major RTU electrical issues!
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  1. #1
    Join Date
    Feb 2006
    Posts
    42

    Confused major RTU electrical issues!

    Hi,
    We own an outlet plaza with multiple RTU's.
    For some time now we have been experiencing components being fried on a regular basis, the likes of relays, transformers,wiring, phase protectors and motors.
    We initially related it to an unreliable utility supply so upon our techs recomendations, installed phase protectors on all the units.
    This has not resolved the issues at all and I am now doubting our initial theory as the only culprit.
    We recently lost power to one of the stores on two occasions (Feb 13th & 19th) resulting in replacement of fuses at the disconnect, and phase protector getting fried along with a few other components(relay, fuses, transformer and wiring) on the RTU.
    We had a similar issue at another store where they lost all three fuses at the disconnect (Feb 10th), and then a few days later the RTU was found to have a fried phase protector and ventor motor along with a few other burnt components (fuses and control board).
    An electrician that was called in seemed to think that it was the rooftops that caused the main fuses to fail? does this seem right?
    Any assistance would be much appreciated as this has been an ongoing problem for some time and is costing us a great deal of money!
    I have a great deal of respect for our various HVAC contractors, they are great guys and I dont doubt thier resolve, but it doesnt hurt to ask for another opinion.

    Yours truly.

    D.M.
    Last edited by davyboy; 02-21-2013 at 02:30 PM.

  2. #2
    Join Date
    Nov 2001
    Location
    Seattle, WA
    Posts
    7,744
    Have the local power company monitor the supply from the transformers into the buildings. They should do it for a while once you tell them of your problems. Then move on from there to the main panel once the power has been shown to be clean and steady.
    "The American Republic will endure until the day Congress discovers it can bribe the public with the public's own money.
    - Alexis de Toqueville, 1835

  3. #3
    Join Date
    Aug 2012
    Posts
    2,502
    Quote Originally Posted by DeltaT View Post
    Have the local power company monitor the supply from the transformers into the buildings. They should do it for a while once you tell them of your problems. Then move on from there to the main panel once the power has been shown to be clean and steady.
    Hopefully they will cooperate, I would like to piggyback on this and ad that the electrical boxes and related breakers should really be inspected very thoughrly also, faulty brekers and loose connection will reak havock on motors etc.
    Trying not to be a Hack.

  4. #4
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    17,708
    Quote Originally Posted by toocoolforschool View Post
    Hopefully they will cooperate, I would like to piggyback on this and ad that the electrical boxes and related breakers should really be inspected very thoughrly also, faulty brekers and loose connection will reak havock on motors etc.
    Yes, particularly on a building over 20 years old.

    When I was a kid, we had a problem with the stepdown transformer that fed my house. We literally had sparks flying out of the fuse box, and it fried the power supply on our 13 inch Admiral B&W TV.

    It is very possible that you have a power issue.

    One building I service has a known issue with the local utility suffering with recurring issues at the local substation.

    Your success will largely depend on how you ask. Explain what has been replaced, and the time period in which this happened.

    I would DEFINITELY consider commercial grade surge protection, too.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

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  5. #5
    Join Date
    Feb 2006
    Location
    Atlanta,GA.
    Posts
    856
    most electrical contractors that I know have equipment to monitor power coming to the bldg if the utility company wont. when was the last time your electrical panels had an infrared survey done?

  6. #6
    Join Date
    Nov 2001
    Location
    Seattle, WA
    Posts
    7,744
    I got involved in a commercial building that was burning out different systems at different times with no apparent sequence. Power company would do nothing so I got looking into things.

    The high leg on the three phase had been switched by the power company when they replaced the transformer. This allow the high leg to see the burnt out mini split that I was replacing along with some other motors, relays, etc. The mini split circuit board would fry from time to time.

    Another building had three phase where the bonding lugs inside of the 600 amp panel were corroded off. The extra power was bled off into the chassis bonding lug and tons of blower motors, relays, circuit boards would burn out at any time yet there were many other ceiling mounted air handers that would not.

    I found out the hard way as I leaned against the cabinet and brushed a piped in the ceiling at the same time. And the disconnect was turned off. The electrician was called in to run separate bonding between all the A/H's and the panel. As I was watching he and his helper doing all this I pointed out the damaged bonds on the grounding lugs. He never noticed them but had been working there 2 days pulling wire.
    "The American Republic will endure until the day Congress discovers it can bribe the public with the public's own money.
    - Alexis de Toqueville, 1835

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