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A newer system out there cycles the heaters during a defrost based on temperature rise of the coil. This wil avoid the scenario Bunny describs. If there is little or no ice, the heaters don't have a place for their heat to go except to raise coil temps too high. Sure, the terminator will pick it up sooner or later, but if it is on a return bend outside the tube sheet it is likely to be later than sooner. The heaters may also run cooler and last longer in this mode.

sorry mspanky- I was looking to find out what krams problem ended up being.

Originally Posted by floodedstart

Did you ever get to the bottom of this issue? I have the exact same situation right now with Krack MS evaporators and would like to hear your solution.

The factory wired the heaters wrong, that was the problem.

Defrost heater failures

Did you ever get to the bottom of this issue? I have the exact same situation right now with Krack MS evaporators and would like to hear your solution.

Originally Posted by Fridge Repairer

I just happened to be up on a lift once when a unit went into defrost. 2 of the heaters glowed cherry red. It turned out the heater were wired in parallel instead of series.

Check your wiring carefully.

Same problem here except it blew multiple holes through the coil.

I just happened to be up on a lift once when a unit went into defrost. 2 of the heaters glowed cherry red. It turned out the heater were wired in parallel instead of series.

Check your wiring carefully.

look up heatcraft sdk controls, these will skip a defrost cycle when possible and will pay for themselves quickly. I use these a lot on many brands of equipment with no issues.

Originally Posted by krams

We are having seroius defrost heater failure on many Krack freezer evaporator defrost heaters. The units are in a 40,000 sq-ft freezer so there are about 14 evaporators here. We have replaced at least 100+ thousands of dollars on the replacement. Krack says it is a humidity issue which is not possible in our view. We believ it is fauly design! Please live me any field examples or feedback you may have? Tim Kramer

I've had experience in an application where there is very little or no frost on the evaporator....this combined with faulty defrost termination so that when the heaters are energized they get much hotter than designed for since there is no ice to melt...and they cook themselves to the point of burning up.

I've only had 2 heaters fail on 26 plus coils installed and I think I burned those up on startup due to miswired termination. I know those big coils are a pain to diagnose which heater is bad. I hope units are wired in seperate conduits to prevent wiring screw ups. Does each condenser have only one evap? If more than one evap it must have multiple defrost contactors and be properly terminated ( control each evap). Start by verifing wiring first. Kramer says humidity issue, are the wiring harnesses burning out or the heaters?

Does the defrost termination work properly? Improperly working termination can cause premature failure of heaters due to unnecessary overheating.

maybe 208V heaters on a 240V supply?

What exactly is the failure? Resistance loads are pretty reliable unless wired wrong, as in Delta or Wye.

Krack Industrial Refrigeration Defrost Heater Issues

We are having seroius defrost heater failure on many Krack freezer evaporator defrost heaters. The units are in a 40,000 sq-ft freezer so there are about 14 evaporators here. We have replaced at least 100+ thousands of dollars on the replacement. Krack says it is a humidity issue which is not possible in our view. We believ it is fauly design! Please live me any field examples or feedback you may have? Tim Kramer