I have had this happen a couple times. First i would ask if you have a 2 stage Heat Exchanger? If so, you can heat water in the kettle, manually shut off the glycol to all of your other fermenters, and turn off the glycol chiller. Run only the gylcol side of the HE and heat up your glycol with the hot water, the hot glycol will heat up your fermenter.
If you only have a single stage HE, like i do at this brewery, it is possible to warm your glycol, but it's a little bit more tricky. Let me know if i can be of any assistance.
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