Current carrying capacity for SWA

[sprocketflup]

Just working out some cable sizes, could someone who has the time please advise a little about SWA cable?

I have BRB open at page 252 appendix 4 but cant decide which table(s) to use, is SWA a 70degree thermoplastic cable (table 4D4) or a 90degree thermosetting cable (table 4E4) please?

Also what is the difference between SWA XLPE and SWA PVC?

Thanks in ignorance

 

[Andy™]

different insulation. XPLE can withstand higher tempreatures than PVC

 

[PC Electrics]

Just working out some cable sizes, could someone who has the time please advise a little about SWA cable?I have BRB open at page 252 appendix 4 but cant decide which table(s) to use, is SWA a 70degree thermoplastic cable (table 4D4) or a 90degree thermosetting cable (table 4E4) please? both

Also what is the difference between SWA XLPE and SWA PVC? XPLE or PVC insulation. XPLE is the 90 deg one

Thanks in ignorance

See blue above

Chances are you'll be buying xple as that's what most wholesalers stock.

You should rate on 70 deg PVC SWA, unless your connected accessories are also rated for 90 deg operation.

 

[sprocketflup]

Thanks very muchly

 

[steptoe]

you can work across both ranges though as Plumber recently confirmed for me,

well he actually done the calcs and stuff.

cable can run at +70 <90 as long as you ensure you terminals will run at <70

 

[steptoe]

but if you are installing to existing?

also, maybe the MCBs are rated 90 , are the busbars/main switches etc,

devils advocate, but if you are not installing from HED to bed then you cannot assume anything, so if in doubt downrate to 70.

or am I wrong?

some of these other guys, canoeboy,sidewinder etc work with this stuff all the time so are better placed to advise.

 

[Chr!s]

Most SWA cable i buy now is standard XLPE 90 Deg C and if you ring most MCB/MCCB manufacturers up (or at least the ones i use) then their terminals are rated to 90degC

I think you will find most are rated to 70 C, but certainly not all, so you need to be careful.

also, maybe the MCBs are rated 90 , are the busbars/main switches etc,

Most MCB MCCBs are rated at 70 C, busbars on the other hand can run at temperature in excess of 70 C due to the fact is just a copper block with no insulation, the issue comes when people need to connect to them.

 

[Chr!s]

You must buy different to me then plumber, all the cable i get from Batt is 90 (they do sell 70 though) and all the Siemens kit i use is rated for 90 at the terminals

Canoe, i wasn't referring to the SWA, as i said in my earlier post XPLE is part of the standard for SWA so most will be at 90 C.

As for Seimans i think you will find that much of there stuff is rated less than 90 C, more like 75 C, and as i said some may be rated to 90.

Hager, MK, Legrand, Eaton and many of the other produce products which are not rated at 90 C and that includes Seimans.

 

[Chr!s]

Well all the siemens kit i use is rated at 90, I'll post the data sheets if you like.And I use predominantly siemens for all my work.

I dont need the date sheets, i have a lot of them

Did a job with MG standard 63amp MCB latter part of last year and that had terminals rated to 90 also, I have the data sheet for that too.

Im not saying you can not get equipment to 90C, im saying in the main its rated to 70 C

I think you'll be surprised to find a lot of newer kit is actually rated higher than you may think.

Well i have the data sheets for the above companies, all this years, and the majority is rated to 70 C, so i disagree.

But always check with the manufacturer

.

I always do, hence why we are posting not to assume that equipment can be connected to 90 C swa, as in the majority of instances equipment will be rated to less.

 

[PC Electrics]

I would imagine that the ability to be able to use 90 deg swa is only likely to make a difference in larger installations where it might enable the use of the next size down and offer a significant cost saving. In these instances it is worth the effort of getting manufacturers data to confirm.

For most small installs it's not really worth the effort . Just calc on 70 and be done with it. It can't be wrong either.

 

[steptoe]

or you could have one similar to mine PC where plumber was able to confirm to me my sizing was OK as long as I used 90rated cable to cope with the extra inherent heat in the ducting, although all terminals etc would be running at much less than 70.

 

[sprocketflup]

Well, ive calculated on 70, its not a huge run so cost wise didnt make too much difference, but didnt get the job anyway as the homeowner is going to do it himself. I think he was expecting a sub

 

[Sidewinder]

For large loads "oversizing" of cables at design/install can actually save money in reduced I^2R losses over the life of the installation.

Think about it and it does make sense.

It can be calculated and there is free software out there to do the calcs.

IIRC the outlay on purchasing an electric motor is much less than the running costs over its expected lifespan, thus higer efficiency motors are catching on.

There are limits and caveats to all such things remember!