Cooling fans won’t stop running on transformer secondary side??

[electrolyte]

We have (4) identical EATON 2500kVA transformers equipped with a QUALTROL 118ITM monitor and the cooling fans on one are stuck in the running position, on the secondary side only.

The transformer is currently in service but some after doing some voltage checks on TB2 at the controller; voltage was found across 5 and 8 but not 1 and 4 which indicates to me that a relay contact is stuck closed somewhere.

Winding temperatures were well below the set point, somewhere around 40C. We can’t take an outage right now to investigate any further but can someone confirm that we are on the right track with our troubleshooting? Sorry for the cruddy picture, it’s attached for reference.

[lester mcmanaway]

at a glance it looks like you should have power at 3+4 and 7+8 always. When the temp. threshold is met the contacts on 1+4 and 5+8 should close completing your fan circuit and energizing the sets of fans. If you de energize the fan controller and put a ohm meter across 5 + 8 it should read open, if not your internal contacts are stuck shut. my 2 cents