Melted Wire

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emtnut
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Re: Melted Wire

Post by emtnut » Mon Dec 10, 2018 9:20 pm

rchesterton wrote:
Mon Dec 10, 2018 7:59 am

2. About 10 feet down the line (toward the box) where the line turned into the wall of the garage and then down into the basement, I had a junction box that served as protection for the line. There was no junction, the line just went from conduit into the box and through the wall into the basement. I didn't know another way to protect the line so I used a box. At that spot, there was blackening around the conduit (where it went into the junction box) and also around the screws that held the clamps together. The line was intact however. No breaks in the insulation or anything like that.
This part may be gone now, but it would have been helpful to see a pic of that.

The blackening around the screws on the clamps make me wonder if there was a problem with the cable install.

If nothing else, a pic of the cable there now in that junction box, and whatever clamps are on the cable may help us.
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Aaron
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Re: Melted Wire

Post by Aaron » Mon Dec 10, 2018 11:11 pm

Yes post pics please. I'm wondering if that heater is hard-wired with an armoured cable whip or uses a corded 240V plug. Read your manual. I'm thinking hardwired...

rchesterton
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Re: Melted Wire

Post by rchesterton » Tue Dec 11, 2018 8:05 am

I took the old wire out and pulled #6 through the same basic setup. I still have to mount the heater in order to run a line from the disconnect box to power it, but yes, it is hard wired.

The bottom box has a clamp on it that I am going to replace with a larger clamp (or more appropriate one if you can tell me that there is one) because it it not big enough to go around the conduit into the box. But, inside the box (sorry I don't have a picture with the cover off) the wire comes from the back (through the wall) and then bends straight up into the conduit. I have the insulation stripped right back to the clamp so there is unshielded 6/2 in the box and going through the conduit up to the service disconnect box. My plan was to use metal flex tubing (with the appropriate clamps) to run line from the service disconnect into the heater itself to allow for heater adjustments if need be.

Pictured: The junction box. The old clamp, if you can see, there are screws there that are slightly blackened (looks like due to heat). They were brand new. The end of the conduit going into the box is also slightly blackened.

As I have been thinking about this, I want to replace that junction box with a more appropriate one. I am sure there is something that will allow that wire to be less stressed as it takes the turn upward along the wall into the conduit. I considered a multi-tap connector but I do not know if that is an appropriate application for this. Is it? Or is there simply a better component used for larger gauge wires that are taking a 90 degree turn like this is?

The rest of the run (behind the wall) goes across the basement ceiling (it is a drop ceiling) and into the breaker box. It is not attached yet, obviously. It is laying across the drop ceiling (but the plan is to staple it onto the joists above as I finish the project.

One thing that I am sure you will point out is that the black going into the service disconnect box is stripped too long. I need to shorten that so the insulation goes right up to the lug like the white one is. They are clamped down very tight, though.

What else? I am open to all critique and learning! I just want to make sure to do it right and be confident in the final result.
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rchesterton
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Re: Melted Wire

Post by rchesterton » Tue Dec 11, 2018 8:07 am

The pics posted sideways, sorry. The bottom of each is facing right screen. The second and third pics are the service disconnect box and the bottom picture is the junction box at the bottom near the floor. The entire setup is the first pic (minus the heater itself).

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Aaron
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Re: Melted Wire

Post by Aaron » Tue Dec 11, 2018 9:19 am

You need to use 3/4" diameter EMT, you are over the fill capacity of 1/2" with the two #6 conductors and the ground.

Also, you're using NM clamps for EMT, which is the wrong box connector to the box. You need to use a box connector like this:
emt-boxconn.jpg
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Also, since you're not doing box offset bends of the EMT so that the conduit runs flush against the wall, you should use a conduit hanger to strap it to the wall:
emt-hanger.jpg
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Aaron
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Re: Melted Wire

Post by Aaron » Tue Dec 11, 2018 9:24 am

That was what I noticed right away... I'll read the rest of your post later. I suggest using a deep 4 11/16" square box for the 90 degree turn into the wall.

