Sub Panel Codes

bergenbldr

question about sub panels and code reqs,is it ok to add a subpanel to exisiting service say 60 or 100 amp,and what maximum amps can sub panel be.Also does sub panel need to be located next to existing service panel or is say panel in garage and sub panel in basment ok.Also can 60 amp panel be replaced or must it be upgraded to 100 amp.

mdshunk

You may add a subpanel to any size of service, but the new load added to that new subpanel may not put your total demand load over the 60 or 100 amp service. The inspector may make you show him the written "demand load claculation" to prove that you don't have more than a 60 or 100 amp demand load.
A subpanel's "size" (ie. rating) is only the rating of how "heavy duty" the subpanel is. You can connect a 200 amp subpanel to a 60 amp service if you so choose, but you can't load that subpanel to 200 amps. The size of the subpanel's total load is restricted by the breaker or fuse in the main panel that serves the subpanel. For instance, it is quite typical to connect a 100 amp subpanel for a garage to a 60 amp breaker in the main panel and run 60 amp rated conductors to that subpanel. Even though the subpanel says "100 amps", it's really restricted to 60 in that case.
The subpanel may be located anywhere on the property. The two restricted areas are bathrooms and clothes closets. You only need 6-1/2 feet of headroom and 30 inches width working space. Heck, you could even mount the subpanel outdoors if it is so rated.
That's a grey area, that required input from the local inspector. The code (since the 1960's) has said that the minimum service size to a dwelling shall be 100 amps. Most inspectors won't let you replace a stitch of 60 amp service equipment without upgrading to 100 amp (at least). The cost difference is almost nothing. If you have a customer with a 60 amp service, and anything much is being added or if any piece of the equipment appears to need attention, you'd be 100% justified in adding the service upgrade into the estimate.

bergenbldr

thank for info,i always try convince customer to upgrade to 200amp service if its only 60 or 100amp.But i see lots of previosly installed subpanels,usally are added as part of ac installation.

mdshunk

Yes, and they are generally all nonconforming installs (illegal). I've seen 140 amps worth of heat pump stuff connected to a 60 amp service. This works until the first heating season and the backup heat kicks in. Since I do mainly old work, and 1 or 2 service upgrades a week, what you describe is quite normal. It is fairly typical to remove half a dozen little sub boxes and replace it with one big modern panel. If you can get ahold of a residential demand load calculation program, that will give you some leverage with the customer. Recommending a service upgrade on a wholesale basis is just guessing. Occasionally, you run across a customer in a small house with gas appliances that still has a 30 amp 120 volt service. This is really the only one that you can safely and strongly state, "This service MUST be upgraded".

bergenbldr

My father in law has a 30amp 2 fuse service in summer house. Been trying to convince him to change it for years.I believe this is the original box from 1930's . btw what panel do you prefer,my electrician uses square d almost exclusivly.

mdshunk

Well, ask 10 guys and you'll get 12 different answers. I'll try to help sort out some of the mystery so that you can make an educated decision.

Square 'D' has been around for a long time, and has much brand recognition. When a customer expresses a preference for Square 'D', I have no trouble installing that brand. If I'm doing a service upgrade and they already have smaller panels of that brand that are getting replaced, I install a new Square 'D' panel so that I can reuse all the old breakers to save them money. There are 5 variants of that brand. There was the "XO" breakers, which are totally obsolete, and are no longer made. There was the "Trilliant" type, which is still available at great expense, but was a marketing flop a decade or so ago. There's the "QO" type, which has been the residential standard for many decades. There is the "QOB", which is a bolt on version of the "QO", generally used in commercial applications. It would be expensive for a dwelling, but is a fine upgrade. Finally, in recent years there is the el-cheapo "Homeline" type, based on an old Westinghouse design. You see Homeline installed where price is the only concern.

I mention this old Westinghouse design, because it is the design that most panel/breaker manufacturer's base their design on. Seimens, Square 'D' Homeline, Cutler-Hammer 'BR', Murray, ITE, Crouse-Hinds, T&B, Westinghouse, General Switch, most GE, etc. There's nothing wrong with this design, but it is low end. It also takes 1" tall breakers, which makes for a bigger panel.

My preference, when the customer expresses none, is Cutler Hammer's 'CH' series. The breakers are 3/4" tall (like the QO's) and the buss bars in the panel are all copper (unlike QO). In addition, the CH breakers have an extra spring around the clips of the breaker where they clip on the bussbar that causes the breaker to clip on very tightly. Burnt bussbar fingers and burnt breakers (as a result of a loose clipped connectino) are common to find on QO panels. I have never observed such a failure on CH panels. The Cutler Hammer 'CH' panels are a little bit more in price than a QO, but better for many subtle reasons, in my opinion. There are many other features about the CH panels that make them easier for the electrician to work with.

The short answer is, if the panel is UL listed, it's perfectly fine to use. It's sort of a Fords vs. Chevy's question. There's reasons on both sides. If money was no object, I'd install a bolt on breaker panel everywhere (like Square D QOB, or Cutler Hammer CHB), but that is just a dream.

There was a brand in the past, called Federal Pacific, that has turned out to be a real hazard. Do a Google on that brand. Wow. If you see any Federal Pacific (FPE, sometimes) in any of your projects, I assure you that it's worth a service call to an electrician to have it looked over really well. Zinsco, Wadsworth, and PushMatic are a few other brands that have faded into the past. If you need to add much stuff to one of these obsolete panels, it is often cheaper to replace the panel than to buy more than one or two new old stock breakers for these obsolete panels.

bergenbldr

His main reason for the square d panel is the number of breaker spaces,these are the smaller breakers. Heard about the federal pacific problems, never seen one though. could you explain what bolt on panel is.

mdshunk

Interesting you say that, because the code limits a panel to 42 spaces max. Most manufacturers make a 42 space panel, but the biggest one Square D makes is 40 spaces. Go figure. Maybe the electrician means that the panel is smaller than a panel with the same number of spaces in another brand.

bergenbldr

I think this is compared to less expensive panels sold at the big box.My own 200amp panel has only 32 spaces,byant murray type.

hansdankers

Get a siemens panel,thats the best and cheapest,the breakers are good and interchangable with westinghouse,
Home depo has a good price on that.
Dont forget to seperate the nutral and ground connection in a subpanel unless you run a seperate independant ground