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  1. #1
    Join Date
    May 2006
    Posts
    312
    over the last two days, we've experienced very long periods of low voltage from our local electric utility. it may have something to do with humidity over 90%, constant rain.

    apart from total blackouts and occasional brownouts, these cause a repeated dimming of lights, something akin to disco lights (sorry) and is disturbing to say the least, worrysome due to the effect on electric motors and the heatpump compressors. the repeated (spaced out in seconds and sometimes just one minute apart) low voltage conditions last for hours.

    what can a regular homeowner do? what can I ask my HVAC contractor? the system is a Trane XL19i and the fear of course is motor/compressors overheating. a total blackout is not a problem as that's handled by the digital thermo but it does nothing for voltage drops.

  2. #2
    Join Date
    Mar 2004
    Posts
    1,042
    The blackouts are a separate issue, but if you're having voltage problems, you should be raising a stink with the electric utility.

  3. #3
    Join Date
    May 2006
    Posts
    312
    so, no equipment suggestions for monitoring line voltage and instantiating a delay similar to a blackout startup delay condition?

    I'm willing to spend 10% of the original cost of the XL19i to protect it, there's got to be some monitoring equipment that can be hooked up to the breaker (40amp) to make it go Off and resume after some programmed delay. If not in that manner then some other type of control.

  4. #4
    Join Date
    Jun 2006
    Posts
    13
    You need a brownout detector. Don't have a name right now but a google will lead to some. Then you can find some one to install it. These things monitor the voltage within specified limits and if the voltage falls outside it will open up the contactor for a time period (some times adjustable). Grainger handles them also.
    Calling the elec. comp. will get you a "ya we know it" and nothing will happen.
    I have the same system and have told myself and looked these things up many times but,,, have not done it yet!!
    The power in California gets worse every year.
    Good luck..

  5. #5
    Join Date
    Nov 2005
    Location
    Northern VA
    Posts
    512
    It's called a "phase monitor" or "voltage monitor".

    http://www.bramec.com/categories/detail.asp?cat=5034

    Also, the XL19i may have built-in brownout protection. I don't have a service manual for it; I know that the Infinity condensers have brownout mode so I would expect that Trane would have it in their high-end equipment as well. Basically, during an undervoltage event the control board shuts down just like it would if, say, a pressure limit opened. After power resumes to normal for a few minutes the fault clears and the condenser returns to normal operation.

    I would get a whole-house surge suppressor, preferably in the meter base, for protection against surges. If someone can confirm that your condenser has brownout mode (check the list of fault conditions for one called "brownout") then you should be fine.. could install one of those voltage monitors for extra protection I guess. Might want to confirm with Trane that they approve of using one, wouldn't want to void your warranty over something like this.

  6. #6
    Join Date
    May 2006
    Location
    Warren, MI
    Posts
    918
    If this "phase monitor" opens up the contactor on ones compressor what about the fan in the air handler? Seems like a "whole system" monitor would be better. Something that monitors the line voltage that powers the whole HVAC system control.
    Bill

  7. #7
    Join Date
    Mar 2004
    Posts
    1,042
    I'd still suggest talking to the power company. You may just get a "yeah, we know" response- if the power to your entire area isn't any good. But there are lots of other possible issues on the utility company's end that could cause this.

    -bad transformer
    -overloaded transformer
    -loose connection in the wiring between the transformer and your house (fire hazard)
    -water getting into the aforementioned connections (just plain dangerous)

    If everyone in your entire neighborhood has the same issues, there may not be a lot to be done- like the previous comment that power quality in California was going downhill. But you mentioned that this has been going on for just a couple of days. That sounds to me like a new, localized problem, and one that may be weather-related.

    Check with your neighbors. If it's only your house, there's probably a lot that can be done. If it's your house and a few neighboring houses, it may be a problem at the transformer, which should not be a big deal for them to correct. Do your lights flicker when your neighbor's central AC starts up?

    If the voltage is always too low, the transformer can be adjusted or replaced. After that you may still have some fluctuation, but at least you'll be fluctuating around 240V instead of fluctuating around some lesser voltage.

    Also while I'm not sure how far your voltage may be dropping, keep in mind that almost all residential equipment can be run on two legs of three phase power- an arrangement that is nominally 208V instead of 240V. So your voltage can drop quite a bit from 240V and still be within spec. I know most Carrier equipment allows for anything between 187V and 253V.

    Not to discourage you from pursuing fancy and expensive equipment protection. It would still behoove you to get the power problem fixed, though, if nothing else to protect your electronics, refrigerator, etc. And you may be able to get the power company to do something faster than you can get a new protection device installed, too.

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