ACRD502 doesn't react to PID settings changes

[Andrej_Korshikov_apc]

This was originally posted on APC forums on 2/26/2016

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One more question about ACRD502 🙂

So, we have two ACRD502 joined to cooling group (in fact, there are 6 units in cooling group, but 4 of them are in "Standby" mode because of insufficient heat load, and only two cooling units are "On").

Configuration type: HACS; Max Fan Speed: 65%; Supply Air Setpoint: 18.0 C; Fan Speed Preference: Medium. There are no warnings or critical alarms, and heat load is constant (return air temperature is 29..30 C). AOS: v3.7.5, Application: acrp v3.7.5.

I have changed P, I and D constants from 0 to 255 (well, I've tried something like 0, 0.5, 1, 10, 100, 200, 250 in different combinations), and I've seen absolutely no effects.

Every time when I've changed PID constants, I've adjusted the supply air setpoint from 18.0 C to 17.0 C or vice versa.

There was no temperature oscillation, and plots of temperature changing were identical irrespective of PID constants.

In what environment ACRD502 PID settings do have sense? May be with more heat load, or with RACS or In-Row configuration type?..

[BillP]

This reply was originally posted by L2SupportServices-Cooling on APC forums on 2/26/2016

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Hello Andrej. We never recommend changing the PID settings on the unit. Is there something you are trying to achieve on these units? Which temperature sensors are you trying to monitor?

Thank you

[Andrej_Korshikov_apc · Accepted solution]

This was originally posted on APC forums on 2/29/2016

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I'm not trying to achieve something special. Just read at the "Operation and Maintenance" manual that "The loop should be tuned periodically to
account for changes in the room load." The room load was significantly changed, so I thought it might be useful to tune the PID loop.

I monitor the Supply Air temperature.