Liebert condenser with a P66 speed controller

[mikeul]

Went to a site today and found a Liebert condenser with 2 motors: 1 single phase motor which is normally controlled with a JCI P66 series speed controller and a 3 phase motor which is controlled by outside air temp. Over the weekend, the single phase motor died and someone hooked up the 3 phase motor to the P66 controller--and it is still running! I took current reading and it is slightly high <10%.

According to the P66 literature, you cannot use on a 3 phase motor. How is this motor working?

[allstar08]

When you figure it out let me know. I have never seen it done. Is the cap wired in? Does the speed change with an increase in pressure?

[flange]

guessing they wired it up as single phase and then helped start the fan manually. it will run for a while, but thne it will fail and they will need two new motors.

[RuralSpaceman]

Gonna need two motors soon!

[pecmsg]

Before you go changing motors, I had an APC system with Heatcraft condensers. 1 3ph fan controlled by OAT stat and 1 1ph fan controlled by P-66. 2 winters in a row I would get an after hrs call the unit is down on high head safety. By the time I got there reset the safety, everything worked fine. Both APC and Heatcraft got involved. Final speculation during cold operating conditions with the right wind speed and direction the p-66 would ramp to low causing the motor to over heat and cut out on thermal. There solution, install a P-70 inline with the start signal on the condenser.

Give me a headmaster anytime!

[kaptnkirk]

This has happened twice to me in the last 6 months on a Liebert. Running fine at the moment and not throwing parts at it.

[mikeul]

I went back and replaced the single phase motor. As far as the 3 phase motor, L1 was feeding through P66 serving as 1st ph, L2 was 2nd ph, L3 was fed from capacitor off of L2.

I rewired appropriately, checked amp draw and all seems to be normal for now.

[kaptnkirk]

pecmsg...Can you be more specific on the P-70???