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[EnergyPlus_Support] Re: How does unit ventilator work

Firstly, don't get discurraged. What you are trying to do is not as easy as it sounds.

Now describe your systems. usually the radiant floor cooling system will run on a water loop with plant exiting temp 18 deg C and a dT of about 4 Kelvin. Your cooling coil in the unit ventilator should be on a different plant loop running at 6 deg C with a dT of 6 K.

This is typical for a German system.

If you are intending air delivery temperatures of 18 deg C, you may find that the required air changes become too much, meaning additional cooling may be required in the zone with like a circulation fancoil unit.

The controller is minimizing the ODA, because it expects recirculation of cool zone air. As you have DOAS, there is no recirculation and so the air coming in cold is not enough to battle the loads. I think this is where it's getting messed up.

Do some rough hand calcs to see how much air you expect and at what delivery temp and then monitor your system. It may be that eplus autosizing is not going to work for you.

PS I would bear in mind that cold air often needs to be reheated. For fancoils usually 14-16 deg C is a delivery air temp, but for AHUs usually not colder than 18, and usually at Setpoint is better.

hope this helps.



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