Connecting a generator to essencial circuits

[spider]

Hi All,

I have a few questions and would like your opinion and advice on please, recently housed local to us have had a power outage for 30hrs, and this got me thinking (dangerous I know) about using a generator to feed essencial circuits.

The house supply is TN-C-S
Crabtree Starbreaker split load CU

What I was thinking is to install a Gewiss GW66004 switched socket oulet fed from a 10A RCBO on the non RCD side of the CU, (The genny is only 2.2kVa)

The genny would be plugged in using a modified plug at the genny end (neutral & earth joined)

Also I would install an earth electrode using 16mm to the CU earth bar

Operation would be:

1 Isolation and locking off of the main incoming supply at the CU when utility power is lost
2 Isolate MCBs except lighting and sockets (loads disconnected except FCU feeding heating)
3 RCBO to genny socket on and backfeed into board

Whats your thoughts, is it feasable.

Cheers

 

[mechelec]

You will need a changover switch in the tails to do this safely so there is no danger of running the mains and generator in parallel.
The local DNO will be knocking on your door if you put a backfeed on the mains when they are working on the supply cable

 

[Guest123]

Hi.

Got to say the "backfeed" idea just doesn't sit right with me at all.

I would suggest a mains changeover switch at the origin, then just leave the breakers for the circuits you want to run off it on.

No chance then, no matter how remote it may be, of energising mains and geney simultaneously.

 

[spider]

Thanks for taking the time to offer your advice.

I realise its a messy way and does introduce the possibility of error, so it looks like a changeover switch is the way to go!

Cheers

 

[mechelec]

Hi.

Got to say the "backfeed" idea just doesn't sit right with me at all.



You have good reason to be concerned about the backfeed onto the supply. A small generator would not have the power to backfeed a mains TX but if the cable was cut whilst being jointed it could give the jointers a nasty tickle!!!!!!!!

 

[Guest123]

The genny would be plugged in using a modified plug at the genny end (neutral & earth joined)

I got to ask why join N+E???

Your geney will supply you with an simple TN-S supply as N+E will be joined in the star point of the geney winding.

All you need to do is install a rod next to the geney and connect to the gen frame (think of it as bonding if you like) although not really bonding, as it wont be part of the fault path unless the earth conductor in th TN-S goes open circuit.


Cheers.

 

[spider]

I got to ask why join N+E???

Your geney will supply you with an simple TN-S supply as N+E will be joined in the star point of the geney winding.

All you need to do is install a rod next to the geney and connect to the gen frame (think of it as bonding if you like) although not really bonding, as it wont be part of the fault path unless the earth conductor in th TN-S goes open circuit.


Cheers.

Yes I see what you mean , I will confirm tomorrow that the star point is connected to the body of the genny as that will remove the issue.

Refering to transfer switch data it recommends doing this modification, (however it is based on a floating earth) Power Transfer Switch

Cheers

 

[Guest123]

What they are saying there I believe is loosely based loosely on the EEBADS protection method and as you rightly say is based on a floating earth.

If they are strapped at the alternator then this would negate the need for it to be done in the plug and also negate the need for the rod as the fault would be cleared by the RCD protection in the geney.

 

[UNG]

What I was thinking is to install a Gewiss GW66004 switched socket oulet fed from a 10A RCBO on the non RCD side of the CU, (The genny is only 2.2kVa)

The genny would be plugged in using a modified plug at the genny end (neutral & earth joined)

I would have concerns over a modified plug into a socket arrangement

As mentioned the system should use a changeover switch and a mains inlet like the type that are fitted to caravans

 

[Darkwood]

You could got an extremely large loan out and fit an automatic change-over unit which brings the gen' on when powers out but when power returns it waits till its frequency cycle matches the mains before doing an uninterupted change over.Tie all this in with a seperate consumer unit with Heating, Alarm, Fridge etc on it and you got everything covered even when your away.

 

[spider]

You could got an extremely large loan out and fit an automatic change-over unit which brings the gen' on when powers out but when power returns it waits till its frequency cycle matches the mains before doing an uninterupted change over.Tie all this in with a seperate consumer unit with Heating, Alarm, Fridge etc on it and you got everything covered even when your away.

