Subpanel instal questions
#1
04-23-03, 11:01 AM
Subpanel instal questions
I upgrading the electrical in my parents home and need to replace the old fuse boxes with a subpanel. The house was remodeled in the 60's and a 200amp service installed. The old service bacame a subpanel with an assortment of small fuse boxes hanging off it. I am replacing that mess with a new subpanel.
My questions concern wiring between the main panel and new sub. Currently there are three wires feeding the subpanel (2 hot, 1 neutral).
Question #1: Do I need to add a ground wire to link the ground buses on the main and subpanels? If so is that the only grounding point for the subpanel?
I know that the neutral and ground busses cannot be linked in the subpanel.
Question #2: Is it permissible to have a splice in the circuit feeding the stove or other major appliance? I would like to run new wire from the subpanel to the old subpanel and use it as a splice box.
My questions concern wiring between the main panel and new sub. Currently there are three wires feeding the subpanel (2 hot, 1 neutral).
Question #1: Do I need to add a ground wire to link the ground buses on the main and subpanels? If so is that the only grounding point for the subpanel?
I know that the neutral and ground busses cannot be linked in the subpanel.
Question #2: Is it permissible to have a splice in the circuit feeding the stove or other major appliance? I would like to run new wire from the subpanel to the old subpanel and use it as a splice box.
#2
04-23-03, 11:22 AM
Member
First a caution: It is almost certainly not legal for you to do wiring work in your parents' home.
Second, I am going to assume that the main panel and subpanel are in the same building. It sounds like they are.
1. Yes, and yes.
2. Yes.
Second, I am going to assume that the main panel and subpanel are in the same building. It sounds like they are.
1. Yes, and yes.
2. Yes.
#3
04-23-03, 11:48 AM
Thanks for the response.
I am an owner of the house so doing my own wiring should be fine. I also obtained a permit for the work since I want to have it inspected and on record when the house is sold.
Follow-up question.
What size ground wire do I need to use? The subpanel is about 35 feet from the main. I assume the ground wire can be bare.
I am an owner of the house so doing my own wiring should be fine. I also obtained a permit for the work since I want to have it inspected and on record when the house is sold.
Follow-up question.
What size ground wire do I need to use? The subpanel is about 35 feet from the main. I assume the ground wire can be bare.
#5
04-23-03, 04:20 PM
I plan replacing the exisitng wire and using #4 wire. I assume the ground has to be the same size as the others.
I have 1" flexible metal conduit in place to the old sub-panel. Just need to pull out the old wires, shorten the conduit and it attach it to the new subpanel.
Is 1" FMC too small for 3-#4 wires plus ground?
Thanks for your assistance.
David
I have 1" flexible metal conduit in place to the old sub-panel. Just need to pull out the old wires, shorten the conduit and it attach it to the new subpanel.
Is 1" FMC too small for 3-#4 wires plus ground?
Thanks for your assistance.
David
#6
04-23-03, 08:19 PM
Member
#8 copper ground is big enough. If the size of the breaker protecting the feeder is no larger than 60 amps, you could even use #10.
#7
04-23-03, 09:02 PM
conduit fill for FMC
From 2002 NEC ANNEX C Table C3
For 1" FMC----Type THHN, THWN, or THWN-2 # 4 = 4 conductors
Ampacity from Table 310.16 (75deg.C column) #4 copper = 85 amps. Ground wire could be #10 copper for a 60 amp feeder or # 8 copper up to a 100 amp feeder.
For 1" FMC----Type THHN, THWN, or THWN-2 # 4 = 4 conductors
Ampacity from Table 310.16 (75deg.C column) #4 copper = 85 amps. Ground wire could be #10 copper for a 60 amp feeder or # 8 copper up to a 100 amp feeder.
