Wiring a generator for backup power

[NickCu]

I have a 2kW generator which I'd like to get wired up into my home electrics so I can switch to generator power during power cuts.

I am not for a moment thinking of doing the work myself!

But I wonder if anyone can give me an idea of what work is involved? Can any electrician do this for me or will I need a specialist?

Nick.

 

[Spark123]

What are you looking to run? - the generator will almost certainly be too small to run the whole house!

 

[ColJack]

the explanation is long winded and not worth the cost for a 2KW generator..
at most you could run the fridge, a few lights or the kettle..

are the power cuts in your area frequent enough and of sufficient duration to warrant the cost involved?
if they are then complain to your supplier..

you would need a change over switch ( 63A shown in link, you would need a 100A one ) for the main tails, between the meter and the CU, and if you are intending to use a partable generator, you would need a suitable wall mounted PLUG ( I say PLUG because it would need to be the plug end on the wall and a socket end on the lead from the generator same as a caravan hook up.. )

 

[NickCu]

Thanks for both replies.

In terms of what I'm hoping to run it is a couple of rooms worth of lights, the control box and possibly pump for the (gas) central heating, maybe the telly and PC. No kettles, electric cookers, or other heavy loads, obviously. I thought that 2kW would probably do this nicely.

We seem to suffer a good half a dozen power cuts a year. They rarely last more than 3-4 hours, but when it happens at kids' bath time on a dark winter night, it is a pain.

Since I inherited the generator essentially for free, the cost of the work would be the only cost involved.

Looks like the changeover switch mentioned costs maybe £75. Add maybe £20 for the wall plug..? What should labour run me, the same again or maybe a little more?

Does the total cost seem totally out of proportion for a working backup power supply?

 

[ericmark]

To keep things simple I would wire those items wanted during a power cut to a separate consumer unit. 2KVA is less than 13A and either you could used a 13A or 16A plug to feed the consumer unit and simply unplug from mains and plug into generator during the power cut.

Of course one can use change over relays and switches but really not worth it for 2KVA.

Much depends on length of power cuts but if you want uninterrupted supply then inverting to DC and back to AC is the way forward you can charge 12 or 24 volt batteries both from mains and generator and then use an inverter to supply the 230Vac supply. However this would only really be done where power loss was critical.

I have not had a suppliers power cut in years which would have damaged food in fridge or freezer and more likely to be caused by a RCD tripping if the food is that expensive then auto resetting RCD are on the market but at £300 each not cheap.

I have emergency lights and that is my limit can't see the time without power is enough of a problem to do anything else.

My son has different outlook and has an inverter and two large 70A 12V alternators on his engine. He has considered changing one for a 230Vac combined alternator inverter set-up where engine speed is not important but decided not worth the expense. He relies on the 300AH bank of batteries in the main the 4th 100AH battery being reserved to start engine. He runs everything from a 16A supply and intends to upgrade inverter to 3KVA but he expects to be away from shore power for days on end. But I also was able to run everything from 16A supply in a caravan and unless you use electric for cooking and hot water 16A should be ample.

The 8A available from a 2KVA generator will not run washing machine etc. But as temporary supply should be ample.

 

[bernardgreen]

To keep things simple I would wire those items wanted during a power cut to a separate consumer unit. 2KVA is less than 13A and either you could used a 13A or 16A plug to feed the consumer unit and simply unplug from mains and plug into generator during the power cut.

This is how a friend has set up his generator connection and it works well. He choose to not use 13 amp plug and sockets in case someone un-plugged the supply to the CU to use the socket.

 

[ricicle]

2kVA should be ample to run a TV, a couple of lights and any electrical controls for your central heating if required. The issue is that these require energisation from the mains as well during normal supply so a suitable 2 pole changeover switch would be required to run these.

 

[ColJack]

eric's solution is a viable one, but I'd use a 16A breaker and a 16A blue plug and socket.. the generator will likely have one anyway so you just use a ready made blue extension lead when the need arrises..

 

[NickCu]

Thanks ericmark and ColJack, I like the simplicity of the solution. I just need to narrow down which 8A of equipment I need and get those hooked up to a new consumer unit.

Now I'm assuming that this would be a straightforward job (again, I'm NOT going to be doing it myself).

Elsewhere someone mentioned that the generator must be earthed, can this be done via the existing mains earth, or is that going to be a problem?

 

[electronicsuk]

Thanks ericmark and ColJack, I like the simplicity of the solution. I just need to narrow down which 8A of equipment I need and get those hooked up to a new consumer unit.

Now I'm assuming that this would be a straightforward job (again, I'm NOT going to be doing it myself).

Elsewhere someone mentioned that the generator must be earthed, can this be done via the existing mains earth, or is that going to be a problem?

I'm not sure why people are suggesting that you install a second CU for generator backed loads, as it's clear you're on a budget. There will be the cost of the CU, then alterations to the existing wiring to get dedicated circuits to wherever you need them, which may very likely involve damage to house decor due to chasing out, removing floorboards, etc. It will NOT be a little job, unless you move across entire existing circuts, which again is pointless for ring finals as you have no idea how much load will be on them.

Realistically, you could get away with little more than a 16A inlet, 100A changeover switch, 30mA RCD + enclosure and then an earth electrode to tie down the genny. As some manual effort will be required in setting up the generator when you have a power cut, it seems reasonable for you to simply turn off any unnecessary loads to keep under 2kW.

 

[Goldberg]

A separate CU is the way to do it.

Migrate the circuits that you want to be powered by the generator into the new CU, and take its supply directly from a changeover switch.

One input to the switch comes from the old CU, with the phase on a new 16A MCB/RCBO, and the other input is connected to a blue plug. If you connect the new CU to the MET then you would expect the system to be earthed in all circumstances.

 

[ColJack]

so the powers off because some numpty went through the cable in the road.. and you've got no earth then...

 

[RF Lighting]

My genny is connected with a widow maker

 

[ColJack]

extension lead with a 13A plug on each end?

not something to recomend to the OP though..

 

[RF Lighting]

No, absoloutly not. It's a stupid thing to do, and will probably kill me one of these days.

I have all the bits ready to wire it up properly, but you know how it is