ECN Forum Forums General Topics of the Trade General Discussion Area correct size of buss fuses?

I was going to do some electric work for a relative, it is a 2 family home. I was checking the system, it is a main disconnect that has two 150 amp buss fuses in it. The main disc is rated at 200 amps. the 2 breaker boxes are 75 amps each. The service entrance cable is 2/0. Shouldn't there be only 2 75amp fuses in that box?. Also this is an old Wadsworth system, with a lot of subpanels that have been added over the years. What I am eventually going to do is replace the whole system with 200amps coming in, & 2 100 amp breaker panels.

you could cal. load of each aptment. put breaker panal for each one, gutter feed both panal(Less than 6 disconnet)if both have main breaker's

no answers on this? The reason I'm asking is one lineman told me that there should only be 2 75 amp fuses in that main. I was told by another one that is incorrect, there is up to 150 amps available on each leg. So who is correct? I havn't worked with this old stuff in awile, but I thought that the 2 150 amp buss fuses was correct.

Danb1,

A little caution when approaching this task will pay off well in the future.

1. Verify what permits are required and pull them. The jurisdiction that the "2 family home" is in may require an electrical contractor, that is locally licensed, bonded and insured, be the only entity to do the work. This is a local legal concern.

2. If you can pull your own permit to do the work, hire a local master electrician to come to the 2 family home and evaluate the system. An old system, such as you describe, is not a simple thing to upgrade. Be prepared to take a lot of notes because the amount of information that is involved with the common "old ******** system with a lot of subpanels" is large.

3. Set up the relationship with the local master electrician that visits the 2 family home so that you can follow up with additional questions.

4. You will almost certainly have to pay for this electrical consulting, but the pay off is that a future disaster is far less likely to occur. It is very cheap insurance.

Respectfully,

Al

thanks for the advice, I will check into the codes if I am allowed to do this myself, I do know some licenced electricians that will be willing to give advice. Learned a lot from them. My relative wants to hold off for awile anyway, after I gave her the price for the new breaker boxes, meter bases & everything else. I have some problems with just moving the meters outside. On the wall that they would go on, there is a cable line & telephone line that might be in the way or too close to where the meter base has to go. I have to check with the utilty to see where it can be set at. The biggest problem, & a safety hazard is that there is a downspout between the insulator & weatherhead. The service entrance cable runs up along the side of the downspout, & the wires are wrapped around the outside of downspout to the wires attached to the insulator, & those wires are up against the downspout. Someone put in a new service entrance cable a few years ago, & it passed inspection!

Hello, to answer your original question, if your main service ent. cable is 2/0, then the main breakers/fuses can be up to 150 amp each. It is common for the panel itself to have a rating higher than the main disconnect, contractors often use the highr rated panel to have additional space(circuits and working clearance) in the panel. a service change is a large project and I would warn you against trying a complete service change yourself if you aren't an experienced electrician, but that's JMHO.

[This message has been edited by Electric Eagle (edited 07-17-2002).]