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Question DetailsAsked on 11/27/2016

Question on proper installation of meter and main and making main panel the sub-panel

We recently added an extension to our house. As a result, we needed to move the electric meter around the corner. When we did this we changed the existing meter base to a meter with main circuit breaker for the house. We then turned the old main panel into a sub panel. When the electrician did this he took out the old main panel disconnect and replaced it with a quantity of 4 200A circuit breakers (at much more expense). I am wondering if it was necessary to replace the old main disconnect with these individual circuit breakers?

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Sounds to me like probably OK - explanation why below, and you likely got a lot safer system in the process - particularly safer for you (or family member) if you ever need to turn the power off to the whole house because of a problem in a breaker / distribution panel.


Your said "at much more expense" - if you are talking probably about (including $200-400 materials) about $500-800 more (maybe up to $1000 in high-cost area) installed cost, that would be about right to install and wire a two-circuit main breaker setup - perhaps NOT including wiring runs to the two inside distribution/breaker panels if a significant distance away (more than 10-15 feet).


The breaker/distribution panel (via its breakers on each household circuit) gives circuit overload (and possibly GFCI/AFCI) protection to the individual circuits in the house and any outdoor ones. However, you need protection for the panel itself in case there is a fault/short in the panel, or in the main feed wires to it from the service connection point at the meter. I can tell you from having seen the result of unprotected circuit breaker panels that you do NOT want a 200-500 amp electrical fire in your panel and not be able to turn it off - or have to access the panel to turn it off. I have, over my life, personally put out four panel electrical fires at neighbor's houses in response to a panicked call from them - due to arcing bus connections or loose main feed wires at the panel entrance point - and I can tell you I would NOT have saved them the 5-15 minute wait for the fire department to get there if those panels had not had outdoor main breakers or disconnects.


The breaker/distribution panel may have full-panel protection breakers at the top (usually only in older panels, like the top main double breaker at the top center, above the individual circuit breakers in the second photo in the following link) -


http://www.diynetwork.com/how-to/skil...


In which case the panel is somewhat protected - against most problems with the individual breakers, but not problems with the incoming main feeds to the panel or with certain types of panel failures, and there have been cases where main breakers fused and failed to trip because of the heat from a failure in the panel itself. Therefore, the current "best practice", though not yet required in all code areas, is to provide a separate shutoff as close to the incoming feed at the meter panel as possible (or in a few areas BEFORE the meter panel), so any problems in the main feed wire into the house or in the breaker panel is protected against and the power to the entire house, including feeds into the house, can be shut off safely. In the old days a disconnect (commonly with fuses or fusible link for overload protection) like you had was used - today breakers are used on residential installations to not only provide a disconnection point but overload protection that is more relaible than a fusible link and is resetable by the homeowner after an overload. This also provides the very important safety feature that you are not getting near a dangerous arcing or burning distribution/breaker panel to turn off the main breaker, and can turn it off outside (in almost all cases) if there is an emergency - not getting near an electrical fire or having to go deeper into a house with fire and/or smoke to turn off the power. A definite plus and money well spent, in my opinion.


So - in your case - you say 4 - 200A breakers were installed. I presume you mean two sets of two in pairs, with each pair tied together with breaker tie bars like this image -


http://waterheatertimer.org/How-to-in...


go a bit over half way down in the article to the photo showing three circuit breakers in the section title "Example Circuit Breakers" - the middle one is your normal 110/120V circuit breaker - the left one with two breakers side-by-side with a tie bar connecting the trip levers so they have to trip together is a 220/240V setup - each breaker protects one "side" or one live feed wire of the two-live-wire feed 220/240V circuit. You will see these, typically in 30A and larger sizes, in your breaker box for electric powered range, water heater, clothes dryer, etc. They are also used, in typically 100A and larger sizes, as MAIN breakers as in your case. Each linked or tied pair would be cut into the main feed wiring to and protect one distribution panel or distribution / breaker panel.


So - if he installed two pairs of these, that means you have two main circuits - presumably one running to the original breaker panel, and one to a new breaker panel for the new addition - each rated at 200A in your case, so this must be a pretty big house or all-electric, or maybe a lot of larger shop power tools or electric heater pool or hot tub or other heavy demands.


BTW - you said he turned the original breaker box into a sub panel - looks to me like if you have two 200A main circuit breakers, it the original breaker panel is probably still a "main" breaker panel - you just have two in the house. A "sub panel" pulls its power from another breaker panel (commonly done in laundry rooms and for garage power tools for instance) - so you might commonly have a 50-100A subpanel coming off a 200-300A rated main breaker panel. Since both your main breakers are 200A, if one is protecting a true subpanel and the other is protecting the main panel that is wrong because the subpanel would be "over-breakered". Since the main panel would be pulling some power at least while the subpanel is in use, the subpanel could not reach 200A without the main panel breaker tripping first because it would be seeing the subpanel load PLUS the load within its own panel, so the main breaker on the subpanel would not be fully effective in doing its job of protecting the subpanel.


However, If both panels are independently wired to the main breakers by/at the meter, as I suspect, then each main breaker protects one breaker panel, both pull off the main power drop coming into the meter base, and each is a "main" panel, not a subpanel - you just have two breaker panels in the house.


Presumably the electrician had the utility upgrade the incoming service drop to the meter base and commonly the meter base would be iupgraded to greater power capapcity as well, or at least checked that they are capable of carrying 400A - because that is at or above the normal installed cable rating for a normal sized residential service fopr a normal sized house - though very large and all-electric houses are commonly sized with that size service drop now. However, older and normal-sized house services are commonly rated at 400A intermittent load (25% overload over continuous rating), but only about 320A continuous load - and the main breakers should never total more than the continuous load rating of the service because they are slow-blow and can take many minutes to trip. For instance, at 100% overload current, a 30 amp or smaller breaker can take 4 minutes to trip and be within spec - for a 200A breaker it is allowed to take 10 minutes at 100% overload. Therefore, if your household system has two 200A 220/240V main breakers, the incoming line and meter base should be rated at 400A.


This is where it gets tricky - some utilities and code jurisdictions treat a 200A main breaker as limiting the circuit to 200A overload, and assume it will have 80% of that (160A) mazimum load, so allow a 400/320 service - 400A intermittent, 320A continuous. Others take the literal approach and say a 200A breaker should not (in theory) trip at LESS than 200A and may will take 250A or so to trip in a reasonable time (as opposed tot he 10 minutes to half hour it may actually take), so they say (quite rightly) that you should not allow an overload on the meter base and service drop, so they should be rated for 400A total load in your case. Other jurisdictions will require the electrician run the calcs for the actual loads and figure the maximum continuous load likely from the house, then rate the service for the greater of that or 125% of the combined main breaker capacity - so usually allowing a 400/320 meter base and service drop in your case. Depends on area and sometimes on the background of the permit inspector you draw.


Answered 1 year ago by LCD

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Answered 1 year ago by Member Services




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