Greetings one and all.
I am an occasional lurker and thought it might be good to get
As I was adjusting my foil hat t'other day I had a whatif moment. You
know the sort of thing, Zombie Apocalypse/WW3/Freak Weather/terrorist
strike on the national grid etc
This was caused by someone in another place highlighting some cheap
I realised at once that 1100 is, effectively no real use to man nor
beast and if I were to invest my hard earned in something bigger then
an ad hoc approach may well not be the way forward.
I took advice from a denizen of t'internet who suggested that a
posting here might help firm up ideas which are, as I write, somewhat
diaphanous in nature.
My, based on nothing much, wish list;
Generator ca 5500 elect start.
Ability to run generator from time to time to change fuel/ check
Quite happy to run cable from Gen to input point as required rather
than perm/semi-perm cable into house.
Don't require auto start or anything posh.
I understand that it needs a changeover switch., but what else?
Note. I will not be doing this myself I have a trained person
This is a photo of the fitting space available (ca 30cm x 30cm) and
layout of the consumer unit/meter area.
Your comments/observations would be welcome.
I don't care to belong to a club that accepts people like me as
members. Groucho Marx
You MUST have a changeover switch that is inline from the generator and
the mains supply incomer so that when you are on mains no connection is
possible to the generator i.e. you do not want mains going to the
And VERY important when the mains power is off-line you MUST NOT let
your generator power go down the mains incomer in case it electrocutes
anyone working on the mains power lines.
A changeover switch of the right type is required like these here.
Automatic ones exist that can sense the mains going off and start the
gennie switchover to the mains then re-connect the mains when that comes
back online and then will turn the gennie off..
This company makes a range of modules that do just that.
I would hope that anyone doing this work for you would know all that
On Thu, 25 Sep 2014 13:59:14 +0100, tony sayer wrote:
This also includes any earth supplied by the DNO. When there is a
supply fault you cannot rely on the state of the supply earth.
So if you are connecting into the house wiring you *have* to supply
your own earth for the house wiring and an earth for one phase of the
gensets alternator(*) that is also bonded to the chassis of the
genset. As getting low enough earth loop impedances can be tricky and
making sure they remain low, I'm pretty sure that the regs will
mandate an RCD at the generators output. Possibly 100 mA time delayed
*if* there is other shock protection down stream. If not it will have
to be a 30 mA normal RCD to provide shock protection.
Trying to use the house wiring opens up a very large can of worms.
TBH it's easier to have the genset phases floating wrt to earth, run
extension cables to the bits of kit that need maintaining
(fridges/freezers/heating system/fish tank) and (optionally but
useful) have an RCD at the generator, so if there is an imbalance on
the phases the power is cut.
No need to install/maintain local earth connections etc.
(*) The alternators produce two balanced phases 180 degrees apart
isolated from the gensets chassis and earth. There is a nominal 240 V
between them. If either phase happens to contact earth due to a fault
or person touching it that phase is pulled down close to that earth
potential and thus presents a much reduced shock hazard. Just like
the 110 V balanced supply as used on building sites. Of course the
other phase has now risen to 240 V above the earth and if you come
into contact with that (second fault) ... OUCH!
1 In the event of supply failure (TN-C-S or TN-S) you cannot rely on the
2 You must not have any form pf switching in the earth conductors or CPCs
That would leave the only options I can see for a fixed genset
a) TT the whole premises
b) Provide a local earth rod or rods bonded to the main earth of the
premises and have suitable RCD protection when supplied by the generator.
Is (b) permissable?
I've often wondered what powers the changeover switches on the auto ones as
during operation, presumably, there is no power from anywhere, batteries?
Also, I'd not want to have a substantial generator inside the house or even
too close due to the annoying noise.
From the Sofa of Brian Gaff Reply address is active
"tony sayer" < firstname.lastname@example.org> wrote in message
On Thu, 25 Sep 2014 16:50:16 +0100, Brian Gaff wrote:
One easy idea. When moving switch to mains mode tension a spring and
set a latch that is held by a solenoid. Lose power, latch releases,
spring operates switch.
But auto switch over to do well and without risking connected
equipment is much more complicated than throwing a switch and
starting a genset. There really needs to be a UPS to maintain the
connected quipment whilst the generator starts and runs up to speed
before being connected to the mains in of the UPS. It may or may not
need to sync with the UPS output depending on the type of UPS, online
There are generators and generators.
