# Interest group forums > Electrical Contracting Industry Forum > Electrical Load Shedding Forum >  Connecting backup generators to existing electrical installation

## Kevin Stubbs

When connecting a generator to the electrical board of my house ,do I have to install cross over switches on the neutral and earth as well

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## Dave A

> When connecting a generator to the electrical board of my house ,do I have to install cross over switches on the neutral and earth as well


Certainly not on the earth. It would be a bastard to seperate anyway unless you were crossing over the entire installation.

I don't see much _need_ to isolate the neutral* - the allowed potential between earth and neutral is so low anyway, but then some electrical appliances need to have isolators (live and neutral disconnect)  :Confused: 

Hopefully a more definitive answer will be forthcoming shortly.

*I'm just a director of an electrical contracting company - but not an electrician.

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## Dave A

Hmm. I've been looking at our wiring diagram (we're using an interlocked contactor rig) and thinking about this. You certainly want the neutral between the generator and the crossover switch isolated when you're on mains power. Which means yes, run the neutral through the cross-over switch.

Whilst I'm about it, I read an article this morning where the ECA had commented on generators. A few points from that:
A COC has to be issued when wiring a generator into an existing installation that also has mains supply.There has been one death by electrocution by a generator in Durban already. (I see the main problem being they don't have earth leakage units.)The "plug generator into a plug point to power your house" is *very* dangerous.
I think I'm going to get my guys to point out to me anything in the SANS electrical installations code to do with generators. Murdock mentioned there was very little in a previous post. This could be interesting.

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## Dave A

I've just run through this neutral issue with my guys. In brief:

On a single phase installation, just like the live line has to be seperated from the main supply whilst under generator power, exactly the same with the neutral.

On a 3 phase installation being powered by a 3 phase generator, the neutral does not need to be isolated from the main supply.

If you are energising just one phase with a generator on a three phase installation, you need to treat that part of the installation as a single phase supply. Thus you'll also need a mechanical isolator to that part of the installation as well as the cross-over switch.

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## topak

gee..i want to learn more about Martinez Electric installation  :Whistling:

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## Dave A

Los Angeles is a whole different world away from South Africa, Topak.

Aren't you guys on 110V in those parts.

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## murdock

a single phase and three phase supply must isolate the neutral... the changeover contact must be a 2 pole for single phase and a 3 phase must be a 4 pole.

the installation must be done by a qualified electrician...who knows and understands generator supplies...lots of electricians i have come acroos recently dont have enough experience to advise or install generators

beware south africa and america have different volatages  earthing systems ie TT...TNC...TNC-S etc and the voltages are diffferent... we have phase to neutral 240 whereas they have phases to phase 240 volts...and  120 volts...60 hz not 50 hz...our electricity supply must not be compared in any way...if you do want to compare it must be with uk and australia.

most generator installation which i have come across are illegal but they work so the customer is not prepared to spend the money to make it right...they say why fix something that works.

i found a changeover other day where they using a contactor as a changeover switch the n/c contact is the generator supply...the n/o...n/c contacts of a contactor are not rated to 30 amps

but unfortunately until they start impossing heavy fines for illegal work the public will be the ones who suffer...and in saying that the public are half the problem because they the ones who are using the unregistered companies...because they are.............yes that is correct.... CHEAPER...in these difficult times who blames them.

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## murdock

> When connecting a generator to the electrical board of my house ,do I have to install cross over switches on the neutral and earth as well


by the question i can only assume you are not qualified to do the installation but if you plan on doing anyway....do you have a 3 phase supply or single phase supply...are you installing a automatic changeover system or manual?
are you feeding the entire electrical installation with the generator or only part....have you made provision for only partial if using a small generator...have you installed an earth spike...are plugs being fed from the generator on earth leakage...have you fitted barriers in the DB if only feeding part of the DB...have you clearly labelled the DB indicating which part of the DB will be fed by the generator...do you have a main switch in the DB if only part of the DB is supplied by the generator to isolate that part of the installation in case of accident leakage...have you done a loop impedance test and earth leakage test to verify if the earth leakage will trip in case of a fault while running on generator power...etc etc etc.

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## Dave A

> i found a changeover other day where they using a contactor as a changeover switch...


Murdock, given that the changeover must be *mechanically and electrically* interlocked, how can this be achieved without contactors?

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## murdock

it is a single phase installation using the main contacts for the supply and the n/c contact for the generator...so there is no way the mains and generator can be on at the same time...the problem is the n/c contact while the generator is running the 30 amps are being drawn through the aux n/c contact which is not rated for 30 amps...but i say it again it doesnt help making a whole lot of rules and not policing them...i need that banging my head on the wall smilie...please add it dave.

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## Dave A

Aaah. Gotcha.

