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CCA
06-08-2013, 08:32 AM
So normally, the big fan on the top of our walk-in cooler will cycle on and off along with the condenser. But we are currently having a problem where the fan runs continuously - it never shuts off! The condenser still clicks on and off as necessary to control the walk-in temperature, but the big loud fan never stops. When the fan is incorrectly stuck in the ON condition, I can tap the big metal control box next to the fan and it will stop. So whatever is responsible for stopping the fan is sticking somehow, and when I hit it, it releases and stops the fan.

Can anyone clue me in as to which component I need to replace to solve this problem?

Thanks!

Scott M
06-08-2013, 01:16 PM
You have a sticking relay contact or contactor. Try opening the control box while the fan is running, thump the box and watch to see what component disengages. If you cannot determine which relay in the box is the problem, call a technician. The condensor fan will usually come on either with the compressor or as a function of the discharge pressure of the compressor. Good Luck....

gitchegumee
06-08-2013, 08:41 PM
I think you mean to say compressor when you write condenser. Condenser is a heat exchanger that doesn't turn on and off. Is this fan inside or outside the cold room? Inside is the evaporator. Outside and typically mounted on a skid is compressor/condenser. Inside evaporator fans don't turn off. Outside turns off with compressor. Which itself is controlled by refrigerant pressure. Either way, if you have to knock something to make it work, you have a faulty electrical element somewhere. Should be easy to track down and replace. If it's your single phase condenser fan, it maybe the auxiliary relay contact that is coupled to the three phase compressor contactor. Good luck!

CCA
06-09-2013, 11:32 AM
Thanks for the help guys. Philip - I'm talking about the fan on the outside that normally cycles on and off with the compressor.

Here's a photo of the contents of my control box:

http://goo.gl/rnyA5

To me, it doesn't look like I have an auxiliary relay for the fan, just the three phase contactor at the top of the photo. Here's a close-up:

http://goo.gl/Lyt1P

Should I replace the entire component, or is there something else I could do? (spray some WD-40 on the sticking contact?)

Starcat
06-09-2013, 12:04 PM
Most likely this is a sticking fan cycle control. They are usually made by ranco, penn, or danfoss. If you follow the line wiring to the fan motor in question, it will be switched through the control I am describing which is a small grey, black or white box which has a copper tube that ports to the compressor high side in one of many possible locations.
This is a refrigerant side control and has to be correctly calibrated when replaced. It is not really a lay persons repairas it deals with a live refrigerant line which operates the control. This failure is common.

Scott M
06-09-2013, 12:26 PM
From just looking at the wiring to your Main Contactor, C1; the fan may be wired directly off the load contacts for the compressor.....

How far away from Oregon are you?

CCA
06-09-2013, 02:42 PM
Scott - I'm in Southern California, so not very close to Oregon. ;)

Yes, I think the fan is wired to the same contacts as the compressor -- i.e. in the photo, I think the three power lines (3-phase) come into the top of the contactor, then the two smaller gauge wires for the fan motor come off of the right and left taps on the bottom of the contactor. The bank of two fuses on the right go to the fan, and I'm assuming the bank of three fuses on the left go to the compressor. So if the compressor is cycling fine but the fan is not, the contactor should be ok right. So maybe Warren's suggestion of the "sticking fan cycle control" is correct. I haven't yet seen the component he describes - it's not inside the same control box. I will look the next time I am at the brewery.

Thanks again guys.

gitchegumee
06-09-2013, 04:07 PM
Doesn't look like you have auxilliary contacts off the main set. This looks like you have a 220v 3 phase compressor and a 220v "single" phase condenser fan motor run through the same contactor, but fuse-protected separately. If this contactor shuts the compressor down, seems like it should shut down the fan. Do you have an electrical schematic? The wires seem to be labeled well. Should be a simple problem. If you are not comfortable with a tester, then it looks like you could use an electrical/refrigeration technician for an hour. Good luck!

Scott M
06-09-2013, 07:21 PM
Easy fix....Replace C1. Not only are the contacts that drive the fan fusing (sticking) together, they are probably single phasing the Compressor. I would do it ASAP....

SoCal...Only 18 hours away..... :-)