British-Canadian differences

[Goldwing]

I am hoping that there is someone who uses the forum who would be able to help me to understand the different terminologies and materials used on British wiring systems compared to Canadian. I have been a journeyman for 35 years and will be part of a team that is traveling to Mozambique in late February or March. While on site it is my responsibility to educate a few nationals about electrical theory and help to give them the basic skills to maintain the facilities electrical systems. I am not concerned about the theory however the wiring terminologies, methods, and materials differ from the ones here in Canada. There is a vehicle repair facility that is being built that needs power as well as various problems with other parts of the sytem with regard to voltage drop and balanced loading of the three phase gen sets. (The sites power is supplied by two privately owned generators)

I am new to the forum and not sure how all the parts of it work so we could use email for communication if need be.

I am looking forward to some constructive advice and information. Our methods, materials, and regulations are somewhat different but I am hopeful that you will be able to help me overcome the obstacles. :21:

Thanks

 

[HandySparks]

Hi Goldwing, welcome to the forums.

Not sure how to help. Obviously if there's someone here who has worked in both Canada and the UK, then they would know the differences.

You could start by getting hold of one of one of the books written about UK wiring practise; for example, the IET On-Site Guide to BS 7671:2008 (2011).
On-Site Guide: BS 7671:2008 Wiring Regulations, incorporating Amendment No 1:2011 Iet Wiring Regulations: Amazon.co.uk: Iet: Books

 

[Richard Burns]

This thread on various acronyms in use may help define some of the terminology in use in the UK.
But other than that this is a vast subject, probably best if you were to list some practices / materials in use in Canada and we could then state the methods that we would use here.
Also not sure how close Mozambique will be to BS7671, there are usually some parts from various regulations applied somewhat haphazardly.

 

[Goldwing]

Thanks for responses so far guys. I will start by asking what your voltage drop percentages are. Here the maximum voltage drop is 5% from point of supply to final utilization. It is divided up based on 2% from point of supply to the mains over-current device with the remaining 3% from the panel to the load. I have a very long run from the generators to the shop that has been built. Somewhere in the area of 450 feet. I would most likely us underground conduit feeding a 60 or 100A 3phase panel. Here we would use parallel runs to reduce the current on each wire. Using our methods that would work out to be #2 aluminum (33.61 mm2) for each of the conductors based on parallel runs feeding a 60A main panel. This would allow for the full 60A available with a voltage drop of 1.72%. Here the wire would be pulled into two conduits, 4 runs in each (3 phase conductors and a neutral), if the wires were too large to fit into the panel lugs they would be terminated in a pad splitter or junction box (box with pads to terminate wires) and then tails at each end to whatever equipment they need to be connected to (ie the panel and the fused disconnect at the generator distribution). What are your requirements for bonding and grounding with this kind of distance? Do you re-establish ground with rods at the far end?

What say you all :confused5:

 

[Engineer54]

I'll let others compare your outlined system to how it would be done in the UK, as i'm almost ready to leave for work... lol!!
But what i can tell you, is that it would be very rare indeed to find Aluminium being used by anyone other than the electrical supply companies in the UK. And the fact that our system is 240/415Volts (or as known in the virtual world as 230/400 lol!!)
So only using copper for our conductors, the cable sizes will be considerably smaller... Oh, and it would also be very rare to use an underground conduit system with single core cables, it would be almost always be SWA cables either direct buried or in PVC ducts...

 

[ian.settle1]

Not to sure why your asking this question unless the specification says that it has to be installed to BS7671 as Mozambique is a former Portugese colony so any installations would be carried out to their regulations.

 

[Engineer54]

Not to sure why your asking this question unless the specification says that it has to be installed to BS7671 as Mozambique is a former Portugese colony so any installations would be carried out to their regulations.

He may be working on a contract with an electrical specification based on/or around BS7671. After all, Mozambique isn't going to have the most vigorous of electrical installation standards are they!!

 

[Richard Burns]

Thanks for responses so far guys. I will start by asking what your voltage drop percentages are. Here the maximum voltage drop is 5% from point of supply to final utilization. It is divided up based on 2% from point of supply to the mains over-current device with the remaining 3% from the panel to the load. I have a very long run from the generators to the shop that has been built. Somewhere in the area of 450 feet. I would most likely us underground conduit feeding a 60 or 100A 3phase panel. Here we would use parallel runs to reduce the current on each wire. Using our methods that would work out to be #2 aluminum (33.61 mm2) for each of the conductors based on parallel runs feeding a 60A main panel. This would allow for the full 60A available with a voltage drop of 1.72%. Here the wire would be pulled into two conduits, 4 runs in each (3 phase conductors and a neutral), if the wires were too large to fit into the panel lugs they would be terminated in a pad splitter or junction box (box with pads to terminate wires) and then tails at each end to whatever equipment they need to be connected to (ie the panel and the fused disconnect at the generator distribution). What are your requirements for bonding and grounding with this kind of distance? Do you re-establish ground with rods at the far end?

