Range wiring size question
restorationday
| Posted in Energy, Heating & Insulation on
Just bought a range that specs a twin 50 amp breaker. There is currently a twin 40 amp in the box and the wire is 10 awg Romex with a 50-60 ft run to the three prong receptacle. Spoke with a sparkie friend and he told me to just replace the 40 amp with a 50 amp breaker.
This seems wrong to me. If I recall right, I need 8 awg for a 50 amp set up. Is this right?
If I do need to run new wire I am inclined to do a 4 wire run instead of the old three wire. Does this matter? Plan would be run THHN in PVC conduit. I would need to run 3/4 conduit, right?
I am questioning myself because of what my fiend said.
Edited 7/13/2009 6:59 am ET by restorationday
Replies
You can use 8ga THHN for 50a, just not a cable. I would spend the extra couple bucks for 1" to make your pull easier but 3/4 will work. (three #8 and a #10 ground.)
fret,
You're right on about the conduit size.
You can use 8ga THHN for 50a, just not a cable
Rewire with 2 hots, a neutral, and a ground: 4-wire. You can use cable if the run doesn't require the protection of conduit. And 8 AWG cable should work if rated at 75 or 90 degrees. 60 degree cable must be 6 AWG.
Any reason 8 AWG cable won't be suitable? Did I miss something?
Jim x 3
There is no normal cable rated to be used beyond 60c column in 310.16 if it is inside. The 75 and 90 columns can only be used for derating."334.80 Ampacity.
The ampacity of Types NM, NMC, and NMS cable shall be determined in accordance with 310.15. The ampacity shall be in accordance with the 60°C (140°F) conductor temperature rating. The 90°C (194°F) rating shall be permitted to be used for ampacity derating purposes, provided the final derated ampacity does not exceed that for a 60°C (140°F) rated conductor."There are similar restrictions for SE, SER, AC and MC cable.
Fret, Thanks. Jim x 3
Thanks guys,Ran the new wire last night, 3 #8 awg and a #10 awg THHN in 1" conduit to the new stove, a double oven range. I needed to run in conduit because the run had to go outside for 12 ft as the new house is a split level and the only way I could figure out how to get the wire there without tearing out a lot of DW was with a short run outside. Not sure what my friend was thinking, just goes to show I should trust my gut and dig my wiring book out of the moving boxes. I ended up finding a good table on Cerro Wire's website.BTW, yes the old setup was a twin 40 amp on a 10-3 NM cable...-Day
I thought romex was
12 ga - 20 amps
10 gage --30 amps
is it safe to have a 40 amp breaker as is now, on a 10 ga wire?
Edited 7/13/2009 2:22 pm ET by edwardh1
R,
Your sparkie friend IS a fiend.
The 2-pole 40A breaker was already too big, so putting in a 50A is going the wrong way.
Rewire with 2 hots, a neutral, and a ground: 4-wire. You can use cable if the run doesn't require the protection of conduit. And 8 AWG cable should work if rated at 75 or 90 degrees. 60 degree cable must be 6 AWG.
Then you can put in your 50A breaker.
Jim x 3