IES-VE User Forum

Hi there,

I have a model using mixed mode with ApSys and Macroflo natural ventilation where the windows opening profile is set to a formula profile that:

• opens the windows when the temperature outside is less than the temperature inside, and
  the room temperature exceeds 23°C.

The cooling is set to 24°C and the heating is set to 22°C to provide a deadband between the modes.

However, the heating is being triggered by having the windows open!
How can I avoid the heating being tricked into running every time the windows open? Would proportional window opening help?

See below graph that demonstrates this



TIA
Garreth

The default reporting interval in IES is set to 1 hour, but the simulation time step is something like 10 minutes.

In other words, every hourly result you see is actually the average of 6 results you do not see (which could be wildly going up and down).

What is likely happening here is that the windows are opening at 23C and a large quantity of air enters the room, making the temperature drop below 22C and making the heating spike hugely to compensate. This is probably happening every few minutes but the averaging of the results masks what is really going on.

When you run the simulation, change the time step and the reporting interval to the smallest they can be and then look at the results. I suspect it will show you a very different picture.

Assuming you are seeing this wild variation then potential fixes could be to add a gentle ramping function to your window openings or possibly increase the size of the deadband or even limit the heating capacity of your room emitters so that your system doesn't 'overshoot' and start fighting with the window openings.

CP