Back up generator on domestic

[growler]

A customer has asked me to connect his back up generator 'properly' as currently he just flicks the main switch and plugs straight into the down stairs ring main.
I admit I have little experience with this and won't take it on unless I'm 100% I'm doing it correctly. It's a 5.5kva generator on a tt.
Can somebody help me with what I need to consider ?
So far I'm thinking
- change over switch
- earth electrode

 

[Lighthouse Phil]

Here we go.
1) your change over switch MUST disconnect Phase/ neutral AND EARTH from your DNO supply
2) Install an earth rod or mat connected to the frame of the genny
3) Link Neutral and Earth in the alternator
4) Unless the alternator has a method of maintaining the correct voltage / frequency, ie an AVR, do not connect any electronic equipment to the output

 

[PEG]

I will give you two other bits of advice,free. 1) your geny is of the wrong type and undersize, 2) Your customer will not pay what you will require to do it properly.....the distance between using the ubiquitous double plug top lead,and the correct system,is about the price of a month cruise to somewhere expensive...bon appetit

 

[johnboy6083]

I personally wouldn't worry about disconnecting the earth, as you're always going to have inadvertent connections via bonding, CPC's and the general mass of earth, between your genny rod, and the DNO earth. In this instance, being a TT system, you needn't disconnect the earth anyway.

 

[HandySparks]

I will give you two other bits of advice,free. 1) your geny is of the wrong type and undersize, 2) Your customer will not pay what you will require to do it properly.....the distance between using the ubiquitous double plug top lead,and the correct system,is about the price of a month cruise to somewhere expensive...bon appetit

Would you care to expand on any of this?

How do you know what type of generator the OP's customer has?
Why do you say that 5.5KVA is too low for domestic backup?
Since the earthing is TT and is likely to already have adequate RCD earth fault protection, why should doing it properly cost the price of a month's cruise?

 

[Engineer54]

Here we go.
1) your change over switch MUST disconnect Phase/ neutral AND EARTH from your DNO supply
2) Install an earth rod or mat connected to the frame of the genny
3) Link Neutral and Earth in the alternator
4) Unless the alternator has a method of maintaining the correct voltage / frequency, ie an AVR, do not connect any electronic equipment to the output

Why would you need to disconnect the DNO earth, come to that,...how would you??

 

[Knobhead]

You can’t rely on the DNO earth as work could be ongoing on the LV system. But as this is TT it’s not a problem.
As Phil has said a positive change over is needed for both L&N.
Linking N&E makes the installation when running on the generator TN-S.

 

[Lighthouse Phil]

Why would you need to disconnect the DNO earth, come to that,...how would you??

During a power outage, you cannot assume the DNO's earth is intact or your own earth rod. Theres also the possibility that the genny will send a voltage down the DNO earth.
The 2poles and earth go to the 'Mains' side of the change over switch / contactor before going to the DB.

- - - Updated - - -

You beat me to it Tony

 

[Engineer54]

During a power outage, you cannot assume the DNO's earth is intact or your own earth rod. Theres also the possibility that the genny will send a voltage down the DNO earth.
The 2poles and earth go to the 'Mains' side of the change over switch / contactor before going to the DB.

- - - Updated - - -

You beat me to it Tony

What are you saying, ...that a 3 pole C/O switch is needed for a single phase supply??

 

[growler]

Should I be running a 2.5 from generator to change over switch and connecting the generator via a 16amp socket ?

 

[growler]

Anybody ? Xx

 

[growler]

I'm not sure what's more dangerous, me connecting up generators or customer continuing to connect generator via 3pin plug straight into the ring main ..

 

[micknew]

I'm not sure what's more dangerous, me connecting up generators or customer continuing to connect generator via 3pin plug straight into the ring main ..

If you not qualified then both options have the same potential danger.
Get a professional in.

 

[growler]

I'll just wack in some 2.5 on an external socket for him to plug into and ride off on me horse.

 

[micknew]

I'll just wack in some 2.5 on an external socket for him to plug into and ride off on me horse.

Another DiIYer pretending to be a sparks!

 

[guest119]

Do a search Growler, the topic has been done to death in here and recently.

Boydy

 

[growler]

Can't find it

 

[growler]

If you not qualified then both options have the same potential danger.
Get a professional in.
im qualified just have no experience in gennys. Surely just because your qualified it doesn't mean you know it all.

 

[snowhead]

Should I be running a 2.5 from generator to change over switch and connecting the generator via a 16amp socket ?

5500 / 230 = ??

 

[growler]

Yes but the output of the generator is via 16amp socket.

 

[guest119]

Can't find it

Just put GENERATOR into the searchbox above and fill your boots.

Boydy

 

[growler]

I'm half way through a rewire and the customer just put it on me that he wants this genny set up, there was no mention of this in the build up to the job. I just don't know what to tell him as I don't feel comfortable doing this and the genny is pretty much like the one I use out on site.

 

[D Skelton]

I'll just wack in some 2.5 on an external socket for him to plug into and ride off on me horse.

External plug you mean, so that he can attach a portable socket on to it.

 

[PEG]

Would you care to expand on any of this?

How do you know what type of generator the OP's customer has?
Why do you say that 5.5KVA is too low for domestic backup?
Since the earthing is TT and is likely to already have adequate RCD earth fault protection, why should doing it properly cost the price of a month's cruise?

