Wonder if any experts out there could cast an eye on my electrical setup...

http://tinyurl.com/d9zoe

The things I am unsure about are...

The size of the earth between the service head and the Henley block (6mm)
(I cant change this, as it is obviously sealed into the head)
Then the same to the split load consumer unit (again 6mm)

Does the generator setup look like it is compliant?
(Especially the earthing sizes, and the SWA connected to free 32A
plugs/sockets - Is that OK?)

What size earthing should be in place for bonding to the services, and where
should the be connected (consumer unit, main Henley block, either?)
Should the services (Water & Gas) both be connected back to the supply, or
can they daisy
chain with only one cable back to the supply?

Should the earth going to the transfer switch from the split CU really be
taken to the Henley block?

The nutruel is tied to earth on the generator (well, in the free plug
connected to the house) should this really be done in the generator?

When running from the generator, the earth (tied to the generator's neutral)
is still connected to the grid provided earth (Armour of main cable) - is
that OK (The transfer switch doesn't seem to have any provision to switch
the earth as well as L & N)

When running from the grid, there is still an earthing rod connected to the
earthing system as well as the grid provided earth - is this OK?

Thanks :-)

Sparks...

Sparks wrote:

http://tinyurl.com/d9zoe
The things I am unsure about are...

The size of the earth between the service head and the Henley block (6mm)
(I cant change this, as it is obviously sealed into the head)

Is it sealed? A PME earth is sealed (but wouldn't be 6 mm^2) but your
picture seems to show a TN-S type supply cut-out where the earth
connection is made by an external clamp onto the cable sheath.

Anyway all the earths in your diagram (except the generator cable)
should be 16 mm^2, so you will have to find a way of changing it.

Then the same to the split load consumer unit (again 6mm)

16 mm^2.

Does the generator setup look like it is compliant?
(Especially the earthing sizes, and the SWA connected to free 32A
plugs/sockets - Is that OK?)

Several points he

- have you consulted with the local mains supply DNO? You are supposed
to "ascertain their requirements" and IME they like to approve standby
generator installation arrangements. Their main concern is to avoid the
risk of someone back-feeding the mains - there shouldn't be a problem in
your case as you have a proper changeover switch.

- the earth from the genny frame to the electrode should be 16 mm^2
(unless protected in conduit);

- the bond between the genny's neutral and earth should be made in the
generator, not at the junction box on the house wall (TN-S system).
Your arrangement has a combined N & E conductor between the genny and
the junction box, which isn't allowed. To be clear you should be
bonding one end of the genny winding and its frame to earth at the
genny. This defines the neutral point for your independent TN-S system.
It may require some modification of the genny's internal wiring as
portable gennies (like the picture) often have floating or
centre-tapped-to-earth outputs;

- you should make your genny installation permanent by fixing the genset
to a floor slab (or whatever) and get rid of the 32 A plug and socket
arrangement. Failing that the 100 mA RCD in the transfer switch will
need to be changed for a 30 mA type (see reg. 551-04-06, re. gensets
that are "not permanently fixed");

- the 6 mm^2 cabling between genny and house is too small. You have a
long run (26 m) and voltage drop would be excessive on 6 mm^2. I'd
recommend 10 mm^2 minimum and preferably 16 mm^2 for this;

- is the 7.5 kVA genny capacity adequate to supply all your load? If
not you are supposed to have automatic load shedding arrangements (see
reg. 551-02-03);

What size earthing should be in place for bonding to the services, and where
should the be connected (consumer unit, main Henley block, either?)

10 mm^2, to the main earth terminal, which in your diagram is the
terminal block just to the right of the supplier's cut-out.

Should the services (Water & Gas) both be connected back to the supply, or
can they daisy chain with only one cable back to the supply?

Either way is acceptable. If daisy-chaining it's common practice to
avoid cutting the conductor at the intermediate points. Just remove a
length of insulation, form a U shape with the wire and insert into the
earth clamp terminal.

Should the earth going to the transfer switch from the split CU really be
taken to the Henley block?