What say you all :confused5:

Not really experienced at this sort of install but I believe the following would be correct for BS7671 wiring regualtions compliance.

Voltage drop permissible is 3% for lighting and 5% for non lighting

As E54 says normally SWA in duct or direct buried for long runs.

Run of 140m with 60A load would require 2x 25mm[SUP]2[/SUP] four core SWA (for ~3% volt drop), fine to use parallel conductors (preferably of the same CSA)

Not sure on pad splitter but sounds OK what you are describing.
If using the armour as the CPC the armour of both the SWAs would be bonded at both ends.

For earthing (not grounding!) the earth system may either be shared with the original source assuming all bonding csa requirements are met.
Or at the remote end the supply earth would be divorced from the earthing (grounding) system at the far end and the far end could be connected as a TT system with a suitable low impedance earth electrode (rod, tape, plate, mesh, structural metal work).

 

[Goldwing]

Thanks Richard. Can I assume that as was indicated previously that the SWA is copper? Do you agree with previous posts regarding the use of aluminum conductors? I have seen aluminum products of this type of cable on some electrical distributor web sites in South Africa but am not sure if they are not allowed under your standard or that they are just seldom used. As I have said, over here aluminum is common although the conductor size is increased to compensate for the reduced current carrying capacity. (I am assuming that if it were able to be used that it would be cheaper then copper unless its rarity of use increases the cost to that of copper)

What are your requirements for depth of burial? Here if it were in a non-vehicular area it would be 450mm plus 75mm of sand above and below with a marker tape halfway of depth. Your suggestion and information regarding the bonding (earthing) is similar to ours. The bond or earthing (not grounding) would not be attached at the far end and the grounding would be re-established using rods or plate electrodes etc if a low impedance path could not be maintained due to distance or differences in potential.

As to termination at both ends of larger conductors, I am not sure of the lug range of your panels. The parallel runs would have to come into something and then tailed to the distribution panel and the supply end. What products would you use for that as I assume that the consumer unit would not allow for parallel run connection or large sizes of wire.

 

[johnboy6083]

if large sizes cannot be accomodated in the distibution panel, or consumer unit, then its fine to terminate both of the paralell cables into an isolator, and then run a smaller conductor (smaller because of less volt drop, no derating ect) to the panel.
The theory of electricity wont deviate between countries, its the implementation that will differ slightly. It sounds like you know what you are doing, so i reckon youll be ok.

Aluminium is allowed in the uk, its seldom used though, although i think with the rise in cable theft, it might gain favour in years to come. Our steel wire armoured cable is as the name suggests, steel armour on the outside, and copper cores on the inside. Are you familiar with glanding this type of cable? The gland is also the means by which you bond the armour.

 

[Goldwing]

I think your cable is different. Isn't the armour on your cables made of smaller steel wires that protect the underlying conductors that have pvc around them? If so then no I have never terminated that kind of a cable. Our underground cables have a steel armor but it is interlocked spiral with a waterproof protective covering. Inside of this are the conductors and a separate bond wire within another pvc jacket. The bond wire is one AWG size smaller then the conductors. Our connectors or glands as you call them have a bonding piece that as you say bonds the steel armour to the connector on the inside and of course the connector bonds to the box, panel, etc. If your cable has steel wires is it obvious how the gland terminates or should you fill me in? By the way can you put me onto a website from a British electrical wholesale company so that I can look at the various products on line to see if there are differences? And just as a side note if the Canadian's and British spell armour with the "U" and this is a British forum you should tell them to get rid of the American spell checker lol

Thanks

 

[Engineer54]

Thanks Richard. Can I assume that as was indicated previously that the SWA is copper? Do you agree with previous posts regarding the use of aluminum conductors? I have seen aluminum products of this type of cable on some electrical distributor web sites in South Africa but am not sure if they are not allowed under your standard or that they are just seldom used. As I have said, over here aluminum is common although the conductor size is increased to compensate for the reduced current carrying capacity. (I am assuming that if it were able to be used that it would be cheaper then copper unless its rarity of use increases the cost to that of copper)

Not particularly, Aluminium is a bugger to get the termination solid and to stay solid, it's just too soft and stretches, not to mention the dissimilar metal problems, that requires special crimping crimping terminations etc. Aluminium cable as has been stated, very rare to see outside of utility suppliers distribution systems. Yes cheaper than copper, but nowhere near as robust or secure as an all copper installation...

