Garage electrical supply: advice welcomed
Bert Coules
cable (2.5mm twin-and-earth) from the house consumer unit: the relevant
module is labeled "B32 - NSB32".
Inside the garage this cable feeds a small consumer unit which has a 30mA
RCD and two modules: a B-6 and a B-16. The 6A circuit feeds two fluorescent
lights, the 16A a single double-socket.
I'd like to add a few more sockets (or have them added by a professional, if
necessary) but I wonder if it's also possible to increase the rating of that
circuit: at present my chop saw draws too much current and trips it.
I haven't looked closely at the garage unit as yet, but I'm hoping that the
modules are removable. Can the B-16 one simply be replaced by one of a
higher value?
Many thanks.
dennis@home
"Bert Coules" <ma...@bertcoules.co.uk> wrote in message
news:WL-dnQki_6kcY6_T...@brightview.co.uk...
I would wonder why a chop saw trips a 16A breaker.
It may just be too quick and trip with the starting current.
I don't recall what type of 16A breaker I have on my outside circuit but my
chop saw doesn't trip it even when the extractor vac is running.
Bert Coules
> I would wonder why a chop saw trips a 16A breaker.
> It may just be too quick and trip with the starting current.
> I don't recall what type of 16A breaker I have on my outside circuit but
> my chop saw doesn't trip it even when the extractor vac is running.
Thanks for that: interesting. I can run the chop saw on an extension lead
plugged into a domestic socket inside the house with no problems at all.
Obviously I don't want to increase the rating of the circuit if it isn't
necessary, but on the other hand I do want to be able to use my saw in the
garage.
I'll also be using a medium-size metal-turning lathe (currently in storage,
so I can't try it) on the same circuit though not, of course, at the same
time as the chop saw or anything else. I don't want to run into the same
problem with that.
Bert
mick
A type B mcb isn't usually much good for motors. Change it for a C16 and
you should be ok. The difference is in the tripping curves, the type B
trips much faster for the same current. I'd be tempted to change the
house end for a C20 too. A 32A mcb is too big to protect a 2.5mm t&e
spur. The C16 at the garage end will still trip first and your cable will
have better protection. Under ideal conditions a 2.5 cable will carry 27A.
--
Mick (Working in a M$-free zone!)
Web: http://www.nascom.info
Filtering everything posted from googlegroups to kill spam.
A.Lee
> My garage has an existing electrical supply via an overhead-slung single
> cable (2.5mm twin-and-earth) from the house consumer unit: the relevant
> module is labeled "B32 - NSB32".
That MCB is too big for that cable. You should have a 20A maximum.
> Inside the garage this cable feeds a small consumer unit which has a 30mA
> RCD and two modules: a B-6 and a B-16. The 6A circuit feeds two fluorescent
> lights, the 16A a single double-socket.
That sounds alright, as diversity means you wont be drawing more than
the 20A that the circuit should be protected by.
> I'd like to add a few more sockets (or have them added by a professional, if
> necessary) but I wonder if it's also possible to increase the rating of that
> circuit: at present my chop saw draws too much current and trips it.
Trips what? The MCB or the RCD?
Inside the house CU or garage CU?
Have you got an RCD in the house CU?
> I haven't looked closely at the garage unit as yet, but I'm hoping that the
> modules are removable. Can the B-16 one simply be replaced by one of a
> higher value?
Not really. 20A is possible with no other circuits, though I wouldnt
advise it. If one item is causing a 16A MCB to trip, then there is
either a fault with the MCB, or the item being used.
What is the Wattage rating of the saw?
Alan.
--
To reply by e-mail, change the ' + ' to 'plus'.
John Rumm
> On Fri, 29 Jul 2011 19:40:01 +0100, Bert Coules wrote:
>
>> My garage has an existing electrical supply via an overhead-slung single
>> cable (2.5mm twin-and-earth) from the house consumer unit: the relevant
>> module is labeled "B32 - NSB32".
>>
>> Inside the garage this cable feeds a small consumer unit which has a
>> 30mA RCD and two modules: a B-6 and a B-16. The 6A circuit feeds two
>> fluorescent lights, the 16A a single double-socket.
>>
>> I'd like to add a few more sockets (or have them added by a
>> professional, if necessary) but I wonder if it's also possible to
>> increase the rating of that circuit: at present my chop saw draws too
>> much current and trips it.
