Discuss 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fuses in the Electrical Forum area at ElectriciansForums.net

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Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

What's the overall length of this 95mm 4 core cable?? You've only indicated you have 30m run in ducting, is that roughly the total length or is it much longer than that 30m??

If it's roughly around the 30m mark, it isn't going to be an overly expensive upgrade, especially if you use a parallel supply, using 2 X 25 or 35mm 4 core SWA cables, the later giving you around 325A, which will be more than enough to de-rate to your hearts content for the ducting!! lol!! Also be a lot easier to man handle during the installation....
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

Mark, go down and get the BS number and manufacturer of the cable, forget what's being said, the oversheath may well be PVC, I doubt the insulation will be!

What's the length of cable entering and exiting the duct with regard to terminations? How is the duct installed, surrounding material etc, what is the ambient being taken as?.

I've got 263 in a duct at 90 C, even if I run it at 70 C it still greater than 200.

You need to assess the install before anything.
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

Why's that squire?...

Remember this is an old installation...



Also worth remembering if designing the circuit for 90 degree cable then connected equipment needs to be rated at that too...

Old installation, New cable is it not? As I have said, SWA standards have changed.

I'm aware of the 90 C, I've already raised that issue with Mark.

No point going any further until Mark addresses the points I've raised.
 
A good example of this is the CCC of 10mm two core armour , I priced a job on Friday eve , bs7671 states approx 60 Amps , TLC website who use manufacturers Data states over 80A
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

especially if you use a parallel supply, using 2 X 25 or 35mm 4 core SWA cables, the later giving you around 325A, which will be more than enough to de-rate to your hearts content for the ducting!!QUOTE]

I may have read this wrong but the rating you have quoted is Reference Method E and what he has is Reference Method D, 115A for 35mm so 230A for parallel cables. If they are installed in the same ducting then you have to de-rate the cable by .75 (cables touching) so you would get 86A or 172A for 2 cables.
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

especially if you use a parallel supply, using 2 X 25 or 35mm 4 core SWA cables, the later giving you around 325A, which will be more than enough to de-rate to your hearts content for the ducting etc!!QUOTE]

I may have read this wrong but the rating you have quoted is Reference Method E and what he has is Reference Method D, 115A for 35mm so 230A for parallel cables. If they are installed in the same ducting then you have to de-rate the cable by .75 (cables touching) so you would get 86A or 172A for 2 cables.


I wasn't comparing ref methods, as i stated, more than enough leeway for any de-rating for duct installation...

They are the same supply cable, be they X 2, X 4 or whatever, you don't de-rate a parallel circuit, de-rating only applies if the cables being de-rated are two different supplies!! Would you de-rate a ring circuit if both legs were run in a conduit/trunking?? lol!!

Depending on any other criteria, i'd be more than happy rating a parallel 35mm supply at or around 280A +. I rarely take much notice of cable ratings in the BGB, i tend to mainly use manufacturers data. But that would be up to the OP and his own experience as to what sort of de-rating factors to apply on any given cable installation etc... Whatever way you go, 2 X 35mm SWA cables are going to fulfill the OPs supply cables requirement....
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

They are the same supply cable, be they X 2, X 4 or whatever, you don't de-rate a parallel circuit, de-rating only applies if the cables being de-rated are two different supplies!! Would you de-rate a ring circuit if both legs were run in a conduit/trunking?? lol!!QUOTE]

Isn't the de-rating of grouped cables down to heat dissipation? If there are two cables together then they don't dessipate heat as well if they are apart, so that is why they are de-rated. It doesn't matter if they are for the same circuit or different circuits. Its grouping of multi-core cables.
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

Mark, go down and get the BS number and manufacturer of the cable, forget what's being said, the oversheath may well be PVC, I doubt the insulation will be!

What's the length of cable entering and exiting the duct with regard to terminations? How is the duct installed, surrounding material etc, what is the ambient being taken as?.


I've got 263 in a duct at 90 C, even if I run it at 70 C it still greater than 200.

You need to assess the install before anything.

Ok.. spoke with someobody in the know that can assure me the cable has been in 25 years plus... i did find a name on the cable.. says AWCO Electric cable 66/1000V BASEc...(crawling around at the back in the dark) No BS number..Cant find anything on AWCO anywhere.. unless im being stupid.. one meter of cable straight out of ducting set in concrete into 200 Amp switchfuses either end..one (old) MEM 200A HRC..off the busbars at the intake... the other 200A TPS-N Hager Fuse combination switch (New)... in building intake cupboard.
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

If an upgrade is to be looked at.. 2 x parallel 35mm cables will certainly be easier to pull than the 150 or 185 needed to upgrade properly according to 4D4A...lol..not that it will be easy.. the road will have to be dug up.. although we may get away with no hydraulic bending equipment and some elbow grease i guess...!..lol.. i think im going to have to quote similar manufacturers figures.. and the regs... and tell them they are full up and to make future plans based on my recommendadtions.. The place is running like a dinosaur anyway.. full of t8 wingback lights.. convection heating everywhere.. might be able to make a few savings the other way... and keep my arse covered..:)
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

They are the same supply cable, be they X 2, X 4 or whatever, you don't de-rate a parallel circuit, de-rating only applies if the cables being de-rated are two different supplies!! Would you de-rate a ring circuit if both legs were run in a conduit/trunking?? lol!!QUOTE]

Isn't the de-rating of grouped cables down to heat dissipation? If there are two cables together then they don't dessipate heat as well if they are apart, so that is why they are de-rated. It doesn't matter if they are for the same circuit or different circuits. Its grouping of multi-core cables.

