Carrier lock out problem

**zorrithod** · 09-08-2011, 10:42 AM

I am hving issues with a Carrier M.N. 38ah124a621da.
When it comes out of unoccupied, or free cooling, Unit will restart, then lock out. I have traced the problem to the oil pressure relay. I have checked my refrigerant levels, and all is well. I have discovered the oil pressure relay is locking the unit out. If I reset unit, and jumper across the relay for a minute, I then get control voltage, and am able to remove jumper. Unit then runs the rest of the day, cyclilng as it should until it goes into unoccupied, or free cooling. This is happening on both circuits. I have checked my oil pressure, and found it to be approx. 20 lbs. This is adequate according to my data sheet. I am wondering if I have an oil switch problem, or if the problem is in the timer motor. Any advice or help would be appreciated.

**coolerinfrederick** · 09-13-2011, 02:03 AM

are crankcase heaters working ?

**zorrithod** · 09-13-2011, 08:51 AM

The crankcase heaters are working. Thanks for responding. This has been an ongoing problem. Any suggestions are appreciated.

**Chris_Worthington** · 09-13-2011, 08:55 AM

The OD temps in the morning are when firing up for the day is?

It is more then likely a flood back on start up causing the lockout, you need to insure that anything that could cause this is addressed.... and

Should all those basis be covered, then consider adding a delay on make timer to the OP switch and give it another few minutes to get the ball rolling again.

Those Carlye compressors will be just fine with low oil pressure for a few minutes, them things are tough.

**zorrithod** · 09-13-2011, 09:37 AM

The OD temp. varies. This has happened when free cooling is disabled at 60 degrees. It has also occurred when the unit is shut down for load shedding. 100 degrees. It doesn't normally happen on free cooling. It seems frequent when the unit goes into unoccupied, or is shut down for any reason. This past winter, when weather began warming, unit was fluctuating between free cooling and normal operation, it transitioned as it should have. In order to avoild the problem, I leave the unit in occupied mode. It operates as it should when in this mode.

**Chris_Worthington** · 09-13-2011, 09:47 AM

It would seem that you liquid refrigerant is piling up in evaporator and causing the flood back on start up. Assuming that this has been a long time issue....

and

"If" what you say is true, one minute bypassed and as is swell, then I would consider up'ing the timing as previously suggested for your OP.

It's either that or your looking at major surgery to correct/prevent the momentary flood back.

**zorrithod** · 09-13-2011, 11:18 AM

Thanks to all for the information! This has been a big help. I will exhaust all of these possibilities, and see if this makes the difference. Thanks again. Zorrithod

**coolerinfrederick** · 09-13-2011, 06:53 PM

can you varify that the outside air dampers are closed when the compressors come on line

**HAWK 87** · 09-13-2011, 08:58 PM

I just had the Carrier class on the new veriable speed compressor today. The instructor mentioned somthing about this today. He said when it comes out of unoccupied, it will lock itself out (I think he said for 2 hours) to ensure the crank case oil is heated.

I hope this helps.

Maybe someone who was paying attention in the class will come along and clean this up for me.

**zorrithod** · 09-14-2011, 08:05 AM

I have verified that the dampers are closed when unit comes online.
When it locks out... It stays locked out until unit is reset by toggling the condenser fan circuit, or interrupting power.
I appreciate all the info.

**Tommy1010** · 09-14-2011, 05:40 PM

i wonder if you may be loosing oil pressure at night time when it colder out and the refrigerant velocity is at it's lowest

make sure the ambient temp fan cycle control is working if equipped with one

**zorrithod** · 09-15-2011, 08:02 AM

Tommy1010
My fan cycling switches are operating normally. The unit doesn't shut down when it's running. Only when it shuts itself down for free cooling, or if it goes into unoccupied, or we load shed. OD temp. doesn't seem to enter into the equation.
I thank you for your interest in helping me solve this problem.

Zorrithod

**partsonorder** · 09-15-2011, 10:11 PM

Is the outdoor unit above the indoor and if it is are there traps installed in the line set?

**Williamsma** · 09-15-2011, 11:27 PM

At the end of a call for cooling is it pumping down? What is your crankcase pressure prior to start up? When the compressor 1st starts up, what is the oil pump temp, is it cold? Even with operating crankcase heaters, refrigrant can still condense in the crankcase.

**zorrithod** · 09-16-2011, 09:03 AM

The condensing unit is on the ground. The evap. unit is elevated about 15-20 ft.
I haven't installed the delay on make timers yet. I have purchased them, but they are still on my desk. The unit has locked out on circuit 1 this morning. I will check the cc pressure, pump temp., and check to see if it pumps down after I reset the unit. Thanks for all the info.

**zorrithod** · 09-16-2011, 11:36 AM

The Crankcase temp. is 100.3 degrees f.
Crankcase pressure when unit is off is 105 psig.
Crankcase pressure when unit is running is 75 psig.
Unit shut down after 2 minutes, so I didn't notice a pumpdown.

**lafittejdubb** · 09-16-2011, 01:28 PM

I'm assuming you've already done this, however have you valved-off your compressors and cleaned all your screens and tested and removed and checked your attached oil pumps?

I only ask because you didn't mention it!

I've seen that long screen (pump inlet screen) on the bottom left of Carlyles appear clean from the outside but be filthy when you remove the sleeve.

**zorrithod** · 09-16-2011, 02:49 PM

I have not checked the pumps and screens on the compressors. I do have 20 plus psig on oil pressure. Thanks for the info. I will check into this.

**Williamsma** · 09-17-2011, 10:39 AM

I had a problem like this with a Trane self contained water cooled 25ton at a bank. During long off cycles, the crankcase would have refrigerant in it. At start up the compresser would loose oil pressure.
The compresser cc heaters worked but there was no pump down. The cc pressure was above the condensing temperature of the oil so during a long off cycle the refrigerant would condense in the crankcase. I made some wiring changes. I wired the control circut for compresser through the safties and low pressure control. I wired the liquid line solonoid so on a demand for cooling it would energize the valve. At the end of a cycle the compresser pumped down. I never saw this problem again. Hope this helps.