>>
>> I haven't looked closely at the garage unit as yet, but I'm hoping that
>> the modules are removable. Can the B-16 one simply be replaced by one
>> of a higher value?
>>
>> Many thanks.
>
>
> A type B mcb isn't usually much good for motors. Change it for a C16 and
> you should be ok. The difference is in the tripping curves, the type B
This is generally true - although normally applies more when using
induction motors with high inrush currents.
> trips much faster for the same current. I'd be tempted to change the
Actually the "curves" for a B and C type breaker are identical. Its the
non curved bit of the response (i.e. the magnetic action responsible for
handing the much larger fault currents) that differs.
Compare:
http://wiki.diyfaq.org.uk/images/d/d4/Curve-MCBTypeB.png
with
http://wiki.diyfaq.org.uk/images/d/d6/Curve-MCBTypeC.png
The speed of response of both is the same for any most overload
scenarios. However the rapid 0.1 to 5 sec response for the C type will
tolerate 160A of inrush before tripping compared to the 80A for a B type.
> house end for a C20 too. A 32A mcb is too big to protect a 2.5mm t&e
> spur. The C16 at the garage end will still trip first and your cable will
> have better protection. Under ideal conditions a 2.5 cable will carry 27A.
Yes good point - I was not paying attention to the size of the feed to
the garage in my previous response. 2.5mm^2 is a tad on the small side
for a submain really (although more than adequate for the original
intended use of providing for lights and one socket).
The 32A house MCB will provide adequate fault protection for the
submain, but not overload protection for it. Hence it will fall to the
garage CU to provide this for its supply cable. So the garage CU is
going to be limited to a 6 and a 20A MCB maximum.
--
Cheers,
John.
/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/
John Rumm
> My garage has an existing electrical supply via an overhead-slung single
> cable (2.5mm twin-and-earth) from the house consumer unit: the relevant
> module is labeled "B32 - NSB32".
ok, we will ignore the unsuitability of T&E being slung from centenary
wires for the moment...
Also are you sure its 2.5mm^2?
Check the dimensions here:
http://wiki.diyfaq.org.uk/index.php?title=Cables#Cable_Sizes
A single 2.5mm^2 cable would not be adequately overload protected by a
32A MCB (although it would offer adequate fault protection) - this will
limit options in the garage at bit.
> Inside the garage this cable feeds a small consumer unit which has a
> 30mA RCD and two modules: a B-6 and a B-16. The 6A circuit feeds two
> fluorescent lights, the 16A a single double-socket.
> I'd like to add a few more sockets (or have them added by a
> professional, if necessary) but I wonder if it's also possible to
You can add the sockets yourself. Extending an existing circuit is not a
controlled activity, and hence does not come under part P.
> increase the rating of that circuit: at present my chop saw draws too
> much current and trips it.
What sort of motor does the chop saw have? If its an induction motor
(there are a small number of chop saws that do) then its not actually
too surprising it trips a 16A breaker, since the inrush current on
induction motors is quite high (five to nine times their nominal current
draw is often quoted).
If its a "normal" universal motor (these are the normal electric drill
style noisy motor - compared to the very quiet and smooth running
induction motors common on workshop tools), then its possible that the
circuit breaker in the CU is faulty and a tad too sensitive.
> I haven't looked closely at the garage unit as yet, but I'm hoping that
> the modules are removable. Can the B-16 one simply be replaced by one of
> a higher value?
Almost certainly - so long as its a MCB that is still available or or
least a design that will accept a competing brand if not.
A little will depend on the wiring in the garage. If the circuit is a
radial, wired in 2.5mm T&E, then you can replace the breaker with a B20.
Alternatively you could add a wire to the end of the radial, and return
that to the same breaker in the garage CU so that it forms a ring, and
change the breaker for a B32 - however the difficulty there is it sounds
like the supply cable to the garage is not really large enough to
support this configuration.
As it sounds like you are planning on using the garage as a workshop, it
might be worth revisiting the RCD arrangements. The way you currently
have it described, the RCD in the garage would if tripped cut both
lights and power. This may not be desirable if you are holding a
spinning power tool and suddenly have no lights. Assuming the main house
CU feed of the garage submain is not RCD protected, then you could
change both MCBs in the garage with RCBOs (i.e. MCBs that include their
own RCD), and replace the RCD with a normal switch. That way a trip of
the power will not kill the lights. A simpler less sophisticated
solution might be to add a non maintained emergency light (<�15) to kick
in when the power goes!