FO noisey ones like my 2 kVA single cylinder diesel open frame
jobbie, it's almost impossible to hold a conversation next to it. To
mobile 160 kVA twinsets that just quietly hum to themselves even at
full chat on both sets. Not that you'd run both sets at full chat at
the same time. The idea is that they synchronously load share most of
the time but if one dies the other seamlessly takes over. I'd like to
see what happens when you suddenly drop 80 kVA onto a set...
The twinsets, as far as Film/TV generators are concerned, are quite
noisey, some you can't tell if they are running without touching them
to feel for vibration.
First thing I can tell you is this:
The use of small emergency/leisure ICE powered generators for
anything more demanding than powering a few lightbulbs, a small fridge
and a portable telly or two with satellite RX box at a remote off grid
location can result in some surprising problems over and above the
(aught to damn well be bleedin' obvious) issues of safety regarding
connecting into a house supply, 'earthing' and preventing backpowering
your local grid connection that has suffered an outage due to a local
fault your side of the substation (a wider area outage on the network
side of the substation will cause an overload on your poxy generator
which will trip the circuit breaker - if it doesn't trip, then the
engine will stall and if it doesn't stall, the generator will simply
burn out in a matter of minutes if not seconds.
Assuming you make all the correct connection arrangements and follow
the rules regarding safe practice, you can then start to deal with the
all the other various operational problems that can arise.
Rather than try and re-iterate them here, I offer this link to a
posting I made in uk.tech.digital-tv just over ten months ago (post
I think I managed to cover pretty well _everything_ you'd need to be
aware of when choosing a genset.
HTH & HAND
I use one of these
3kW - can power a kettle
inverter - can power computers
electric start (wife/parents-in-law can start it)
and tlc changeover switch
On Thu, 25 Sep 2014 16:50:16 +0100, Brian Gaff wrote:
There are several ways. The most common is to let the mains supply hold
the mains switch in then use the generator supply to close the generator
switch. For supplies up to 100A or so it's quite common to use
mechanically interlocked contactors for the switches. They are relatively
cheap and cheerful. If the generator is given the signal to start on
mains failure that gives a nice delay between the mains going off and the
generator coming on line. Going the other way it's usual to run a timer
from the mains supply - in case it's just blipped on. The timer would
open the generator switch then close the mains switch.
Not allowed - it would be unsafe - unless just feeding some appliances with
extension leads from the genny.
So a 5.5kW genny will give you about 23A max to play with. That should be
enough to keep you going for a while and allow you to boil a kettle and
leave the lights, central heating and the TV on and still keep fridge going
for cold beers. What more could you want?
You will need a hard wired set up with an earth rod or two. That's a piece
of piss - it's called hammering an earth rod into the ground and is very
similar to hammering a nail into a piece of wood. Best done on a lawn etc
and not a concrete driveway. Probably a 30mA RCD mains unit for the genny
and a 100A changeover switch
Where do you plan to run the genny? It will need to be waterproof or
undercover and as far away as possible from the bedroom window if you want
to sleep at night with the CH on.
That's about a thousand quid dearer than the cheapest 3KW inverter
genset I saw when I was researching the pricing nearly a year back. It
didn't have electric start or a changeover switch but at a thousand
quid price premium for the luxury of electric start, that's one luxury
I'm happy enough to forgo.
Even so, 800 odd quid for even a cheap inverter unit is a
considerable investment against a prolonged outage that so far has
failed to materialise over the past 30 odd years (although we did
suffer a 3 or 4 hour outage over 25 years ago due to a faulty
underground cable joint).
Another round of searching produced this result:
There are a couple of 3.5KW peak/3KW max continuous inverter suitcase
gensets. The 750 quid (+VAT?) offers remote start (electric start one
might reasonably assume) and has display for run hours and
voltage/current/KW. The 550 quid unit appears to forego the luxury of
remote start and a run hours display panel.
This seems to be about as cheap as it gets for new unused inverter
gensets. I'd be only too happy to be proved wrong in this regard. :-)
I can't speak for the reputation of this company, CPS, which appears
to be based somewhere in the UK. As with any traders on E-bay, you
need to dig a little deeper than just simply relying upon 100%
positive feedback ratings.
It's just a little disconcerting to see that a lot, if not most, have
a "or best offer" auction price option. The 750 quid unit, btw, has 25
days and 17 hours left to go.
Why would a manufacturer even consider selling below their normal
retail price? If the bidders are canny enough to wait until the last
second to put in a single winning bid, they could find themselves
honour bound to sell it for less than half price. If their product is
any good, they're way cheaper than the competition afaict.
Oh, btw, what is a " tlc changeover switch"?
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