Protecting both legs in 240v circuit
#1
09-29-13, 07:43 AM
Protecting both legs in 240v circuit
Hi,I know that two breakers are ganged together in a 240v circuit so that both legs are disconnected if there is a short in either leg. I have an older service panel that has a pullout block for a range that has a shotgun-type fuse in each leg. How does this work then? Just one fuse blows? Thank you.
#4
09-29-13, 11:11 AM
Can I hook up it up to a subpanel with a 20 amp breaker to it to provide 240v to a submersible well pump?
#7
09-29-13, 11:39 AM
If the 240 volt pump(around 6 amps) was the only thing I would be running off this subpanel then could I feed it with NMB 12-2 with ground. Or do I need to run 3 wires with ground?
#10
09-29-13, 12:45 PM
so if I wanted to add a 120v circuit(along with the 240v) to the subpanel, would I then have to feed the subpanel with 3 wires plus ground?
I feed it with NMB 12-2 with ground.
#11
09-29-13, 01:05 PM
Or, if I use a 30 amp fuse, I could run 10-3 plus ground for 120/240? Also, I've read that I should use a slow-blow fuse if it's feeding a motor. Is this true even if it's running through a 20 amp breaker in the subpanel?
Last edited by brucers; 09-29-13 at 01:43 PM.
#12
09-29-13, 03:06 PM
Or, if I use a 30 amp fuse, I could run 10-3 plus ground for 120/240? Also, I've read that I should use a slow-blow fuse if it's feeding a motor.
#13
09-29-13, 03:06 PM
Or, if I use a 30 amp fuse, I could run 10-3 plus ground for 120/240?
I've read that I should use a slow-blow fuse if it's feeding a motor.
Is this true even if it's running through a 20 amp breaker in the subpanel?
#14
09-30-13, 09:31 AM
What amp rating size of subpanel would I need? Say I'm going to use a 40 amp fuse and 8-3 wire, is there a maximum amp rating of the subpanel. Can I put in a 100 amp 6 slot as long as my total current figures less than say 80% of 40 amps?
#15
09-30-13, 09:47 AM
It doesn't matter what the rating of the subpanel is so long as it is large enough to handle the total load. Just size the overcurrent protection in the panel you're feeding from to protect the feeder conductors.
How far away is the well pump? How long will the conductors be from the subpanel to the pump? Will they be individual conductors in conduit?
Can I hook up it up to a subpanel with a 20 amp breaker to it to provide 240v to a submersible well pump?
#16
09-30-13, 09:59 AM
"How far away is the well pump? How long will the conductors be from the subpanel to the pump? Will they be individual conductors in conduit?"
The well will be drilled about 20 ft from the house and the wells in this area are around 200 ft deep. So, about 220 ft from the pump to the subpanel. Not sure what size 240v pump they will put in, but the driller told me the pumps draw around 6 amps. The wires are not in conduit.
The well will be drilled about 20 ft from the house and the wells in this area are around 200 ft deep. So, about 220 ft from the pump to the subpanel. Not sure what size 240v pump they will put in, but the driller told me the pumps draw around 6 amps. The wires are not in conduit.
#17
09-30-13, 12:29 PM
about 220 ft from the pump to the subpanel. Not sure what size 240v pump they will put in, but the driller told me the pumps draw around 6 amps.
#19
10-01-13, 11:25 AM
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Because fuses are not ganged together , if short is only on one leg, that legs fuse will blow not both fuses. I hope this will clear up any confusion with our moderators.
#20
10-01-13, 11:56 AM
Because fuses are not ganged together , if short is only on one leg, that legs fuse will blow not both fuses. I hope this will clear up any confusion with our moderators.
#21
10-01-13, 09:00 PM
Because fuses are not ganged together , if short is only on one leg, that legs fuse will blow not both fuses. I hope this will clear up any confusion with our moderators.
Originally Posted by brucers, in post #1
I have an older service panel that has a pullout block for a range that has a shotgun-type fuse in each leg. How does this work then? Just one fuse blows?
Originally Posted by pcboss, in post #2
You are correct. The one leg would continue to supply power.
#22
10-01-13, 11:43 PM
"A time delay or slow blow fuse is OK, that's what I'd use. You'll probably have to also buy a set of fuse reducers to fit the range pull-out of your panel if you go with 30 amp fuses. "
Last edited by brucers; 10-02-13 at 12:47 AM.
#23
10-02-13, 04:04 AM
Do I need time-delay in the Main block too(50 or 60 amp)?J
Last edited by ray2047; 10-02-13 at 06:21 AM.
#24
10-02-13, 05:32 AM
Best to use them. As I wrote earlier most homes now use breakers and the common residential breaker is slow blow allowing for momentary overload.
#25
10-02-13, 06:20 AM
If the pump normally draws 6 amps, what is the maximum surge/startup current one would expect?
