1000kcm Asbestos ava cable

[dm9289]

We are replacing some breakers and contactors for a heating grid and I was not sure our cable had the proper ampacity.
Basically we have a heating grid 220v that draws 600 amps on or off no throttling
My thoughts were this would be treated as a continuos load NEC 210.19A and 427.4
So I feel we need cable or cables rated at 600A x 1.25= 750A
Can anyone help me on the ratings of asbestos ava cable 1000kcm

 

[GoldDigger]

We are replacing some breakers and contactors for a heating grid and I was not sure our cable had the proper ampacity.
Basically we have a heating grid 220v that draws 600 amps on or off no throttling
My thoughts were this would be treated as a continuos load NEC 210.19A and 427.4
So I feel we need cable or cables rated at 600A x 1.25= 750A
Can anyone help me on the ratings of asbestos ava cable 1000kcm

Some Asbestos/Varnished Cambric insulated wire (AV wire) is rated for 90C use (AVB), other kinds for 110C use (AVA) according to Southwire. Other than that the ampacity will depend on the size of the conductor.
It does not appear to be an NEC recognized type, if it ever was, so its use should be limited to inside manufactured high temperature machinery. Based on the asbestos content, I have to assume that this is pretty old equipment?
The ampacity will also be affected by the likelihood of high ambient temperatures where it is used. And the termination temperatures of the breakers and contactors it connects to.

 

[dm9289]

The cable goes to a heating grid, but connects to a long straight piece of grid and then to many u shaped pieces of grid that surrounds a vessel used to make molten zinc. Yes the cabling was put in in 1956. I figured if we purchased 90c lugs that was the best possible rating, but as you mentioned might be ok for 110c.

Either way even at 90c its only good for 615 unless you know of another rating for 110c

 

[GoldDigger]

The cable goes to a heating grid, but connects to a long straight piece of grid and then to many u shaped pieces of grid that surrounds a vessel used to make molten zinc. Yes the cabling was put in in 1956. I figured if we purchased 90c lugs that was the best possible rating, but as you mentioned might be ok for 110c.

Either way even at 90c its only good for 615 unless you know of another rating for 110c

I am not sure that the code would consider this continuous just because it is on-off controlled. Can you say how long at a time the grid would be full on? Is there some temperature regulation by switching it on and off, or does it run full blast whenever there is zinc in the crucible? And if full blast, will that go on for more than 3 hours at a time?

You are aware that OSHA is going to cause you all sorts of grief since you have to work with the exposed ends of the asbestos insulation when re-terminating the wire?

 

[dm9289]

It is usually on 10 minutes at a time when the pot is full, moving steel pulls heat into crucible aiding heating. We change formulation and have to pump then melt for 12hrs at a time 10 times a year approximately.

Yes i get the osha thing it may play a bigger part if we try to remove the cable about 100ft one way, 3 grids 6 wires.

 

[GoldDigger]

It is usually on 10 minutes at a time when the pot is full, moving steel pulls heat into crucible aiding heating. We change formulation and have to pump then melt for 12hrs at a time 10 times a year approximately.

Yes i get the osha thing it may play a bigger part if we try to remove the cable about 100ft one way, 3 grids 6 wires.

It sounds like for those 10 times a year, it will be running continuously, but I am not sure that the Code cares about that.
You could set the thermostat in your house so high that the electric furnace runs continuously, but NEC still has you calculate it as a non-continuous load.