Bert Coules
one reply.
Alan asked,
> What is the Wattage rating of the saw?
It's 1800W.
and,
> Trips what? The MCB or the RCD? Inside the house CU or garage CU?
It's the garage CU which trips, but I don't recall if it's the MCB or the
RCD.
> Have you got an RCD in the house CU?
Yes, there's an RCD in the house CU (80A 30mA) which appears to protect only
some of the circuits: the kitchen ring circuit (NSB32), the garage spur
(NSB32) and an unconnected MCB (NSB20).
John Rumm wrote:
> ...we will ignore the unsuitability of T&E being slung from centenary
> wires for the moment...
Yes, I'm well aware that this is far from ideal, and I plan to change it as
soon as possible. I don't think it's going to be practical to bury the
cable, but I can at least raise the wire a fair bit (it's not much above
head height at present) and run the cable through plastic trunking.
> Also are you sure its 2.5mm^2?
I think I was mistaken. A closer look today reveals this on the cable:
BASEC 300/500V 6242Y 4.0. So: 4mm^2, yes?
> You can add the sockets yourself. Extending an existing circuit is not a
> controlled activity, and hence does not come under part P.
Ah, excellent.
> What sort of motor does the chop saw have? If its an induction motor...
I don't know, and there's nothing on the spec plate or in the manual to
enlighten me. It's a Nutool MSR 250, bought about ten years ago.
> ...the inrush current on induction motors is quite high
> (five to nine times their nominal current draw is often quoted).
It does kick on with an almighty surge, or seems to. And the tripping was
instantaneous. But on the other hand...
> If it's a "normal" universal motor (these are the normal electric drill
> style noisy motor... compared to the very quiet and smooth running
> induction motors common on workshop tools)...
It's a very noisy motor.
> ...then it's possible that the circuit breaker in the CU is faulty
> and a tad too sensitive.
So... given that the feed cable is 4.00mm^2, what's my best course?
Replace the B16 with a C16? Or something higher? The garage circuit is a
radial in 2.5mm T&E. It would be possible to make it a ring, if that would
be better.
Thanks for the thought about lighting. An emergency light will be the
easiest arrangement, I think.
Many thanks,
Bert
John Rumm
> On 2011-07-30, John Rumm<see.my.s...@nowhere.null> wrote:
>> On 29/07/2011 19:40, Bert Coules wrote:
>>> My garage has an existing electrical supply via an overhead-slung single
>>> cable (2.5mm twin-and-earth) from the house consumer unit: the relevant
>>> module is labeled "B32 - NSB32".
>>
>> ok, we will ignore the unsuitability of T&E being slung from centenary
>
Good these spell checkers ;-)
John Rumm
> Thanks to everyone for the responses. I'll try to collect my answers
> into one reply.
>
> Alan asked,
>
>> What is the Wattage rating of the saw?
>
> It's 1800W.
>
> and,
>
>> Trips what? The MCB or the RCD? Inside the house CU or garage CU?
>
> It's the garage CU which trips, but I don't recall if it's the MCB or
> the RCD.
ok, that alters things a bit. You need to establish which trips before
we can give any useful advice.
>> Have you got an RCD in the house CU?
>
> Yes, there's an RCD in the house CU (80A 30mA) which appears to protect
> only some of the circuits: the kitchen ring circuit (NSB32), the garage
> spur (NSB32) and an unconnected MCB (NSB20).
If the house RCD protects the garage submain, then no amount of fiddling
on the garage will fix that. That really leaves two options; either
moving the garage feed to the non RCD side of the CU in the house, or
going the emergency lighting route in the garage.
> John Rumm wrote:
>
>> ...we will ignore the unsuitability of T&E being slung from centenary
>> wires for the moment...
>
> Yes, I'm well aware that this is far from ideal, and I plan to change it
> as soon as possible. I don't think it's going to be practical to bury
> the cable, but I can at least raise the wire a fair bit (it's not much
> above head height at present) and run the cable through plastic trunking.
If you use a flexible cable that is designed for the application, then
you can do away with trunking. TLC's Hi-Tuf would be an ok choice for this.
>> Also are you sure its 2.5mm^2?
>
> I think I was mistaken. A closer look today reveals this on the cable:
> BASEC 300/500V 6242Y 4.0. So: 4mm^2, yes?
