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Skunky,
Your situation is acceptable.
Bob is correct, it’s O.K. because you never expect ALL the circuits loaded to their maxima at the same time. If that does happen, the main breaker will open to protect the busbar in the panel (busbar = the metal plate that carries the current from the main breaker to the branch circuit and feeder breakers–the thing that the breakers snap onto) and the service entrance conductors from the utility drop to the main breaker.
Suggestions on your shop wiring (not that you asked):
1) install a cutoff box (main switch)in a readily accessible spot in the shop for all circuits but the lights (which should be on a separate circuit).
2) Put in 240 v receptacle outlets for your stationary power tools (tablesaw, joiner, shaper). It’s worth it to reconfigure the tools for 240; current draw is one-half that at 120 v.
3) For receptacle outlet branch circuits, go up a gage in wire size (use 10ga with a 20A breaker). Tool motors will last longer.
4) Consider using conduit and pulling in conductors. That will provide you the most flexibility for future upgrades, if you use 3/4″ or 1″ EMT.
5) If you are going to use EMT and surface-mounted boxes, consider using weathertite boxes and couduit fittings to help keep sawdust out.
6) Hard wire in some fire detectors–temperature sensors (smoke detectors would probably be fouled up by sawdust). Link them to a detector upstairs (common signalling). You need to know if something’s burning in the shop and you’re not in it.
7) Put a subpanel in the garage and install arc-fault circuit detectors. These are new, and open the circuit if they detect an arcing fault. Will be required soon (Jan 2001?) by current Code in sleeping areas of dwellings for new construction.
Have fun….
Replies
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Skunky,
Your situation is acceptable.
Bob is correct, it's O.K. because you never expect ALL the circuits loaded to their maxima at the same time. If that does happen, the main breaker will open to protect the busbar in the panel (busbar = the metal plate that carries the current from the main breaker to the branch circuit and feeder breakers--the thing that the breakers snap onto) and the service entrance conductors from the utility drop to the main breaker.
Suggestions on your shop wiring (not that you asked):
1) install a cutoff box (main switch)in a readily accessible spot in the shop for all circuits but the lights (which should be on a separate circuit).
2) Put in 240 v receptacle outlets for your stationary power tools (tablesaw, joiner, shaper). It's worth it to reconfigure the tools for 240; current draw is one-half that at 120 v.
3) For receptacle outlet branch circuits, go up a gage in wire size (use 10ga with a 20A breaker). Tool motors will last longer.
4) Consider using conduit and pulling in conductors. That will provide you the most flexibility for future upgrades, if you use 3/4" or 1" EMT.
5) If you are going to use EMT and surface-mounted boxes, consider using weathertite boxes and couduit fittings to help keep sawdust out.
6) Hard wire in some fire detectors--temperature sensors (smoke detectors would probably be fouled up by sawdust). Link them to a detector upstairs (common signalling). You need to know if something's burning in the shop and you're not in it.
7) Put a subpanel in the garage and install arc-fault circuit detectors. These are new, and open the circuit if they detect an arcing fault. Will be required soon (Jan 2001?) by current Code in sleeping areas of dwellings for new construction.
Have fun....
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230 amps worth of breakers in a 200 amp service panel isn't a problem. Circuit breakers are sized to protect the weakest component in the attached circuit. If you wired 15 amp outlets with #10 wire, the circuit breaker would be sized for 15 amp even though the wire could carry 30 amps. The panel is sized based on your expected maximum current usage and the maximum power available at your site. The latter situation is usually not a limiting factor, but it could be.
One interesting thing I discovered is that the power company is not bound by the NEC codes, at least with regards to wire size. Your 200 amp service must be fed by #4-0 aluminum in most areas (250 mcm aluminum in some places) from the meter to your panel. The feed from the transformer to the meter, which is supplied by the power company,does not have to be #4-0 aluminum. In this area it is often #1-0 aluminum. The reason it works most of the time is that few people use more than 125 amps of power at any one time. Since the power company owns and maintains this part of your electrical service, they don't need to abide by the NEC codes.
