Fuse panel; what's wrong

[mark petty]

Just not that good with old fuse panels. Crouse Hinds - It is out in a shed in the rear yard - no visible signs of connections such as fences or phone wires. The main feeds are at the bottom / right. The only thing I know for sure is that the fuses are oversized and by flipping the main switch; the lights only stay on in mid throw. If you could; need help a.s.a.p. as I have to get the report out. Thanks, Mark

[Jerry Peck]

First, tell me that the wire at the top is connecting the two line terminals together, that they are not coming in through a small hole in the back of the enclosure.

[mark petty]

First, tell me that the wire at the top is connecting the two line terminals together, that they are not coming in through a small hole in the back of the enclosure.
Yes; correct, not coming through small hole

- - - Updated - - -


Yes; correct, not coming through small hole
There is a shadow between the two terminals

[Jerry Peck]

First, tell me that the wire at the top is connecting the two line terminals together, ...


Yes; correct, not coming through small hole

Okay, that means that one of the two cables coming up through the bottom is the feed and the other is the circuit after the overcurrent protection and disconnect - did you by chance use a meter or voltage sniffer to determine which cable was always 'hot' (the feeders) and which was switched? That doesn't affect the following, just curious.

Let's say, for discussion purposes, that the feeder is the right cable and that the circuit is the left cable (could be the opposite and not affect anything) - with that being the case, the feeder feeds a fuse, which is jumper over to the other fuse, which is connected to the circuit ... which means there are two fuses in series (overkill, but not a hazard as either one could blow and kill the power).

The photo is not is crisp focus, and zooming in to get a better look doesn't do that much good due to that lack of focus, but ... the way knife switches work is that the handle rotates an insulated bar with contacts on one side at the fuses ("load" side) which always make contact, and 'knife' blades on the insulated bar to make contact with "line" contacts (at the top in your photo); when the handle is closed ("on") the knife blades make electrical contact with contact at the top (the contact has two tensioned surfaces which maintain contact with the knife blade); when handle is opened ("off") the knife blades are pulled out of the contact, and there is no electrical contact from the supply (line) side.

The unusual part of your question is this part:

The only thing I know for sure is that ... flipping the main switch; the lights only stay on in mid throw.

At "mid-throw", the knife blades may be out of the line contacts ... or maybe not quite out ... depending on how far through "mid-throw" the handle is.

It is possible ... possible ... that the knife blades are not actually making electrical contact with the contact's side contact surfaces when the handle is fully closed to "on", but the knife blades are only making electrical contact with the contact's surfaces as the knife blades are at the top edge of the contact's surfaces and at that point the lights turn on (the contact's surfaces may be at an angle, may be forced apart when the knife blades are fully in, may be many things).

When the handle is opened enough to pull the knife blades fully out of the contacts, then the knife switch is "off", as it should be.

The end result, though, is that: Have electrical contractor replace the knife switch due to the various electrical conditions in the knife switch, including (list the things you found (one of the things you found was that the 'knife switch only turns the lights on when the handle is about mid-throw', not when fully 'on').

[mark petty]

Okay, that means that one of the two cables coming up through the bottom is the feed and the other is the circuit after the overcurrent protection and disconnect - did you by chance use a meter or voltage sniffer to determine which cable was always 'hot' (the feeders) and which was switched? That doesn't affect the following, just curious.

Let's say, for discussion purposes, that the feeder is the right cable and that the circuit is the left cable (could be the opposite and not affect anything) - with that being the case, the feeder feeds a fuse, which is jumper over to the other fuse, which is connected to the circuit ... which means there are two fuses in series (overkill, but not a hazard as either one could blow and kill the power).

The photo is not is crisp focus, and zooming in to get a better look doesn't do that much good due to that lack of focus, but ... the way knife switches work is that the handle rotates an insulated bar with contacts on one side at the fuses ("load" side) which always make contact, and 'knife' blades on the insulated bar to make contact with "line" contacts (at the top in your photo); when the handle is closed ("on") the knife blades make electrical contact with contact at the top (the contact has two tensioned surfaces which maintain contact with the knife blade); when handle is opened ("off") the knife blades are pulled out of the contact, and there is no electrical contact from the supply (line) side.