The wife thinks I'm nuts anyway, we have never had an outage over 2hrs since we have lived here (3 years), she thinks I'm being disproportionate, a bloke, never lol

(do like the idea of an auto start genny though)

Cheers & hapy xmas

 

[Darkwood]

The wife thinks I'm nuts anyway, we have never had an outage over 2hrs since we have lived here (3 years), she thinks I'm being disproportionate, a bloke, never lol

(do like the idea of an auto start genny though)

Cheers & hapy xmas

Just compare your cost and time for your project to her make-up box and its yearly cost and im sure you will win the argument hands down, but dont bring in the no' pairs of shoes she has to have and the different outfits for each pair as this is only to win the argument and not to lose the wife.

 

[mechelec]

I got to ask why join N+E???

Your geney will supply you with an simple TN-S supply as N+E will be joined in the star point of the geney winding.



Not always.Many generators run an "electrically seperate" earth system where the neutral point of the windings is connected to the neutral of the socket and the frame is bonded to the generator body only. Do a continuity test between the neutral in the socket to the frame and you will find most small gennies are seperate. If you want an RCD to operate then as previously stated the neutral and earth will need to be connected.

 

[cbw]

I am in a similar situation, we live in a very rural area and often lose our power.

I have a small 1kw generator in my shed, this has an earth spike to it case, an rcd in the front of it and this then runs a long extension lead which powers tv/dvd/sky, 1 low energy bulb in each room, telephone and most importantly the boiler controls(oil fired) which gives us heating and hot water.

It is just a 'make do' but it keeps us warm and lit.......also the elderly neighbours!

 

[spider]

Looks like my wish list for santa includes one of these, at £89.00 not bad (would like the gucci Briggs Stratton jobbie but need more overtime).

So all I have to do now is sort out how to get the incoming MEM isolator seals opened and re-sealed afterwards ( strange that its sealed on the consumer side after its been metered), looks like I'll be on the phone to my DNO for a while

Found a place for £75.40, now her indoors must be happy!

 

[ajelec10]

Another way to provide interlock between the generator and the main switch is to have (hope fully already installed) lockable isolaters you can then get two padlocks with a trapped key this then makes the two isolators interlocked with a bit of modifaction.

 

[spider]

Well, got the changeover switch from Senate Electrical in Peterborough and its just the job, had a chat to e-on and I just have to give 5 days notice and they will cut the seal, and the same day, reseal at no cost.

Just got to get a few more items in preparation for the big day in the new year.

 

[Davey101]

Interesting thread. I've wondered about the best (and cheapest) way of doing this in a house in the past, as the only backup/genny stuff I have done has been in larger installations. Keep us updated.

 

[wattsup]

You can get a 6kva diesel set pre-wired for auto start for about £1000, the auto transfer switch itself about £400 extra. Care needs taking not to overload the set, so its wise to allow only essential circuits to energise on changeover.
I would always use manual transfer for small sets (under 12kva) unless alterations to existing circuits can be made. B&S have a nice manual switch, 40A max on generator supply, auxillary skt, and warning lights about 200 quid tho

 

[spider]

Just a quick update before the festivities, total expendature to date is £136.00, only things left to get are a couple of 50cm lengths of 25mm meter tails.

I will post up some pics in the new year when you are sick of turkey and any distraction would be welcomed, the rough drawings I have attached show, current set up, proposed and a cable schedule to go with the house file.

Have a great Xmas & new year.

Cheers

 

[spider]

Just checked my small portable generator (2.2kVa) and the body of the machine is not common with the Neutral terminal as mechelec suggested.

I will be maiking up a bespoke lead for this emergency duty anyway, so will connect the nuetral & earth together at the generator plug to allow the RCD protected circuits to operate as normal on the consumer unit.

 

[Guest123]

I will be maiking up a bespoke lead for this emergency duty anyway, so will connect the nuetral & earth together at the generator plug to allow the RCD protected circuits to operate as normal on the consumer unit.

Seems your easiest option.

