Subpanel Questions

[mikemuirhead]

Hello all. I have a 100amp main panel and I'm out of breaker spaces. I am planning to add a 125amp main lug as a subpanel being fed by a 60amp breaker from the main. The panels will be right next to each other so the run will be about a foot and voltage drop shouldn't an issue. I have some 6-3 nm copper laying around but it doesn't have a ground. Will #10 copper be OK to use for the ground wire and is the 6-3 sufficient to use as the feeder? I don't need a separate disconnect for the sub since it is being fed by the breaker on the main which is literally right beside it, correct? I will have over 6 circuits in the sub. Thanks for your help.
Mike

[dbhost]

Let me get this straight. You want to pull an additional 60 amps off of an already loaded 100 amp main panel? I am no electrician, but I suspect you are asking for trouble with this idea.

It cost me more to do it this way, but I bumped my 150 amp to 200 amp service to run my 60 amp sub panel (100 amp box with a 60 amp main breaker so I can cut it all off from within the shop).

Consult with a qualified electrician. It is money well spent.

[cabinetman]

Consult with a qualified electrician. It is money well spent.

+1. Absolutely.

.

[Stytooner]

I would also caution about adding onto a loaded panel.
If it is full, that generally translates to maxed out. I would check the size of the feed going into the 100 A panel now.
The only real way to do it is if it is oversized already. If that is the case, then you might be able to split off the main to an additional 60. If not, then pulling new wire and upgrading your panel may be the only safe and up to code method.

If the conduit is sufficient size without too many bends, that may not cost as much as you might think.
If it has a lot of bends and inaccessible areas, costs can be extreme.

I would certainly call a licensed Electrician though. This is serious business.

[BobSch]

When we added our three season porch we had a 200 amp panel put in as a new main and ran our original panel as a sub from the new one.

Then a couple of years ago, I added a 100 amp sub in the garage.

[woodturner]

Hello all. I have a 100amp main panel and I'm out of breaker spaces. I am planning to add a 125amp main lug as a subpanel being fed by a 60amp breaker from the main.

You may be better off to switch some of the breakers in the main panel to half size breakers, if your panel supports them and you have not already done that. This would free up additional slots to add new breakers.

However, you really need to do a load calculation to make sure you are within NEC requirements with the new loads, and to make sure you are not creating a fire hazard. If you don't know how to do this and don't want to learn, you should have an electrician do this for you.

Briefly, NEC specifies how to derate circuit loads to estimate the total continuous load on the panel. In other words, NEC alloww more than 100A worth of circuit breakers to be installed in a 100A panel, provided the circuits are properly derated.

Regarding your specific questions, 10 gauge wire is not sufficient for the ground - the ground must be sized to carry the full load of all the circuits. Normally we would use four or six gauge solid copper.

Six gauge should be adequate for the hot and neutral for 60A. Remember that the ground/neutral bond in the subpanel must be removed, so that the only connection point between ground and neutral is in the main panel (assuming that is where your utility wants the bonding to occur, based on your post).

[mikemuirhead]

Thanks for all of your replies. I have contacted several electricians and so far I would be well over $2000 for a panel upgrade. I would need to replace my meter socket to one with a higher rating and a disconnect, remove a large portion of my back deck/patio, retrench for the new wire, get approx 35 feet of wire from the meter to the panel underground, plus the cost of the new panel.
My original panel is a 12 position with six of those being used for 240 v service to the stove, A/C unit and Dryer. The remaining six are 1 tandem 20 amp and 5 tandem 15 amp breakers. Based on the loads being used, I'm at about 50-60 amps. An electrician I talked to said that a sub panel is a viable solution. I would move four circuits from the main to make space for the 60 amp breaker and add them to the sub. I want to add a 240 circuit for a compressor and heater(same plug so the will not be used at the same time). Any more thoughts?

[toolguy1000]

Hello all. I have a 100amp main panel and I'm out of breaker spaces. I am planning to add a 125amp main lug as a subpanel being fed by a 60amp breaker from the main. The panels will be right next to each other so the run will be about a foot and voltage drop shouldn't an issue. I have some 6-3 nm copper laying around but it doesn't have a ground. Will #10 copper be OK to use for the ground wire and is the 6-3 sufficient to use as the feeder?

my electrician told me to use 6/3, which is 3 conductors and a ground. is your 6/3 really 6/2 (2 conductors , black and white, and a ground?)

I don't need a separate disconnect for the sub since it is being fed by the breaker on the main which is literally right beside it, correct?

correct

I will have over 6 circuits in the sub.

again, the number of permitted circuits is noted in/on the sub panel box.

Thanks for your help.
Mike

while you are doing exactly what i've done (and it's been blessed by a licensed master electrician here in NY), it may not be approved in your jurisdiction, so i'd verify that first. i would follow the suggestion to change from full size to half size breakers, as long as the circuit count for your main panel isn't exceeded (spaces and allowed circuits counts are usually printed/stamped into a panel box or cover).

being in a suburb north of NYC, we have natural gas for heat, HW, cooking abd drying, as well as municipal water. our demand for electricity is relatively low with the fridge and central AC (the primary reason for the sub panel) being the heaviest consumers. and yes, i run a 3 ton central AC system off my 60A subpanel and have NEVER dropped a breaker or even seen the lights dim when the compressor activates. load balancing is very important.