I'm amazed I never added the banghead smilie... Maybe it's time to add a new batch.

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## Kevin Stubbs

> by the question i can only assume you are not qualified to do the installation but if you plan on doing anyway....do you have a 3 phase supply or single phase supply...are you installing a automatic changeover system or manual?
> are you feeding the entire electrical installation with the generator or only part....have you made provision for only partial if using a small generator...have you installed an earth spike...are plugs being fed from the generator on earth leakage...have you fitted barriers in the DB if only feeding part of the DB...have you clearly labelled the DB indicating which part of the DB will be fed by the generator...do you have a main switch in the DB if only part of the DB is supplied by the generator to isolate that part of the installation in case of accident leakage...have you done a loop impedance test and earth leakage test to verify if the earth leakage will trip in case of a fault while running on generator power...etc etc etc.


This goes back a long way, Thanks for your reply.
The supply is single Phaze. I would feed the entire electrical instalation. Manual change over. The DB has earth leakage and it does work on the generator.
My main question is ,does the crossover/change over switch have to include the neutral and earth, I have had mixed answers on that point from people in the profession.
Some say I dont have to switch the neutral and earth as well, some say I have to switch the neutral but dont have to do the earth.
Kevin

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## AndyD

You must switch both the live and neutral. No switching of the earth, earth bonds must be permanant connections.

If you're not qualified I would urge you to seek professional help with this. Firstly mistakes could kill someone (most likely the next electrician on site) and secondly mistakes can be expensive when it comes to generator damage.

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Dave A (10-Feb-10)

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## murdock

there is now a section 7:12 which covers generators and other alternative supplies...boy does it get interesting when you read it...what blows my mind are the variety of responses from people including generator suppliers and installers...

this section covers this topic quite well...and if not read properly can be a bit misleading.

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## murdock

and just to put a spanner in the works....no matter what the code says...you have to abide by the local supply authourity requirements and i am told that in durban you have to use a 4 pole transfer switch as required by them (yet to get some formal document as i am sure you will understand why :Banghead: )

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## Sparks

The problem now arrises: how many Wholesalers stock a 4pole? It is not just the change-over that should be 4pole but if a closer look is taken it will be obvious that the "Main Switch" of any 3phase DB is also supposed to be 4pole. My 2 regular wholsale suppliers do not keep "slow moving" stock.

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## murdock

what you have to consider...who is gona go down when you install the incorrect equipment (if we ever actually get the policing of the industry going) i can assure you not the wholesaler...because he doesnt sign the COC to verify all the goods he sold you are sabs approved.

this industry has too many loop holes and too few skilled enough people and not enough money in the budget to waste on trival things like the electrical industry...not enough people are killed from electrical problems to warrent money being wasted on policing the industry...or that how it looks to me looking from the outside.

just think if they got smart and thought like the road traffic department thinks...they could make billions...train up people and send them out to bussiness and homes and fine people if their electrical installtion was not up to standard or if they cant produce a COC...if you dont wear a seat belt you get a fine...even though you are not endangering anyone elses lives you still get a huge fine....its aj oke but it must be one of the biggest money making rackets in SA...after hidden camers for speeding...cameras in the bush must actually print money...i dont know about making the road any safer...just bigger bonuses for the fat cats.

just think they could make you put a code on you meter box which would verify that your house has a COC ...which the meter reader scans and then they could check it on the system and if your COC had expired or you dont have one the computer log it and another person in a different department would be asigned to go and investigate...creating employment....making electrical installtions safer and i could become a billionare for coming up with the idea...and then add appliance testing like hey do in the UK and create even more employment...create more opitunities for conferences to waste more of our tax money...create more task teams to waste  even more of our tax money...the only catch is you need skilled people...not like washing street signs...the people would actually have to be able to switch on a pc.

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## murdock

if anyone can get hold of the electricity department bylaws in durban...please let me know...i have left numerous messages for sherwyn from customer services but he doesnt return his calls...and when you speak to customers services help line nobody has aclue what i am talking about...they dont know what methods and standards...and there fore cannot put me through to someone in that department...sad...and we wonder why our industry is in such a "shocking" state.

after making that statement it cant be that bad...how often do you hear of buildings burning down and people getting electricuted...not that often...maybe our standards are just too high.

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## inusjvr

the municipality i work for requires the consumers to inform them if they intend to use a generator during a planned power outage! they also state that it must be installed by a qualified electrician! we have lost a contractor a few years back due a generator backfeeding on a 11kV line he was working on! i suppose every municipality might have different criteria but the basics should be the same! get a qualified person to do the installation and get a criteria from your municipality. if you dont come right at the bottom go to the top! phone the electrical engineer or his assistant!

