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Does anyone know the history behind the now illegal split breaker panels that were used in the 1970’s? I’m referring to the type that do not have a maser breaker and instead use large 70A+ breaker(s) to feed additional sub-breakers.
Why were they used in the first place – lower cost?
Why are they now outlawed – safty?
Thanks,
Tom
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Tomm,
It is very unclear what you are talking about. You say that these panels "do not have a maser breaker". I assume that you mean to say "master" by which you mean main breaker. Well, what is this 70A+ breaker if not a main breaker? Since the 1970's there has been considerable standardization of electrical equipment. Are you sure that these things to which you refer are no longer legal, or could it be that they are simply a brand that is no longer used? There are a lot of breaker configurations that are no longer used much, the old Zinsco, the old Square D, the old Federal Pacific. Replacement breakers are available for most of these.
*I've occasionally seen these as well and would like to know the basis/reasons for this being an illegal configuration. What I've encountered in '50's - '70's homes is this type with 4 x 50amps or 4 x 70amps across the top where the main breaker normally is placed. If these were to be replaced with a single main breaker, do you calculate the replacement breaker by adding the four individuals together? When calculating loads from multiple breakers I've always used the NEC formula - but I'm not sure if this applies to what is essentially mutiple main breakers. What would be really useful is a simple and instant way?The one nice thing about this configuration is that you can depower the portion you are working on while leaving some power on in the house.
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Mike,
Sorry I wasn't clear. I'll describe my specific breaker box. By "maser" I meant main. At the top of the breaker panel are four 240V breakers that are fed directly from the meter. These breakers directly feed the range, drier, etc. Below these 240V breakers is a 70A breaker that feeds the remaining ten 120V breakers. To shut power off to all the loads in the house requires each of the four 240V breakers to be turned off individually and the 70A breaker as well. I've read that this was a common configuration in the 1970's but is no longer allowed in new construction.
Any info would be appreciated.
Tomm
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I got ya now. I can't say specifically why this configuration is no longer used, I think it was called a split-bus. My guess would be that a positive means of disconnecting the whole sub-panel rather than part of it should be required. The only advantage to this configuration would be the savings in the cost of the main breaker. Breakers today are much cheaper than they used to be.
*Tomm, My guess why this may now be illegal is that in an emergency a person that did not understand the system would not have one clear breaker to flip. Imagine the confusion a person would feel that had only seen systems with one main breaker!
*I think Cosmo hit the answer. Just went over the 'main disconnect' issue with the electrical inspector. A single 'main disconnect' MUST be located either outside the structure or at the closest posible point inside the structure after the 'service conductor' enters the structure, according to the 1999 NEC.It's not entirely clear to me, but I think this 'main disconnect' could be a simple switch with the 'overcurrent' protection, or breaker, protecting the equipment separately. If that's the case, maybe divided panels and breakers would be OK. Sounds like an inspector question.
*I think that they may be still legal. I believe that "six motions of the hand" to turn off everything is still in the code. I will check my new 1999 copy and repost if I find anything else. Of course it may not meet LOCAL codes.Ron
*I think Ron's close on this...Near the stream watchin the code change biannually,J
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Does anyone know the history behind the now illegal split breaker panels that were used in the 1970's? I'm referring to the type that do not have a maser breaker and instead use large 70A+ breaker(s) to feed additional sub-breakers.
Why were they used in the first place - lower cost?
Why are they now outlawed - safty?
Thanks,
Tom