[toolguy1000]

Thanks for all of your replies. I have contacted several electricians and so far I would be well over $2000 for a panel upgrade. I would need to replace my meter socket to one with a higher rating and a disconnect, remove a large portion of my back deck/patio, retrench for the new wire, get approx 35 feet of wire from the meter to the panel underground, plus the cost of the new panel.
My original panel is a 12 position with six of those being used for 240 v service to the stove, A/C unit and Dryer. The remaining six are 1 tandem 20 amp and 5 tandem 15 amp breakers. Based on the loads being used, I'm at about 50-60 amps. An electrician I talked to said that a sub panel is a viable solution. I would move four circuits from the main to make space for the 60 amp breaker and add them to the sub. I want to add a 240 circuit for a compressor and heater(same plug so the will not be used at the same time). Any more thoughts?

IMHO, i'd pop for the upgraded service. you could get by with a sub panel, but more amperage is always a good thing.

[chopnhack]

being in a suburb north of NYC.

Is romex allowed in NY now? Or was it just not in NYC?

[cabinetman]

Any more thoughts?

My thoughts are that it's all well and good to read replies that are taken from the NEC, and you could go to the NEC and get more details. You could likely go to the codes for your specific area. But if you have limited knowledge or experience with electrical work, as indicated by your questions, to continue with an electrician to get specific details and to get it done. As for the cost, you could get other opinions/bids.

There is extreme liability and hazards with shock and fire with taking on a project like this, not only with you personally and your family, but to include surrounding structures and their inhabitants. Just my opinion.

.

[atgcpaul]

My thoughts are that it's all well and good to read replies that are taken from the NEC, and you could go to the NEC and get more details. You could likely go to the codes for your specific area. But if you have limited knowledge or experience with electrical work, as indicated by your questions, to continue with an electrician to get specific details and to get it done. As for the cost, you could get other opinions/bids.

There is extreme liability and hazards with shock and fire with taking on a project like this, not only with you personally and your family, but to include surrounding structures and their inhabitants. Just my opinion.

.

+1.

My official electrician (when it's over my head) lets me play apprentice for a day to save money. I dug the trench from the house to the garage for the conduit to the new sub. I bought the materials (using his account to get his trade price) and I helped him pull wire from here to there. I let him do all the nitty gritty stuff when I didn't want to get fried. He got the panel installed then I put in the breakers/wires to all the outlets I installed.

He is our realtor's husband so that helps he was amenable to letting me help.

[jseklund]

It will cost you $2000 to upgrade and do it right. You will also probably have room for future needs at this point.

What will a house fire cost you?

It's electrical and no one ever thinks their house will catch fire, but I've seen 2-3 in the last couple years just in my small town.

I added a subpanel at my parent's house for my dad's shed and he has a huge service (300 amp I think) coming into his house. I ran #10 wires through conduit in the ground into a small box for a 60A service out in the shed. As stated above, the electrician let me do a bunch of the work myself. I paid a landscaping company $200 to dig a 100' long trench 2 feet deep and I dropped the conduit and pulled all the wires myself. I even wired up the shed for outlets and switches and lighting myself. The electrician came and hooked it all up to make it live. Total cost turned out to be about $700 including materials - but I didn't have to upgrade the main panel either.

You don't need an electrical fire that you caused to burn down your house. Do it right.

[cwsmith]

I just had a 100-amp service run to my unattached garage which set behind my house, at the edge of the property. It cost me $2000 just for that, which included the trench, cable, conduit, new box, fittings, and initial wiring for two outlets and a switch for the lights. (One outlet box was for the garage door opener.)

When I bought this house six years ago, it had a 100-amp breaker box in the basement. First thing we did was had it upgraded to 200-amp. That required a new box, weatherhead, and cable in from the pole. The old cable was much too small (about 1-inch dia visually... the new wire is about 2-inch or so).

It is absolutely essential that everything be done properly! While I can certainly run new, troubleshoot, and repair typical househole circuits, I feel you need a "pro" when it comes to doing a new service (even though I've had experience with that too). Code changes all the time, and a somebody in the business with be totally up on both NEC and local code requirements.

Point is you are maxxed out now with your older 100-amp box, and to now expect to add a secondary break-out with 60-amps of additional capacity is really asking for trouble IMHO.

I know it is a big expense, but it's better than loosing your house or worse. Go for doing it properly, you won't be sorry.

CWS

[mikemuirhead]

Thanks to all who replied. As much as I would like to upgrade the main, it really isn't in the budget.
Toolguy- all of my 120v breakers are already 1/2 size so that's not an option for me. My feeder line is definitely 6/3 black/red/white with no ground. I'll probably just strip off a length of left over neutral #6 and relabel it for the ground instead of using the #10 although I have been told that it is OK to downsize the ground by 2 sizes.