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Re: Melted Wire

Post by rchesterton » Tue Dec 11, 2018 1:49 pm

Thanks for that information so far. I do wonder about using one of these for where it comes in from the wall?
Conduit Body .jpg
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Aaron
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Re: Melted Wire

Post by Aaron » Tue Dec 11, 2018 6:59 pm

Sure, you could use that ell body. It's typically used more for exterior applications, but it's perfectly fine to use it inside. You may want to use 1" sized conduit to negotiate the cable around the bend more easily.

You also need bushings on the inside of every box you have your #6 coming in and out. They're either metal or plastic screw-on rings that go over the lock washers of the box connectors. They're required for larger diameter sizes of conduit and especially with heavier gauge cable. Bushings look like this:

bushing.jpg
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emtnut
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Re: Melted Wire

Post by emtnut » Wed Dec 12, 2018 9:22 am

Agree with Aaron on either a larger box, or an oversized LB.

Minimum distance between where the cable enters and exits the box needs to be 4.5". So you would probably need at least a 6" or possibly 8" box to accomodate that.
A 1" LB, with reducers should work as well.

That 1/2 EMT was even to small for your previous #8 cable, as well as the junction box.

I don't see the blackened fittings you mentioned, but if the conduit was getting that hot, there was either something seriously wrong with the other heater, or you had a partial short in your wiring ??
You should either buy or borrow a clamp meter and measure the current draw when you have finished the install.

Another issue could be how long the unit is running. If the unit has to run continuously when it's cold out, that usually will cause problems. These things can/will burn out if used that way.
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rchesterton
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Re: Melted Wire

Post by rchesterton » Thu Dec 13, 2018 9:48 pm

Thanks for all of the input on this project. I am always amazed at how much I learn from every project like this. I'll get back to work on this over the weekend and let you know how it comes out.

I did buy a clamp (Klein type). Still figuring out how to use it, really. It was a great excuse to get a new toy!

I stated above that when I undid everything I set up the first time around for some reason one of the conductors going into the actual breaker was fairly loose (the black one). I guess I will never really know if it was the heater itself or a poor connection that caused the issue.

Either way, I think this time I am setting up in a successful way.

Thanks again.

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Shannon
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Re: Melted Wire

Post by Shannon » Fri Dec 14, 2018 8:27 am

That loose connection for sure could have been the problem originally.
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rchesterton
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Re: Melted Wire

Post by rchesterton » Fri Dec 14, 2018 9:15 am

Is it common for larger appliances / gauge wire to become loose over time due to the current? I know that I tightened them - I am always very careful and meticulous about my work. I ask just to know if I should make a habit out of going back after a couple of days and really tightening them down a bit - if that is a known issue that can occur.

Plus I am looking for an excuse so I don't feel like it is completely my fault! :mrgreen:

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Aaron
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Re: Melted Wire

Post by Aaron » Fri Dec 14, 2018 9:38 am

Well you could have certainly tightened them but perhaps you had tension on the cable or something and it wiggled loose. You were using undersized conduit so there could have been some strain previously. We'll never know for sure.

No certainly current has no effect on a physical connection. Imagine having to worry about tightning the lugs all the time on your main breaker.

rchesterton
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Re: Melted Wire

Post by rchesterton » Fri Dec 14, 2018 9:49 am

Yeah, makes sense. I wasn't sure if it was due to heat with such high voltage (shrinking/expanding the copper?) or not. Thanks again for all of the attention you all have given this project of mine...over 70 threads! Yikes. I'll follow up and let you all know how it goes.

Thanks

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emtnut
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Re: Melted Wire

Post by emtnut » Fri Dec 14, 2018 8:23 pm

rchesterton wrote:
Fri Dec 14, 2018 9:49 am
Yeah, makes sense. I wasn't sure if it was due to heat with such high voltage (shrinking/expanding the copper?) or not. Thanks again for all of the attention you all have given this project of mine...over 70 threads! Yikes. I'll follow up and let you all know how it goes.

Thanks
All we ask is that we get a pic of the new toy... I mean meter, showing the current draw of the new heater :lol:

Good luck this weekend !
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