Power outages related to Air Conditioner?

[Johnny C.]

I have a client who has been experiencing periodic power loss to various circuits in the house. Various lights and outlets, the fridge, range and HVAC system. My initial thought was have the power company check things on their end for a bad connection at the pole or damage to the transformer. Their tech came back with nothing although I'm not sure how thorough he was.
Next option was the breaker panel which is 40+ years old and showing signs of wear on the bus bar. I replaced it with a brand new panel and breakers and the power outages seemed to stop. But after almost a month they experienced another outage so I'm back to square one. I haven't had a chance yet to explore the household wiring in much detail yet but these outages are weird. The most recent one was only for a second or two according to my client but some lasted for hours prior to the panel change. No breakers tripped during the outages but power would just go out to some (but not all) of the house. This is why I suspected maybe they were loosing a leg of the service supply intermittently. I am planning to have the utility hook up a meter and run a power survey on the house. However, I've also been looking at information on A/C units with bad capacitors causing weird problems with the electrical system. Anyone out there experienced anything similar to this? I'm hoping to get a clue as to where to look in case the power survey comes back clean. Thanks.

 

[zbang]

IMHO the panel probably wasn't the problem. With all that, it probably is the service, whether the PoCo admits it or not.

You can have the customer record the time/date and location of each "outage" then map that back to individual breakers which leg of the service they're on. You might also get your own power monitor and hang that on the service, then you'll have your own event log.

 

[Amps]

Is it an underground service? Many years ago I wired a townhome development with underground services. The utility company ran aluminum triplex in a trench with sand to each townhome's meter. The development took about 3 years to complete and during that time there were at least four separate townhome services that lost a phase. The triplex insulation was probably nicked during installation and it didn't take long for it to corrode and open circuit. I was called to check these power issues first, and some only lost the phase under load, like when the central AC was on. I suppose there was heavy arching going on with a phase in the trench to maintain a connection until the gap finally became too wide. Hope this makes sense.

 

[ptonsparky]

Look at all the connections. Usually it will be obvious but a thermal scan, imaging camera or good old hands on FOP testing works.

Bad underground is a common issue. Finding and repairing them made up a good portion of my income.

 

[ramsy]

IMHO the panel probably wasn't the problem. With all that, it probably is the service, whether the PoCo admits it or not.

Panel flippers typically leave old service drop or lateral in place after 200 Amp upgrades.

If old #6 Tripex doesn't become the fuse when new car charger runs, the new 125A tankless water heater should do it.

 

[Fred B]

I have a client who has been experiencing periodic power loss to various circuits in the house. Various lights and outlets, the fridge, range and HVAC system. My initial thought was have the power company check things on their end for a bad connection at the pole or damage to the transformer. Their tech came back with nothing although I'm not sure how thorough he was.

99% of time the first POCO tech out would clear the POCO wire as being responsible. Even when it was their connections or equipment they would deny it was their stuff. Had such case recently that had a dropped or bad neutral. After providing my meter readings they came back out to "check on things". They said they remade the connections but it wasn't their equipment, but magically the problem resolved.

Next option was the breaker panel which is 40+ years old and showing signs of wear on the bus bar. I replaced it with a brand new panel and breakers and the power outages seemed to stop. But after almost a month they experienced another outage so I'm back to square one. I haven't had a chance yet to explore the household wiring in much detail yet but these outages are weird. The most recent one was only for a second or two according to my client but some lasted for hours prior to the panel change. No breakers tripped during the outages but power would just go out to some (but not all) of the house. This is why I suspected maybe they were loosing a leg of the service supply intermittently. I am planning to have the utility hook up a meter and run a power survey on the house. However, I've also been looking at information on A/C units with bad capacitors causing weird problems with the electrical system. Anyone out there experienced anything similar to this? I'm hoping to get a clue as to where to look in case the power survey comes back clean. Thanks.

I'm with others here, likely service wire an issue whether POCO or the private section. Likely opening under load then as the shorting conductor cools back off it closes the gap.
Have you been there to witness the outage? I would be trying to replicate conditions that led to the outage. Then determine the last point that normal voltages can be measured, if your measurements go beyond the private service equipment then POCO definitely has an issue.
Had one that was a 120V underground to a garage, with no loads it would measure 120V, but put a load on it and the lights would initially come on then gradually dim to out. The underground was compromised and the heating of the bad section would open the circuit under load but would be close enough that without load would measure 120V. So for OP if your power failure only occur under loads I would say your service wire is failing somewhere.

 

[kwired]

Put some significant load on it. Whatever is failing is probably heating up and opening, then making connection again when it cools. It probably will not do this for long before total failure, but loading things up can make it open again and you can better test where you do and don't have what is expected. If you determine is on POCO equipment, get them there and perform same thing for them.

 

[Jraef]

Had one recently where it was a corroded connection on the meter jaw. In that subdivision, the utility responsibility stopped at the LINE terminals of the meter socket, so they didn’t check the jaws themselves. Had to pull the meter and replace the socket, after which everything went back to normal.