Melted cable spiral wrap

[sysrq]

Haven't seen anything like this before. Star-delta starter for a 30 kW motor has been entirely wired up using conductors (looks like 2.5-4 mm2, 3.5 mm external diameter) cut out from sy cable and the like and wrapped with spiral wrap which has melted. Motor current mostly stays around 20 to 30 Amps and only rarely jumps above 50 Amps depending on material being processed.
Surprisingly PVC insulation hasn't melted yet. D60 type breaker inside control panel haven't tripped yet, only the 40 Amp type D breaker inside distribution board has been tripping when the belts start to slip.
According to correction factor the current carrying capacity for 3 tri-rated wires bunched together should be 26.65 Amps. Seems like PVC insulation hasn't melted yet as the current stays in the range of temperature equilibrium for the most part.

 

[Wilko]

Hi - Some spiral wraps can tolerate high temps -(| Spiral Wrap 2.6mm PTFE | - https://uk.rs-online.com/web/p/cable-spiral-wrapping/2443055/) - but this won't be one of them, I'll bet. Nothing nice to say about how it's been used either, I'm afraid ...

 

[Pete999]

Hi - Some spiral wraps can tolerate high temps -(| Spiral Wrap 2.6mm PTFE | - https://uk.rs-online.com/web/p/cable-spiral-wrapping/2443055/) - but this won't be one of them, I'll bet. Nothing nice to say about how it's been used either, I'm afraid ...

What Wilko said

 

[sysrq]

Hi - Some spiral wraps can tolerate high temps -(| Spiral Wrap 2.6mm PTFE | - https://uk.rs-online.com/web/p/cable-spiral-wrapping/2443055/) - but this won't be one of them, I'll bet. Nothing nice to say about how it's been used either, I'm afraid ...

That might do the trick.

 

[ipf]

So...you're just going to change the spiral wrap???
I'll bet that cable's rock solid, at contactor connection points at least. Above 50amps in some instances?
Cable rating way out.
Serious fire hazard.

 

[sysrq]

So...you're just going to change the spiral wrap???
I'll bet that cable's rock solid, at contactor connection points at least. Above 50amps in some instances?
Cable rating way out.
Serious fire hazard.

As far as I know particular installation has been carried out by senior electrician. Might have just run out of materials and decided to use what's at hand so everything's understandable. Seems like fairly light loading has been taken into account as well, hence the use of undersized conductors. Normally cable size for internal panel wiring in case of a 30 kW motor is at least 25 mm2 though.

The cables aren't rock solid yet, but might be one day.

 

[westward10]

Your solution just to replace the spiroband is somewhat bizarre especially if it is exposed as it does not provide suitable containment. That aside this is an accident waiting to happen.

 

[ipf]

Your solution just to replace the spiroband is somewhat bizarre especially if it is exposed as it does not provide suitable containment. That aside this is an accident waiting to happen.

From the read, I'm presuming it's in a control panel...with 60amp internal breaker for motor and 40amp supplying panel. Not much thought, all round and like you indicate, it's not 'if' but 'when'.
If spiro external, well........

 

[Darkwood]

As far as I know particular installation has been carried out by senior electrician. Might have just run out of materials and decided to use what's at hand so everything's understandable. Seems like fairly light loading has been taken into account as well, hence the use of undersized conductors. Normally cable size for internal panel wiring in case of a 30 kW motor is at least 25 mm2 though.

I think you are mistaken there, I assume you have seen panels serving more load than just the 30kw motor and your just seeing the looping supply across the contactors. A 30kw motor only requires panel wiring on the supply side of 10mm tri-rated, if star/delta controlled and a short run then 4mm will be plenty to connect the motor up even if running at FLC.
This sounds like a total bodge from start to finish, the breaker tripping is due to the current spike as the belt grabs back and the motor is suddenly loaded, the breakers are incorrect and shouldn't be mcb's, interested to know what the ELI is as I bet this won't comply with regulations ... needs fully redesigning by someone competent in this field.

As others have hinted at, changing the spiral wrap and walking here is professional suicide as you take on the responsibility of this install by repairing it, your insurance will be void if anything happened after this as ignorance is not an excuse, I am very concerned if that is what you intended doing as comes across in your posts.

 

[123]

As far as I know particular installation has been carried out by senior electrician. Might have just run out of materials and decided to use what's at hand so everything's understandable. Seems like fairly light loading has been taken into account as well, hence the use of undersized conductors. Normally cable size for internal panel wiring in case of a 30 kW motor is at least 25 mm2 though.

The cables aren't rock solid yet, but might be one day.

I don't see how that's understandable, or in anyway acceptable.

 

[Adam W]

It could be that this senior electrician was ordered to "just make it work" by cobbling together whatever was at hand to get production up and running, or that it was tripping for some reason and the only solution anyone could think of was to put a bigger breaker in. Neither would surprise me.

You don't mention any kind of overload, just the type D MCBs - does it have one?
Could you post a picture of the panel?

 

[sysrq]

It could be that this senior electrician was ordered to "just make it work" by cobbling together whatever was at hand to get production up and running, or that it was tripping for some reason and the only solution anyone could think of was to put a bigger breaker in. Neither would surprise me.

You don't mention any kind of overload, just the type D MCBs - does it have one?
Could you post a picture of the panel?

There is one but it's dysfunctional, not the first time when coming across oversized overloads. Have seen a lot of machinery with oversized overloads over the years for some odd reason.
I'm afraid intelligibility of the picture will be insufficient as everything has been squeezed into smallest enclosure possible.

 

[sysrq]

A 30kw motor only requires panel wiring on the supply side of 10mm tri-rated, if star/delta controlled and a short run then 4mm will be plenty to connect the motor up even if running at FLC.

.

There is something which looks like 4mm or 2.5mm on the supply side between the isolator and 63 Amp MCB and contactors. Haven't seen spiroband being used on power circuits before.