checking 220 voltage question

[jnrwood]

Hello- I was helping out a neighbor whose well pump stopped working. So, originally, the owner backed up his electric stove to the wall too far and mashed the metal cover over the terminals and shorted the thing out. plastic was melted, wires seemed ok. At this point, the well pump stopped working and the stove would only work on warm and some of the lights.
Checked for voltage at pump and stove outlet, which should be 220, and i'm getting like 9 volts or 13 volts..ac. If i test between one or the other hot terminal and ground, i get 120 volts or so each. I thought that was weird. I checked my meter at home on my water heater, one test probe on each hot terminal and i get 243 volts. Plan to go over w/ another test meter to see what it says, but in the meantime i'm wondering what's going on.?
I also checked the breakers, which seemed and tested fine, and the wiring behind the stove outlet, no burning or anything. any ideas?

 

[wwhitney]

If on a 120V/240V system you have 3 wires, say black, red, and green (EGC), and you get 0V black-red, 120V black-green, and 120V red-green, most likely black and red are shorted together upstream. If at the panel you have 240V black-red, that black-red short would have to be in addition to black or red being interrupted. I.e. a break in black, with the free load end of the break shorted to red. Or vice versa.

Another possibility is just a break in the black or red, with the 120V reading from it to green being "phantom". To check for that, you could see if you can power a test (incandescent) lamp black-green as well as red-green. Maybe this possibility is more likely, as it only requires a single fault, not two faults.

Cheers, Wayne

 

[Sponsor]

 

[jnrwood]

That's good info, thanks. Next time i'm over i'll do the lamp test. I'm getting the same readings off the panel. red-black 4-15 volts. red-green- 120, black-green- 120. so sounds like a short between panel and pump. I still want to check it all w/ a different meter, can't hurt..

 

[Reach4]

I expect you have a 2-pole breaker for the stove, and a 2-pole breaker for the well pump. I would remove the cover, and measure the voltage between the hots on each of those breakers.

You could also measure the voltage across the two hots of the WH breaker for comparison.

 

[wwhitney]

That's good info, thanks. Next time i'm over i'll do the lamp test. I'm getting the same readings off the panel. red-black 4-15 volts. red-green- 120, black-green- 120. so sounds like a short between panel and pump. I still want to check it all w/ a different meter, can't hurt..

The fault would be between the utility and wherever you are getting those readings. So you could check the service disconnect; if you get 240V back-red there, you know the problem is within the house wiring.

Cheers, Wayne

 

[jnrwood]

I did measure the hots on the panel and got same readings. Also checked the service disconnect- WH breaker- and i just confirmed
w/the owner that i got same readings out there (My memory had faded) meter did not show 240 on 2 hots...so?? would that point to a problem in the supply? Should also mention that they have a lot of other electrical weird happenings, some outlets not working, lights flickering at times..

 

[wwhitney]

Roughly speaking, if you are not getting the correct voltages on the line side of the service disconnect, then it is time to call the utility. Great care is required taking such a measurement, as the service conductors are effectively unfused. So call an electrician if you are not qualified to take the measurement yourself.

Cheers, Wayne

 

[jnrwood]

Roughly speaking, if you are not getting the correct voltages on the line side of the service disconnect, then it is time to call the utility. Great care is required taking such a measurement, as the service conductors are effectively unfused. So call an electrician if you are not qualified to take the measurement yourself.

Cheers, Wayne

ok, i'll do that. Still it perplexes me that the whole thing started when the stove shorted out, and pump went at the same time. Which made me think there was a short in the house wiring. My idea was to disconnect the old wiring, and run a temporary wire from the house panel to the pump through the house just as a test. if it worked then run it properly. i will keep in mind your warning about the service conductors. gonna double check everything w/ another meter just to be sure.

 

[Reach4]

I did measure the hots on the panel and got same readings. Also checked the service disconnect- WH breaker- and i just confirmed
w/the owner that i got same readings out there (My memory had faded) meter did not show 240 on 2 hots...so?? would that point to a problem in the supply?

I am not sure what you are saying. When you said you got the same readings .... what readings were those?

Are you saying that you think you did not measure 243 volts at any point, or are you saying that you checked the output of the WH breaker and it measured about 240 volts?

