Genny for house

[outinthestix]

Hi all, i am thinking of purchasing one of the portable generators which can also be run as a 200 amp welder. The models i have seen develop from 5 up to 7.5 kva. Would one of these be suitable for powering our house during occaisional power cuts ? The last one we had last winter went on for 4 days and the fridge and freezer food was ruined.
Of course i will get in a pro to fit the change over switch but just wondered if you guys could give me some idea if it's plausible first. Our house is 3 bedroom size and load would consist of fridge, freezer, lights, heating. Our cooker is not electric and we could get by on heating from a small wood burner but our hot water comes from an oil boiler so would need to run that. the welder facility will be usefull at other times of year. Thanks in advance, Stix.

 

[mfarrow]

It's certainly plausible. Just remember to do as you suggest and get the changeover switch done professionally, as you'll need to ensure that your supply is completely separate from a DNO's, which means a 3-pole switch if you're anything but TT.

 

[Adam_151]

which means a 3-pole switch if you're anything but TT.

I hope you are not suggesting that the earth be switched

 

[plugwash]

IIRC you don't normally have to switch the earth for a generator install but you do have to have an earth rod to ensure that there still is an earth when running on generator.

 

[outinthestix]

Thanks for that guys. What kva would you advise as being the minimum for this type of job or do you go on a different criterion. Stix.

 

[electronicsuk]

There's no set minimum as it depends on the load, but to be sensible, I'd say 3kVA or more. That will allow you to run the fridge, a few lights, and the TV/radio. You can turn off any circuits that aren't necessary or draw too much power when running on the genny, or you can install a second consumer unit and split the circuits so that one board is fed by the generator/mains via the changeover, and the other board is permanently fed via the grid.

 

[outinthestix]

Many thanks for the info. I'll get the local sparky to sort it now that i know it's all possible. Stix.

 

[plugwash]

Thanks for that guys. What kva would you advise as being the minimum for this type of job or do you go on a different criterion. Stix.

Ultimately you have to decide what you want to be able to run while on generator. You can then decide how big a generator you want and how you are going to wire it in.

Unless it's a huge generator (say over 7KW) I would reccomend having two consumer units. The first one with big high load stuff that you don't want to use on generator. A 32A MCB in the first CU would then feed to one side of a changeover switch with the generator feeding the other side. The output of the changeover switch would then feed the second CU which would feed the stuff you do want to run on the generator.

The advantages of doing it this way are that you can use a cheaper 32A changeover switch and there is less risk of accidently overloading the generator by leaving a big appliance on. The downside is that the stuff on the second CU is limited to 32A total even when on grid power.