Wondering if anyone has had any experience with this...
As per normal, I have my grid power entering my house, this then goes
through a 80A fuse that belongs to the electricity board, it then continues
to my electricity meter, and then onto my consumer unit...
The thing is, I want to disconnect the tails that come from my meter, and
connect them to a generator transfer switch - this then connects back to my
consumer unit, and also to a generator.
The options I have are..
Do it live - not a clever idea, especially as my consumer unit has a metal
Pull the electricity boards fuse out, move it, and replace the fuse (minus
the metal tag/seal)
Call the electricity board, and see what extortionate rate they will charge
I have however read about someone calling the electricity board up, and them
saying, "just pull the fuse, ring us when you are done, and we will send
someone out to check the installation, and replace the fuse and seal it up
Any advise would be greatly appreciated!!
I go with pulling the fuse and then having it sealed again. Job's done.
The thing that's getting me though, is the fact that your tapping in to the
mains tails. Why ? Can't you take the bridge from the BUS bar side of the
mains switch in the CU ? Doing it this way gives you at least some sort of
isolation if you have to carry out any maintenance on the new system.
So do you think I just do it, and plead ignorance if the missing/broken seal
or do I call the electricity company and ask them (slightly harder to
subsequently plead ignorance after that!)
Another thing, is we had the meter changed about a year ago, so all the
seals are new :-/
In my CU, the meter tails go directly into the main breaker, (there is no
simple switch) and then two wire connect from this same point to the other
On the other side of both breakers, there is a copper bar that feeds all the
mcb's for both circuits - this way, if the main power breaker trips, we are
not left in the dark
Probably standard practice, but as I have never looked inside another split
load box before, I can't comment!
I want my generator connected before both of these breakers, and to both
circuits (so we can use the lights, and the sockets!)
I was actually going to purchase a 100A isolator, and connect the meter
tails to this, then on to the transfer switch, for the reason you suggest
...and possible upgrade to an automatic system later.
Apparently some people have an electricity board provided isolator between
their meter, and their CU - I am not that lucky :-s
Woa up there horsey !!! A generator doesn't have neutral potential on it.
Both connections become live feeds and if it is to take over supplying the
house in the event of a power cut, then you'll need to upgrade the earthing
and take only a single phase from the genny, to feed the house.
It works by making the grounding spike in to your neutral potential. Very
dangerous if not done properly. Not to mention the fact that, if the mains
supply then comes back on while the genny is running, then it could blow
every fuse you have in the house and may even trip out at the local sub
station if it is a large capacity generator.
I originally thought that you had automatic change over, to bring the genny
online when the mains failed. But you say "possible upgrade to an automatic
system later". That's a big NO NO !!!!!
FYI A proper automatic transfer switch makes it impossible for both grid and
generator feed to get connected together!
Generally speaking, with a non synchronised genset, the grid fails, so the
ATS disconnects all power to the house, starts the generator, waits for the
generator to stabilise, then switched the house from nothing, to generator
If the grid is then restored, it will wait a bit, to make sure the grid is
staying on, then it disconnects the house, waits a bit, then switches over
to the grid (If the grid and genset are not synced then switching directly
would be messy!)
It then keeps the generator running for a bit, then finally shuts it off
I understand where you are coming from, as I wouldn't want to try to supply
power to my whole road! or kill someone working on the street wiring by back
feeding (I presume a step-down transformer would work in reverse, ramping my
230v up to 1000's!)
You could use a step down tranni' as a supressed earth to give a decent
neutral potential to supply the house circuits, and reduce the fuel
consumption of the generator into the bargain, using the transformer looped
from phase to primary winding, then on to the secondary winding and out to
earth. But as I say, both connections on an AC genny are phase, so it
literally doesn't have a neutral and is dangerous if used with capacitative
You could ruin your tele' or damage any IF filters in other appliances if
they rely on a phase to neutral supply, so it then becomes a very expensive
installation if you have replace everything. The grid itself is literally
phase and earth connections, but an AC generator is alternating phase /
I have a "power conditioner" rated at 40A - this contains a bloody great
(it must weigh about 50KG!)
It is not a step-down transformer, as the generator's output is the voltage
Excuse my ignorance, but how is a petrol generator different to the output
of the grid?
I was under the impression the grid's Neutral was connected to earth, so
they only need to run live cables - this being the reason people got
electrocuted - they touch the live, and this shorts to earth, or neutral!
