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Old 06-07-2017, 06:03 PM   #1
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Default strange voltage off breaker

Here's the situation: A month ago I'm called out to a restaurant to see why a dishwasher is tripping the breaker. It's fed by a 3pole 70A breaker (dedicated newly installed circuit..hits a fused disconnect first, and then to the unit) What isn't so new is the panel, which is a FPE bolt-on. (Most of the original breakers are Challenger brand, but that's beside the point..) The breaker will trip anywhere from 5 min. to a couple hrs. under load, and the Ecolab tech who is in charge of maintaining the dishwasher says that he's gone through everything he can think of on the unit, and suggests that it has to be something on 'my end'. I don't know what to think of other than the breaker is weak (the countless number of times it's tripped so far, not to mention that I guess there once had a been a problem with the equipment that had caused this breaker to trip)....
Yesterday I show up with a new breaker and install it, check voltage--good.
Later in the day, get called back out there to confirm what the Ecolab tech has been called out to find--no voltage between the black and red legs. (keep in mind the breaker has tripped atleast a couple time already)
At the breaker, 120v to ground off each leg, 208v between black and blue, 208v between red and blue, 0v between black and red. I take the wires off the breaker and try it..same thing. I immediately check voltages on the buss--good. Turn the breaker on and off couple times.. now we're good again.
But.. the breaker trips in 5 min of the unit being on and working. A
Also, there's no reason to think there's on overload--my meter shows a continuous 43-46 amp draw, on each leg, and then breaker will just trip--doesn't peak at all right before (atleast that the meter can detect).
The restaurant manager says that for the past month, the old breaker had been holding a lot better than this new one has, and so for the time being, the old one is back in as we speak.
So... I guess I have two questions:
1) can a breaker be messed up so bad that you get 120V to ground off all three, but then 0v between two poles (as if at that moment the two breaker terminals were actually the same leg)?
2) any idea wtf is wrong with this dishwasher that this guy might be missing..could it be a contactor going bad??
thanks..
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Old 06-07-2017, 06:12 PM   #2
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Seems pretty simple. bad connection on the bus. Move the breaker and see what that does.
Should be a money making change out.
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Old 06-07-2017, 06:20 PM   #3
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Check these voltages again in your main panel,
if they are still wrong there /
Then call POCO
Some three phase motors will run sort of
with only two phases, they run rough
but they do run.

this would also explain the breaker blowing
a missing phase !

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Old 06-07-2017, 06:20 PM   #4
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Originally Posted by sbrn33 View Post
Seems pretty simple. bad connection on the bus. Move the breaker and see what that does.
Should be a money making change out.
thanks, but I don't know how there could be a bad connection at the buss when all three points' screws are securely tightened to the buss.. no signs of over heating, etc.. like I said-- 120v to ground between all three terminals on the breaker, but not 208v between the 1st and 2nd.
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Old 06-07-2017, 06:23 PM   #5
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Quote:
Originally Posted by dmxtothemax View Post
Check these voltages again in your main panel,
if they are still wrong there /
Then call POCO
Some three phase motors will run sort of
with only two phases, they run rough
but they do run.

this would also explain the breaker blowing
a missing phase !

Attachment 106609
thanks, but I had these weird voltages off the breaker while there were no conductors under the breaker. I checked the voltages at the breaker, then at the buss, at the breaker.. plenty of times as I thought I was losing my mind by what I was seeing
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Old 06-07-2017, 06:25 PM   #6
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the missing phase could be due to a local transformer with one of the three coils being open circuit or high resistance.
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Old 06-07-2017, 06:31 PM   #7
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holy crap, not to be a ****, I appreciate the responses, but are you guys thoroughly reading my post?
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Old 06-07-2017, 06:43 PM   #8
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Quote:
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holy crap, not to be a ****, I appreciate the responses, but are you guys thoroughly reading my post?
Your post was very long and heavy, and therefore the bottom third got itself completely sunk down in the mud...................... We got two tow truck operators , one named Big John and the other named Jraef that might be along shortly to get you towed back out of that mess you got into.......
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Old 06-07-2017, 06:51 PM   #9
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did you actually verify incoming voltage in the panel?

could be a bad section of busbar before the breaker feeding the dishwasher also
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Old 06-07-2017, 06:59 PM   #10
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1) None the less, have the utilty check their equipment.
2) What exactly is the dishwasher doing? Where exactly is it in the cycle?
3) Be patient. Intermittent problems are the hardest to troubleshoot.
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Old 06-07-2017, 07:09 PM   #11
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Quote:
Originally Posted by dmxtothemax View Post
Check these voltages again in your main panel,
if they are still wrong there /
Then call POCO
Some three phase motors will run sort of
with only two phases, they run rough
but they do run.

this would also explain the breaker blowing
a missing phase !

