Installing generator transfer switch

[JasperW]

Hi All

I am in the process of buying a small 3.3Kwh generator to act as a backup power supply for the house. Although I could run extension leads into the house ideally I would like to be able to plug the generator into the house mains wiring so the central heating and lights work as normal. I live in central London and power outages lasting more than a few minutes are extremely rare so hopefully this is not something I am going to need. Working in IT I am, however, concerned that for the next few years we are at risk of the energy companies being AI hacked and having outages that might last for a few days, hence the purchase now!!

I am assuming that I can get away with a 125 Amp 240V Generator Changeover Transfer Switch and a suitable socket in the basement where the meters are (see photo). My system already has an isolation switch from when the smart meters were installed so I assume it would be a quickish job for an electrician to fit the transfer switch. What sort of socket socket should I specify for the generator? My generator has a 13A socket as a power out and my plan is to run a heavy duty extension cable from the shed into the house connecting to a short cable coming from the transfer switch. Some of the YouTube videos I have seen show a standard 13A plug at the end of a cable coming out of the transfer box, this instinctively feels wrong but then that cable is receiving not delivering powers so maybe it is OK. Any thoughts?

The house typically runs at about 400w - 600w during the winter (providing I don't use the kettle, dishwasher etc.) so the generator should be more than up to powering essentials. We have gas central heating and a gas hob and I could use the air frier if I were careful with what else is running at the same time.

This is the sort of transfer box I am thinking of (125A) and are about £45 on Amazon.

I want to keep the system as simple and basic as possible, whilst still being compliant and safe to use.

Any advice or suggestions gratefully received and an idea of which I should be budgeting in terms of installation cost.

Thanks

Jasper

 

[ericmark]

Question one has to be how to earth. So one has to look at the premisses and work out where an earth rod can be put, this would be easy with this house, but with some it can be a problem.

Second is how do you know no high user is turned on before you turn to generator, with a power cut, clearly you can't see what is switched on.

I have the inverter and battery just work freezers and central heating, the more I have the faster my battery will deplete.

With you the more fuel you will use.

My living room light has 8 x 6 watt bulbs, but in a power cut 4 watt would be ample, so something like this that automatically turns on with a power cut, is likely better than having the main lights on a generator as it turns on with power cut.

With a generator you need to get to it to start it, so need something to light your way. Also how will you know when the power returns?

So really need just some selected sockets which are supplied from the generator so you don't have to go around the house first seeing what is switched on.

 

[endecotp]

Earthing is the key thing, and is a complex subject. Will your RCDs work as you expect? Note that if you are connecting your boiler (etc.) that will connect the electrical earth to the gas and water pipework.

There are documents that offer advice but many are not available free of charge (i.e. BS standards and IET documents). For example, the IET’s “Practitioner’s Guide to Temporary Power Systems” sounds like just what you need but it’s £31.90.

I don’t know exactly what you should do. Beware that some of the advice you’ll find online is dangerous - or worse American, where they only have “electricity lite”. If you post what you propose to do on here, maybe someone experienced will give you an opinion.

Personally I’d avoid a literal changeover switch. I’d want something where you can disconnect one supply, do some checking, and then connect the other. While also making it completely impossible to connect the two supplies together, of course!

 

[JasperW]

Thanks for the comments, the consumer unit is earthed to the gas pipe at the point just before in disappears into the ground so I am assuming that if I earth the generator into ground close by they will share a common earth. In any event my consumer unit is an old style one with simple circuit breakers rather than RCDs, and yes, I have been thinking for sometime I really should get the consumer unit upgraded

If I did have a power cut I would need a check list to make sure that no high bower devices were running when I started the generator . But that would be limited to checking the cooker, dishwasher, washing machine, and dryer.

A bigger issue will be remembering to cycle the petrol in the 10L fuel can through the car and to refill the can every 6 months as well as periodically running the generator to keep it lubricated. If I need more fuel I can syphon it from the car.

We do have several mag-lite torches around the house.

 

[endecotp]

my consumer unit is an old style one with simple circuit breakers rather than RCDs, and yes, I have been thinking for sometime I really should get the consumer unit upgraded

That is a great deal more urgent than preparing for the AI-apocalypse IMO.