Just install your earth rod and away to go.

 

[wattsup]

Ditto to above, don't convert generator....nearly always

 

[Frenchsparky]

That is pretty good details about the UK useage with generators however I will give you both USA and France verison of generator useage.

USA side

There are few ways it can be done .,

Manual changeover

Automatic changeover

Localized conneciton

For manual changeover it is most common and cheaper than automatique changeover useally by few hundreds Euros even thousand Euros with larger units.

However the typical North American standby manual units typically use any generator from 7.5Kw to 15 Kw { 12.5 Kw is most common } some are cord set up and some are hardwired units but pretty good percentage of homeowner do have portable gennys they are typically from 3 to 8 Kw size { half of the time they don't work due they never exerized it at all }

For Automatique set up due the current code { regualations } they have to be sized to matched the service size in USA side typically 200 amp service will require 48 Kw generator and IMO that is plain silly and will cause serious issue espcally with diesel units and I know I did check the total load what they normally load it up and they don't go over 50~70 amp the most ditto with 100 amp service which they require 24 Kw genny that is alot more than it need to be used.

It is fine for Hosptail or large industrail useage where they can sized the unit to pick up the whole load

France verison

We do have manual or automatique changeover point switch some are before the CU and some after the CU to size it I useally sized it under the max rating of CU unit.
The reguations is almost simauir to your UK reguataions

Merci,Marc

 

[spider]

Quick Update:

The Transfer switch is now ready after the addition of a multifunction meter which will display, volts, amps. kW and frequency.

I have wrote to EDF Energy seeking permission to install the switch in the external meter cupboard, if this is declined, I have a little bit more work to do, but it will fit local to the CU.

I have a picture for your entertainment

 

[dragon-av]

Nice looking unit and may i say a very tidy office/desk wish mine looked like that. How will you wire the MCB to make sure only the specified circuits get transferred? My uncle has a similar thing done I dont know how its wired it was put in as part or a rewire/upgrade he had done and he had the genny out to run some bits while the board was changed and the spark said he could aire it in for him but i dont know how it was gone and doubt he does i think there is a large SWA running from garage where genny is to the house in addition to the SWA feed to garage.

In fact I have just bee having a google on the subject quite interesting really just been looking at LGP conversions for gen sets (ideal in a fixed install and cheaper to run if its used regularly and easier to change fuel over while genny is running...

found a useful american guide here PM: INSTALLING A BACKUP GENERATOR: MARCH 98

lpg kits here Edge Technology - Benefits of LPG Gas.

Auto changer over regulator TPA - ACR6 Two Cylinder Automatic Changeover - LPG Calor Gas Propane Regulator (TPA01) - Auto Change Over Va

now just need an auto changeover for the power and apart from checking the tanks its fully automated power backup....

This looks ideal Honda EM5500s electric start generator + dual fuel LPG on eBay (end time 29-Jan-10 14:01:15 GMT)

 

[andyh]

Quick Update:

The Transfer switch is now ready after the addition of a multifunction meter which will display, volts, amps. kW and frequency.

I have wrote to EDF Energy seeking permission to install the switch in the external meter cupboard, if this is declined, I have a little bit more work to do, but it will fit local to the CU.

I have a picture for your entertainment

Excellent information on your setup. I'm carrying out a similar setup but am starting from scratch on a new build. I've been researching transfer switches and best manual one seems to be the B&S one. Expensive though! Like the setup you have and wonder if you can tell us how you wired up the switch with the multi meter and what the connections look like inside?

During my research I came across this control panel which is roughly the same price as the B&S but seems to offer much more and has an auto changeover.
Automatic Generator Transfer Switch Controller with Metering

I've emailed the manufacturers to see if this would be suitable in a domestic situation. Anyone have any comments on the above system and whether it could be utilised with normal 25mm meter tails as the mains feed?

 

[spider]

As the use of this project will hopefully be so infrequent that it doesn't warrant an auto starting generator, but that peice of control kit looks really good.

I have written a procedure, prior to use, and in that it lists the breakers to isolate before starting and transfering load to the generator to prevent overloading, the spliting of essencial loads can be manually managed in my case.