Yup sounds like it. Should measure about 6.1 x 11.4 mm overall.
>> You can add the sockets yourself. Extending an existing circuit is not
>> a controlled activity, and hence does not come under part P.
>
> Ah, excellent.
>
>> What sort of motor does the chop saw have? If its an induction motor...
>
> I don't know, and there's nothing on the spec plate or in the manual to
> enlighten me. It's a Nutool MSR 250, bought about ten years ago.
>
>> ...the inrush current on induction motors is quite high
>> (five to nine times their nominal current draw is often quoted).
>
> It does kick on with an almighty surge, or seems to. And the tripping
> was instantaneous. But on the other hand...
Almost certainly a universal motor then. Less of a problem regarding
inrush current, although the nature of these saws can still mean a
moderate starting current with any type of motor.
>> ...then it's possible that the circuit breaker in the CU is faulty
>> and a tad too sensitive.
>
> So... given that the feed cable is 4.00mm^2, what's my best course?
If it is, then you have more flexibility since the MCB on its origin
will offer the submain both fault and overload protection. Hence no need
to mitigate for that when making choices in the garage.
> Replace the B16 with a C16? Or something higher? The garage circuit is a
> radial in 2.5mm T&E. It would be possible to make it a ring, if that
> would be better.
If you are using this as a workshop, then one 16A circuit may be a bit
on the skimpy side - especially if you plan on needing some heating in
the winter. I would be tempted to extend the socket wiring and form a
ring, and protect that with a B32. That way you can stick in plenty of
sockets, and have enough capacity available for heating, lighting, power
tool, and dust extraction all concurrently. It may leave you with a
discrimination problem - in that a fault or overload in the garage might
result in a trip of the house MCB rather than the garage one. Having
said this, if its not a long walk to reset that, and you have emergency
lighting you may decide this is acceptable. (replacing the MCB in the
house with a 32A fuse holder may resolve that)
The other thing to have a bit of think about is the distances involved
and hence any voltage drop problems. Again unlikely to be an issue if
the garage is not far away. If you are replacing the submain at some
point anyway, then you could always go up a size then.
polygonum
> On 2011-07-30, John Rumm <see.my.s...@nowhere.null> wrote:
>> On 30/07/2011 10:04, Huge wrote:
>>> On 2011-07-30, John Rumm<see.my.s...@nowhere.null> wrote:
>>>> On 29/07/2011 19:40, Bert Coules wrote:
>>>>> My garage has an existing electrical supply via an overhead-slung
>>>>> single
>>>>> cable (2.5mm twin-and-earth) from the house consumer unit: the
>>>>> relevant
>>>>> module is labeled "B32 - NSB32".
>>>>
>>>> ok, we will ignore the unsuitability of T&E being slung from centenary
>>>
>>> Catenary. You're welcome.
>>
>> Good these spell checkers ;-)
>
> What's a spell checker?
>
>
What other-side-of-pondians call a spelling checker. :-)
To me, a spell checker would be more appropriate to Harry Potter...
--
Rod
Bert Coules
>> It's the garage CU which trips, but I don't recall if it's the MCB or
>> the RCD.
>
> ok, that alters things a bit. You need to establish which trips before we
> can give any useful advice.
Right, I'll give it a try tomorrow and report back.
> I would be tempted to extend the socket wiring and form a ring, and
> protect that with a B32. That way you can stick in plenty of sockets, and
> have enough capacity available for heating, lighting, power tool, and dust
> extraction all concurrently.
Assuming that I can get a compatible B32, that sounds like a good approach.
The garage CU seems to be branded SAIP, not a manufacturer I know, or have
found so far with Google.
> The other thing to have a bit of think about is the distances involved and
> hence any voltage drop problems. Again unlikely to be an issue if the
> garage is not far away.
That's the case. There are sockets in the house further away from the main
CU than the farthest point of the garage.
Many thanks.
Bert
ARWadsworth
> Assuming that I can get a compatible B32, that sounds like a good
> approach. The garage CU seems to be branded SAIP, not a manufacturer
> I know, or have found so far with Google.
I have seen them before. ISTR that your Wylex MCBs will fit. There is an
easy way to find out......
