kengineering
22-02-2018, 10:30 PM
Hi guys,
We have been building this model display case for years. Copeland has retired the condensing unit we had been using and recently replaced it with a new model. Other than the new condensing unit, nothing has changed. I say this with regard to all aspects of the case including evaporator, piping and controls. We have built a few cases with this new unit without issue.
It is a 1/2 hp. 404A Copeland reciprocating condensing unit. 115Volt / 60hz. Cap start/ induction run. It is brand new out of the box from Copeland.
The problem;
At the initial start-up there are no issues. Cycling through the initial pull-down the t-stat preset temperature is satisfied and the unit cycles off. Everything about this initial cycle is as expected. The operating pressures are as we expect and even the sound of a running cycle is fine. When the t-stat calls for the second cycle and subsequent starts thereafter, the external over-load trips a few times before compressor starts. Unplug the unit for half an hour or so and the above scenario repeats.
What is known;
Ambient Temperature 68°f
Supply Volts, 116V
Running Volts, 116V
LRA 39.5A specs are 40.0A
RLA 9.8A specs are 10.0A
Discharge PSIG 210 running
Suction PSIG 55 running
Windings; run .8 start 3.8
My first thoughts are to just replace the start components, so that's exactly what I did. Cap, Relay and O/L. Same issues.
It is a TXV system and although the charge is standard for us and head wasn't high, I reduced the charge. Same result.
Thanks for letting me pick your brains.
Ken
We have been building this model display case for years. Copeland has retired the condensing unit we had been using and recently replaced it with a new model. Other than the new condensing unit, nothing has changed. I say this with regard to all aspects of the case including evaporator, piping and controls. We have built a few cases with this new unit without issue.
It is a 1/2 hp. 404A Copeland reciprocating condensing unit. 115Volt / 60hz. Cap start/ induction run. It is brand new out of the box from Copeland.
The problem;
At the initial start-up there are no issues. Cycling through the initial pull-down the t-stat preset temperature is satisfied and the unit cycles off. Everything about this initial cycle is as expected. The operating pressures are as we expect and even the sound of a running cycle is fine. When the t-stat calls for the second cycle and subsequent starts thereafter, the external over-load trips a few times before compressor starts. Unplug the unit for half an hour or so and the above scenario repeats.
What is known;
Ambient Temperature 68°f
Supply Volts, 116V
Running Volts, 116V
LRA 39.5A specs are 40.0A
RLA 9.8A specs are 10.0A
Discharge PSIG 210 running
Suction PSIG 55 running
Windings; run .8 start 3.8
My first thoughts are to just replace the start components, so that's exactly what I did. Cap, Relay and O/L. Same issues.
It is a TXV system and although the charge is standard for us and head wasn't high, I reduced the charge. Same result.
Thanks for letting me pick your brains.
Ken