[Question] generators and change over switches

[murdock]

according to sans page 355 anexure S a 3 pole change over switch is required...with a common neutral...to be connected at the generator to earth...

i am hearing from other electricians i have spoken to that a 4 pole changeover switch is required according to new regulations...

help...now i am confused i dont see any new regulation and i cant find any info regarding a 4 pole changeover switch.

[Martinco]

Hi Murdock, The sparky that installed my genset told me that by law it must be a 4 pole changeover and the reason given was that if it is only 3 pole with common earth and something goes wrong on the municipality/Eskom side there is the possibility of 11K volt finding its way along the earth line and effectively making your genset "live" on the outside. I had a 3 pole interlocked double contactor that was previously installed but he refused to use it.
This was the reason given BUT surely the same can happen with your 220 v kettle that is plugged into the wall socket ? The earth is not switched off by the EL or any other circuit breaker for that matter.
So.............does not make sense to me !

[murdock]

thanks for the feed back...

i need page numbers or relevant regulation refered to in the sans book...or a sans code...or oshact reference.

i am hearing the same thing from other electricians but nobody can give me a code or reference.

[murdock]

some other feedback...4 pole changeover switch required if only part of the installation is supplied from the generator...and 3 pole required if the entire installation is powered by the generator...mmm now for for some literature to backup these statements? anybody have any.

[Sparks]

Hi Murdock, my disc and PC are in PE, I only get there Wednesday morning. The closest reg. that I can think of and which I use, is that pertaining to isolators. All phase conductors must be broken. Both live and neutral. I can let you have the reg. numbers when I get there if no-one supplies it in the meantime. The changeover is after all installed for the purpose of isolation.

[Dave A]

I know you're looking for regs, but from a logic point of view:

some other feedback...4 pole changeover switch required if only part of the installation is supplied from the generator...and 3 pole required if the entire installation is powered by the generator...mmm now for for some literature to backup these statements? anybody have any.

The problem I see with that logic is now you have an isolated neutral phase in the genset part of the installation, which you're going to have to bridge to the neutral at or close to the genset, which in turn has to be grounded and connected to your central earthing point for the installation, which is going to be connected to the earth for the mains supply, which is going to be bridged to the neutral of the mains supply at some point...

On the flip side I think it's important to differentiate between the neutral as a phase return and earth, particularly if for whatever reason the neutral to earth bridge isn't what it should be.

[murdock]

i found the answer in 7:12 sans code...if the generator is mounted in a remote location away from the transfomer a 4 pole changeover switch is required...the only time a 3 pole changeove ris acceptable is if the generator is mounted next to the supply transfomer.

[murdock]

if you are a generator installation person or plan on signing off COCs for generators i would highly recomend you read the sans section 7:12....and unless you are familar with this code you will get yourself into some serious financial difficulties if you dont...for example a ATS for a 500 kva+ generator is a little more than the workmanship gaurentee the ECA offer...

[murdock]

now heres the scary part...not one company or person who i have spoken to i recent weeks about these issues can actually give me an answer in writting other than what is in the sans book under section 7:12

i contacted the durban electricity department and when i enquired about the bylaws...the response from their customer services department was "do we have bylaws...i thought it was done by private companies"

the second response from someone a little higher was " we work according to the sans book and dont have our own bylaws with regards to generators installations"

so as a private contractor what do you do...just do it as you think it should be done and if there is an equiry hope that nobody knows any better than you do...otherwise you are in the dwang...all i can say is thank GOd there is no policing in this industry...because even the people who try do things right cant do things right because there is no call centre or backup for the sans rules.

the fact that electrical contractors have to ask questions with regards to the electrical industry on a public bussiness forum to try get answers is a clear indication of how bad it is...

i use to report contractors and make a big thing of illegal installations...but have since looked at it with an open mind and reallised that it is not the contractors electricians...inspectors who are to blame its the people who make the rules and dont educate the people who are to blame...we have a small group of well informed people who threaten us will all sorts of prosecution if we dont abide by the rules they make...but not having a support system in place just makes all the rules a waste of time and paper.

the reality is just like the V-O-V generator connection...the way to overcome that problem would be just to tell the customer to say the generator was installed before 2008 when the new laws came out.

[Dave A]

the fact that electrical contractors have to ask questions with regards to the electrical industry on a public bussiness forum to try get answers is a clear indication of how bad it is...

Don't knock it too much - it was this very gap in technical support that pushed me into launching The Forum SA in the first place
Yeah - I had other hopes and irritations too, but that was the desperate need for me that got me off my ass to actually do something about it.

[BEVIN]

GENERATOR CONNECTION

HI ALL THANKS FOR ALL THE GREAT ADVICE GUYS
PLEASE TELL ME IF THE FOLLOWING IS ACCEPTABLE
INFORMING HOME OWNER THAT GEYSER AND STOVE IS NOT TO BE USED WHILST THE GENNIE IS RUNNING
IN OTHER WORDS 3POLE CHANGE OVER CAN BE USED
THANK YOU

[GCE]

HI ALL THANKS FOR ALL THE GREAT ADVICE GUYS
PLEASE TELL ME IF THE FOLLOWING IS ACCEPTABLE
INFORMING HOME OWNER THAT GEYSER AND STOVE IS NOT TO BE USED WHILST THE GENNIE IS RUNNING
IN OTHER WORDS 3POLE CHANGE OVER CAN BE USED
THANK YOU

Not sure I understand the question 100% - you thinking that if the complete installation is fed by genset then a 3 pole can be used vs a 4 pole ?

Simply answer is NO

When talking full load it means full load of minisub/transformer - you may not earth the neutral unless you are the supplier


SANS 10142-Ed3.1
6.1.6 The neutral conductor shall not be connected direct to earth or to the
earth continuity conductor on the load side of the point of control except as
allowed in 7.16.4.

[BEVIN]

Hi there .Mr Murdoch.what is the purpose of the third Pol?

[Isetech]

A double pole is used for single phase and a triple/4 pole is used for 3 phase.

Depending on the size of the generator, you would would need to split the DB into essential and non essential.

IF you use a 15 kva single phase generator for a 60 amp amp single phase supply, there would be no need to spilt the DB.

However if you connect a single 5 kva generator, then you would use a double pole 32/40 amp changeover switch, you would need to split the DB and it would be advisable to install overload protection for the generator.

One of the issues I have identified with using "smaller" generators and automatic transfer switches, people tend to connect them directly the main DB without splitting the DB. The contactors in the ATS is only rated for 25 amps (5 kva unit) yet they have the full 60 amps going through a 25 amp rated contactor. This is a big problem.

[BEVIN]

Thanks for that answer Isetech
And that's exactly what I will be doing.connecting a 6 KVA Hennie to the db.i have seen however that many guys do not split the db. But
Inform the user (homeowner) to switch off the stove and geysers before switching to the generator.this is not acceptable?