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| Subject - single phase from three phase | |
| tonytude20@aol.com | I am doing some wiring for a friend of mine on a small commercial building. I notice that the main service was 3 phase.Then to get single phase they installed an 70 amp dbl pole breaker on the a,b 110/120 legs (c being the high/wild leg), and jumpered the neutral. Is this code? Would it not make the three phase unbalanced? |
| wareagle | You have a delta connected secondary. The single phase loads are connected between 2 of the phases. Three phase loads use the other phase. Yes, the loads will cause an unbalance on the transformers but thats the way it is. I'm not sure what you mean by "jumpered the neutral". |
| tonytude | So, your saying that this setup will work, but its not the right way to do it? "Jumpered to neutral" I was saying that they jumped a wire from the neutral bar on the single phase to the neutral bar on the three phase(which i dont think is an actual neutral), correct me if im wrong . |
| JimmyDee | quote: If I'm following you correctly, yes the neutral bar in the 3 phase panel is actually a neutral, if the service is actually a 4 wire service. Has the neutral been installed from the meter to the first panel. If so, then it is a neutral and was done properly. This system is usually an open delta system and has one large transformer and another small one. The unbalance is designed into the power company's setup and works just fine for the customer. Jim |
| tonytude | Thanks for the imfo....I was getting tired of beating my tiny brain to death . Was worried about the unbalance. And yes its a 4 wire service provided thru the meter......"open delta" hmmm, learn something new everyday.. Thanks again....you have been very helpfull. |
| JimmyDee | This is what it looks like. Jim |
| tonytude | A picture paints a thousand words....thanks again |