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

Sorry Mark, misunderstood, i thought you had replaced the mains like for like lol for some reason.

No worries Chris.. to be honest this has been a good learning curve for me.. thanks for your help.
 
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.

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

Anyone know where i can pull some manufactureres data for a cable like this.. one rpe XLPE.. every site i look at seems to be the latter.. or if anyone has heard of AWCO?
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

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?

In simplistic terms Yes, the parallel circuit ensures equal current carrying between the two conductors, (and are considered as a Single cable), whereas the two separate circuits that are supplying different loads will not. The cable grouping de-rating table(s) in the BGB are based on the cables carrying the full load current being present, on each of the grouped cables/conductors, when in the real world that is almost never the case, and why you always end up with over sized cables!!...
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

Aluminium wire and cable co, good chance this is a Soidal Aluminium cable?

Im sure one of the previous tests (of which i only have the results for one...or this fixed wire test done in August would have said so.. definately says copper on the sheet...) Gulp.. ha.. i certainly hope so or the cable derates down even more! Must admit ive never worked with aluminium cable.. am hoping AWCO made copper SWA too...
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

just found this on the IET forum.. a guy that used to be a cheif electrical engineer for BACO posted it...
''This BACO company had a cable manufacturing company in Swansea producing their "Solidal" cable.''


Qustion to post - ''I guess that was the old Aluminium Wire and Cable Co (AWCO) Jaymack ?''

Reply ''Correct, I took a couple of BACO maintenance electricians there for 2 day's hands on training.''

Hmmm.. anyone enlighten me on this soidal cable? if that is what it is?

- - - Updated - - -

Aluminium wire and cable co, good chance this is a Soidal Aluminium cable?

Very kind.. have you worked with it before?
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

Alot of confusion in this thread regarding grouping and same source/supply parallel cables...

Im on the understanding myself the grouping factor is to be applied to parallel runs same circuit too, the reason is the derating factor is designed to allow for the reduced surface area of which the thermal energy can dissapate away from the copper, with this in mind the fact it the same circuit has no bearing as surface area will still be reduced and cable sized will be selected with relation to ccc of each cable added together. When running parallel cables in trenches or cable-tray its common to seperate them apart so grouping isnt applicable....

The problem and why i believe most are misled is the reg's titles grouping factor for cables of different circuits but if you refer to appendix 10 and read the first paragraph of no'2 (overload protection....) then at the end of this paragraph it does clearly state 'with the appropriate grouping and other factors applied'.

In essence of the reason grouping factor is applied in the first place then both cables of a parallel supply are still subject to dissapating their thermal energy much the same as cables of different circuits i cant see the any reason why having parallel 'same circuit' cables would be exempt from the grouping factor.

Ive been digging wider trenches for years and spacing the cables subject to calculation relative to diameter for yrs to avoid derating for grouping :uhoh2:
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

Elecsa table actually confirms the rating of 169 Amps as it is a 4 core cable. The switch for the building is fed via main busbars.. 200 amp fuses... then a 30 m run underground up into an intake cupboard to main isolator for building. I can probably see a metre of the cable at each end if i am lucky so am honestly asking how i find out manufacturers information on the cable.. if i cant see anything pointing to manufacturer.. surely then tables must be used.... i would understand if the drop was negligeable.. but 169 amps.. to 200 amps is not...
that elecsa table is based on the following

Table 4D1A – Single core 70[SUP]0[/SUP]c thermoplastic insulated cables (e.g. PVC Singles), non-armoured with or without sheath. All values assume an ambient temperature of 30[SUP]0[/SUP]c and a conductor operating temperature of 70[SUP]0[/SUP]c.
Ambient ground temperature peaks at more like 15 deg C in summer, maybe a little more under a building if the basement is heated and not insulated from the ground, but it'll never get anthing like 30 deg.
 
200 amp fuses

best to follow manufacturers data rather than book.

for example 2.5 twin can carry around 27 amps ish

but 1.5 tri rated can carry 21 amps but they would question it if you put it on a 16a breaker
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

Alot of confusion in this thread regarding grouping and same source/supply parallel cables...

Im on the understanding myself the grouping factor is to be applied to parallel runs same circuit too, the reason is the derating factor is designed to allow for the reduced surface area of which the thermal energy can dissapate away from the copper, with this in mind the fact it the same circuit has no bearing as surface area will still be reduced and cable sized will be selected with relation to ccc of each cable added together. When running parallel cables in trenches or cable-tray its common to seperate them apart so grouping isnt applicable....

The problem and why i believe most are misled is the reg's titles grouping factor for cables of different circuits but if you refer to appendix 10 and read the first paragraph of no'2 (overload protection....) then at the end of this paragraph it does clearly state 'with the appropriate grouping and other factors applied'.

In essence of the reason grouping factor is applied in the first place then both cables of a parallel supply are still subject to dissapating their thermal energy much the same as cables of different circuits i cant see the any reason why having parallel 'same circuit' cables would be exempt from the grouping factor.

Ive been digging wider trenches for years and spacing the cables subject to calculation relative to diameter for yrs to avoid derating for grouping :uhoh2:


No confusion here!! lol!!

So you too would apply a grouping factor to a ring circuit if both legs were run in a conduit or other containment. That'll be a first for me!!! lol!!
 
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Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

So you too would apply a grouping factor to a ring circuit if both legs were run in a conduit or other containment. That'll be a first for me!!! lol!!
Can you explain why not?

Is the derating factor not down to the additional heat stemming from the additional cable, and the lower surface area available for heat to be lost through?

And why would this not apply just because both cables are part of the same circuit?

if anything I'd think it should apply even more, as both cables will always be under full load at the same time, whereas in cables on different circuits will be under different loading levels to each other.

The only logical reason I could see for this not being the case would be if this was automatically taken into account already in the figures for those cables.
 
Re: 95 mm 4 core cable, 30 m run, in ducting under buildings backed up by 200 amp fus

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..

Let's get things absolutely clear on the length of this cable, it's approximately 30m Yes?? What size is the duct this cable is running through and what's it made of ?? (Metal, PVC, Ceramic)

It's extremely unlikely that any of the bends in this duct are going to be tight bends, otherwise they would never have been able to pull the cable into the duct in the first place. All professionally installed ducting will have slow/long bends, for this very reason. So there shouldn't be any need to dig up a road or whatever to replace this cable. The only time you would need to dig up this road would be, if clowns installed this duct and fitted the duct over the cable during installation, a bit at a time! ...lol!! But then why bother installing a duct system, you might just as well direct bury the cable for what good or use the duct would be!! lol!!

Depending on the amount of bends in this shortish duct, you may well need to hire a pulling machine (and maybe cable rollers) to remove old cable and replace with new!!

The copper should be worth a few bob from the old cable, at the scrapie's!! lol!!
 

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