What are your requirements for depth of burial? Here if it were in a non-vehicular area it would be 450mm plus 75mm of sand above and below with a marker tape halfway of depth. Your suggestion and information regarding the bonding (earthing) is similar to ours. the bond or earthing (not grounding) would not be attached at the far end and the grounding would be re-established using rods or plate electrodes etc if a low impedance path could not be maintained due to distance or differences in potential.

Generally speaking 600mm, ...deeper in areas that are prone to agriculture or other disturbance.
Officially the make-up would be similar to yours, with the addition of cable protection tiles at least 15cm above laid cable/duct....

Depends on the overall CSA of both the parallel cables and/or the source earthing system, whether or not you would change the earthing system from the source. Unfortunately the standard sized earth rods these days in the UK seem to be 1.2m X 3/8'' non extendible twigs, unlike your 5/8''- 3/4'' X 8'-10' rods!!! Which isn't going to re-establish much of an earthing system...lol!!!

As to termination at both ends of larger conductors, I am not sure of the lug range of your panels. The parallel runs would have to come into something and then tailed to the distribution panel and the supply end. What products would you use for that as I assume that the consumer unit would not allow for parallel run connection or large sizes of wire.

Either as johnboy stated, or In as far as your example, and the use of 25mm conductor sizes to supply the required load, it's doubtful that any transitional means would be necessary where lug and bar connections are involved at the load end main isolator/MCCB.

Our underground cables have a steel armor but it is interlocked spiral with a waterproof protective covering. Inside of this are the conductors and a separate bond wire within another pvc jacket. The bond wire is one AWG size smaller then the conductors.

Our closest armoured cable for use in underground installations to yours, would have been the old steel tape armoured cable (STA) or the steel double wrapped taped armoured cable (DWSTA),... now they were a real pig to terminate!! Thankfully i haven't seen them for years now... lol!!

Our SWA cables generally come with all full sized conductors, half sized neutral conductors are available, but rarely used these days. All our SWA cables now, will generally have XPLE conductor core insulation rather than PVC. ...We use as stated before, the armouring as our CPC where the CSA of the armouring meets our Regulation requirements, (which is usually met upto 95mm for 2 core cables). Or where necessary, a suitably sized single PVC insulated CPC conductor run with the SWA cable(s) for either solely as the CPC, or to include bonding requirements, if extraneous earthed elements are present on a TNC-S source supply (metallic water/gas services, steel frame buildings, etc)...

If you go on U TUBE and search '' terminating SWA'' you should find an assortment of Video's showing how to terminate. Pretty simple stuff really, until you get up into the much bigger cable CSA sizes (185mm and above) in tight working spaces!!

I think generally, you mainly use only TNC-S and TT earthing systems in Canada, similar to the US. Where we still have quite a widespread use of TN-S. Certain requirements are different and more stringent for TNC-S and TT installations than they are for TN-S...

 

[Engineer54]

Run of 140m with 60A load would require 2x 25mm[SUP]2[/SUP] four core SWA (for ~3% volt drop), fine to use parallel conductors (preferably of the same CSA)

No, Not preferably, they MUST be of the same CSA, of equal overall length, same type of cable make-up etc....

 

[Richard Burns]

Or you have an engineering study done to consider the equal current sharing of different shaped and sized conductors and come up with a reasonable result that does allow this, however I would agree that this may well be considered OTT in all situations (except perhaps if you were designing some new regulations for a country).
Or you could use way oversized conductors so that they are never overheated, but this would defeat the point of parallel conductors.
Just playing Devil's advocate that there are a few very unlikely situations where it maybe possible to avoid the need to have equal current sharing enforced by the use of same type, length, shape, material, conductors.

Still you are right, I just wasn't covering the detail!

 

[Goldwing]

Thanks all for input on the feeders. I am aware of the necessity for same type, length etc of parallel runs so I had that in my mind anyway. I think I am getting the overall picture a lot clearer in this area now. Are your protection tiles something that is readily available or can I get away with just burying the cable deeper? No doubt I may run into problems ordering the correct materials for the whole job due to things like, quantity, plus any little twists that I will not see until I get there. It will not be like I can just run to the wholesalers and get more or different materials.

I will follow with a few questions about the branch circuits. I see that the rules for your bathrooms are different then ours. I was going to install a GFCI protected outlet (if you have such a thing) or a current limiting transformer approved for shaver along side the sink with a light above the sink. The shower stall could use a downlight, as it is walled in on three sides. I assume that there is an approved fixture for that type of location with a shower trim. I was going to locate all of the switches outside of the room as you seem to have some stringent rules with regard to areas around the shower or tub. Is it common over there for a light above the shower stall?

Thanks again gentleman