Emergency Generator ponderings

[The Other Mike]

Was this by chance somewhere that has a close association with the transmission/ distribution of electricity?

[Fred]

Would something like this be sufficient:

44gbp exc vat and delivery, the price sounds too good to be true.

I'm not sure I could ever see me going down this route because the idea of joining the generator's neutral and earth would frighten me too much. I 'd be afraid of touching the generator and getting a shock! Presumably you must only connect the N and E together if also connected to an earth rod.

I would also be nervous about fitting a switch in the house's earth to switch between grid earth and generator earth. I would be afraid of the switch failing leaving me without an earth and all metal objects going live. I seem to have a phobia about live cases don't I!

This is something beyond my comfort zone, so I will stick to using torches in power cuts. Wouldn't gas lamps set off the (battery backed-up) smoke alarms?

[John Williamson]

For a full house supply, it is. It's only capable of carrying a fraction of the normal domestic supply. It'd be okay for a single ring main, and maybe a couple of lights.

For an extra couple of quid:-

four times the current and is designed for the job.

NOt really a problem if you get a qualified electrician to do it.

No more than a gas cooker will, I'd have thought.

[Dave Liquorice]

Why should they? All they produce is CO2 and H2O no smoke unless very badly out of kilter. The do get HOT so things near by/above might start to smoke...

Gas lights are by far the best source of emergency light IMHO, more light than a 60W light bulb with ease and in all directions.

Torches produce beams and eat batteries when used continusly. Small battery lanterns tend not to have long run times and produce little light. I do have a twin tube flourescent jobbie that lasts a good

8hrs in single tube mode with a fully charged 6v SLA battery. Also produces a decent amount of light over a good area and will auto switch on when connected to the mains when that fails. Handy to have setup when the weathers a bit bad and the lights are flickering... Uniross DL828 but it appears to be discontinued now.

[John Rumm]

Just how much current do you expect to get out of a domestic genset?

[John Rumm]

If you house has TN-C-S (PME) earthing, then you would not switch it as such, just add your own earth rod to it - and that could be left connected all the time even when on mains.

Make sure you have supplementary equipotential bonding in high risk locations, and you mitigate that...

[Frank Erskine]

But it still has to be capable of carrying the "normal" house current. :-)

[Dave Liquorice]

Not sure that is a good idea. Under no supply conditions you can't rely on the supply wires still doing what they are supposed to do. If the upstream N-E bond broke the N would then be a floating phase, in theory your earth rod should pull that back down but you do have to make sure that your earth rod is fully up to spec regarding impedance etc otherwise you'll have to treat the installation as TT.

Aye, it's voltage differences that are the problem. Tie everything together and things become safer. But note that should the supply N-E bonding fail things can start to get "interesting" again.

[Dave Liquorice]

I was wondering what he has that fully loads a domestic ring and must be powered... Base load of an occupied house is about 1kW, call it

2kW a nominal 8A.

But of course this is in circuit all the time so has to be able to handle the *full* load (say 20kW, 80A) when on mains...

[Tim Watts]

Unless the house was next to the substation and/or the rod set in Marconite deep in wet ground, I doubt you could ever hope to get down to 0.8 Ohm L-E loop impedance. So generally if a rod is involved, best to assume TT by default.