Size of generator required for power cut backup?

[cg360]

Hi,
Thanks for any help offered in advance!

Where I live is quite remote and we typically suffer 2-3 48-hour power cuts a year (we are on a spur line which is fragile and exposed, apparently).

As I have 2 young kids and a cold-sensitive wife, our main issues with these outages are a) keeping warm, and b) not sitting in the dark after 4pm (not so important for the kids).

Our heating is LPG-fuelled, and controlled by an electric programmer. My question is really what size of generator can I get away with - I estimate 100W for the CH pump, 20W for the controller and 2-3 60W bulbs, maybe a portable DVD player for the kids at 25W? Even with a healthy overhead on top, I reckon an 850-900kW gen would be adequate. Would you agree?

Also, I don't wish to have this wired into my house circuit. My CH programmer takes power from a standard 13A socket mounted below it. My idea is just to run an extension cable (weather protected) from the generator through the foundations into the house and run extensions to the programmer and the living room. Not ideal with cables lying around, but no large loads and nothing I'd worry about running on an extension cable anyway. The gen would be earthed by rod outside, as I know of the dangers in using my mainline earth during an outage.

Would this be okay or have I got it all wrong?

Thanks again!

 

[Monkeh]

I reckon an 850-900kW gen would be adequate. Would you agree?

Exactly how much space do you have out there?

 

[TicklyT]

Another load worth considering is your fridge and freezer (although in the depths of winter, a cardboard box on the doorstep could make a good substitute for a fridge and maybe even the freezer)

I will leave others to comment on how to make a safe installation.

 

[ban-all-sheds]

Bear in mind that many small generators are not very well regulated and (on this I'm less sure) may not put out proper sine waves.

 

[AndyPRK]

If I suffered those sort of power cuts I would want it connected to the main house wiring. (for lighting if nothing else!)

 

[cg360]

Of course I meant 850-900 Watts!

I don't want to go to the expense of having it connected up to the house as we can always ship out to my parents, who live only a few miles away. This would just save us having to do so every time, which is a bind when we could get by with a little heat - I'd rather do it this way than with a Calor gas heater.

Fridge etc. always seem fine after these cuts, and we don't keep a lot in the freezer. Essentially, this is just like running a caravan generator - I just wonder how much capacity I really need?

850kW may be excessive, as pointed out!

 

[Wooshzz99]

15KVA would be fine mine is hard wired mains fail auto start.

 

[Corgigrouch]

Well, if you are going to run a little genny for 48 hours at a time, then I would consider the quality of the engine and generator rather than how small (And cheap) it should be... You may well find yourself refuelling it a little too frequently for your liking too. Add to that the fact that has already been raised about voltage regulation and I would be inclined to have a look at something a little better built and robust.

I have and have had for some years, a 5 kW Generac, It is a good little generator, well regulated with a twentyfive litre (Or thereabout) fuel tank. Granted it is bigger than you need, but it is small enough to be portable and robust enough to last and yeaa it does cope with the start up load of small compressor motors and kettles..

 

[efiste2]

private generation is becoming a big problem for DNO's especially the less than proffesional installation. eg the metre long flex with a 13A plug top on each end, and plugged straight into any socket in the house....

 

[plugwash]

Personally what I'd do for a small generator is fit a second CU next to the first and move lights and other critical stuff on to it (may involve some new circuits). Then have a transfer switch to switch that second CU between mains and generator feeds. Switching everything onto a small generator is a bad idea because it increases the risk of overloading the generator and also means you need a much larger transfer swtich.

Earthing is something that needs to be considered, you must maintain the equipotential zone of the house under all circumstances. Best bet is probablly just to connect the mains and generator earths together (still have a rod for the generator though so you aren't reliant on the mains earth while running on generator). Switching earths opens up a huge can of worms particulally if you aren't switching the whole install.

 

[ban-all-sheds]

 

[cg360]

private generation is becoming a big problem for DNO's especially the less than proffesional installation. eg the metre long flex with a 13A plug top on each end, and plugged straight into any socket in the house....

If you read my post, I didn't suggest this. I'm well aware of the issues surrounding cowboy installs, which is why I'm not undertaking something which I can't afford to do properly in a cavalier and unsafe manner. My solution is akin to running a generator for power to a caravan - no inrtegration with mains at all.

I just want to run my central heating (which is powered via a 13A plug) for about an hour at a time, and lights for a little while at night. I'm not looking for a nuclear bunker installation - as I've already said, if we really need to ship out, we can go to my parents.

All I'm looking to do is put off the upheaval of doing that for a couple of nights, which means a bit of heat to keep the kids warm and a bit of light. No kettles (gas hob), no TVs, no tumble dryer.

The gen won't be running for 48 hours non-stop, just an hour or two at a time, but I take the point about longevity etc. I was just looking for a rough output so I could go shopping.

Thanks for the install advice regardless, it will be handy if I ever have a generator wired in properly.

 

[ban-all-sheds]

Whether you use it continuously, or only for an hour ot two at a time, or for 1 minute every Feb 29th, it still needs to be just as safe.

Got an Aldi near you?

 

[plugwash]

Personally I'd much rather see the changeover switch fed from an appropriate breaker in the main CU than from a feed that is only protected by the service fuse.

 

[ban-all-sheds]

Yup, if you don't use an appropriately rated C/O switch.