Breaker to subpanel tripping

9 years ago

I live in an old, but updated home - and am a bit of an electrical novice.

I added a double pole 30 amp breaker to my garage sub-panel for an additional dryer. When I use both of my dryers, the 60 amp breaker supplying the sub-panel pops.

I have now researched 'why' and it's quite obvious. I have two 30 amp dryers, two washers, a room of computers, and the lights for 2 rooms and a hallway all running on that sub-panel that is only being provided 60 amps!! Before this, I didn't even know what a sub-panel was.

Anyway, I have researched the wiring requirements, and believe I know what I need to do to upgrade it, but I would love confirmation.

The red wire in this diagram is probably 6 gauge wire, but it is unmarked. The red wire is about 10-12 feet long, and runs through conduit then under the home to another box, and is then joined with wire nuts to the 4 gauge wire leading to the sub-panel.

I believe all I need to do is get some 4-4-4-6 copper and replace the red 10-12 foot portion of this, and upgrade the 60 amp to a 100 amp.

Am I correct?

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Comments (5)

Vith
9 years ago
last modified: 9 years ago
THHN (or 90 degree wire) would require 3 gauge for 100A. Id replace the whole wire to be without a junction. What I linked below has its own jacket is for 90 degrees, and can order by the foot. Then you need the 100A breaker that will fit your panel, it depends on brand.

http://www.cerrowire.com/ampacity-charts

http://www.homedepot.com/p/Southwire-By-the-Foot-3-3-3-5-Gray-Stranded-CU-SER-Cable-27757499/205001797

http://www.homedepot.com/s/100%2520amp%2520breaker?NCNI-5

Pricey fix if you add up per foot, but you do have a subpanel that takes up half of your main capacity.
jedobaTX9b thanked Vith
jedobaTX9b
Original Author
9 years ago
Thank you very much for your answer. I truly appreciate you.

I believe I could also upgrade to a 90amp and still keep the 4 gauge leg. It would save quite a bit of money, and I believe it would be sufficient since I only added a 30 amp. I found some 4 gauge couplers that 'look' good.

https://www.walmart.com/ip/Polaris-It-Series-Insulated-Connector-4-14-Awg/110335012?wmlspartner=wlpa&selectedSellerId=0&adid=22222222227069117749&wmlspartner=wmtlabs&wl0=&wl1=g&wl2=c&wl3=176607737218&wl4=pla-282596616956&wl5=9027823&wl6=&wl7=&wl8=&wl9=pla&wl10=8175035&wl11=online&wl12=110335012&wl13=&veh=sem#about-item

Do you think that would work?
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Vith
9 years ago
last modified: 9 years ago
It looks like a type of screw down splice to me. You would need four of those. You can use the non weatherproof ones inside instead. You just crimp them on.

Otherwise you can use four of this other splice kit which you screw down and heat shrink the protective and insulating covering over. This might be an easier option considering crimping 4 gauge may prove difficult. I havent done it with 4 gauge. Make sure you put the protective cover on first before you splice the wires.

I probably wouldnt use the ones you listed because one of the wires would have to be bent significantly to continue the same direction and that is not easy with thick wire.
jedobaTX9b thanked Vith
jedobaTX9b
Original Author
9 years ago
Thank you so much for your assistance.
randy427
9 years ago
If you run new wires underground, make sure they are THWN-2, rated for wet locations and 90 degrees. Underground conduit is a wet location by definition. Most THHN is dual rated THWN, but the '-2' indicates the 90 degree spec.
jedobaTX9b thanked randy427