New electrical question

[Junkman]

I have a 200 amp main panel and want to add a 3 sub panels in various parts of the house to this main panel. My question is, can I add two 100 amp and one 60 amp sub panel without overloading the 200 amp panel? I know about the 4 wire isolated grounding situation that is also neccessary.... thanks ... The Original Junk /forums/images/graemlins/wink.gif

 

[chim]

Overloading depends entirely on the loads you'll be connecting to the panels. I have a 200A panel in my house that has run out of spaces. The actual load on the panel is minimal, around 13 amps max most of the time (till the A/C kicks in or Wifey fires up the electric range).

Why do you feel you need to add these panels? If you are planning on putting a banquet hall one place, a welding shop another, and a bakery in yet another - that's different.

As long as you have the wiring protected with the proper fuses or breakers, there's hardly any chance of anything worse than tripping a breaker....................chim

 

[Junkman]

I have a 60 amp panel that takes care of the upstairs master bedroom bathroom. There is very little draw on that except when the jetted bathtub and heater are on. Other than that, just some lighting. I have run out of room in the main panel in the cellar and without going to Siamese breakers, I need more room and I already have a 100 amp sub panel that I can install there. Then there is the new shop. I have installed a 100 amp sub panel out there, but the most that will ever be on it is my 5 HP compressor and some lighting. It does have a provision for my welder, but I doubt that I will be using it very much. Just want to stay in code in the even there is ever a problem. Don't want to give the insurance company a reason to be able to back out of a claim. The reason the main panel is already full, is that when the house was built, there were many circuits added that didn't have very much draw on them. Every room has at least 2 circuits for the wall outlets and one for the lighting. The kitchen is broken up into many circuits also. Even the garage door operators are on there own circuits.

 

[johnbilt]

Should be fine. There is nothing unsafe about doing this. The main 200A breaker will protect you from overloading the feeder wires.

Most residential loads are small and will never get close to exceeding a 200A service. The breakers are sized according to the size of the branch wires and are not indicative of actual load.

Be sure to size your branch, feeder ,and ground wires appropriately and you will be good to go.

John

 

[boustany]

No problemo.

Just make sure the feed for the sub panels use the right breaker (i.e. 100 AMP and 60 AMP) and the feed cable is sized for the load on the breaker and the distance to the panel.

You rarely max out a sub panel, let alone your main panel. In fact, I believe the average load on a house is something like 5kW, or less than 30 amps on 220. There are, of course, huges swings in peaks demand.

I got sub panels all over my house (3 in the house itself, 1 in the barn fed from the house). Sub panels greatly simplify wiring because you don't need as many 'home runs'.

 

[fractal]

Just make sure the breakers in the main panel are sized for the wire leading to the sub panel. That is the key factor. I just upgraded the panel in my garage to what is sold as a 100a panel. I bought it because I needed more breaker spots. It is still fed by the same wire with the same 40 amp breaker that the old, 60 amp, panel had. One thing that people sometimes forget is that panels are rated not only by the maximum current and the number of breakers but by the number of wires. I have had an electrician tell me that the main in our house is at the wire limit for the box even though there are still a half dozen single breakers that could theoretically be swapped out for duals.

The breaker in the main panel protects the wire between the main and the sub. The breakers in the sub protect the wire between the sub and the plug or wired device. Try to draw more current than the wiring can handle and the protective element should trip.

An electrician can tell you the code for how you can evaluate the rating on your circuits. I won't pretend to do that. I find that I run out of breaker positions long before I run out of supply current. It may have something to do with my dedicating a circuit to every outlet in the garage and rarely have more than one or two things plugged in /forums/images/graemlins/wink.gif

 

[notamustang]

Two ckts in everyroom, I have worked in comercial spaces that were no where near that good /forums/images/graemlins/grin.gif. If you can afford the panels and the breakers than your more than fine. I completely understand having enough dedicated ckts with proper wire sizeing. Now when you try to sell this to someone wanting to upgrade their service or just add an outlet to a 20A ckt running at 19A which is 3A over NEC regs.

 

[Junkman]

I used to manage a shopping center. Every time a tenant moved out and a new one moved in and did a complete remodel, the old panels, breakers, wire, etc. was removed and all new installed. To me it was a waste of money, but to the tenants contractors, it was faster than trying to figure out what was done in the past and how to make it work for there project. I just collected the old panels and breakers when they were removed. I have a abundant supply of Square D breakers and few panels. Unfortunately many of the panels were 3 phase, so I only took the breakers that I knew I could use in the future. This was before e bay got going. I only wish that I had takes some of the ceiling fixtures. They make great garage lighting. If the old tenant used a lot of track lighting and the new one didn't want it, out it came. I couldn't get them to take it down carefully, they usually just pulled it down with the ceiling. I have a box of old track light fixtures that I have used the bulbs out of in the cellar. Any one want them? If I get my garage wired the way I want to, it will be bright. I have 30 single tube 4' strip fluorescent fixtures to put along the wall. I even got a huge Onan generator that was on the second floor of the building and no one knew how to get it out of the building. I just waited till the next tenent started to remodel and had the excavator that was doing some of the work lift it down off the balcony and into my trailer. That tenent gutted the entire building to make a grocery store. The excavator was in there to dig up the concrete floor. They don't call me the Junkman for nothing. /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

 

[techman]

One quick note. Code Sec. 250-24(a)(5) requires that the sub-panel not be "bonded". This means that the neutral and ground not be tied together in the sub-panel, only in the main breaker box. There is usually a screw or copper or aluminium strap provided to "bond" the sub-panel. Remove the link or screw.

If the neutral and ground are connected at both places, you can get circulating currents, also known as ground loops, which can cause current in the ground line, which is not desirable from a safety perspective.

paul

 

[notamustang]

</font><font color="blue" class="small">( which is not desirable from a safety perspective. )</font>

Its also not fun when your the one who finds the problem /forums/images/graemlins/grin.gif

That was a very good point to bring up !