bolted pressure switch

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dross48

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anderson indiana
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?
 
Are you showing those voltages with a load still connected to the switch ?
 
When was the last time the switch was actually cleaned and maintained?
Are the blades fully separating?

Between what points are you measuring voltage?
L-L
L-N
L-G

For troubleshooting, I like to know all 9 possible voltages (and sometimes N-G).
 
Note also that the sum of the two phase voltages is equal to the third, a good sign that the real or phantom voltage is coming from a single phase source.
If you read this with no loads connected, it is almost certainly a phantom voltage and measuring with a low impedance meter will give you a more meaningful reading.
If you see this with loads present, look at the current in each if the phase wires to try to identify the source.
You may even have a problem with your ground reference for your readings.

Tapatalk...
 
Since this is a nursing home there is likely a required standby system of some kind, is it running while performing these tests? If so maybe some crossover between normal and standby systems somewhere? Also make sure you are using a low impedance meter to ensure you are not reading any capacitively coupled voltages with no usable power behind them.
 
Or there is a UPS or some other backup power supply on something (or multiple things) somewhere in the nursing home and this is the leakage through the diodes on the rectifier. As was said, using a high impedance tester like a Wiggy would show you if it's real or something like that which means nothing. Diode leakage can show as voltage on a digital VOM, but has no energy, no current. So a high impedance tester becomes a load on it, which drives the voltage to zero as soon as it is hooked up.

D'oh! Basically just said what kwired said. Must learn to read before posting...
 
Last edited:
Jraef said:
Or there is a UPS or some other backup power supply on something (or multiple things) somewhere in the nursing home and this is the leakage through the diodes on the rectifier. As was said, using a high impedance tester like a Wiggy would show you if it's real or something like that which means nothing. Diode leakage can show as voltage on a digital VOM, but has no energy, no current. So a high impedance tester becomes a load on it, which drives the voltage to zero as soon as it is hooked up.

D'oh! Basically just said what kwired said. Must learn to read before posting...
Click to expand...
And after posting.
"high impedance" --> "low impedance"
 
jim dungar said:
When was the last time the switch was actually cleaned and maintained?
Are the blades fully separating?

Between what points are you measuring voltage?
L-L
L-N
L-G

For troubleshooting, I like to know all 9 possible voltages (and sometimes N-G).
Click to expand...

Ditto Jim,
Is this yet another post where the PO asked a vague question that needs more details and we never here from him again?
Dave
 
kwired said:
"PO" or "OP"? Or maybe the OP got PO'd:)
Click to expand...
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.
 
jim dungar said:
When was the last time the switch was actually cleaned and maintained?
Are the blades fully separating?

Between what points are you measuring voltage?
L-L
L-N
L-G

For troubleshooting, I like to know all 9 possible voltages (and sometimes N-G).
Click to expand...
To my knowledge never has it been cleaned, i believe it was installed in the early 80s
 
jim dungar said:
When was the last time the switch was actually cleaned and maintained?
Are the blades fully separating?

Between what points are you measuring voltage?
L-L
L-N
L-G

For troubleshooting, I like to know all 9 possible voltages (and sometimes N-G).
Click to expand...
To my knowledge never has it been cleaned, i believe it was installed in the early 80s i took readings from line to ground and line to neutral, im going back there later today and i will take readings between phases
 
kwired said:
Since this is a nursing home there is likely a required standby system of some kind, is it running while performing these tests? If so maybe some crossover between normal and standby systems somewhere? Also make sure you are using a low impedance meter to ensure you are not reading any capacitively coupled voltages with no usable power behind them.
Click to expand...
There is a gen set though it was not running, the building has two sources of power being fed from two transformers, the original 2500 amp is the one im having issues with, and a new switchgear and service that was installed a couple years ago, they both feed the same transfer switch. There is usable voltage when the switch is open lighting that is being fed from a sub panel was blinking witch is how we came to find the problem in the first place.
 
kwired said:
Since this is a nursing home there is likely a required standby system of some kind, is it running while performing these tests? If so maybe some crossover between normal and standby systems somewhere? Also make sure you are using a low impedance meter to ensure you are not reading any capacitively coupled voltages with no usable power behind them.
Click to expand...
There are two sources of power feeding the same building in the same mechanical room one 2500 amp witch is the one I am having issues with is for the original building built in early 80s, and another 2500 amp feeding the new addition, both are using the same transfer switch to feed separate emergency loads. when the main switch is open there is office lights being fed from a panel box that flicker on and off, with the main open I was getting the voltages to this office panel
 
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