I think I know what happened, but..

edward

Senior Member
Location
CA
Occupation
Electronologist
The lights went hay wire, dim, bright, dim, bright, funny noises.. then the power went out for a while. Brown out and then black out which to me it means lost neutral from utility. Now, this is what I don't understand, three of the 240V loads were damaged (well pump and controller) and the A/C compressor was making funny noises and it would run erratically until the breaker was shut off. Most of the 120V loads were OK, even the electronic dimmers. Only 120V damage was to motorized shades.

If it was a lost neutral, why would the 240V appliances get damaged. The property does have a SPD on the main service and it is OK indicating the issue was a lost neutral. If it was a surge, then why did the SPD survive?

Thank you for your input.
 

edward

Senior Member
Location
CA
Occupation
Electronologist
By "bad line" I assume you mean loose or lost connection on the energized conductor, correct?

My guess that the motors were damaged is because they were running at the time when this happened, correct?

What could have saved the motors?
 

edward

Senior Member
Location
CA
Occupation
Electronologist
If it was a lose neutral any straight 240 loads would not be damaged, and you would probably have more 120 volt loads destroyed I agree with post #2
That was my thought, then again I noticed the SPD was not triggered. I don't know much about the details and the internals of such device. So the event would not be considered a surge for the SPD to activate.

Besides the SPD that was not damaged, is there anything that can be incorporated in the electrical system to prevent damage from such event?
 

Electromatic

Senior Member
Location
Virginia
If there was something quirky going on with the utility, you could have under- and/or over-voltages that might be enough to damage some equipment but not necessarily enough to be seen as a "surge" by the SPD let alone make it self-sacrifice. There are phase-loss relays and under/over voltage relays that could be used, but it could become overly complicated for a typical residential setup.
 

synchro

Senior Member
Location
Chicago, IL
Occupation
EE
Most of the equipment that you mentioned was damaged had motors in them. As noted above, undervoltages can damage motors due to increases in running current, and especially in starting current if there was a failure to start. Other types of loads like lighting, etc. will typically not be damaged by an undervoltage.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Most of the equipment that you mentioned was damaged had motors in them. As noted above, undervoltages can damage motors due to increases in running current, and especially in starting current if there was a failure to start. Other types of loads like lighting, etc. will typically not be damaged by an undervoltage.
That's what led me to my conclusion.
 

edward

Senior Member
Location
CA
Occupation
Electronologist
Thank you for your replies.

If anyone has experience, would you please direct me to phase-loss relays and/or under/over voltage relays.
 

Electromatic

Senior Member
Location
Virginia
Here's a page from Allied Electronics:

You'll have to figure out what voltages you want to monitor and what your tolerances would be. Also, most of the relays are probably not rated to carry a well pump or compressor. You'd have to have the relay controlling a contactor. As I noted before, going through all of this for a residential application is likely not worth it unless you have a really unreliable utility provider.
 
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