I have a single 16a circuit in my main fuse box that controls the boiler and heating pump. I also have a suitably large generator.
Is there a switch I could install to isolate the fuse box and then allow the generator to supply just this one circuit when there is a power cut? Obviously it needs to be installed such that it is impossible for the generator to be connected to a live feed - is there a suitable 16A switch?
Secondly if the above were possible then I should install a proper earth on the generator (located in an outhouse)?
On 30 May 2006 14:59:02 -0700 someone who may be snipped-for-privacy@gmail.com wrote this:-
There are many.
You cannot rely on the external earthing (assuming there is any) when there is a power cut. The "electricity board" may have chopped out a section of the cable to repair it.
What you need is a suitably qualified electrical engineer to work out what to do. This will probably involve changing from one earthing system to another on changeover. There are a number of possibilities.
It may well be a 16 amp radial circuit but you don't need anything like this for the average central heating system. I have a home made UPS doing this function which will run the system for many hours using a car sized battery. The UPS peak output is only 300 watts - and the CH never reaches this even when switching, etc.
FWIW, the little Screwfix/Wolf 2-stroke gene will run a domestic-sized oil fired combi.
The blower and pump motors don't sound as comfortable as they do with real sine waves from the power station, but the whole thing works for long enough to heat up the rads and the internal hot water tank. Likewise it will run the small fridge OR the small freezer for long enough to keep them going.
Since this is only for emergencies, and the gene won't run more than one thing at a time, all the "switching" can be done by swapping around the
13A plugs. When the tuit arrives, I'll put a large waterproof box on the outside wall to hold a couple of metres of cable and 13A plug to connect the gene, and tuck the incoming extension lead away under the kitchen units.
As a higher priority, I'll convert the plain 13A socket on the gene to a more waterproof type that can stand being rained or snowed on.
Obviously this isn't as good as a fully engineered solution, but last winter made us very glad to have it.
FWIW, continued: the same gene will power a 2kg SDS drill or a 4.5in angle grinder. Performance may be a bit down compared with mains, but it's really quite hard to notice. Certainly it's perfectly functional for intermittent use - 18mm hole in solid rock, nae bother (given the pilot hole that you'd drill anyway).
That is a large can of worms and really dependant on what type your existing power supply is. Though most of it revolves around connecting the supply earth with your local earth and various fault conditions. When the mains power goes you can't rely on the mains earth also being present and you don't want a fault at your premises making the mains earth live from your genny.
Having said that the genny should have it's own good local earth bonded to it's frame and one phase of the generator(*). It would also be prudent to put the generators ouput through and RCD at the generator.
Take a google over that last couple of year in here for various other threads on the subject.
(*) These small generators "single phase" generators are really two phase balance jobbies but with the phases 180 degrees apart. In some circumstances having two floating phases instead of a "normal" live and neutral supply can be safer but when connecting to equipment that expects L&N two floating phases can produce highly dangerous conditions that can remain hidden until someone comes into contact with something that shouldn't be live but is... That something can be exposed and "earthed" metalwork or kit "switched off" but only by a single pole switch.
Thanks everyone for the sensible advice. I have read up on this further and agree with the general consensus that to do this properly will require a professional and lots of money :-) It will also be too much for what I need.
I think I will investigate simply swapping a couple of 13-amp plugs over and doing it that way on the rare occassion I need the heating running. Next on the list is to sort out thermostats etc to see what needs power!
The complete CH system should be fed from a single mains supply, probably switched and fuse connection unit somewhere. Easy enough to fit a 13A plug and socket downstream of that. Fridges and freezers can simply be unplugged from the mains and plugged into the genny.
I'd still have a good local earth at the generator bonded to it's chassis and one of it's phases to simulate the normal, unbalanced, mains. Particulary if more than one appliance is connected to the genny at any one time. I'd also have an RCD at the generator.
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