If not, I'll scan a few different makes of MCB for you to see if you can
find a match (and if I have a 32A one then I'll post it to you)
Cheers
--
Adam
Bert Coules
> If not, I'll scan a few different makes of MCB for you to see if you can
> find a match (and if I have a 32A one then I'll post it to you)
Adam, that's very good of you. Tomorrow I'll remove one of the MCBs and
have a look at the exact fitting.
Bert
Tim Lamb
<adamwa...@blueyonder.co.uk> writes
There was a recall on Electrium MCBs a year or so back. Wylex, Crabtree
and Volex.
I never discovered what the actual problem was. Anyone know?
http://www.mcbexchange.co.uk/electrium/
http://www.mcbexchange.co.uk/electrium/RecallAdvertWeb.jpg
Posted by Andy Wade 03/04/2010
regards
--
Tim Lamb
ARWadsworth
Additional info here.
http://s428.photobucket.com/albums/qq6/adamko2020/?action=view¤t=img073.jpg
--
Adam
ARWadsworth
>> I never discovered what the actual problem was. Anyone know?
Sorry, missed that bit.
The easy answer is that they did not trip when overloaded:-) I have no idea
of the part that was faulty or why they did not trip.
--
Adam
John Rumm
> On 2011-07-30, John Rumm<see.my.s...@nowhere.null> wrote:
>> On 30/07/2011 10:04, Huge wrote:
>>> On 2011-07-30, John Rumm<see.my.s...@nowhere.null> wrote:
>>>> On 29/07/2011 19:40, Bert Coules wrote:
>>>>> My garage has an existing electrical supply via an overhead-slung single
>>>>> cable (2.5mm twin-and-earth) from the house consumer unit: the relevant
>>>>> module is labeled "B32 - NSB32".
>>>>
>>>> ok, we will ignore the unsuitability of T&E being slung from centenary
>>>
>>> Catenary. You're welcome.
>>
>> Good these spell checkers ;-)
>
You it would seem ;-)
(or failing that. something that us folks who can't spell rely on to get
some semi credible output into print!)
Bert Coules
> The easy answer is that they did not trip when overloaded:-)
Well, I suppose if you're going to be an MCB with a flaw, you might as well
make it a whopper.
Bert
Andy Burns
Counterfeits are scarier ...
<http://schneider-qa.bsky.net/internet/pws/pws.nsf/luAllByID/F2DAEE42760F06F3802573F3004D040C>
ARWadsworth
I would have been a lot easier if you had asked yeasterday.
I had a second hand SAIP box that I fitted this morning:-(
--
Adam
Tim Lamb
<adamwa...@blueyonder.co.uk> writes
Yes. Ta.
regards
--
Tim Lamb
Bert Coules
> I would have been a lot easier if you had asked yeasterday.
Ah, timing is everything... Thanks for the info about the SAIP unit using a
standard DIN rail fitting. I checked out the MCBs today's: they're 80mm
high x 18mm wide x 67mm deep. The central raised portion on the face (the
bit that sticks through the aperture in the faceplate) is 45mm high. So all
I have to do is look at the various makes of MCB to find one with the same
dimensions.
There is one thing about the wiring of the garage CU which I'd like to
check: at the bottom of the plastic casing is a nut and bolt and a securing
plate. The earth wires for the garage lights and sockets are both bolted to
this connector, and so is a substantial individual earth cable which runs
outside to a ground pole. But the incoming earth - the one on the cable
from the house CU - isn't connected to the same terminal. Instead, it's
looped around one of the screws which hold down the DIN rail.
I assume this is so that the metal parts of the garage CU are earthed via
the house, since they have no connection at all to the earth terminal in the
garage CU. Is this correct?
If my description's not clear, please do say and I'll post a sketch.
Many thanks,
Bert
ARWadsworth
> ARWadsworth wrote:
>
>> I would have been a lot easier if you had asked yeasterday.
>
> Ah, timing is everything... Thanks for the info about the SAIP unit
> using a standard DIN rail fitting. I checked out the MCBs today's:
> they're 80mm high x 18mm wide x 67mm deep. The central raised
> portion on the face (the bit that sticks through the aperture in the
> faceplate) is 45mm high. So all I have to do is look at the various
> makes of MCB to find one with the same dimensions.
Yep, and I'll measure a few to get some recommendations.
