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Old 10-03-2011, 05:32 PM   #1
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Question: Had a short circuit - burned through cable


We have a well pump outside. It has a new well pump in it. The cable leads to an old exterior fuse box mounted on the exterior of the house. Inside it are 30 amp fuses. The power comes from main panel inside into exterior fuse box, which doubles as a switch. The main panel has a 20 amp circuit breaker controlling this (dedicated) circuit. The romex cable that brings the power to the fuse box just had a short in it and sparks burnt through the casing, luckily on the exterior of the house. we are having new fiber cement siding installed on house, so I assume the cable got disturbed when the fuse box was removed and that caused the short. My questions are:

Do I need to install a 30 amp breaker in the main panel for a well pump, or are the existing fuses over-sized?

Do i even need this fusebox at all? Can I not just install an interior Jbox and make the connection of the cable from the pump and the romex from the panel inside the house, away from the elements?

Do I really need a switch at this location? I would foresee leaving the well pump circuit alive all the time, except, maybe, in the Winter, so we can use the well whenever we want without throwing a switch.

I would like to get this squared away very quickly, so any prompt answers are greatly appreciated. Attached are shots of existing conditions.
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Question: Had a short circuit - burned through cable-exterior-fuses.jpg   Question: Had a short circuit - burned through cable-short-circuit.jpg  

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Old 10-03-2011, 07:30 PM   #2
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Question: Had a short circuit - burned through cable


You need a disconnect for pump power so something is needed on the outside. I don't see any water tight fittings or an approved whip supplying power to the pump. The power feed looks to have just a romex box connector.
Surprised the breakers or those fuses didn't trip or blow.
If you get just a box that has a disconnect that will be fine because the panel breakers will provide the circuit protection.

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Old 10-03-2011, 07:38 PM   #3
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Question: Had a short circuit - burned through cable


True. Something like an AC uses for a disconnect would work and look ok.
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Old 10-03-2011, 08:05 PM   #4
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Question: Had a short circuit - burned through cable


a7e, we would have shore power cables catch on fire all of the time in Philly, and they would never trip the disconnect, either on board ship or on the shore in the cabinet. You could set a clock daily, due to the shear high amount of cables that would burn up.

As long as there was power still going through the cable, it would continue to be powered up, until it either ran out of energy, or someone disconnected that phase. Do a search on youtube for electrical wire fires. http://www.youtube.com/watch?v=X8ENhrKdkKg
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Old 10-04-2011, 06:19 AM   #5
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Question: Had a short circuit - burned through cable


Do you think I should install a 30 amp breaker at the main panel, because those exterior fuses were 30 amp, or would the existing 20 amp be OK?
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Old 10-04-2011, 07:13 AM   #6
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Question: Had a short circuit - burned through cable


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Do you think I should install a 30 amp breaker at the main panel, because those exterior fuses were 30 amp, or would the existing 20 amp be OK?
Need to keep the 20A, unless all the wiring is #10 or larger. Even if it were suitably heavy wiring, it's generally not a good idea to use a larger breaker than required to operate the equipment. If the 20A breaker has not been tripping then there's no reason to increase it. Using larger fuses in the disconnect switch than the breaker feeding it is a trick that basically turns the fused disconnect into an unfused disconnect - it guarantees that the breaker will trip before the fuses blow, thus controlling where the overload protection function is performed and letting you just reset the breaker instead of having to replace fuses. This trick assumes the right type of fuse is chosen (typically a time delay fuse) to ensure that the breaker trips before it blows.
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Old 10-04-2011, 07:25 AM   #7
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Question: Had a short circuit - burned through cable


I am not sure that the current disconnect is even rated for use outside.
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Old 10-04-2011, 07:26 AM   #8
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Question: Had a short circuit - burned through cable


So as A7ecorsair said above, I don't really even need a fused connection at the switch box, right? I can just connect a cut-off switch at an external box and the 20 amp breaker at the main panel will guard the circuit?
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Old 10-04-2011, 07:31 AM   #9
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Question: Had a short circuit - burned through cable


Unless the well pump requires fused protection, you only need a means of disconnect.
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Old 10-04-2011, 07:43 AM   #10
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Question: Had a short circuit - burned through cable


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I am not sure that the current disconnect is even rated for use outside.
Nor the romex connector on the side

I'm not a great fan of HD but their site is great for heisting pictures. Here is what you need.
http://www.homedepot.com/webapp/wcs/...cats-_-Hero_01
Bring your feed straight into the back so it it hidden.

Then add one of these:
http://www.homedepot.com/Electrical-...atalogId=10053

You many need something longer but this is the idea.
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Old 10-04-2011, 07:49 AM   #11
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Question: Had a short circuit - burned through cable


Thanks for the pics and links. I will take those to HD tonight and pick up the right stuff. I had planned to relocate the new box over the existing hole and come in to the back of the box. Not sure where the whip would go though. The black pump cable comes up from underground conduit (which stops about 4" above grade) and is exposed. I was hoping to run the pump cable through exterior PVC conduit to the new box, IF I can make the connection to the existing underground conduit end. Would that be OK?
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Old 10-04-2011, 08:14 AM   #12
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Question: Had a short circuit - burned through cable


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I was hoping to run the pump cable through exterior PVC conduit to the new box, IF I can make the connection to the existing underground conduit end. Would that be OK?
Forget the whip. Do you have enough length in your cable so you can re-strip the wires? Liquidtight conduit might be a good choice.
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Old 10-04-2011, 08:20 AM   #13
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Question: Had a short circuit - burned through cable


I believe I have enough wire to run into a new exterior box, and strip and connect them. It will be close though.
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Old 10-04-2011, 08:53 AM   #14
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Question: Had a short circuit - burned through cable


Quote:
Originally Posted by a7ecorsair View Post
Nor the romex connector on the side

I'm not a great fan of HD but their site is great for heisting pictures. Here is what you need.
http://www.homedepot.com/webapp/wcs/...cats-_-Hero_01
Bring your feed straight into the back so it it hidden.

Then add one of these:
http://www.homedepot.com/Electrical-...atalogId=10053

You many need something longer but this is the idea.
You can actually get the whip & disco all in one for around $20.00 At least that is what I got it for at Menard's a year ago.

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