...Expand i will... Firstly,the OP has said it is 5.5 KVa geny,i am taking a guess it will not be suitable for ALL types of equipment likely to be connected to it,because he did not specify it would be,could be wrong there,but he has not given details. Secondly.he said "domestic backup",so how much,domestically speaking,will that power at its expected duty-cycle?Some lighting and a good kettle? Thirdly,because i know the cost of a suitable sized and rated back-up generator and the associated arrangement, that would cope with an average household,and also know the cost of a cruise,and,am able to compare two numerical figures accurately.....i did. Apologies for over-expansion.

 

[growler]

Could I maybe install a change over switch and an external plug and then it's down to the customer what he does after that ?

 

[HandySparks]

...Expand i will... Firstly,the OP has said it is 5.5 KVa geny,i am taking a guess it will not be suitable for ALL types of equipment likely to be connected to it,because he did not specify it would be,could be wrong there,but he has not given details. Secondly.he said "domestic backup",so how much,domestically speaking,will that power at its expected duty-cycle?Some lighting and a good kettle? Thirdly,because i know the cost of a suitable sized and rated back-up generator and the associated arrangement, that would cope with an average household,and also know the cost of a cruise,and,am able to compare two numerical figures accurately.....i did. Apologies for over-expansion.

OK, so you're just guessing about the type of generator.
If I were buying one of that size, I'd probably go for one of these:
Honda EU65is Petrol quiet Inverter Generator

Decent, reliable make, quiet, and an inverter output for stability.

For a normal domestic property, I recon that 5.5kVA would do most loads except an electric shower or hob, or multiple heating devices. ie, should be good for a kettle, plus lighting, central heating pump, fridge, freezer, PCs, TV, etc. Yes, you could go for bigger, but once you've covered the 'essentials' and the small stuff, I think there's little point in paying more.

As for the cost of installing, I assumed that the generator itself was already paid for, as the OP's customer has one (assuming that it is, in fact, suitable).

 

[HandySparks]

In fact, if you're really disciplined and have gas heating and a gas hob, or other non-electric cooking, I think you could 'make do' with not much more than 1kW.

It's a 'project' that I'm currently considering for my own use. I have one of the wireless electricity consumption meters on my desk, and most of the time it's reading under 1kW, with occasional peaks above that level when someone runs the kettle, washing machine, dishwasher, tumble dryer or oven.

 

[PEG]

Fair enough,but the problem occurs in separating the circuits the geny can cope with the ones it cannot...this is not a problem for a genuine "back-up generator",as it is capable of backing-up the the primary supply. Folk generally require the same functionality from their homes when using generator back-up,they accept the cost,supervising and upkeep as a trade off to keep warm,clean and entertained... Otherwise,any geny and lead would give some benefit (as does the downstairs ring only method) There are other factors with back-up generation for a domestic supply,that require consideration,but are often overlooked initially. Siting,is one.Is the unit to be positioned where it will be run? How long will it be running? Fueling store and filling.Security,noise,neighbours,remote starting? A lot of my customers imagined a quick pull start,jealous onlookers and sit down for Sunday dinner....not happening. I don't know if you are old enough to remember to power cuts around 1980,my mates mum had a dance studio,and had always kept this old Tecumseh 4KVa geny fueled and ready in the garage for the lights only...We had started and played with it dozens of times,so,door open,fueled and running,all lights blazing...3 hours later,lights off,get outside,bloke opposite said 2 lads in a transit van took it,and he was glad coz he had a headache! :joker:

 

[Geordie Spark]

Fair enough,but the problem occurs in separating the circuits the geny can cope with the ones it cannot...this is not a problem for a genuine "back-up generator",as it is capable of backing-up the the primary supply. Folk generally require the same functionality from their homes when using generator back-up,they accept the cost,supervising and upkeep as a trade off to keep warm,clean and entertained... Otherwise,any geny and lead would give some benefit (as does the downstairs ring only method) There are other factors with back-up generation for a domestic supply,that require consideration,but are often overlooked initially. Siting,is one.Is the unit to be positioned where it will be run? How long will it be running? Fueling store and filling.Security,noise,neighbours,remote starting? A lot of my customers imagined a quick pull start,jealous onlookers and sit down for Sunday dinner....not happening. I don't know if you are old enough to remember to power cuts around 1980,my mates mum had a dance studio,and had always kept this old Tecumseh 4KVa geny fueled and ready in the garage for the lights only...We had started and played with it dozens of times,so,door open,fueled and running,all lights blazing...3 hours later,lights off,get outside,bloke opposite said 2 lads in a transit van took it,and he was glad coz he had a headache! :joker:

You're just a wet-behind-the-ears bairn!

I remember the real power cuts of 1973 when the miners kicked Ted Heath's arse out of office!

and that was why Thatcher wrecked the mining industry - and everything else - ten years later. It's called revenge folks - pure, mindless, spiteful revenge!

 

[Robotstar5]

I remember the real power cuts of 1973 when the miners kicked Ted Heath's arse out of office!

My old man wasn't too happy, he'd not long paid to have electric storage heaters fitted. Due to doing a lot of camping, at least we had lighting and cooking stove.