> There is one thing about the wiring of the garage CU which I'd like to
> check: at the bottom of the plastic casing is a nut and bolt and a
> securing plate. The earth wires for the garage lights and sockets
> are both bolted to this connector, and so is a substantial individual
> earth cable which runs outside to a ground pole. But the incoming
> earth - the one on the cable from the house CU - isn't connected to
> the same terminal. Instead, it's looped around one of the screws
> which hold down the DIN rail.
> I assume this is so that the metal parts of the garage CU are earthed
> via the house, since they have no connection at all to the earth
> terminal in the garage CU. Is this correct?
Have a look at
http://wiki.diyfaq.org.uk/index.php?title=Taking_electricity_outside#Exporting_an_earth
It seems that your workshop CU has been installed as a TT supply.
Is the workshop CU a plastic one?
How far is the workshop from the house CU and are there any buried metal
parts in your workshop (eg waterpipes or structual steel)?
--
Adam
Bert Coules
> It seems that your workshop CU has been installed as a TT supply.
Thanks for the link: I'll go through the article in detail (though even on a
cursory glance, I see that my earth rod should be protected by "a suitable
enclosure and a warning notice", neither of which it has.
> Is the workshop CU a plastic one?
Yes, it's all plastic. The only metal components (apart from those in the
RCD and MCBs and the various securing screws) appear to be the DIN rail and
the nut/bolt/plate earth fixing.
> How far is the workshop from the house CU...
At its nearest point, 13 feet. At its farthest, 29 feet.
> ...and are there any buried metal parts in your workshop (eg waterpipes or
> structual steel)?
No, nothing like that at all.
Bert
ARWadsworth
> ARWadsworth wrote:
>
>> I would have been a lot easier if you had asked yeasterday.
>
> Ah, timing is everything... Thanks for the info about the SAIP unit
> using a standard DIN rail fitting. I checked out the MCBs today's:
> they're 80mm high x 18mm wide x 67mm deep. The central raised
> portion on the face (the bit that sticks through the aperture in the
> faceplate) is 45mm high. So all I have to do is look at the various
> makes of MCB to find one with the same dimensions.
Well that bit is easy. I have just gone to my stores and sat there was a
SAIP 2 way CU.
Now the 32A MCB in it is made by BG, it fits perfectly and it's all yours if
you want it.
--
Adam
Bert Coules
> Now the 32A MCB in it is made by BG, it fits perfectly and it's all yours
> if you want it.
Adam, that's enormously kind of you: I've sent you a private email.
Bert
ARWadsworth
> ARWadsworth wrote:
>
>> It seems that your workshop CU has been installed as a TT supply.
>
> Thanks for the link: I'll go through the article in detail (though
> even on a cursory glance, I see that my earth rod should be protected
> by "a suitable enclosure and a warning notice", neither of which it
> has.
Very few are:-)
>> Is the workshop CU a plastic one?
>
> Yes, it's all plastic. The only metal components (apart from those
> in the RCD and MCBs and the various securing screws) appear to be the
> DIN rail and the nut/bolt/plate earth fixing.
The DIN rail would not normally be earthed.
>> How far is the workshop from the house CU...
>
> At its nearest point, 13 feet. At its farthest, 29 feet.
>
>> ...and are there any buried metal parts in your workshop (eg
>> waterpipes or structual steel)?
>
> No, nothing like that at all.
So the workshop would not need to be TT due to equipotential bonding.
The workshop could have been made TT to provide discrimination between the
workshop and house RCDs.
Hopefully someone else can offer other reasons why you have such a set up.
There does not seem to be anything wrong with the setup (indeed it seems
better than most apart from the 16A MCB and only one socket).
Finally, can you comfirm that the 4mm T&E runs all the way from the house CU
to the workshop?
--
Adam
m...@privacy.net
"Bert Coules" <ma...@bertcoules.co.uk> wrote:
> Ah, timing is everything... Thanks for the info about the SAIP unit using
> a standard DIN rail fitting. I checked out the MCBs today's: they're 80mm
> high x 18mm wide x 67mm deep. The central raised portion on the face (the
> bit that sticks through the aperture in the faceplate) is 45mm high. So
> all I have to do is look at the various makes of MCB to find one with the
> same dimensions.
A dimension you might come unstuck on is busbar height, manufacturers vary.
--
B Thumbs
Change lycos to yahoo to reply
Bert Coules
> Hopefully someone else can offer other reasons why you have such a set up.
> There does not seem to be anything wrong with the setup (indeed it seems
> better than most apart from the 16A MCB and only one socket).
