What are the rules concerning the installation of a 240 to 120 single phase transformer that will supply a load center. Can I install a jumper between the 2 main lugs in the load center to supply both busses? Where are the grounding connections made, and to what? Do they make a 120 volt panel?
Transformer connection
- Thread starter cnj
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Ed MacLaren
Senior Member
Re: Transformer connection
I am trying to think of a reason for going to that much expense to install a 120 volt panel, instead of just using the common 120/240 volt type.
Is it a control transformer? Could you explain, just to satisfy my curiosity?
Ed
[ March 13, 2004, 05:37 PM: Message edited by: Ed MacLaren ]
I am trying to think of a reason for going to that much expense to install a 120 volt panel, instead of just using the common 120/240 volt type.
Is it a control transformer? Could you explain, just to satisfy my curiosity?
Ed
[ March 13, 2004, 05:37 PM: Message edited by: Ed MacLaren ]
Re: Transformer connection
Well the building has a 3 phase 240 volt service without a neutral and I am looking at installing a transformer that will supply me with a 240/120 secondary with a neutral, so I can feed a 120/240 3 wire panel. Maybe this is a better way to ask this question.
[ March 13, 2004, 05:42 PM: Message edited by: cnj ]
Well the building has a 3 phase 240 volt service without a neutral and I am looking at installing a transformer that will supply me with a 240/120 secondary with a neutral, so I can feed a 120/240 3 wire panel. Maybe this is a better way to ask this question.
[ March 13, 2004, 05:42 PM: Message edited by: cnj ]
- Location
- Massachusetts
Re: Transformer connection
Cnj Can I ask what kind of contractor you are?
Cnj Can I ask what kind of contractor you are?
Re: Transformer connection
Good morning Ronald. I wasn't very clear
but I was referring to a 240v single phase primary to a 120v/240v center tapped (grounded) single phase secondary, with the loads shared somewhat equally.
Roger
Good morning Ronald. I wasn't very clear
but I was referring to a 240v single phase primary to a 120v/240v center tapped (grounded) single phase secondary, with the loads shared somewhat equally.Roger
Re: Transformer connection
Roger thanks for the reply
I have been gone for a while and just noticed your reply. You probably think I'm crazy but are you referring to using the 120/240 volt in the circuit like a zigzag transformer and just use the one secondary winding? like a 480 to 120/240 and just use the secondary in the circuit to obtain a neutral and not even use your primary?
I don't think this would be a NEC violation because your not modifying the transformer?
Ronald
Roger thanks for the reply
I have been gone for a while and just noticed your reply. You probably think I'm crazy but are you referring to using the 120/240 volt in the circuit like a zigzag transformer and just use the one secondary winding? like a 480 to 120/240 and just use the secondary in the circuit to obtain a neutral and not even use your primary?
I don't think this would be a NEC violation because your not modifying the transformer?
Ronald
Re: Transformer connection
Hello Ronald, I would simply install an off the shelf single phase transformer which would be a SDS with the x2 - x3 points grounded to an approved Grounding Electrode.
I may not be understanding what you're saying so you may think I'm crazy too.
Roger
Hello Ronald, I would simply install an off the shelf single phase transformer which would be a SDS with the x2 - x3 points grounded to an approved Grounding Electrode.
I may not be understanding what you're saying so you may think I'm crazy too.
Roger
charlie
Senior Member
- Location
- Indianapolis
Re: Transformer connection
You might give the electric utility a call. In general, all pole mounted transformers have center tap bushings on the 240 volt transformers. It would be simple for them to tie the center tap of one of the transformers to the MGN and run the grounded conductor in to you.
You would have to run a grounded service conductor with your service entrance conductors and land it on your grounding bar in your service equipment. That would have to be done for every service that is fed from that bank. You would then be able to take a 120/240 volt single phase feeder from the existing service equipment to feed your new distribution panelboard without the cost of a transformer.
You might give the electric utility a call. In general, all pole mounted transformers have center tap bushings on the 240 volt transformers. It would be simple for them to tie the center tap of one of the transformers to the MGN and run the grounded conductor in to you.
You would have to run a grounded service conductor with your service entrance conductors and land it on your grounding bar in your service equipment. That would have to be done for every service that is fed from that bank. You would then be able to take a 120/240 volt single phase feeder from the existing service equipment to feed your new distribution panelboard without the cost of a transformer.
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