I checked my meter at home on my water heater, one test probe on each hot terminal and i get 243 volts.

 

[jnrwood]

output on WH breaker did not measure 243 volts on 2 hots, same as inside 120 on each leg to ground. that's why i want to double check everything w/ another meter. Then i guess call our utility if the problem seems to be the supply. hopefully tomorrow should have some answers..thanks for the help.

 

[wwhitney]

FWIW, it is possible, although not likely, that the utility transformer has some fuses on the secondary side, and that the oven shorting event causes one of them to blow, rather than causing a breaker within the house to trip. However, utilities usually don't have such fuses for precisely this reason.

Another possibility is that the service disconnect breaker or some other double pole breaker within the supply wiring failed in a way that one side no longer works. That's why it's important to measure voltage on both the supply side and the load side of the breaker when tracing down a problem like this. If you get 240V L-L on the line side of a double pole breaker, but 0V L-L on the load side of the breaker, that breaker needs replacing (assuming you've properly reset it by turning it off before turning it back on).

Cheers, Wayne

 

[Fitter30]

Just because most people call it 240 vac doesn't mean a reading can't be + or - 10% utility company doesn't regulate power that close. If incoming power is 120 vac to ground per leg is good but if one leg is lower by more than a few volts a call needs to be made to the utility company.

 

[jnrwood]

FWIW, it is possible, although not likely, that the utility transformer has some fuses on the secondary side, and that the oven shorting event causes one of them to blow, rather than causing a breaker within the house to trip. However, utilities usually don't have such fuses for precisely this reason.

Another possibility is that the service disconnect breaker or some other double pole breaker within the supply wiring failed in a way that one side no longer works. That's why it's important to measure voltage on both the supply side and the load side of the breaker when tracing down a problem like this. If you get 240V L-L on the line side of a double pole breaker, but 0V L-L on the load side of the breaker, that breaker needs replacing (assuming you've properly reset it by turning it off before turning it back on).

Cheers, Wayne

Got it, thanks

 

[jnrwood]

Just because most people call it 240 vac doesn't mean a reading can't be + or - 10% utility company doesn't regulate power that close. If incoming power is 120 vac to ground per leg is good but if one leg is lower by more than a few volts a call needs to be made to the utility company.

i'll take note of that when i check it again, thanks

 

[jnrwood]

Finally got over to check the service disconnect box with another meter. Checked it at home on my water heater first, says 240.
taking some safety precautions (insulated gloves and rubber mat to stand on instead of snow, eye protection) probably overkill, but better safe than sorry as the saying goes. The line side read 0 , red-black, again. The supply side read 122 volts- on 2 hots. Same reading while checking it with the breaker shut off. So it seems to be a problem w/ supply and the utility is being called to hopefully fix it. We will see. Thanks for all the help and benefit of your knowledge and experience.

 

[Fitter30]

Main panel top lugs see two larger wires.
Between the two 240 vac
From each lug to ground or neutral 120vac
Good power
Anything else not working? If not possible bad breaker. Did you turn breaker off and back on and recheck.voltage.
At the breaker either a bad breaker or where the breaker connects to bus bar.

 

[jnrwood]

Between top lugs-122 vac., after turning breaker off , still 120. Thought this would isolate the test to the supply. This is at the outdoor service disconnect breaker box. can't remember whether i rechecked it after back on- think i did, but i had turned it off and on the previous time there, so that would have reset it, right? Some outlets in house not working, or working sometimes. some lights working but flickering at times. I did not check each each leg to ground as i did at the inside house panel, but since i didn't see 240 at supply i decided the problem was before the panel. should mention, someone ran into pole and cracked conduit on wires going into ground, no obvious damage on wires themselves. now i'm having ??s again, but the wheels are in motion or will be for utility to come out and check their end, so i think i'll wait + see what they say. thanks for the input

 

[Fitter30]

Call your power company

 

[jnrwood]

Yes, being done by residents there. should have a pretty quick response from power company since its winter and very cold up here in the northern catskills...

 

[JohnCT]

I've seen several failures of the connections right outside the house where the crimps are made between the utility and the home taking out one side only. Hopefully the neutral doesn't open...

John