I have attached two pics, one showing the rear of the power meter, the other the connection arrangment.

Tip: Don't trust the meter template that comes with the instructions to be accurate grrrr, centre punched through the template, marked out, drilled, only to find the holes were out, luckily the front covers up the mistake.

Connection wise, I have used bootlace ferruls on the cables to make them tidy, neutral uses a straight through DIN rail mounted connection, the live passes through a fused DIN rail mounted connection.

I did have to extend the current transformers connections to allow the lid sufficent slack to be moved out of the way during serviceing at a later date.

The sleeving has a conductive drain wire, hence the use of a pyro copper clip to earth.

Thanks for the links and info, I found loads of stuff on youtube about the connection and use of home generators, was seriously sad, sat infront of the lappy, headphones on listening to some guy in a check shirt talking about his setup

 

[dragon-av]

Thanks for the links and info, I found loads of stuff on youtube about the connection and use of home generators, was seriously sad, sat infront of the lappy, headphones on listening to some guy in a check shirt talking about his setup

Thats me most of the time....Oh to have the money to buy a shell and do it properly...

http://www.smartpowershop.co.uk/UserFiles/File/pdfs/X008_00003.pdf is nice only missing (although easily doable) is the GSM modem to send SMS or call to alertl you gen set is active and running...

I have a client who was thinging of UPS for his security system and has a genny on site (was being used before mains connected and i recon the Auto start unit is cheaper than a UPS) May need a small UPS for change over.

A mate who used to engineer in hotels had cathedral gensets and massive power factor correction capacitor banks they used to kick the genny in regularly to keep the load on the grid down to specified amounts but that used air breakers a bit over kill for a house?

 

[spider]

Excellent information on your setup. I'm carrying out a similar setup but am starting from scratch on a new build. I've been researching transfer switches and best manual one seems to be the B&S one. Expensive though! Like the setup you have and wonder if you can tell us how you wired up the switch with the multi meter and what the connections look like inside?

During my research I came across this control panel which is roughly the same price as the B&S but seems to offer much more and has an auto changeover.
Automatic Generator Transfer Switch Controller with Metering

I've emailed the manufacturers to see if this would be suitable in a domestic situation. Anyone have any comments on the above system and whether it could be utilised with normal 25mm meter tails as the mains feed?

Andy,

Save your money and slot this little baby in

[ame=http://www.youtube.com/watch?v=1j8rQEOf6zE]YouTube - Double pull Double Throw Changeover switch.divx[/ame]

 

[andyh]

Andy,

Save your money and slot this little baby in

YouTube - Double pull Double Throw Changeover switch.divx

Heaven help us! Still makes the rest of us look good!!

 

[spider]

I have read on forums that you are not permitted to install consumers equipment on a meter cupboard board, is this a fact? or urban myth?, if fact, a point of referance would be good.

I have made numerous phone calls trying to confirm or otherwise to my electricity provider and network supplier and both are passing me back an too.

Guidance notes recommend not doing it, but that is all they are, and that is inconsistant!

My generator transfer switch will hopefully live in the meter cupboard if their are no red cards.

Any help would be good

Cheers

 

[andyh]

I have read on forums that you are not permitted to install consumers equipment on a meter cupboard board, is this a fact? or urban myth?, if fact, a point of referance would be good.

I have made numerous phone calls trying to confirm or otherwise to my electricity provider and network supplier and both are passing me back an too.

Guidance notes recommend not doing it, but that is all they are, and that is inconsistant!

My generator transfer switch will hopefully live in the meter cupboard if their are no red cards.

Any help would be good

Cheers

It seems to vary from one DNO to another. That's not much help I know but from my own research there isn't really a definitive answer. I've had a verbal assurance they don't mind provided you don't interfere with their equipment. In essence, for my new build, I bought the meter box which came with the back board. The DNO simply installed the meter and cutout into it. From my point of view, I own the meter box and can therefore put what I want in it provided it's safe and is not against any specific regulation. However the DNO could ask you to remove non standard equipment if they came to inspect or change the meter.

