[TRNSYS-users] Type 56 with AHU

[Jean Marais]

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
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