[TRNSYS-users] Type 56 with AHU

[Jean Marais <jeannieboef@gmail.com>]

Dear Group,

I'm stuck with a fundemental catch22. I report QSENS, the heating/cooling DEMAND from the building object Type 56. This, however does not report the demand, but instead the minimum of the demand and available "power". This means when, eg. "heating power" is set to 0, QSENS will report zero and when set to "unlimited" QSENS will report the actual demand to hit the defined setpoint.

Going on to the zone...The cooling heating setpoints can only be assigned to the zone to do the previous calculation QSENS for the zone, when the heating/cooling is clicked "on".

Thus, the actual demand for the zone QSENS can only be read out when the limit is set to "unlimited" and the heating/cooling is set as "on".

HERE'S THE CATCH:
I used QSENS to tell my AHU how much it should try and heat/cool. I send the resulting air into the zone which could be anything and does't matter, because even if the AHU can't meet the loads (or there is a power failure and the AHU is off for 2 hous), the resulting air temperature will never go outside of my heating/cooling setpoints (20/26), because unlimited cooling energy exists in the zone. This again is bad as the extracted air from zones is read from the building to be no higher than 26, which affects the heatexchanger, economizer, etc.

At the moment I don't see a work around. The best I can do is report when the AHU Q does not meet the sum of zones Q at which point the simulation becomes "inaccurate".

pls. advise,

Kind regards,

JEAN MARAIS