EV SWA Feed Cable Sizing - Oversizing Payback

[binky]

I suppose when the dangers of electricity were first realised, and the first attempts at regulating installations were published, the focus was on the method to make sure it was safe. Unfortunately, BS7671 has lost its way. It has become embroiled in anything and everything. It's sad really because the opportunity to keep it simple and avoid all the baggage enveloping it has long gone. When you attempt to involve energy saving, environment, types of user, and all the other stuff too long to list, it loses its effectiveness. Electricity can be installed safely. That's what the Regulations SHOULD have limited themselves to. Other aspects like energy saving, as one example, are a separate issue entirely from safety. In fact too much dialogue in BS7671 wonders off in to territories it should not ever get involved. The result is an ever expanding wordy document that trys to be all encompassing. In many respects it is almost naive in its approach, trying to pretend it improves safety. Safety is embedded in it but sadly it is lost in an overwhelming conglomeration of unnecessary padding that does not belong. If it focused on safe installation of wires, it would be so much more effective. A simple example is bare conductors. Unsafe. Put insulation around it. Safe. The current approach is to add a thousand words and embroil a hundred factors to that. I would call it being smart arsed. That's the result of trying to be too clever.

I always thought it maybe wise to separate small domestic works from everything else. However, I wouldn't describe it as wordy, that's what all the supporting docs do.

 

[Captain Kirk]

Sorry to say but this is all smoke and mirrors isn’t it?
At which point do you stop? One size up two sizes up or five sizes up for future proofing?
And are we really going to see ALL participating in this or will it just be the ‘qualified’ brigade?
I often select a cable on a commercial/industrial job the next size up but that’s purely a future proof never an energy saving motive!
And who is going to benefit from this energy saving? You will say the end user but reality tells me that the price of energy will just increase to maintain Profit for the Cats??

 

[unphased]

Hmm. Ad: Has your electrician installed a consumer unit in the last 25 years? If so, you may be entitled to compensation. We prosecute anybody.com is a no-win-no-fee claim service that can get you compensation for a mis-installed consumer unit no matter what make or size. If the measured Ze or PFC is outside of the tolerance, or there was no 30mA RCD installed, rest assured we can help. If you or anybody in your family has experienced this traumatic event, just go online and fill in the form.

 

[Captain Kirk]

Correct - lowering cable sizes with a view to energy savings is nonsense.

The design of non-domestic installations should include a percentage redundancy on cable size calculations particularly in the case of SWA which is the main choice of cable.

The key issue with SWA cable is the use of the the steel armour as the cpc. The UK is one of the few countries which allows the cpc to be a different material and size to the phase conductors. There are still some SWA cable sizes that require an additional cpc to be installed with the SWA.

If we are ever to catch up with the EU and other major countries the CPC will have to be the same size and material, and incorporated as an insulated core in the cable. Some designers deliberately oversize SWA in order to meet the design R1 + R2 values without the additional cpc, as the lower R1 value contributes to a lower total R1 + R2.

In hazardous area installations such as petrol pumps the cpc has to be incorporated as a core in the cable to avoid fault arcing across exposed external cpc connections with the armour being earthed at one end only. i.e. 3 core SWA for a single phase circuit.

Its high time the SWA - BS required the cpc to be an internal copper core in the cable. SWA sizes need to be selected on the R1 = R2 values first then design current.

Minimising cable size on energy saving issues is a contradiction of the integrity of safety in the spirit of BS 7671., and is a very dangerous proposal indeed.

 

[UNG]

Hmm. Ad: Has your electrician installed a consumer unit in the last 25 years? If so, you may be entitled to compensation. We prosecute anybody.com is a no-win-no-fee claim service that can get you compensation for a mis-installed consumer unit no matter what make or size. If the measured Ze or PFC is outside of the tolerance, or there was no 30mA RCD installed, rest assured we can help. If you or anybody in your family has experienced this traumatic event, just go online and fill in the form.

And the point you are trying to make is.............

 

[unphased]

And the point you are trying to make is.............

I'm not trying to make a point! Just light hearted humour...remember light hearted humour?

 

[unphased]

Correct - lowering cable sizes with a view to energy savings is nonsense.

The design of non-domestic installations should include a percentage redundancy on cable size calculations particularly in the case of SWA which is the main choice of cable.

The key issue with SWA cable is the use of the the steel armour as the cpc. The UK is one of the few countries which allows the cpc to be a different material and size to the phase conductors. There are still some SWA cable sizes that require an additional cpc to be installed with the SWA.

If we are ever to catch up with the EU and other major countries the CPC will have to be the same size and material, and incorporated as an insulated core in the cable. Some designers deliberately oversize SWA in order to meet the design R1 + R2 values without the additional cpc, as the lower R1 value contributes to a lower total R1 + R2.

In hazardous area installations such as petrol pumps the cpc has to be incorporated as a core in the cable to avoid fault arcing across exposed external cpc connections with the armour being earthed at one end only. i.e. 3 core SWA for a single phase circuit.

Its high time the SWA - BS required the cpc to be an internal copper core in the cable. SWA sizes need to be selected on the R1 = R2 values first then design current.

Minimising cable size on energy saving issues is a contradiction of the integrity of safety in the spirit of BS 7671., and is a very dangerous proposal indeed.

Agree but you wouldn't minimise cable size...the concept, which I find a little trivial, is increase the conductor cross sectional area thus reducing impedance and since P=V x I you save a little on energy.

 

[unphased]

btw UNG, if it did ever get to the point where litigation became a genuine obstacle for us to be able to do our jobs (electrician) for fear of courts and solicitors it would be a sad day for everybody. I think I made my point in my post further back, how it was meant to sound, that of unnecessary embroilment that BS7671 seems to expand into more and more with each successive edition, in all things outside basic safety, that the Regulations suffer badly from doing. Energy saving has no place in wiring Regulations. That's for environmental regulations to deal with. I wasn't having a dig at you.

 

[UNG]

I'm not trying to make a point! Just light hearted humour...remember light hearted humour?

Unfortunately what you believe to be light heart humour could / will likely become a reality at some point when the legal profession carry on their where there is blame there is a claim culture and move on to their next moneyspinning claim process

btw UNG, if it did ever get to the point where litigation became a genuine obstacle for us to be able to do our jobs (electrician) for fear of courts and solicitors it would be a sad day for everybody.

Under which stone have you been hiding, there has been plenty of litigation against electricians and people carrying out electrical work while not properly qualified, when you sign an EICR do you not consider that you are producing potential evidence for the prosecution if something subsequently occurs that results in serious injury or a fatality

I think I made my point in my post further back, how it was meant to sound, that of unnecessary embroilment that BS7671 seems to expand into more and more with each successive edition, in all things outside basic safety, that the Regulations suffer badly from doing. Energy saving has no place in wiring Regulations. That's for environmental regulations to deal with. I wasn't having a dig at you.

Given that the regs are really an ACOP and a means to gain compliance with the statutory regulations and requirements laid down in law is it wrong that they stray into areas that you think they should not. We all moan about the cost of keeping upto date with all the documents needed these days so is it wrong for BS7671 to stray from it's main focus when it could just mention purchasing many more documents in order to comply when currently the IET and BS charge / make enough money from us as it is

 

[unphased]

I believe I have strong and valid arguments against the Regulations, UNG