Well, the MCB will be replaced with one of a higher rating (thanks again)
and I can upgrade the radial circuit to a ring, as you suggest. So as long
as the present earthing setup will still be satisfactory, I shall be happy
to keep it.
> Finally, can you comfirm that the 4mm T&E runs
> all the way from the house CU to the workshop?
Yes, it definitely does, in one unbroken cable.
Bert
Bert Coules
> A dimension you might come unstuck on is
> busbar height, manufacturers vary.
Ah, right; thanks.
Bert
ARWadsworth
> ARWadsworth wrote:
>
>> Hopefully someone else can offer other reasons why you have such a
>> set up. There does not seem to be anything wrong with the setup
>> (indeed it seems better than most apart from the 16A MCB and only
>> one socket).
>
> Well, the MCB will be replaced with one of a higher rating (thanks
> again) and I can upgrade the radial circuit to a ring, as you
> suggest. So as long as the present earthing setup will still be
> satisfactory, I shall be happy to keep it.
It should be fine. You can also use a 4mm 32A radial if you wish.
>> Finally, can you comfirm that the 4mm T&E runs
>> all the way from the house CU to the workshop?
>
> Yes, it definitely does, in one unbroken cable.
So that means there is no problems regarding the house MCB overloading.
--
Adam
Bert Coules
> It should be fine. You can also use a
> 4mm 32A radial if you wish.
I think I'll go with the 2.5mm ring: the layout of the garage is suitable
and the smaller cable is slightly easier to work with.
> So that means there is no problems regarding
> the house MCB overloading.
Excellent. Many thanks.
Bert
Bert Coules
now up and running: with the old 16A radial circuit upgraded to 32A, my chop
saw no longer trips the MCB on startup.
Now I'm all set to plan out the new socket placements and new lights and
install the extended wiring for the ring circuit.
What a splendid resource this group is.
Bert
Bert Coules
I like the answer of installing a master-switch to kill the power to all the
sockets on my planned 32A workshop ring circuit. Is there any reason why I
shouldn't put a 45A cooker switch with a neon indicator into the ring?
Would that work?
Many thanks,
Bert
John Rumm
"In" a ring it would only cut power to one of the legs. Although
slightly unconventional, you would need to wire a radial to the switch
and both legs of the ring from its output.
A more conventional approach for this sort of setup is to use a
contactor in the CU with the output from it being latched via one or
more emergency stop buttons. That way you can hit any button to kill
power to the sockets.
(I thought about doing this in my workshop, but concluded in the end
that it was probably not worth it, since I am usually working alone and
each machine has its own NVR switch where required).
Bert Coules
> "In" a ring it would only cut power to one of the legs.
Naive question again, but wouldn't that be enough to prevent any plugged-in
machine from being accidentally activated? That was my main concern.
> (I thought about doing this in my workshop, but concluded in the end that
> it was probably not worth it...)
I'll be in much the same position, so it's possibly not worth doing for me,
too.
Thanks for the speedy reply.
Bert
ARWadsworth
> On 05/08/2011 12:37, Bert Coules wrote:
>> Perhaps I could ask one more slightly naive electrical question:
>>
>> I like the answer of installing a master-switch to kill the power to
>> all the sockets on my planned 32A workshop ring circuit. Is there
>> any reason why I shouldn't put a 45A cooker switch with a neon
>> indicator into the ring? Would that work?
>
> "In" a ring it would only cut power to one of the legs.
Would it not turn it into a radial and not cut any power?
>Although
> slightly unconventional, you would need to wire a radial to the switch
> and both legs of the ring from its output.
You could also take the ring from the CU and put both "legs" into the supply
side of the switch with the workshop ring supplied from the load side.
> A more conventional approach for this sort of setup is to use a
> contactor in the CU with the output from it being latched via one or
> more emergency stop buttons. That way you can hit any button to kill
> power to the sockets.
>
> (I thought about doing this in my workshop, but concluded in the end
> that it was probably not worth it, since I am usually working alone
> and each machine has its own NVR switch where required).
I wondered if a switch would be a little OTT.
--
Adam
"Who is pissed off as his new toy does not work."
Bert Coules
> I wondered if a switch would be a little OTT.
Yes, on reflection I think it would...
Many thanks.
Bert
John Rumm
> John Rumm wrote:
>
>> "In" a ring it would only cut power to one of the legs.
