What can I use to switch from mains to generator ?

bloodnok

Thanks for all your replies, they've been very helpful.
It will give him plenty to think about !
:T :beer: :T

spud17

I agree with all of the above advice.

Most of my working life has been spent on large farms complete with grading lines and grain stores.

Where a generator was installed it always had a manual changeover switch rated at something like 125amps.

In one instance the capacity of the grain handling setup was doubled, this meant the local supply was nowhere near adequate. An upgraded supply would have cost £0000's so a 3 phase generator was installed, this turned out to be incredibly cheap to run (don't know now, 8years on).

Sorry, my point is it could be cheaper to do away with mains completely if it is that unreliable.

Firing up the generator can be set up so that literally flipping on a light switch will do it.

I used to use an isolated weighbridge, where the generator would fire up when you put on the light in the little office, this would then activate all the electronics for the weigh system.

Sorry to rabbit on. R

vikanuf

bloodnok wrote: »

Not sure if I'm on the right board but an uncle of mine has a workshop with a couple of lathes, heater, and other woodworking equipment ( All 240v single phase ) all working off mains electricity, but where he is in Mid Wales his electricity supply is quite often interupted, usually in the middle of something he's making.
He's now bought a diesel generator and asked me if there was a simple switch that could be fitted so that if his electricity failed, he could just press a button or throw a switch to instantly disconnect the mains and connect the generator.
Hope I've explained what's required............One switch with a mains and generator feed and one outlet to his equipement..... switchable.
You were the only brainboxes I could think of asking !
Thanks

Hi, I found a controller few weeks ago on http://www.gencontrol.co.uk and it works just great! When my mains goes off, it disconnects my house from the mains, then starts my generator and waits 20 sec if mains comes back on, if not, it will connect my house to the running genny! All done automatically!
Cheers!

owenewo

Hi, i'm an electrician and came accross your post. The cheapest way of connecting the generator to supply your workshop is with a manual double pole (DP) changeover switch. Basical a rotery switch that has three positions selcting the supply. The first position being the mains, second being completely disconnected, and the third being the genny. These are also called break-before-make switches. Its a requirement of the iie regs (part 552-01 i think off the top my head) to isolate the suppliers connection before its possible for the generator to connect (protect from backfeeding supply, electrocuting workmen repairing line etc - also protects your genny/equipment.) There are plenty of other posts here explaing all that, dont bother looking for one online, your local electrcal wholesaler is the best bet (CEF/LINKS/EDMUNDSONS etc)

Other points that you HAVE to do which no-one else has mentioned is about earthing and RCD's. When you use the generator as your supply you have to treat the installation as a TT system, you cannot rely on the suppliers earth. This means that an earth electrode (rod driven into ground) has to be installed and connected to the installation and the metalwork of the generator frame.

All circuits have to be RCD protected to 100mA and socket outlets that may be reasonably expected to power handheld equipment outdoors must be protected by a 30mA RCD. (Unless your workshop is a few storeys up, it would be hard to argue your socket outlets couldnt reasonbly be used to power stuff outside like a lawnmower on an extension lead etc).

The earth from your main supplyer is a fixed point (ground) and in most cases pme (linked to the neutral terminal in your service cut-out). Generators have a "floating" earth and this may prevent your RCD's from operating correctly, so you should also install a neutral-earth link to the generator hook-up lead. A warning label will also need to be installed preventing the lead from being plugged into the mains.

The work done to your installation would also need to be certified, and although you could argue that a "new circuit" hasnt been installed it is more than minor works and in my opinion need to be submitted under part-p. Even if classified as minor works electrical testing is imperitive to ensure accpetable earth loop and rcd times etc and a qualified electrician would be required.

I'm sure you dont want the expense of an electrician but to do the job right and have all the neccesary paperwork (hefty fines if you dont and invalidates your home insurance.) theres no getting around it. If you have an electrical fire as a result of the work and you dont have the paperwork to show it complied and test certificate completed, insurance company wont pay-out. If you already have RCD's installed and everything is accessible, it is only a few hours work for a good sparkie. He should be able to supply the change-over switch, earth rod and cable etc cheaper than you can get it yourself so the extra cost of him doing the work shouldn't be too great.

Hope this helps, oh yeah and dont forget that the change-over switch has to be rated to at least the same current as the fuse or circuit breaker protecting it. If the workshop is not fed from a fuseboard or fused isolator, it will most likely be your service cut-out. (Big black fuse next to your meter. Typicaly 60, 80 or 100A, printed on side so check)

Good luck.