De rating of XLPE SWA cable

[Amp David]

Does anyone bother de rating XLPE 90 deg C max CCC to PVC 70 deg C max CCC, when connecting to accessories rated at 70 deg max?

Only reason I ask is this week I was given very strange looks when I pointed out that some 16mm XLPE clipped direct would require a 63 amp fuse and not 80 like they had in place.

Is it me just taking the actually regs to seriously are something?

 

[johnboy6083]

I don't think your too serious mate. If that cable was to be loaded tocapacity, then the terminals will deteriorate, creating a real fire hazard.

 

[Amp David]

Cheers, good to know i'm not going mad.

Seen it on more than 1 occasion where its already been installed and pointed it out, but nothings been done to sort.

 

[Knobhead]

Not wanting to

View attachment 8077

But this has always struck me as an odd situation. We now have a cable type of a higher temperature rating than the termination devices. It all seems a bit out of kilter to me. OK the cable will cope with higher ambient temperatures along the run, but it’s still got to terminate somewhere and copper being what it is heat will travel along it.
I may be totally off course with this but I’m curious (as the bishop said to the actress).

 

[Inteificio]

When rating higher temp cables it clearly states that the what you attach the cable too has to be able to take the higher temp.

I am glad I read this thread, I would never have thought to de-rate, but will from now on!

 

[telectrix]

how do we know, without a lot of research , what temperature terminals etc. will withstand without deterioration. OK, their spec. will state that they are capable of running at 70deg. C, as that has always been ( generally speaking ) the max. temp. of cable. who's to say they won't happliy run at 90deg.C without corresponding with manufacturers?

 

[johnboy6083]

To be honest we tend to oversize cables for actual demand in the smaller sizes anyway, and the larger sizes of cable are terminated to switchfuses, DB's, ect, which I bet are rated to 90deg anyway. Obviously this is not confirmed, and should always be checked.

 

[Chr!s]

Id have a read of REG 523.

If the accessories are not adequately rated then the cable will need derating.

Manufactures specify the temp limits for there equipment, some are less than 70C. As stated above its probably prudent to design to a max of 60 - 65 degrees where possible.

Regards Chris

Regards Chris