This side of it i will need to look into IF they decide to do something.. which i very much doubt..)
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

Depending on any other criteria, i'd be more than happy rating a parallel 35mm supply at or around 280A +. I rarely take much notice of cable ratings in the BGB, i tend to mainly use manufacturers data.....

Ever heard of AWCO? or am barking up the wrong tree
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

They are the same supply cable, be they X 2, X 4 or whatever, you don't de-rate a parallel circuit, de-rating only applies if the cables being de-rated are two different supplies!! Would you de-rate a ring circuit if both legs were run in a conduit/trunking?? lol!!QUOTE]

Isn't the de-rating of grouped cables down to heat dissipation? If there are two cables together then they don't dessipate heat as well if they are apart, so that is why they are de-rated. It doesn't matter if they are for the same circuit or different circuits. Its grouping of multi-core cables.

No it doesn't work like that!! The 2 or more cables of a parallel circuit are equally sharring a single point load, so it's a single circuit!! In other words it is considered as a SINGLE cable, not multible cables supplying different loads etc. As i said above, would you actually de-rate a ring circuit contained in a suitably sized conduit or other containment??
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

If an upgrade is to be looked at.. 2 x parallel 35mm cables will certainly be easier to pull than the 150 or 185 needed to upgrade properly according to 4D4A...lol..not that it will be easy.. the road will have to be dug up.. although we may get away with no hydraulic bending equipment and some elbow grease i guess...!..lol.. i think im going to have to quote similar manufacturers figures.. and the regs... and tell them they are full up and to make future plans based on my recommendadtions.. The place is running like a dinosaur anyway.. full of t8 wingback lights.. convection heating everywhere.. might be able to make a few savings the other way... and keep my arse covered..:)

That's just how ridiculous some of these cable and de-rating tables can end up, ...with totally silly cable sizes!! Who in their right mind would install a 150 or 185mm cable to satisfy a 200A to 225A supply requirement??

Thought you said this cable was in a duct, why would you need to dig the road up for god's sake??
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

You need to take a look at ERA report 69.30

this has cable sizes for sustained and cyclic loads. It's one of the methods that DNO's use to size their cables.
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

You need to take a look at ERA report 69.30

this has cable sizes for sustained and cyclic loads. It's one of the methods that DNO's use to size their cables.

Have you got a link to this report??
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

Ok.. spoke with someobody in the know that can assure me the cable has been in 25 years plus... i did find a name on the cable.. says AWCO Electric cable 66/1000V BASEc...(crawling around at the back in the dark) No BS number..Cant find anything on AWCO anywhere.. unless im being stupid.. one meter of cable straight out of ducting set in concrete into 200 Amp switchfuses either end..one (old) MEM 200A HRC..off the busbars at the intake... the other 200A TPS-N Hager Fuse combination switch (New)... in building intake cupboard.

Sorry Mark, misunderstood, i thought you had replaced the mains like for like lol for some reason.
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

No it doesn't work like that!! The 2 or more cables of a parallel circuit are equally sharring a single point load, so it's a single circuit!! In other words it is considered as a SINGLE cable, not multible cables supplying different loads etc. As i said above, would you actually de-rate a ring circuit contained in a suitably sized conduit or other containment??

Ok, (example 1) so we have a circuit taking 200A run in conduit. The intention is to use 2 cables, each taking 100A. Each producing heat.
Lets just say we also have 2 additional circuits (example 2) each using 100A, supplied with two cables in a ducting. (different ducting to example 1.)
You are saying that the re-rating factor applies to example 2 but not to example 1? How does that work?
 
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Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

That's just how ridiculous some of these cable and de-rating tables can end up, ...with totally silly cable sizes!! Who in their right mind would install a 150 or 185mm cable to satisfy a 200A to 225A supply requirement??

Thought you said this cable was in a duct, why would you need to dig the road up for god's sake??

It does enter the building in a duct...Im trying to explain the installation without EVERY detail.. but that duct goes out under the floor... a meter down the side of a buildingoutside into a duct in the road.. then around multiple bends with no access panels of any type..There are no draws in.. from my experience.. pulling any sort of heavy duty armoured around corners is tough.. i dont have any groundworks drawings or a CAT scanner to hand...lol... so i think my observations are a fair assessment.. but still..
 

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