One additional suggestion to add, is to try and balance the 120 volt loads. Your panel is feed by 2 hot legs and a neutral wire. A volt meter attached across the 2 hot legs will read 220-240 volts. If you measure between one hot leg and the neutral, you will see 110-120 volts. If you have a bunch of 110 volt circuits that draw lots of power try to spread these between both hot legs. It is conceivable to have one leg trying to supply more than 200 amps which would cause the main to trip, even though the other leg isn't anywhere close to 200 amps. By moving some of the breakers to the other leg you would balance the loads and avoid the tripping problem. This is only applicable to the 110 volt breakers, not the 220 ones, in a single phase system.
*Gordon,FWIW, I've been told that the sizing of the service lines to the meter (for weatherhead/ free air lines) can be smaller because any heat buildup will disipate in the air.Bob
*Thanks guys, I thought I opened a can of worms... on to the next project... Hmmm, what's in this can over here... worms?BTW CAP, thanks for the tips on wiring the shop. I planned on a using conduit and putting the tool receptacles on a 20A, 12-gauge line, but I’ll up it to 10-gauge on your advice. The Main cut-off switches were also in the plan, thanks again. Unfortunately, my budget doesn’t allow for floor machines that could be switched to 240V. Maybe in the future…And Gordon, thanks for the tip on balancing the load across the 2 hot legs, it makes sense. But then again, my common sense is what started this string!
*Per the NEC, they have tables which rate "conductors in free air", so the fact that they can or cannot dissipate heat is already in the equation. (Wouldn't direct burial dissipate heat to the ground better than to the air?)Someone earlier mentioned that it is the power co who decides what to use based on the counstruction/use and distance. When the home/service is designed, they determine the loads and spec the cable size. I always try to over-estimate with as many possible loads as I can justify: it is better than (years down the road) trying to prove to them you are getting transient voltage drops in the future and they'll need to pull new cable.Adam
*What about underground? Heat disipation would be the same. The homeowner side has to be #4-0, the power company side is typically #1-0. My information comes from my own personal experience with the power company. I mis-understood the requirements and thought that I had to supply the wire between the transformer and the meter. I buried #4-0 for them, but it wasn't in conduit. They refused to hook it up, so I dug it up, and waited for them to install their wire. They brought #1-0 on their truck. My wife mangaged to talk the service guy into installing my #4-0 inside their conduit. Otherwise we would have gotten #1-0. I talked to the guy in the office about this and he just shrugged his shoulders. He told us we were getting #1-0 aluminum wire and that was that. Fortunately the service crew was a bit more flexible about this. When my wife asked him about it, he said "Why didn't you tell us you wanted #4-0, we would brought it out". That isn't what the guy in the office said.
*The NEC has a good safety margin built in. The power companies go with what works most of the time. If their cables are undersized occasionally it doesn't cause deaths and fires, whereas bad wiring inside buildings will.Lee
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An electrical panel will allow for twice its main breaker rating plus 20%. This is due to the load being split over two hot leads both rated at the main breaker output. So if you have a 200 amp panel you could use a total of 480 amps. This is the national standard. I just upgraded a 100 amp service to 200 amps with total breakers adding up to 525. The inspector had no problem with this. I must mention that the 100 amp panel I replaced was originally wired with a total of 425 amps. In the 44years this panel served this house I never had a breaker trip. I was forced to upgrade when I built a room addition and added five more circuits, with no more slots in the old panel.
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I am putting a shop in my basement (new house) and I started mapping all the circuits in the house. I didn't know whether I had enough unused breakers, or needed to find capacity on other breakers to at least jump the lights off of (besides, I wanted to have a complete list).
I knew it was a 200 amp service, but I just noticed that there are 230 amps in breakers (2-15 amp and 10-20 amp) in the panel. I just was wondering if this was acceptable? I've checked a few wiring books, but they make no mention of whether or not to do this. I assume not, (sue me for using common sense!) but I don't want to replace the breakers if it's not called for. Thanks in advance.
*I'm not an electrician, but my understanding is that you don't just add up the circuit amperages and see if they "fit/match" the main breaker; there are formulas to be used. E.g., you wouldn't add amperage used by a central A/C and by a furnace, since they shouldn't be running at the same time.I _think_ that in most cases 230 amps worth of breakers would be ok in a 200 A box, but lets see what the experts say.Bob