Only way I can imagine this happening simultaneously is if one transformer phase on the utility pole went out. Have a look at your power meter - is the disk turning at all? If you feel safe doing so and have a decent voltmeter, you could open the service panel and check for voltage between the bus bars. Check each bus bar to the neutral line, and to each other; there should be 115 volts between each phase and neutral, and 230 between the two bus bars.
If there's not, you have a problem. My own inclination would be next to check at the terminals right on the master breaker, if they're accessible (not easy on some designs), on the house side; if you still have a loss of voltage, then I'd check on the other side of the breaker. If the problem exists on both sides of the breaker, call the hydro company. If the supply side is good but the service panel side isn't, call your favourite electrician.
WARNING: Don't do this if you are at all unsure of what you're doing! Wear electrical safety gloves rated to at least 1000 V, long-sleeved shirt and trousers (sleeves rolled down), rubber-soled boots and stand on a piece of rubber mat while you do this. Have someone stand by with a
3 or 4-foot length of wood - 2x2 will do nicely; if you have an unfinished (i.e., not varnished or painted) wooden cane, even better. Their job will be to knock you clear of the panel if something happens and you accidentally contact something.
Sorry if this is stuff you already know, but better safe than sorry - and it may be of use to others.
Yours aye, W. Underhill (who, the other day, proved the axiom that familiarity breeds contempt and as a result was bitten by 440 V on an auxiliary relay...)
Well, I do know what I am doing around a breaker panel, but I had an electrician anyway testing the breakers. They are working perfectly. Full power on the business leads of the double breaker. The other end (at the dryer and A/C) is where the problems manifest themselves.
One thing of possible import: I am having a new room added to the back of the house, and an electrician ran a new wire into the breaker panel, though he did it rather blind (he could not see exactly where the drill came out in the basement.
It seemed to me that had he hit the 240V line, sparks (or something) would fly. None of that happened. But, if he had nicked both 240V lines, would that explain the power loss (which is not total)?
It sounds like you lost one pole of each double pole breaker. Just loosing
11 volts wouldn't stop it from working. If you lost one pole of each of those breakers you probably lost one leg of the main breaker or the entire service. In a modern breaker panel, there is pretty much no way to loose one leg of just two breakers
Each of the two double pole breakers reads 240 volts at the breaker, but something less at the dryer and at the AC. What exactly is the reading across the two hot legs at the dryer and the AC?
It sounds like you lost one leg of each cable, but I can't imagine how that could have happened. At this point you'd need to disconnect each cable from the breaker and at the load end, and do a continuity test to verify each conductor
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