>
> Naive question again, but wouldn't that be enough to prevent any
> plugged-in machine from being accidentally activated? That was my main
> concern.
Nope - if you thing of a ring, there are two routes for the neutral and
two for the line at each socket. Adding a switch as described just has
the effect of opening the ring into two radials (for which the cables
are now inadequately sized).
>
>> (I thought about doing this in my workshop, but concluded in the end
>> that it was probably not worth it...)
>
> I'll be in much the same position, so it's possibly not worth doing for
> me, too.
>
> Thanks for the speedy reply.
>
> Bert
>
John Rumm
> John Rumm<see.my.s...@nowhere.null> wrote:
>> On 05/08/2011 12:37, Bert Coules wrote:
>>> Perhaps I could ask one more slightly naive electrical question:
>>>
>>> I like the answer of installing a master-switch to kill the power to
>>> all the sockets on my planned 32A workshop ring circuit. Is there
>>> any reason why I shouldn't put a 45A cooker switch with a neon
>>> indicator into the ring? Would that work?
>>
>> "In" a ring it would only cut power to one of the legs.
>
> Would it not turn it into a radial and not cut any power?
Precisely - a pair of radials in fact - both still connected to the CU.
>> Although
>> slightly unconventional, you would need to wire a radial to the switch
>> and both legs of the ring from its output.
>
> You could also take the ring from the CU and put both "legs" into the supply
> side of the switch with the workshop ring supplied from the load side.
You could - creating a "figure of eight" circuit topology, although not
much point...
>> A more conventional approach for this sort of setup is to use a
>> contactor in the CU with the output from it being latched via one or
>> more emergency stop buttons. That way you can hit any button to kill
>> power to the sockets.
>>
>> (I thought about doing this in my workshop, but concluded in the end
>> that it was probably not worth it, since I am usually working alone
>> and each machine has its own NVR switch where required).
>
> I wondered if a switch would be a little OTT.
Well I concluded it was in the end. The "emergency stop" type of
functionality makes sense in a room with several people working - that
way if someone gets into trouble, someone else can kill the power from
wherever they are. In a domestic environment its less convincing.
John Williamson
> On 05/08/2011 13:06, ARWadsworth wrote:
>> I wondered if a switch would be a little OTT.
>
> Well I concluded it was in the end. The "emergency stop" type of
> functionality makes sense in a room with several people working - that
> way if someone gets into trouble, someone else can kill the power from
> wherever they are. In a domestic environment its less convincing.
>
>
linked to a circuit breaker cutting power to everything except the
lighting makes very good sense, especially if your workshop is out of
shouting range of the house, or you are in it when everyone else is out.
Linking the circuit breaker to an alarm outside the workshop is also a
good idea, as is an intercom system or auto answering hands-free phone.
I'd say that an accessible emergency cut-off for all workshop power was
more important in the domestic setting than in a commercial workshop, as
you are the only safety back-up.
--
Tciao for Now!
John.
John Rumm
> John Rumm wrote:
>> On 05/08/2011 13:06, ARWadsworth wrote:
>>> I wondered if a switch would be a little OTT.
>>
>> Well I concluded it was in the end. The "emergency stop" type of
>> functionality makes sense in a room with several people working - that
>> way if someone gets into trouble, someone else can kill the power from
>> wherever they are. In a domestic environment its less convincing.
>>
>>
> Floor mounted and accessible push buttons near every fixed power tool,
> linked to a circuit breaker cutting power to everything except the
> lighting makes very good sense, especially if your workshop is out of
> shouting range of the house, or you are in it when everyone else is out.
> Linking the circuit breaker to an alarm outside the workshop is also a
> good idea, as is an intercom system or auto answering hands-free phone.
The limitation in my workshop is the "fixed" bit. Even the table saw is
on a wheeled dolly so that it can be moved to the most handy place for
the job. Alas one of the limitations of a 17 x 12' space.
So the only practical place for the stop buttons would be on the wall,
and that will often be further away than the built in NVR on the tool.
> I'd say that an accessible emergency cut-off for all workshop power was
> more important in the domestic setting than in a commercial workshop, as
> you are the only safety back-up.
You can only be in one place at a time though. Decent RCD protection and
a phone are obviously worth having. Not convinced about the cut switch
(which would actually do more harm than good on some tools. My mitre saw
has electric breaking for example, so stops much quicker when still
powered).