CGAF chiller head pressure swings

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11-13-2012, 09:08 PM
randystoker

CGAF chiller head pressure swings

I have a Trane R-22 60-ton CGAF chiller w/ 2 refrigerant circuits with 3 fans for each and the first-stage condenser fans have motorized dampers. It was working okay until the weather cooled down recently. I had a service call to the chiller this morning and circuit #1 was off on low pressure trip and circuit # 2 was off on "compressor trip". When I started the chiller, circuit # 1's head pressure rose up above 320 psig before the 2nd & 3rd condenser fans came on and then the 1st condenser fan damper opened. Then the head pressure dropped rapidly down to 155 psig, then rose above 320 psig (swung back & forth) . Tried activating circuit # 2 to get chilled water to the bldg and it had similiar symptoms with the pressure rising slightly above 300 before the 2nd & 3rd condenser fan on and the damper for fan # 1 opened up. Then the head pressure dropped down to 155 psig and display read "compressor trip" for that circuit. Does anyone have any suggestions? I tried adjusting the head pressure ctrl on the display to the same settings as two other CGAF chillers nearby, still have the big swings.
11-13-2012, 09:30 PM
r404a

randy

was a bulletin on this, may have to wire a pressure switch in parrell with the output from the board on that first fan to get it to activate sooner. will try to find that bulletin
11-13-2012, 10:03 PM
jayguy

there are a bunch of settings that could have been changed in the HI...Low Ambient Maximum Stroke, Low Ambient Minimum and Maximum Voltage and Low Ambient Acting, Saturated Condenser Temp Control Band (Lower and Upper Limit), Temporary Low Limit Suppression, Low Ambient Control Point, Low Ambient Control Deadband...what are they set at?
11-13-2012, 10:23 PM
Sicofthis

Did you hook gauges up or get pressures from display?
11-13-2012, 10:28 PM
randystoker

I hooked gages to both circuits. I did notice on the circuit # 1 that had the biggest swing, there was a discrepancy between what the gage indicated and what the display showed. (the display showed 20 psi lower on the high-side saturation pressure).
11-13-2012, 10:36 PM
randystoker

Here is some of the info. requested: Saturated condenser temp. ctrl band, Lower limit--85F, upper limit--110F, Low limit suppression--10F, efficiency check point--100F, low ambient ctrl point--80F, low ambient ctrl deadband--4.0F, O.A. temperature setpoint--40F,
11-13-2012, 10:59 PM
Sicofthis

Lol more questions.
What was outdoor temp and was display reading it correctly?
11-14-2012, 04:41 PM
jayguy

Quote:

Originally Posted by randystoker

Here is some of the info. requested: Saturated condenser temp. ctrl band, Lower limit--85F, upper limit--110F, Low limit suppression--10F, efficiency check point--100F, low ambient ctrl point--80F, low ambient ctrl deadband--4.0F, O.A. temperature setpoint--40F,

several items are set lower than the defaults, why? upper limit default: 125F, Check Point: 110F, Low Ambient Control Point default: 100F

you did make sure that all of the dampers are moving from full open to full close right? and they are open with a high pressure and closed with a low pressure, right?