I think you'll find it hard to get a common opinion on this and, as stated, some DNOs allow it and others say no. If I was you, I'd install the switch in the meter box and take the chance. Sounds like you've done your best to confirm what they allow.

Good luck and let us know how the install goes.

 

[spider]

I spoke to EDF (my DNO) several times and they were only interested to the service head, but they would not confirm in writing that is was acceptable (or conversley, that is was not)

Maybe I'm looking to deep into this!

Last thing I want is for the meter reader to flag up a problem, chances are I will fit it in the cupboard.

 

[spider]

Update 5/2/10.

E.ON confirmed over the phone that their would be no charge to move the isolator 3" to make way for a Transfer Switch.

Seimens Meter Man turns up with 'connect & test' on his job card, not move the isolator!, he said that I can't put my equipment in the meter cupboard in case the room was needed for a check meter or economy 7.

Explained that I had made numerous phone calls to confirm or otherwise that it was OK for me to install my equipment and unless EDF have formally adopted my meter box, it belongs to me, and I can put in it what I wished, unless of course he knew differently and could point me to a regulation or supply T&C.

He rang his boss, who said do the job, result Spider 1 Seimens 0


Pics will follow as the switch and ancillary equipment go in.

 

[spider]

Just some more pics of the transfer switch decied after chatting on here that a method to announce that the utility power had restored when running on genny would be a good idea, hence the switch which when in the off position will mute the local 230v sounder.

The switch is a lockable one i.e you have to lift the toggle to allow it to either turn on or off, bit like selecting reverse on your car , this is so it can't be knocked either on or off.

will show you a wiring picci when its loomed nice.

 

[andyh]

Just some more pics of the transfer switch decied after chatting on here that a method to announce that the utility power had restored when running on genny would be a good idea, hence the switch which when in the off position will mute the local 230v sounder.

The switch is a lockable one i.e you have to lift the toggle to allow it to either turn on or off, bit like selecting reverse on your car , this is so it can't be knocked either on or off.

will show you a wiring picci when its loomed nice.

Fantastic setup and very well put together. This is definitely the route I will take. Look forward to seeing the finished switch installed and working.

Will start working on my own now!

 

[spider]

Fantastic setup and very well put together. This is definitely the route I will take. Look forward to seeing the finished switch installed and working.

Will start working on my own now!

Cheers Andy,

Some of the links for the kit used:

PRO SIGNAL|ABI-027-RC|PIEZO BUZZER, MAINS VOLTAGE | Farnell United Kingdom
TYCO ELECTRONICS|FTN59|SWITCH, DPDT, LOCKING | Farnell United Kingdom
230V Green LED for Switch Panel

Expandable sleeving from ebay

If anyone wants the lable template its created in Visio, I can PM it out

 

[andyh]

Cheers Andy,

Some of the links for the kit used:

PRO SIGNAL|ABI-027-RC|PIEZO BUZZER, MAINS VOLTAGE | Farnell United Kingdom
TYCO ELECTRONICS|FTN59|SWITCH, DPDT, LOCKING | Farnell United Kingdom
230V Green LED for Switch Panel

Expandable sleeving from ebay

If anyone wants the lable template its created in Visio, I can PM it out

Thanks for the links. That saves me a lot of time sourcing the components. I'd love a copy of the template. The only thing I might change on mine is putting in a three position rotary switch for Mains, Off & Generator. That means I can isolate all power if I need to work on the main CU. Obviously yours would do this as well if you switch to generator and the generator isn't running!

 

[Reelsaver]

(however it is based on a floating earth)

As your system is a TN-C-S system even when the main switch is open the earth is still connected.
If you connect an additional earth to the star point of the generator (common for island mode operation) you are in danger of introducing circulating currents into the system which could overload current caryying capacity of your main cabling.
As previously postedy others the safest and best way of connecting a generator is via a change-over switch (either manual or automatic)
If your generator is not expected to pick up the full load of the property you could fit undervoltage devices to all non essential circuits, that way when the mains fails the circuits will automatically disconnect; when the generator runs up to speed and closes onto the bus bar only essential cisrcuits are still connected.