Absolutely yes, to avoid any confusion over which is the main earth
terminal.

The nutruel is tied to earth on the generator (well, in the free plug
connected to the house) should this really be done in the generator?

Yes, see above.

When running from the generator, the earth (tied to the generator's neutral)
is still connected to the grid provided earth (Armour of main cable) - is
that OK (The transfer switch doesn't seem to have any provision to switch
the earth as well as L & N)

Yes, that's OK, the earths are in parallel but if the mains cable is
completely severed your independent system still has its own earth.

When running from the grid, there is still an earthing rod connected to the
earthing system as well as the grid provided earth - is this OK?

Yes, ditto.

HTH
--
Andy

"Andy Wade" wrote in message
...
Sparks wrote:

http://tinyurl.com/d9zoe
The things I am unsure about are...

The size of the earth between the service head and the Henley block (6mm)
(I cant change this, as it is obviously sealed into the head)

Is it sealed? A PME earth is sealed (but wouldn't be 6 mm^2) but your
picture seems to show a TN-S type supply cut-out where the earth
connection is made by an external clamp onto the cable sheath.

You are quite correct, I thought it went into the head, but after removing a
load of insulation tape, it appears to be connected to a clamp round the
main cable (and it's loose!)

It is clamped around a solid part (looks like a pipe) - Can I just use a
normal earth clamp used on pipes on it?

Anyway all the earths in your diagram (except the generator cable) should
be 16 mm^2, so you will have to find a way of changing it.

Now I can see this will be easy!

What size should the generator's earth be - currently it is mainly 2.5mm in
the 6mm T&E)

Then the same to the split load consumer unit (again 6mm)

16 mm^2.

Okay, easily changed!

Both the head to the Henley block, and the Henley block to the split load
has always been 6mm since it was installed (By a "proper sparkie") was this
ever acceptable? (Installed, probably 20 years ago)

Does the generator setup look like it is compliant?
(Especially the earthing sizes, and the SWA connected to free 32A
plugs/sockets - Is that OK?)

Several points he

- have you consulted with the local mains supply DNO?

Errm, nope! (What does DNO stand for! and how do I find them!)

You are supposed to "ascertain their requirements" and IME they like to
approve standby generator installation arrangements. Their main concern
is to avoid the risk of someone back-feeding the mains - there shouldn't
be a problem in your case as you have a proper changeover switch.

- the earth from the genny frame to the electrode should be 16 mm^2
(unless protected in conduit);

do you mean from the frame to the earth rod, or the earthing terminal in the
house?


- the bond between the genny's neutral and earth should be made in the
generator, not at the junction box on the house wall (TN-S system).

I have a wooden box with forced air flow though it that genny lives in - In
there I also have a "Power Conditioner" - not sure of it's model - it
weighs, probably 50-60KG
It has "Watford Control" on the side
Picture of it here (The amp meter is broken, as you will see!)
http://www.altphuk.co.uk/images/power_conditioner.jpg

Your arrangement has a combined N & E conductor between the genny and the
junction box, which isn't allowed. To be clear you should be bonding one
end of the genny winding and its frame to earth at the genny. This
defines the neutral point for your independent TN-S system. It may require
some modification of the genny's internal wiring as portable gennies (like
the picture) often have floating or centre-tapped-to-earth outputs;

Sounds right, if I measure the voltage on the generator, across the L & N I
get 230
but if I measure from L to E or N to E I get 115v but with the bonding of N
to E, I get 230 from L to E and N to L

So, inside the generator, so I just connect the L and the E together and
break this connection in the box on the side of the house?


- you should make your genny installation permanent by fixing the genset
to a floor slab (or whatever) and get rid of the 32 A plug and socket
arrangement.

The reason I wanted this plug and socket, is I have another much smaller
generator (2KW) so if the main one blows up, I can plug this in - Overkill
or what :-) (This spare one was given to me!)

Could I clamp the generator to the box it is in, and screw the box down, but
still keep the plug/socket?

