Supply air temperature as a function of exhaust air temp?

[KarinaA]

Hi all,

So, I am trying to model a room (or actually a bunch of rooms) in version 6.0.4, where the room supply air temperature is varying according to the exhaust air temperature. It can be described in the following way: if the exhaust room air temperature>22 degC, the supply air is 18degC, else 20degC) The building has quite large internal- and solar gains so the room air temperature gets heated up quite much.

I'm a bit confused about how to put the controllers in order to get it right. What I wan't to do is to control a cooling coil according to the room exhaust air temperature, but the controller (independent controller with sensor) don't seem to accept any modulating profile that includes room air temperature (ta) as a variable. It is defined now so that the controller is ON if ta>22. This does not work. Neither for any other room variables. I have put the sensor directly downstream of the room. How can I control this in order to get it right?

Thanks!

/Karina

[JosephG]

You can do this with an independent controller with sensor, the sensor being located downstream of the room (IESVE makes no distinction between the exhaust temperature and the room temperature) and control point downstream of cooling coil.

Variable being controlled: Dry-bulb temperature
Dry bulb temperature at maximum signal: 18

Proportional control: active
Midband variation: constant
Midband (°C) : 22
Proportional bandwidth: 0
Dry bulb temperature at minimum signal: 20

Don't use Apache Profile equations here. To my knowledge the only Apache Profile outputs that APHVAC accepts are on a time switch profile. This should work, let me know if it doesn't.

[IanogPM]

Hi, I am having the same problem. the system that i am using is a simple CAV system on full re-circ, is there a way of the ApacheHVAC app calculating the supply air temperatures required to keep the room at a steady temperature?

Thanks,
Ian

[david373348]

For me, even if the sensor is placed downstream the control stills work with outside temperature,

Regards,
David Garcia