the trouble call from hell......

[Article 90.1]

If you lost a phase at or before the panel and 120 volts is feeding through any of the 240 volt loads, then nothing is inherently in series (except for the 240 volt loads, which are in series with what is a giant feeder looping around the branch circuit and back to the panel. Draw it out really quick and you will see what everyone has explained.

A few voltage measurements at the mains and meter should give you your answer in a few minutes.

 

[growler]

ok, all of you gifts to the electrical industry.... what is the problem?

A few voltage measurements at the mains and meter should give you your answer in a few minutes.

I don't even try to figure out a problem based on a few mysterious symptoms provided by a homeowner. I will go on a service call and diagnose the problem and give an estimate for repair cost.

I would go straight to the main panel and turn of the AC breaker and check to see what's there without the AC even in the system. It sounds like a missing leg feeding back through the compressor motor but it's hard to believe that motor hasn't burned up. It's just a lot easier to check it out and know for sure what's wrong rather than to guess at it.

 

[bigjohn67]

I didnt read through all the post.
But it appears you have a blown main fuse.
One 120v side is simply going through a 220 connected load, AC condenser, stove.
When you turn these items on, it sends power to phase B.

 

[rclacey]

I'm also too lazy too read all of the posts. I had two similar calls this past summer that went something like this. Everything in the house going haywire with no ryme or reason. I found the problem within an hour: One of the load side jaws in the meter socket was toast. It was good enough to make a connection under very small loads, but when they did anything that pulled maybe more than 12 amps or so on that leg (turn on the mircowave or whatever) That connection between the meter and the socket wouldn't hold. Loose connections do really funny things. New Meter socket, problem gone. About a month later, a different customer calls with the same problem. He thought his whole house needed to be re-wired. I knew right where to go to find the problem. Another load side lug in the meter socket that was just about black. He couldn't beleive how fast I found the problem. It is easy to 'overthink' problems like this. If everything in the house was working fine at somepoint, and things started to go haywire with out the help of any 'handy home electricians' then there's a pretty darn good chance its a loose connection someplace. The service equipment outdoors takes the most abuse, with high temperature fluxuations, moisture, etc.

FWIW, both of those meter sockets were made by anchor, and both about 30 to 35 years old. I'm sure there are many more anchor sockets out there ready to quit.

 

[e57]

Sounds easy... Checking for voltage both legs to ground - one is dead???? But that is how you are describing it the problem.... But you say you get 71V - Ask yourself how that is happening.... A resistive splice -or breaker?

It could alternatively be a lost neutral. The low reading of voltage at the outlets and the low or too dim to notice lighting, and then they work... IMO this could suggest the AC unit re-adjusts the 'neutral' load point. This could be confirmed if you are getting the balance of 120<71 (~49V) on the other leg that is 'supposed' to be 'working'... If you got ~170 on the other, and then changed the load and this voltage changed - that would be what is called a 'Hi/Low voltage event' AKA 'lost neutral'.

 

[revolt]

Get a Priest

 

[electricalperson]

i agree with the missing phase. measure volts on the load side of the main breaker. ive seen the splices at the top of the service burn up too. check main breaker, meter socket and if you have too the splices

 

[macmikeman]

I don't know if anybody solved this cause I didn't read all posts exactly, but my thought is a 120 volt t-stat that gets fed from the lighting circuit and someplace is a j-box with all the right conductors and all the wrong splices... Lights run off t-stat on the cooling side contact.

 

[Mr.Sparkle]

Oooh I been following the thread and didn't even think of that mac.....A+ for you.


Oh, and mac we had some great surf this week, OH+, straight offshore and water at a lovely 48 degrees and dropping daily.....

 

[ultramegabob]

I don't know if anybody solved this cause I didn't read all posts exactly, but my thought is a 120 volt t-stat that gets fed from the lighting circuit and someplace is a j-box with all the right conductors and all the wrong splices... Lights run off t-stat on the cooling side contact.

The original post said it was a low voltage thermostat

 

[Aledrell]

My money says that half of the main breaker is bad, check to see if you have 240v. on the load side of the main. Whats happening is power is being fed backwards through tha AC unit to the other half of the panel when the thermostat calls for the unit to come on.

I'm going to have to agree with Bob. There must be a loose connection at the panel causing intermitant power during heavey load. Could be loose in meter, utility J-box, transformer, cracked panel buss, bad main, or fried buss behind the main (in my experience this tends to be the case). We have way to many Crouse-Hinz panels out here. Worst panel made, mains always burn to the extent it's one of the Mains carried by the depot, etc. But I want to thank you ever made it for the job security .

 

[Power Tech]

Loose connection somewhere, could be in an appliance.

 

[jaylectricity]

My money says that half of the main breaker is bad, check to see if you have 240v. on the load side of the main. Whats happening is power is being fed backwards through tha AC unit to the other half of the panel when the thermostat calls for the unit to come on.

Having only read the first page, this totally makes sense.