Failing that the 100 mA RCD in the transfer switch will need to be changed
for a 30 mA type (see reg. 551-04-06, re. gensets that are "not
permanently fixed");

The transfer switch did originally have a 30mA RCD, but it kept tripping
(but the other RCD's downstream of it didn't)
So I changed it presuming it was faulty, I though 100mA would be ok as it is
TT (This one behaves)

- the 6 mm^2 cabling between genny and house is too small. You have a
long run (26 m) and voltage drop would be excessive on 6 mm^2. I'd
recommend 10 mm^2 minimum and preferably 16 mm^2 for this;

Okay, the bit in the house is reasonably easy to change, (when I say easy,
it does result in the front room & hall carpet and floorboards coming up,
and the kitchen kick plates being removed!) but the 5m SWA between the
generator and the house is going to be a right pain in the arse (most of it
is under the {new} patio!) would just upgrading the main T&E Run be ok?

- is the 7.5 kVA genny capacity adequate to supply all your load? If not
you are supposed to have automatic load shedding arrangements (see reg.
551-02-03);

No, but as the generator is not automatic, can I just have some instructions
to turn X Y and Z off on the consumer units?
otherwise I would need another split load CU, just for the generator
circuits (and that would mean no rings on it, as one 32A main would overload
it!)

What size earthing should be in place for bonding to the services, and
where
should the be connected (consumer unit, main Henley block, either?)

10 mm^2, to the main earth terminal, which in your diagram is the terminal
block just to the right of the supplier's cut-out.

Good, that's what I ran not too long ago (as there wasn't any bonding at
all!)

Should the services (Water & Gas) both be connected back to the supply,
or can they daisy chain with only one cable back to the supply?

Either way is acceptable. If daisy-chaining it's common practice to avoid
cutting the conductor at the intermediate points. Just remove a length of
insulation, form a U shape with the wire and insert into the earth clamp
terminal.

Okay, I did do two runs, just in case!

Should the earth going to the transfer switch from the split CU really be
taken to the Henley block?

Absolutely yes, to avoid any confusion over which is the main earth
terminal.

Will change this then.

The nutruel is tied to earth on the generator (well, in the free plug
connected to the house) should this really be done in the generator?

Yes, see above.

When running from the generator, the earth (tied to the generator's
neutral) is still connected to the grid provided earth (Armour of main
cable) - is that OK (The transfer switch doesn't seem to have any
provision to switch the earth as well as L & N)

Yes, that's OK, the earths are in parallel but if the mains cable is
completely severed your independent system still has its own earth.

Great - how can I test this rod is providing an acceptable earth?

When running from the grid, there is still an earthing rod connected to
the earthing system as well as the grid provided earth - is this OK?

Yes, ditto.

Sparks wrote:

You are quite correct, I thought it went into the head, but after removing a
load of insulation tape, it appears to be connected to a clamp round the
main cable (and it's loose!)

It is clamped around a solid part (looks like a pipe) - Can I just use a
normal earth clamp used on pipes on it?

Yes, but remember that it's a soft lead pipe with old wires inside, so
don't overtighten the clamp!

What size should the generator's earth be - currently it is mainly 2.5mm in
the 6mm T&E)

I pondered on that, and wondered whether to recommend that the earth
should be the same size as the phase and neutral. It should be really,
but since there's an RCD in-line it's not really that important. But I
did say upgrade that 6 mm^2 to 10 or 16. The best job really would be
to use 10 or 16 mm^2 2-core SWA all the way from the genny shed to the
transfer switch.

Both the head to the Henley block, and the Henley block to the split load
has always been 6mm since it was installed (By a "proper sparkie") was this
ever acceptable? (Installed, probably 20 years ago)

Yes 6 was used in the 14th Edition days when the standard meter tail
size was 16 mm^2. The change would have been around 1981.

- have you consulted with the local mains supply DNO?
Errm, nope! (What does DNO stand for! and how do I find them!)