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## AndyD

> the municipality i work for requires the consumers to inform them if they intend to use a generator during a planned power outage! they also state that it must be installed by a qualified electrician! we have lost a contractor a few years back due a generator backfeeding on a 11kV line he was working on!


I don't think there's enough awareness about how dangerous back-up generators are, not only for the user of the installation but also for the guys working on the upstream networks. I'm actually surprised there hasn't been a lot more fatalities. 

I think acombination of factors are to blame. Retailers and wholesalers alike are selling site generators as a domestic back-up solution to the end users. Many of these generators are completely unsuitable as domestic premises backup because of the way their windings are configured and they're often temporarily installed using a lead with a plug top on each side with little or no regard for interlocked isolation of the main Eskom supply or safe local earthing arrangements.

Many qualified electricians are sadly lacking in this area as well, I've seen many installations that were done 'professionally' but have been unsafe or non-compliant.

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## TAP

SANS 10142-1:2012
Edition 1.8
(As amended Jan. 2003, Dec. 2003, 2008 and 2012)
Annex S  (informative) Has Examples of emergency power installation configuration

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## Leecatt

I am now the proud recipient of my brand new, shiny 2013 Load Shedding Schedule  (Remember them saying there will be no more load shedding this year?)
Yup I can now forecast exactly when I will be without electricity, Ha!
Twice we have had a shutdown for an extended period and neither time has it coincided with the schedule.
My suggestion is this: Instead of destroying the forests by sending us schedules to which you are not going to stick to why not use the wasted money to improve the electricity infrastructure?

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## AndyD

Oh goodie, I love load shedding. Servicing my back-up generator has been on my to-do list for a couple of months, it's now at the top of the list.

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## AndyD

Have they actually started load shedding yet, according to my power monitor we haven't had an outage for over a year and even that was due to allowing our pre-paid to run out of units.

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## ericlowry

ESCOM did an upgrade on the overhead supply in our street a couple of weeks ago and the pole caught fire just afterwards, is this the new way of load shedding or just a sign of the times? Seriously I could not believe it. These guys are getting worse  and it was ESCOM.

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## AndyD

Maybe it'sa new communal heating system they're trying out. We've had a run of customers with supply problems recently, I've logged four fault reports in as many days. I still haven't heard of any load shedding in Cape Town yet and we should be past the worst stage of the high winter loads.

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## ericlowry

I think it's a new form of lighting, called a total loss system just like the rest of their projects. Another reason to go to the first world ASAP

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## Dave A

> Another reason to go to the first world ASAP


In every problem lies an opportunity  :Smile:

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## AndyD

> Another reason to go to the first world ASAP


You obviously have very little clue about the state of the UK electrical industry at the moment. Between Part P and domestic installers they've turned it into the Wild West. I'd rather take my chances here if I were you. If you're a fully qualified Master Electrcian you should never be short of work in this country, you might not die a multimillionaire but you'll earn a decent salary.

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## ericlowry

Any advice or suggestions about the UK electrical industry are most welcomed. I'm going because of the lifestyle. How is the UK system different? we have our single phase testers, domestic sparks here as well and it is very competitive.

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## AndyD

Well the lifestyle is completely different in many respects and the electrical industry even more so. This is probably the largest UK electrical forum I'd recommend you do some bedtime reading before taking the plunge.

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## MullerR

> Oh goodie, I love load shedding. Servicing my back-up generator has been on my to-do list for a couple of months, it's now at the top of the list.


What is the correct generators to use for back up as the wholesalers gen sets are not the right ones for back up?

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## AndyD

There's several different types of generator available from wholesalers, many of the smaller units aren't suitable for connection into a DB because of their wiring arrangement. Are you looking to install it into your DB with a changeover switch or just use it with extension leads? What items are you wanting to plug into it?

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## MullerR

I am aware of the V-O-V wiring arangement. I want a genny to install it into by db with a changeover. I have the powermaster 5.5kW SRGE6500D genny. The voltages are 220v live to neutral, 110v L-E and 110v N-E which makes is a v-o-v configuration if im correct. I dont want to wire it into my db as it is not safe to do so and to connect the neutral to earth and then to an earthspike im also not 100% sure if thats still 'legal' or preferred? If thats the case, I guess I'll have to use the genny with extention leads to power whichever appliances I need.

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## Dave A

> The voltages are 220v live to neutral, 110v L-E and 110v N-E which makes is a v-o-v configuration if im correct.


Even if it isn't a v-o-v configuration, you'll still get those results if the neutral hasn't been bridged to earth yet as the neutral will be floating.

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## MullerR

> Even if it isn't a v-o-v configuration, you'll still get those results if the neutral hasn't been bridged to earth yet as the neutral will be floating.


Then how do one determine if it is V-O-V?

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