no node 0.

#1.a Water-side thermal simulation is not supported by ApacheHVAC. I'd consider another simulation package if it's really needed, but unless you're doing thermal simulation of the heating coil itself I'm not sure what that's going to achieve. You don't have to replicate every last feature of every piece of equipment, most times the "black box" approach is sufficient.

#1.b Off-coil temperature is the air temperature immediately downstream of the heating / cooling coil but before the fan. It is not the outlet temperature from the AHU.

#1.c Because you're expected to change the controller values from default.


#2 ApacheVAC sometimes behaves in weird ways and the error messages are useless in figuring out the problem (that being said, it's much better than it was a few years back). In such a situation, what works for me is creating a new version and deleting branches of the system, and trying it until it works. When it suddenly works I know where the problem is, and it's usually my error or (another) bug in the software.