bolted pressure switch

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dross48 said:
I have a 2500 amp switch being used as the main for a nursing home when I open the switch voltage bleeds through 47 volts on A phase 52 volts on B phase and 120 volts on C phase is there a way to fix this problem without buying a new switch?
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Now that we pretty much ruled out capacitive coupling, since phase C has 120 volts (assuming this is a 208/120 system here) it may not be opening clearly and the other voltages are back feed voltages through connected loads. I would think you would have more than just that one light still operating, but maybe you noticed it only because it was the only thing nearby connected to that phase.
 
kwired said:
Now that we pretty much ruled out capacitive coupling, since phase C has 120 volts (assuming this is a 208/120 system here) it may not be opening clearly and the other voltages are back feed voltages through connected loads. I would think you would have more than just that one light still operating, but maybe you noticed it only because it was the only thing nearby connected to that phase.
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Yes it is a 208/120 and there were other lights on and flickering it just happened to be next to electrical room and it was then that we recognized the problem, I am starting to think maybe because this switch has never been maintained and is very old if it would just need to be cleaned and serviced.
 
templdl said:
You have to wonder why we get sucked into these OPs that ask a very vague question and when you ask for more details and clarification they are never to be heard from again.
I would like to think that were are discussing a serious topic that often involves the danger of loss of life and/or property. I have always been concerned about someone going away with a loaded gun the we have just handed them.
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Didn't mean to leave folks hanging just got busy that day and yes this a very serious discussion as the power to this side of the building cannot be fully shut off, the maintenance crew is relying on me to solve problem as cost effective as possible.
 
dross48 said:
I have a 2500 amp switch being used as the main for a nursing home when I open the switch voltage bleeds through 47 volts on A phase 52 volts on B phase and 120 volts on C phase is there a way to fix this problem without buying a new switch?
Click to expand...

Can you remove the conductors from the load side of the switch and then measure voltage at both the load side of the switch and also at the conductors?

This should give you some direction.
 
mgookin said:
Can you remove the conductors from the load side of the switch and then measure voltage at both the load side of the switch and also at the conductors?

This should give you some direction.
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No, well at least not easily the switch is bolted to bus bars, if this switch has never been cleaned or maintained could it simply be that there is some cleaning and adjusting that needs to be done I have read that these things do need regular cleaning and maintaining
 
Can you turn off both service switches long enough to see what happens with the voltage ?
I would not rule out "leakage" thru the bolted switch, but I would be more suspicious of some type of back feed from the other service.
It seems possible if someone has accidentally fed the same load from both services you could have 120v on the one leg and the other voltages are from backfeeds thru other mutli=phase equipment.
To me, the flickering lights support the back feed situation.

(Would not be the first time many of us have seen one load getting power from two panels.)
 
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augie47 said:
Can you turn off both service switches long enough to see what happens with the voltage ?
I would not rule out "leakage" thru the bolted switch, but I would be more suspicious of some type of back feed from the other service.
It seems possible if someone has accidentally fed the same load from both services you could have 120v on the one leg and the other voltages are from backfeeds thru other mutli=phase equipment.
To me, the flickering lights support the back feed situation.

(Would not be the first time many of us have seen one load getting power from two panels.)
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You ever been changing a panel out and have everything off and when disconnecting neutral conductors you find one that has load on it? Then hope you did not interrupt the only neutral path for what amounts to a multiwire circuit?
 
dross48 said:
No, well at least not easily the switch is bolted to bus bars, if this switch has never been cleaned or maintained could it simply be that there is some cleaning and adjusting that needs to be done I have read that these things do need regular cleaning and maintaining
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If you know it needs periodic maintenance and that maintenance was never done and you have a problem with it, by all means do the maintenance.
 
augie47 said:
Can you turn off both service switches long enough to see what happens with the voltage ?
I would not rule out "leakage" thru the bolted switch, but I would be more suspicious of some type of back feed from the other service.
It seems possible if someone has accidentally fed the same load from both services you could have 120v on the one leg and the other voltages are from backfeeds thru other mutli=phase equipment.
To me, the flickering lights support the back feed situation.

(Would not be the first time many of us have seen one load getting power from two panels.)
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Good idea Ill give it a try, the addition and rewire of building a few years back could very well have voltages from two different sources in same conduit run and therefore back feeding in that way, though I did open all the fused switches in that switch gear including main but after thirty years in trade nothing will surprise me any more.Thank you for your help I'll let you no what I find.
 
augie47 said:
Please do.
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Thank you every one for your help and suggestions what I found was after a closer look and investigation that the blades/contacts were burnt or somewhat arked together and did not open fully resulting in voltage leaking through from power company transformer, now my search is for a replacement.
 
dross48 said:
Thank you every one for your help and suggestions what I found was after a closer look and investigation that the blades/contacts were burnt or somewhat arked together and did not open fully resulting in voltage leaking through from power company transformer, now my search is for a replacement.
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I will have one, just need all the details.
 
dross48 said:
Thank you every one for your help and suggestions what I found was after a closer look and investigation that the blades/contacts were burnt or somewhat arked together and did not open fully resulting in voltage leaking through from power company transformer, now my search is for a replacement.
Click to expand...

It is not unusual to find a 50%, or higher, failure rate for these switches if they have not been operated at least once every 3 years.

If it is just a case of stickiness, then a good service shop can properly maintain it for you. FWIW, if the service techs show up with just 'WD-40' and some rages, do not let them in the door.
If parts need to be replaced, there are lots of rebuilt units available. There are even options for replacement, in place, using breakers instead of fuses (which can be helpful in some arc flash mitigation when fault currents are low)
 
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