Continuity between all phases, neutral and ground

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mikejf

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Hello, long time reader first time poster. A little about myself, I have over 10 years manufacturing/facilities maintenance and automation experience where I was the plant electrician. I also have over 20 years of large food service equipment installation / maintenance / service and repair.

Here is my first question: I recently relocated a 45kva transformer from one location of my building to another. I removed all wires from both the 480 volt disconnect and from the 208 panel and left all connections inside of the transformer intact. All phase wires, neutral wire and ground wires were all color coded previously. The transformer was fed from the building's MDP and the transformer fed a 120/208 3phase panel that only had a few circuits coming out of it. There is another 120/208 panel right next to this one that is fed from a 150kva transformer. I relocated the few circuits to the 2nd panel and then that is when I removed the 45kva transformer. After relocating the transformer to it's new permanent location, I ran the 480 volt wires from the same breaker that was used before but in a different location in the MDP. I then connected the secondary wires to a different 120/208 3 phase panel (I did not relocate the old panel). I removed this 120/208 panel from our previous location and re-installed it in the new location with the 45kva transformer. Before I was about to turn the breaker on to supply power to the transformer I took my multi-meter and checked for continuity between phases, neutral and ground and the meter read continuity between all. All phase wires, the neutral wire and the ground wire inside of the 120/208 panel have continuity between them all. I checked for continuity between the phase wires coming off of the breaker in the 480 volt panel that feeds the transformer and they have continuity between them as well. I am obviously hesitant to power the transformer and potentially injure myself or the equipment.

Is this situation normal? Why would I have continuity between phase wires coming off of a breaker that was previously in working condition and to have continuity between all wires inside of the 120/208 panel? Like I mentioned earlier, the transformer is fed from the same 480 volt panel that it was previously the only difference is the 120/208 volt panel which was also working fine previously. Any insight would be greatly appreciated.
 
Where exactly did you put the meter leads. Remember the transformer is three coils all connected to one another in either wye or delta configuration - not having continuity between two leads is an indication something is not right with the transformer.
 
mikejf said:
Hello, long time reader first time poster. A little about myself, I have over 10 years manufacturing/facilities maintenance and automation experience where I was the plant electrician. I also have over 20 years of large food service equipment installation / maintenance / service and repair.

Here is my first question: I recently relocated a 45kva transformer from one location of my building to another. I removed all wires from both the 480 volt disconnect and from the 208 panel and left all connections inside of the transformer intact. All phase wires, neutral wire and ground wires were all color coded previously. The transformer was fed from the building's MDP and the transformer fed a 120/208 3phase panel that only had a few circuits coming out of it. There is another 120/208 panel right next to this one that is fed from a 150kva transformer. I relocated the few circuits to the 2nd panel and then that is when I removed the 45kva transformer. After relocating the transformer to it's new permanent location, I ran the 480 volt wires from the same breaker that was used before but in a different location in the MDP. I then connected the secondary wires to a different 120/208 3 phase panel (I did not relocate the old panel). I removed this 120/208 panel from our previous location and re-installed it in the new location with the 45kva transformer. Before I was about to turn the breaker on to supply power to the transformer I took my multi-meter and checked for continuity between phases, neutral and ground and the meter read continuity between all. All phase wires, the neutral wire and the ground wire inside of the 120/208 panel have continuity between them all. I checked for continuity between the phase wires coming off of the breaker in the 480 volt panel that feeds the transformer and they have continuity between them as well. I am obviously hesitant to power the transformer and potentially injure myself or the equipment.

Is this situation normal? Why would I have continuity between phase wires coming off of a breaker that was previously in working condition and to have continuity between all wires inside of the 120/208 panel? Like I mentioned earlier, the transformer is fed from the same 480 volt panel that it was previously the only difference is the 120/208 volt panel which was also working fine previously. Any insight would be greatly appreciated.
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Is the 3-phase connected to any loads when you are checking for continuity?
 
kwired said:
Where exactly did you put the meter leads. Remember the transformer is three coils all connected to one another in either wye or delta configuration - not having continuity between two leads is an indication something is not right with the transformer.
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In the 120/208 panel, I put one lead on the neutral lug and then the checked each phase lug and then the ground bar, all have continuity.
In the 480 panel on the breaker, I checked L1-L2, L1-L3, L2-L3, all have continuity.
 