Distribution network operator, i.e. the company which has taken over
running the LV network from the old electricity board. If you don't
know the name, your electricity supplier (the one wot sends you bills)
should be able to tell you who to contact.

- the earth from the genny frame to the electrode should be 16 mm^2
(unless protected in conduit);

do you mean from the frame to the earth rod, or the earthing terminal in the
house?

Genny frame to earth rod, including the section buried in the ground.
Assuming an insulated wire with no other protection this needs to be 16
mm^2 in order to have adequate mechanical strength.

- the bond between the genny's neutral and earth should be made in the
generator, not at the junction box on the house wall (TN-S system).

I have a wooden box with forced air flow though it that genny lives in - In
there I also have a "Power Conditioner" - not sure of it's model - it
weighs, probably 50-60KG
It has "Watford Control" on the side
Picture of it here (The amp meter is broken, as you will see!)
http://www.altphuk.co.uk/images/power_conditioner.jpg

Are you wiring that in-line with the genny's output? If it contains an
isolating transformer then you'd have to move the N-E bonding point to
the secondary side.

Your arrangement has a combined N & E conductor between the genny and the
junction box, which isn't allowed. To be clear you should be bonding one
end of the genny winding and its frame to earth at the genny. This
defines the neutral point for your independent TN-S system. It may require
some modification of the genny's internal wiring as portable gennies (like
the picture) often have floating or centre-tapped-to-earth outputs;

Sounds right, if I measure the voltage on the generator, across the L & N I
get 230
but if I measure from L to E or N to E I get 115v but with the bonding of N
to E, I get 230 from L to E and N to L

So it sounds as if the output (when unbonded) is floating. If there was
a centre-tap already connected to earth then something would go bang
when you also earthed the neutral. To be absolutely sure temporarily
connect N to E through an ordinary 100 W lamp and make sure that the
lamp doesn't light at all and you still have 230 V L-N and L-E and 0 V N-E.

So, inside the generator, so I just connect the L and the E together and
break this connection in the box on the side of the house?

Assuming you meant N and E, then yes.

- you should make your genny installation permanent by fixing the
genset
to a floor slab (or whatever) and get rid of the 32 A plug and socket
arrangement.

The reason I wanted this plug and socket, is I have another much smaller
generator (2KW) so if the main one blows up, I can plug this in - Overkill
or what :-) (This spare one was given to me!)

Could I clamp the generator to the box it is in, and screw the box down, but
still keep the plug/socket?

I was giving you chapter and verse on the regs (BS 7671). It's open to
interpretation though. As you seem to have a dedicated genny shed then
we can probably say that the installation is permanent, so the
regulation is satisfied, even with the plug & socket.

Failing that the 100 mA RCD in the transfer switch will need to be changed
for a 30 mA type (see reg. 551-04-06, re. gensets that are "not
permanently fixed");

The transfer switch did originally have a 30mA RCD, but it kept tripping
(but the other RCD's downstream of it didn't)
So I changed it presuming it was faulty, I though 100mA would be ok as it is
TT (This one behaves)

I agree that a 100 mA RCD is a much more sensible choice, and is legit
now that we've decided that the genny installation is permanent. Your
system is not TT though, it's TN-S, because you have a metallic earth
path back to the "earthed point of the supply source" - i.e. the N-E
bonding point on the genny output. A TT system relies on conduction
through the soil for earth protection and that's not the case here.

- the 6 mm^2 cabling between genny and house is too small. You have a
long run (26 m) and voltage drop would be excessive on 6 mm^2. I'd
recommend 10 mm^2 minimum and preferably 16 mm^2 for this;

Okay, the bit in the house is reasonably easy to change, (when I say easy,
it does result in the front room & hall carpet and floorboards coming up,
and the kitchen kick plates being removed!) but the 5m SWA between the
generator and the house is going to be a right pain in the arse (most of it
is under the {new} patio!) would just upgrading the main T&E Run be ok?

OIC, it's all in place already. You now have to decide whether it's
worth changing. Certainly do the T&E section when you can and take that
up to 16 mm^2. I'd leave the SWA section.

