Split Bus Panel


Old 12-07-14, 07:39 AM
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Split Bus Panel

Hi All

A few questions about Split Bus Panels. Looking at finishing a residental basement. Located in NJ.

House has a split bus panel which is a Murray. The panel has 4 double pole breakers in the top half in the service disconnect area. They are 40amp (range), 40amp (AC), 30 amp (dryer - not used) and 60amp (Lighting+everything else). House also has a redundant hot water circuit on a separate meter (not live).

The lower branch section has around 8 breaker positions - top six will take 1/2" according to the panel label. Furnace is NG. 70amp breaker rating max for the entire panel.

First question: The panel says 125 amps load for the top positions. Installed breakers total 170amps currently. I've read various discussions around whether the total of the breakers in the upper section can exceed the panel rating or not. A rough load calc says its currently ok but clearly if everything was used to the max rating on the installed breakers it would exceed 125 amps. What is the correct approach here ?

Second question: Basement will require 3 circuits - possibly 4. (1 for Lights, 1 for receptacles, 1 for bathroom and potentially 1 for sewage ejector). Within the existing panel 2 can be added to the lower section (switch 1 inch for 1/2 inch). Is it acceptable to utilize the dryer double pole in the upper section for 2 additional circuits (20amp multi-wire branch circuit) ?

Or is it better to switch out the entire panel ? Could not get a look at the Service Cable due to the rain last night but meter is direct behind the panel location. It looks to be 1/0 but will see if I can actually get a reference from the cable today.

All will be inspected - the basement will be done by me (homeowner) but replacing the panel looks challenging - mostly due to the timing/scheduling around getting the PoCo out to pull the meter.

Current preference is to probably have the panel replaced first by electrician and then start on the basement once all of the panel is sorted out.

Any other options ? Cost is a constraint - hence from a cost standpoint I'd prefer to leave the existing panel in place but I do read that they are not allowed in new residential and its making me think its better to replace it all before the basement is sealed up!

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Old 12-07-14, 07:49 AM
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You have what was about the cheapest panel available when your house was built about 35 or more years ago. It's probably an Arrow-Hart Murray aluminum bus panel. I would definitely replace the panel and possible the entire service including the meter socket, service cable and weatherhead after a careful inspection of the outside components. 1/0 aluminum cable tells me it's probably a 125 amp service. 35 years is about as long as service cable will typically last outside.
Old 12-07-14, 08:29 AM
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I would say a lot would depend on the condition of the service cable also. If it is in poor shape you are better off to start fresh with the new panel.

It does not matter that split bus is not installed anymore. Yours is existing and can continue to be used.

I have no knowledge of that brand of panel so I can't give an opinion on any issues with them.
Old 12-07-14, 08:52 AM
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pcboss and CasualJoe - thanks for the comments here.

Yes it is an arrow hart. Will see what the pro turns up when looking at the entire service.


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