The unusual part of your question is this part:
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At "mid-throw", the knife blades may be out of the line contacts ... or maybe not quite out ... depending on how far through "mid-throw" the handle is.

It is possible ... possible ... that the knife blades are not actually making electrical contact with the contact's side contact surfaces when the handle is fully closed to "on", but the knife blades are only making electrical contact with the contact's surfaces as the knife blades are at the top edge of the contact's surfaces and at that point the lights turn on (the contact's surfaces may be at an angle, may be forced apart when the knife blades are fully in, may be many things).

When the handle is opened enough to pull the knife blades fully out of the contacts, then the knife switch is "off", as it should be.

The end result, though, is that: Have electrical contractor replace the knife switch due to the various electrical conditions in the knife switch, including (list the things you found (one of the things you found was that the 'knife switch only turns the lights on when the handle is about mid-throw', not when fully 'on').

Yes; bottom right is the feed; always have trouble with subs in separate buildings having a three wire feed and having neutrals and grounds bonded (old method vs today's standards). I have a good boilerplate narrative explaining this to customers to have sparky make upgrades as needed. Once again; thank you for your help Jerry.

[Bill Kriegh]

It is entirely possible that there is a loose contact that the blade(s) of the switch are moving into and out of depending on handle position. If this is the condition of the contact, the "mid" position of the handle may be pushing the contact against the the screw that attaches it to the buss in the switch, and away from it on both ends of the blade throw. Probably an easy fix. The fuse size doesn't matter as the circuit is protected by a fuse or breaker, likely at the main structure (house)

A lot of people see the requirement for a disconnect in a free standing shed as requiring this type of disconnect switch when in reality a regular wall-type switch of the correct rating is all that is required. I don't think a suggestion that this be done is out of line since a repair is necessary anyway.

The grounded and grounding conductors definitely need to be separated. A grounding electrode isn't required in this instance (at the shed) but may not be a bad idea depending on how often and bad thunderstorms are. If the circuit runs underground a grounding electrode may help prevent lightning from pinholeing the other conductor's insulation, allowing moisture to contact the current carrying conductors and causing eventual conductor failure and other issues prior to complete failure.

[Don Hawley]

I only see one ground wire. If the ground is on the branch circuit, which is most likely the case, the grounds and neutrals cannot be separated. Recommend a qualified electrician repair as necessary

[david shapiro]

I only see one ground wire. If the ground is on the branch circuit, which is most likely the case, the grounds and neutrals cannot be separated. Recommend a qualified electrician repair as necessary

Your eyes are better than mine, Don. I don't see any ground wire, and assumed from what little I could make out of the RH connector that this was BX.

If there are any receptacles in or on the outbuilding, I'd recommend a combo switch + GFCI as the replacement, even though this could result in the need for further troubleshooting/replacement.

[Mike Clarke]

DIY without a clue
If only 120 then only needed one side, top service and bottom circuit, having the two in series is not really a problem just not standard practice
I would be concerned with fuse sizing and proper grounding and neutral isolation

[Bill Kriegh]

I see two ground wires. I see what looks like UF cable in both connectors at the bottom and see 3 wires in each.

If all that is needed to be done here is fix the blade contacts, the neutrals could simply be removed from the ground lug and wire nutted together. Then the grounds could each be placed in a separate terminal like they are supposed to be. (I think I see two wires in the terminal used for the ground(s) but focus is an issue in being sure) It is entirely possible that removing the jumper from one of the switches and wire nutting it to the input or output would suffice.

Again, nothing but a switch needs to be there, and as long as the fuses are large enough to handle the loads they can be any size larger. The circuit is protected by whatever the supply cable feeds from. And yes, it's crappy work.

Anything else done here by a contractor to fix this isn't going to be up to snuff either unless there is enough slack in both cables to get the required free wire length. I'd sure prefer to see a 4 square box with a 20 amp toggle switch in place if this mis-mash