Besoeker said:
Is the 3-phase connected to any loads when you are checking for continuity?
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No. The breaker feeding the transformer is off. I was ready to turn it on but it was after the continuity test in the 120/208 panel that has me a little worried and also the continuity on the 3 phase breaker in the 480 panel. I have yet to turn power on to the transformer which will power the 120/208 panel.
 
mikejf said:
In the 120/208 panel, I put one lead on the neutral lug and then the checked each phase lug and then the ground bar, all have continuity.
In the 480 panel on the breaker, I checked L1-L2, L1-L3, L2-L3, all have continuity.
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In the 120/208 panel you are reading through either connected loads or through the transformer secondary windings the only open continuity test you would be able to perform is the load side of main breaker with the breaker open and with no loads connected. Supply side of the main breaker will have continuity through the transformer secondary coils. If it doesn't the transformer secondary has open circuit conditions and will not work as intended.

In the 480 volt panel, I am assuming you are checking the circuit conductors that supply the transformer - the transformer is a load from this perspective, if you don't have continuity the thing will be an open circuit and will not work as intended.
 
mikejf said:
No. The breaker feeding the transformer is off. I was ready to turn it on but it was after the continuity test in the 120/208 panel that has me a little worried and also the continuity on the 3 phase breaker in the 480 panel. I have yet to turn power on to the transformer which will power the 120/208 panel.
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Are any loads connected on the three phase. Connected, not powered.
 
kwired said:
In the 120/208 panel you are reading through either connected loads or through the transformer secondary windings the only open continuity test you would be able to perform is the load side of main breaker with the breaker open and with no loads connected. Supply side of the main breaker will have continuity through the transformer secondary coils. If it doesn't the transformer secondary has open circuit conditions and will not work as intended.

In the 480 volt panel, I am assuming you are checking the circuit conductors that supply the transformer - the transformer is a load from this perspective, if you don't have continuity the thing will be an open circuit and will not work as intended.
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There is not a main breaker in the 120/208 panel, just main lugs which are fed directly from the transformer (I should have mentioned this in my original post). Also, there are no loads connected. I wanted to do all of the wiring/testing between the 480 panel - transformer - 120/208 panel before running branch circuits.
 
Continuity between all secondary transformer leads is what you should expece - same for the primary leads.

Both sides are built from three coils of conductor and are interconnected to one another, lack of continuity on either side would mean something is wrong.
 
kwired said:
Continuity between all secondary transformer leads is what you should expece - same for the primary leads.

Both sides are built from three coils of conductor and are interconnected to one another, lack of continuity on either side would mean something is wrong.
Click to expand...

What about the continuity between the neutral and the 3 secondary leads inside of the 120/208 panel?
 
mikejf said:
There is not a main breaker in the 120/208 panel, just main lugs which are fed directly from the transformer (I should have mentioned this in my original post). Also, there are no loads connected. I wanted to do all of the wiring/testing between the 480 panel - transformer - 120/208 panel before running branch circuits.
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If you have no main breaker, then how are the secondary transformer conductors and the 208/120V panel being protected?
 
jumper said:
If you have no main breaker, then how are the secondary transformer conductors and the 208/120V panel being protected?
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It is not. I see the issue now. When I removed everything originally there was neither a main disconnect nor main breaker between the transformer and the panel and it didn't even occur to me to install one. Looks like a trip to the supply house before energizing the transformer.
 
mikejf said:
What about the continuity between the neutral and the 3 secondary leads inside of the 120/208 panel?
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With no main breaker in that panel, which is most likely a code violation, you have no isolation and if everything is in working condition you will have continuity between all four secondary leads. In a wye configuration one side of each of the three windings are all tied together (the wye point).

In a delta configuration each end of a winding is tied to another winding- there is continuity between all three leads to that system.
 
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