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  1. #1
    Join Date
    Feb 2007
    Posts
    81

    Complete Frustration

    Had a call today "Temps up in freezer". The freezer has an older evap with a history of blowing heaters. Found the evap frozen right through to the fans. Spent a few hours to clear all the ice with water as the heater fuses were blown and I couldn't use them at this point. Once all ice was cleared I looked first to see if there was one that was visually obvious that it was burnt. No luck. So I get out my meter and start ohming them out and Im getting some very high readings to ground on almost every one which I do see often with my meter. Side note I quite often can pick up readings to ground with my meter and still have motors run fine. So as this seemed to be getting me no where because they all have some sort of reading I get out my megger and test them. I found 13 of 18 heaters registered BAD and 2 in caution range with only 3 in the high end of GOOD. WTF . So now I only hook up one side of heaters and run them with new fuses and everything seems ok even though the majority of them were BAD Anyways my frustration is I know my megger is good and I have seen this before a few times but it can really mess you up and piss you off when you are trying to find the badest of the bad heaters

  2. #2
    Join Date
    Jul 2011
    Location
    Lehigh Valley, PA
    Posts
    427
    Did you test resistance readings of the heater coils themselves and compare to manf spec?? End to end with at least one end disconnected? Is the incoming voltage high? Higher volts increase amps in a heater circuit. Single phase or 3 phase? Delta or Y? If it's 3p on the roof, single in the evap, maybe you are on the stinger leg if a Delta configuration. Just a guess on my part? Bust still shouldn't add too much extra current. Also check for corrosion connections. This will add current too or could.

  3. #3
    Join Date
    Jun 2009
    Location
    DFW, TX
    Posts
    664
    Checking to ground can be misleading when everything is wet.

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