Interesting fuse/breaker behavior

[brianl703]

How bout that thin tin filler in the old bx cable I've seen that used as a ground and at sometime the bx lost its bond at the load center or wall box... no good

I've heard that a fault can result in the bx cable glowing like a space heater because the bx jacket has a high resistance, in later versions they added a bonding wire to reduce it's resistance.

 

[Schandyman]

Wow that's something I didn't hear of. But yes the tin bonding wire in conjunction with the clad sheathing was acceptable as ground.

 

[JHZR2]

whats the supply voltage in the above pictured disconnect? 120 or 240v? if it's 240 where are you pulling a neutral for lighting and 120 receptacles? Looks like old 2 wire cloth cable bringing service to the disconnect. Is the white a fused neutral or being used for the 2nd hot leg?

Its a two pole switch, but just has one feed in, numbered to the second pole. Back in the day it could have been used for 220 with both hots fused and a neutral. That’s not how it was set up. It’s essentially a big junction, no 220v loads, one hot jumpered from pole to pole.

So what happened was when the one fluorescent failed, it blew the fuse on that part of the circuit. The rest of the circuit was operational still. Neutrals aren’t fused.

It’s essentially:

Main - 15A CAFCI - switch pole 1 - 30A fuse - loads
- switch pole 2 - 30A fuse - loads

The CAFCI provides overcurrent protection.

But in the short the fuse opened first.

 

[JHZR2]

you'll most likely find out there is a neutral/ground issue.. either neutrals being shared or neutral touching ground.

No, it’s an ungrounded circuit and it was due to a very old 8’ fluorescent light ballast failing. There’s a pair of them in the loft. One let out the magic smoke. It’s all fine now. But the old switch/fuse remains.

Is it a ton of work to eliminate that old fuse/disconnect box?

I don't see how doing so could cause more issues other than taking some time and effort.

Like said above, it's only going to eliminate potential problem spots likes loose/dirty/corroded connections, scuffed wires or insulation.

Seeing that cloth insulated wire takes me back to most of my (personal) home reno work. LOL. Nothing wrong with the wire itself. Just everything else with it. Can't imagine how many feet of that stuff I've pulled out and redone.

Yes, it is. It’s one circuit for all the legacy lighting on the building. Much of it is old wiring pulled through heavy metal conduit. There are some switch loops and whatnot, but it services both levels. I estimated cable needs to replace all of it just to re-hardwire all the legacy lighting, and it’s 150ft of 15ga romex. Plus removal of all the old stuff, new switches, boxes, etc.

Since I’m putting in new receptacles for loads I want to support, and don’t need a lot of load on the old stuff, a CAFCI is the best bet for safety and protection of this old circuit.

The old cloth stuff is dangerous. I’ve worked with and around it for years always better to pull new cable whenever possible. Whenever stuck with using it for existing work I would cut it back splice in a junction box and run 18-24” of new cable to lighting fixtures or ceiling fans. Good chance 99% of the time the conductor insulation is compromised and new didn’t have the temperature ratings that newer cable and wire have.

Except that if this circuit sees more than 3A I’ll be surprised. So I’m not worried about heating. The CAFCI protects it in case anything is compromised.

My limited time is better served installing real circuits for the big loads I want to power, versus wasting tons of money for over a hundred feet of wire to completely replace a circuit that spiders across 2000 sf of building that will see 3A on a very intermittent basis.

 

[Schandyman]

How do you have a hot on ea pole? If your 15a circuit is 120v?

 

[Schandyman]

Jumping to the 2nd pole doesn't increase ampacity of the circuit it was better off just wiring past the fuses and being used as a junction splice box and protecting it from the 15a afci breaker.

 

[Schandyman]

Glad you got the situation straightened out. The wiring appeared undersized for 30a fuses besides looked like 12awg wire

 

[JHZR2]

How do you have a hot on ea pole? If your 15a circuit is 120v?

As I drew it. There was one feeder and it jumpered to both poles on the switch. Nothing complex here.

Jumping to the 2nd pole doesn't increase ampacity of the circuit it was better off just wiring past the fuses and being used as a junction splice box and protecting it from the 15a afci breaker.

I never implied that it would increase ampacity. It was not wiring past the fuses - the fuse protecting the upstairs fluorescent wiring obviously did the job. It was being used as a junction as I mentioned previously.

It is sorted out now fwiw, I just need to fix the light. That’s a separate thread.

 

[Schandyman]

As I drew it. There was one feeder and it jumpered to both poles on the switch. Nothing complex here.


I never implied that it would increase ampacity. It was not wiring past the fuses - the fuse protecting the upstairs fluorescent wiring obviously did the job. It was being used as a junction as I mentioned previously.

It is sorted out now fwiw, I just need to fix the light. That’s a separate thread.

Can you send a link to that thread?

 

[JTK]

Yes, it is. It’s one circuit for all the legacy lighting on the building. Much of it is old wiring pulled through heavy metal conduit. There are some switch loops and whatnot, but it services both levels. I estimated cable needs to replace all of it just to re-hardwire all the legacy lighting, and it’s 150ft of 15ga romex. Plus removal of all the old stuff, new switches, boxes, etc.

Since I’m putting in new receptacles for loads I want to support, and don’t need a lot of load on the old stuff, a CAFCI is the best bet for safety and protection of this old circuit.

Understood. Just keeping the old stuff for the old lighting I get.

How many old 8 footer fluorescents are there? Each twin pack is around 200 watts of juice consumed IIRC. The worst part about them is replacement 8ft tubes are garbage these days as are the ballasts. Some replacement lamps would only last a matter of weeks at work, even with new ballasts. We retro'd them with 8 foot LED tubes 2-3yrs ago. Not a failure or issue yet and none of them are ever turned off. They give off so much light you only need one tube per twin pack

 

[JHZR2]

Understood. Just keeping the old stuff for the old lighting I get.

How many old 8 footer fluorescents are there? Each twin pack is around 200 watts of juice consumed IIRC. The worst part about them is replacement 8ft tubes are garbage these days as are the ballasts. Some replacement lamps would only last a matter of weeks at work, even with new ballasts. We retro'd them with 8 foot LED tubes 2-3yrs ago. Not a failure or issue yet and none of them are ever turned off. They give off so much light you only need one tube per twin pack

There are two 8’ twin light fixtures high up on the second floor, and three downstairs. Then a number of smaller fixtures.

No more than two are controlled by any one switch, and no more than two are needed for basic space lighting of each ~1000sf area. Task lighting is used beyond that.

I’m not opposed to putting in LED, especially if they’re quality… but I’m not sure they are…

 

[JHZR2]

So… retrofit is out of the equation…

Truly obnoxious smell after I opened it up (while up on a ladder). Made me gag. No interest in fixing it up. I’ll get two of the HF 5000 lumen lights for $17.99 as I think that’s probably the best value right now. It seems everything is from overseas.

 

[Schandyman]

So… retrofit is out of the equation…

View attachment 104357

Truly obnoxious smell after I opened it up (while up on a ladder). Made me gag. No interest in fixing it up. I’ll get two of the HF 5000 lumen lights for $17.99 as I think that’s probably the best value right now. It seems everything is from overseas.

Junk'd