We install isolation transformers in bathrooms, and on building sites, so
the neutral is no longer connected to earth, making electrocution impossible
unless you touch both live and neutral together - surely a generator is
safer then the grid, due to the neutral/earth isolation?
Please correct me if I am wrong, it is just how it seems to work from my
point of view!
You're right about the grid supply being phase and neutral, but a generator
supply is phase / phase with no earth / neutral potential. This means that
any appliances you have in the house may not be switched off when you think
they are and may actually continue to heat even if you think they are
Do this simple test with a meter.
Set your meter to the appropriate setting to take the AC Voltage of your
Place one test probe on the earth connection of your mains supply and the
other probe on the neutral connection. You should see that the test meter
doesn't show any or shows very, very little voltage flow. If anything does
show, then it more than likely it has no current large enough to run
anything other than a small torch bulb and would dissappear if any large
load were connected across them.
Now, keeping one probe on the earth terminal, place the other probe on the
live connection. Your meter should now be showing the full supply voltage
of your system and it will carry a very large current potential. This
allows you to run all your appliances.
Next, go and start up your generator and carry out the same tests as above.
You should see that both, what are known as live and neutral, are showing
half of the rated voltage to earth, that it is said to supply. This is
because an AC generator works on the principle of each phase being 180
degrees out of phase with the other, therefore, it supplies + phase on one
side and - phase on the other, and the phases alternate between supplying +
and - of the supply at the rated hertz frequency of the generator.
There is no neutral / earth potential from a generator and it must be
properly connected to the AC supply system, when and if the load has any
capacitative loads, i.e. televisions, IF filters in appliances, etc. etc.
Please be careful if you intend to use a generator as a backup supply for
your domestic system.
An isolation transfomer only works by bringing in different tapps on a
transfomer to supply an increasing current load. It is nothing fancy and
sure won't help in the situation of supplying a domestic AC electrical
Ok, did the tests, and as I expected, you were right!
The next question, what can I do about this? - My generator seems to satisfy
all four of my UPS'
A small standby
a larger Line interactive
and two online large units (35KG jobbies!)
How would I run things like TV's etc. from the generator without risking
causing them damage?
I watched the man change my electricity meter. When he took the fuse
out he put a plastic blanking plug in the live end of the fuse
receptacle. I'd have given a leg to have had one of those when I last
had my fuse out. There's something about a little shiny piece of metal
that can fry you in a heartbeat. anyway, he also took out the neutral
as well, if that's worthwhile knowing.
On the question of generators being used when mains failures occur,
these obviously aren't used indoors. No problem in a rural area, but
isn't noise a possible problem in built-up areas?
I'm assuming the genny would be running during evening/night time
I have put my generator in a box, with air forced through the box for
cooling (Large fan unit mounted on the side of the box) - This has reduced
the noise considerably.
Also, where I have located the generator, it is shielded from almost all
sides, so the noise mainly goes upwards
If I run the generator at night, then walk across the road to my neighbours
house, you can only just hear it running.
If I go next door, then you cant hear it at all.
So it doesn't piss the neighbours off!
(Plus, if there is a power cut, they know they can watch TV at my house!)
I had no seal on my fuse for years and no meter reader ever noticed or
bothered to comment on it. A month ago I had my meter replaced, and to
save any questions I made up my own seal - stripped the plastic off a
thin piece of multi-strand elec wire and attached it with a piece cut
off an crimp. It looked reasonable enough, but even if it didn't and
anybody had said anything I wouldn't have cared too much. After all,
what are they likely to do? Take you to court for cutting off a
When I moved in to my current house, there wasn't a seal on the main fuse
either; I asked the lecky company to check it over just in case the previous
owners had been fiddling the meter. They (eventually) sent someone round,
and just fitted a new seal, they didn't give a ... about checking the meter.
If you search for previous threads on this topic you'll find plenty of
people here who have pulled the fuse to work on the electrics.
Some have informed the Elec. Co. before hand, some after and some
haven't, either way the co. 's don't seemed bothered about it.
Fit a dp isolator with an insulated case! I would advise takeing a look at
the 16th Ed of the wireing regs, there is a whole chapter about private
generation. You may also want to advise the supply company so they are
Contact your local electricity company and ask them to fit an isolator -
I say local electricity company, but depending on how anal they want to
get, the request *may* need to come from your supplier (the ones you pay
your bill to) which may be a different company.
If you need to go via your supplier, the request will be sent via a back-
end computer system called the Data Transfer Network (DTN), will be known
as a "flow", and will probably end up with their metering department -
it`s a simple job, usually free of charge.
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