- is the 7.5 kVA genny capacity adequate to supply all your load? If not
you are supposed to have automatic load shedding arrangements (see reg.
551-02-03);

No, but as the generator is not automatic, can I just have some instructions
to turn X Y and Z off on the consumer units?

Again BS 7671 does say automatic - but I think what you propose is quite
adequate. Unless you've got extensive electric space heating or
electric showers then 7.5 kVA is unlikely to be exceeded anyway.

Yes, that's OK, the earths are in parallel but if the mains cable is
completely severed your independent system still has its own earth.

Great - how can I test this rod is providing an acceptable earth?

If you have a loop tester then you can do a direct measurement between
the mains phase and the electrode. If not then see
http://groups.google.com/groups?as_umsgid=01bd6c2d%240cd8b9e0%24LocalHost@d og40
for my DIY method.

--
Andy

Just a further thought on your plug and socket arrangement in the genny
shed.

A better arrangement would be to have the inlet connector (the one on
the end of the cable from the house) mounted in a box on the wall. The
flying socket from the genny then plugs into this. I would also make
the N-E bond and the connection to the earth electrode inside this box,
with an additional 10 mm^2 bonding conductor going to the generator
frame. That way your earth continuity is not dependent on a plug and
socket connection.

--
Andy

"Andy Wade" wrote in message
...
Just a further thought on your plug and socket arrangement in the genny
shed.

A better arrangement would be to have the inlet connector (the one on the
end of the cable from the house) mounted in a box on the wall. The flying
socket from the genny then plugs into this. I would also make the N-E
bond and the connection to the earth electrode inside this box, with an
additional 10 mm^2 bonding conductor going to the generator frame. That
way your earth continuity is not dependent on a plug and socket
connection.

--
Andy

Andy,

Manu thanks for your time looking at this for me, it's most appreciated!

I was intending on terminating the SWA that comes from the house in a wall
mounted plug, just haven't got one yet!

In your previous post, you said
"The best job really would be to use 10 or 16 mm^2 2-core SWA all the way
from the genny shed to the transfer switch."

Would I be using the armour as the earth here, or did you mean 3 core?

As it is all in place, I think I will just upgrade the 6mm T&E with 16mm (Or
would it be better to use 2 core SWA and use the armour as earth, as this is
10p per meter cheaper from TLC :-)

Ta

Sparks...

Sparks wrote:

In your previous post, you said
"The best job really would be to use 10 or 16 mm^2 2-core SWA all the way
from the genny shed to the transfer switch."

Would I be using the armour as the earth here, or did you mean 3 core?

The armour alone would be quite satisfactory, no need for 3-core.

As it is all in place, I think I will just upgrade the 6mm T&E with 16mm (Or
would it be better to use 2 core SWA and use the armour as earth, as this is
10p per meter cheaper from TLC :-)

Either. The T&E would be much easier to handle indoors though,
especially if there are any fiddly bits & confined spaces to get through.

You must have very unreliable mains to be going to all this trouble.

--
Andy

"Andy Wade" wrote in message
...
Sparks wrote:

In your previous post, you said
"The best job really would be to use 10 or 16 mm^2 2-core SWA all the way
from the genny shed to the transfer switch."

Would I be using the armour as the earth here, or did you mean 3 core?

The armour alone would be quite satisfactory, no need for 3-core.

As it is all in place, I think I will just upgrade the 6mm T&E with 16mm
(Or would it be better to use 2 core SWA and use the armour as earth, as
this is 10p per meter cheaper from TLC :-)

Either. The T&E would be much easier to handle indoors though, especially
if there are any fiddly bits & confined spaces to get through.

You must have very unreliable mains to be going to all this trouble.

Not at all (now!)

I bought the generator about a year ago, before that we got a fair few
outages, the moment I bought the generator, we have not had one power cut -
typical!
Still, I would rather have it and not use it, than not, and need to!

I like to do it properly if I am doing something!


Sparks...
And thanks again for the advise!