Attachment 106609
Some Three phase motors can run off two phases AFTER STARTING on 3 phases, try to start in a single phase condition (only 2 phases present) and you will fry the windings.
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Old 06-07-2017, 07:12 PM   #12
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Originally Posted by drspec View Post
did you actually verify incoming voltage in the panel?

could be a bad section of busbar before the breaker feeding the dishwasher also
seriously?
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Old 06-07-2017, 07:15 PM   #13
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This is an overload/thermal issue find what is resulting in the heat.

It is possible to have a NEW bad circuit breaker.


With the dishwasher in operation perform a FOP (Fall of Potential) test between


1. The main bus and the load conductors.
2. The main lugs and the load conductors.


Your voltage drop reading should be similar, any high voltage drop tells you have a high resistance connection.
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Old 06-07-2017, 07:15 PM   #14
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all right guys.. from now on I'll write my posts in five lines or less so we can all keep up, otherwise I won't waste our time. thanks for the effort.
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Old 06-07-2017, 07:17 PM   #15
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all right guys.. from now on I'll write my posts in five lines or less so we can all keep up, otherwise I won't waste our time. thanks for the effort.
Read what I posted this stuff is not magic a few simple test should resolve any issues with a molded case thermal magnetic circuit breaker.
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Old 06-07-2017, 07:18 PM   #16
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seriously?
Yes, such as

one phase lug to bus connection

Bus finger to bus
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Old 06-07-2017, 07:35 PM   #17
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seriously?
yes seriously

I couldnt tell you the amount of times guys will check at the breaker itself but fail to check or verify the incoming voltage or test various breakers BEFORE the circuit theyre having trouble with

you ask for help and yet act like a **** when someone asks if your verified something

for that I hope you NEVER fix the issue and the company calls a real electrician that knows what they are doing
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Old 06-07-2017, 07:56 PM   #18
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yes seriously

I couldnt tell you the amount of times guys will check at the breaker itself but fail to check or verify the incoming voltage or test various breakers BEFORE the circuit theyre having trouble with

you ask for help and yet act like a **** when someone asks if your verified something

for that I hope you NEVER fix the issue and the company calls a real electrician that knows what they are doing
I guess you detected my sarcasm by asking you 'seriously?' I would've typed a longer sentence such as, "seriously?, if you'd read my post you would have known that I checked the voltage before the breaker", but I figured that might be too many words and you'd might get lost in it..
OK, seriously.. I'll admit I'm being a complete ass right now. You're getting the brunt of it which wasn't fair, it just seemed the two guys before you didn't read it all either. I know it's a long and tedious one.
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Old 06-07-2017, 08:08 PM   #19
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One of your phases has a ground fault?
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Old 06-07-2017, 08:32 PM   #20
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One of your phases has a ground fault?
No. Here's what my original question should have been: So you got a panel, and EVERYWHERE in the panel you have 120V to ground where you'd expect it; at the lugs where the feeders terminate, at every point on the buss, and at every terminal on the breaker.
AND..
between any two points in the panel where you have different phases, you get 208V, whether it's between A and B, B or C, A or C lugs where the feeders come in, breaker 1 and 3, 13 and 15, 16 and 18, etc.. and the same is such for any sequence of readings on the buss where the breakers bolt-on the buss.
EXCEPT!..
for this one particular 3 pole breaker where at one point in time, you get 0 volts between two output terminals on the breaker (keep in mind that there are no conductors hooked up to the breaker where you could have a bad fuse cause backfeeding or some crap like that, etc...)
THEN, you flip the breaker on and off a few times and suddenly that voltage isn't 0 anymore it's 208 like it should be.
My questions is, as hard as it is to believe it could be a jacked up breaker, what else could it be?
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