Now, to read the ensuing pages and see how this thread turns out.

It's like one of those books where you make a decision to decide the outcome of the plot.

 

[jaylectricity]

In addition to the backfeed on the main panel, there could also be some other problems.

But I'm sticking with ultramegabob on this one.

 

[quogueelectric]

It is late and I havent had time to read all posts but when this type of conditions exist it is usually a burned up feed and other equipment backfeeding through 240v equipment only when it is on. Try turning off all 2 pole breakers and I will check back tomorror when I have more sleep.

 

[e57]

If these types of problems only happen under load - and they often do - I find this type of tool pretty valuable in locating the problem. In fact I had to use one at my own home for a poco spice... (Found the thread about it too... Still have to do that service change...)

 

[Fulthrotl]

It is late and I havent had time to read all posts but when this type of conditions exist it is usually a burned up feed and other equipment backfeeding through 240v equipment only when it is on. Try turning off all 2 pole breakers and I will check back tomorror when I have more sleep.

i went to bed, and slept in late as well... after posting what i felt was a
witty rebuttal so a somewhat rude post, and then george got up early,
and deleted about half of the thread..... i didn't get to read the downward
spiral, or take umbrage at my besmirched talents, or *anything*..... snif.

but... but... but.... george......

bless his heart, he's never seen the photos of the
van, or gotten a load of my "tool time" posts. ;-)

but after breakie this morning, when jill took off with her sisters to
christmas shop, i was bored, and it wasn't raining, so i hopped in
the van, and did a drive by on the house, as it's empty, and nearby,
and slapped a fluke 12 meter on the load side of the main, to see if
it was hot on both sides, which i had not done on the initial service
call, as i had a realtor in a hurry with me the other day,
who wanted a speedy diagnosis.

with the AC off, it's hot on both legs of the main.

;-p

now, it could be intermittent. wished i'd taken the time to pull
the panel cover and check the other day, as i could not go
inside the house to check voltages today.

the most likely problem is what the group consensus here came up
with, that there is a open leg, either in the poco feed, or in a bad main
breaker.

with a small but vocal minority opinion that i'm an idiot.
while that position does have merit, i'm feeling smarter than
normal this morning, and so i suspect the following.....

if it's not an intermittent issue that wasn't repeating this morning,
then there is an open neutral, and the 220 motor load is acting in
somewhat of a bizarre fashion, to generate the appearance of a
neutral path where one does not actually exist.

and, to prove that i am in fact an electrical contractor, i was contacted
by the buyer yesterday afternoon to provide a written quote to rewire
complete and patch any holes made in the process, for $10,000 complete,
before escrow closes, to be paid out of escrow funds.

10k? paid out of escrow? on todays icky work market? yes, sir, i can do
that. which is the real reason i was prompted to go over there this
morning, and do some checking.

insulting me isn't enough to get me to do something. you have to be
willing to pay me, too....

there.... does that qualify me as an electrical contractor?

enjoy your sunday, one and all.......


randy

 

[e57]

Both the open neutral - and/or phase could alternately hold true - but only under load, otherwise it may look fine with no load - they are the tricky finds that the IR thermometer helps find. While I do not suggest using any house loads that can not be easily replaced - like line voltage incandescent lights - I usually use a bunch of 500 and 1000w halogen floods to mimic a load. As if it is a lost neutral you risk torching some other types of electronics and power supplies.

In this thread - at my own home - testing of voltage resulted in your average 120/240 readings, but at a certain point of loading and time - the connection would slightly open with the heating of the bad connection, arch, and then cool and close just in seconds.... In my case it was a bad POCO splice on a phase/leg, but it very easily could do the same, and act very much the same on the neutral as well...

The very split seconds where voltage might change could be so brief that it would make it elusive to pin-point, but the heat generated at the splice would not be too hard to nail down. You can load it much as you want - watch it get hotter, and measure voltage at that point when it peaks open or becomes resistive...

 

[marcerrin]

I'm going to have to agree with Bob. There must be a loose connection at the panel causing intermitant power during heavey load. Could be loose in meter, utility J-box, transformer, cracked panel buss, bad main, or fried buss behind the main (in my experience this tends to be the case). We have way to many Crouse-Hinz panels out here. Worst panel made, mains always burn to the extent it's one of the Mains carried by the depot, etc. But I want to thank you ever made it for the job security .

A/C would not work at all if the main breaker was bad. I think you have a bad splice, or an old scar in one of the feeders that has oxidized or over time. When the large load of the a/c is on, it makes contact, when the a/c shuts off the connection is lost. Open the meter and see what you find.

 

[e57]

When the large load of the a/c is on, it makes contact, when the a/c shuts off the connection is lost.

I have found that the opposite is most often true - additional load will break or make the connection resistive - and it can happen within breakers as well as splices and terminations.

Either way if can be said that the faulty connection is prior or common to both the AC and the lighting circuit this is noticed on. (But not limited to just these two items...)