Earth bonding

Cross bonding NOT needed in kitchens.
Water and gas mains need main Equipotential bonding at source.(plus some other services/items)
Supp. bonding in bath needed.
This is not an exclusive list.
regards

 

There is no specific requirement in BS 7671 to supplementry bond the following..

Kitchen pipes,sinks or draining boards

Metal furniture in kitchens

Metal pipes and wash hand basins in domestic locations other than bathrooms

OSG page 26

 

Did the report say supplementary bonding to boiler or main bond to boiler required. Supplementary bonding to a boiler is not usually required whereas a main bond between incoming oil pipe ? and consumer unit is.(Only if the oil pipe is in electrical contact with earth outside the premises)

 

the trouble im having is that this survey that i had
done with these recommendations is part of my
mortgage, that is the work has to be done to satify my
mortgage company, and he has put on his nikky sheet
that bathroom , kitchen and central heating boiler
req supplementary bonding, so what can i do ? i can
supplementary bond bathroom, kitchen to nearest
socket but what about central heating boiler ? where
does that start and end ?

regards

I sympathise with you. This sort of thing just goes on and on and its pointless arguing with them. Luck of the draw who does your survey. Just asking for asking sake. As all other posts have said there is no requirement in BS7671 to supplementary bond a boiler it is just something that is done as good practice by plumbers. However, if you must you must. Supplementary bonding to your CH boiler is probably simplest of the lot. Just link all the pipework immediately below your boiler together. Usually around 5 pipes. Put a bonding clamp on each one and loop together in 4mm2 g/y cable. Thats it. Dont need to link to board, earth bar or anything else.

 

the trouble im having is that this survey that i
had
done with these recommendations is part of my
mortgage, that is the work has to be done to satify
my
mortgage company, and he has put on his nikky
sheet
that bathroom , kitchen and central heating boiler
req supplementary bonding, so what can i do ? i
can
supplementary bond bathroom, kitchen to nearest
socket but what about central heating boiler ?
where
does that start and end ?

regards

I sympathise with you. This sort of thing just goes
on and on and its pointless arguing with them. Luck
of the draw who does your survey. Just asking for
asking sake. As all other posts have said there is
no requirement in BS7671 to supplementary bond a
boiler it is just something that is done as good
practice by plumbers. However, if you must you must.
Supplementary bonding to your CH boiler is probably
simplest of the lot. Just link all the pipework
immediately below your boiler together. Usually
around 5 pipes. Put a bonding clamp on each one and
loop together in 4mm2 g/y cable. Thats it. Dont need
to link to board, earth bar or anything else.

One thing to consider though. If the pipework to the boiler is not extraneous bonding it will cause it to become live in the event of a fault to other extraneous parts. Err, for .4 of a second I guess.

 

do you regard a boiler and cu pipes to be exposed conductive parts OR extraneous conductive parts ?

 

Extraneous

 

Extranposed part.

 

Pro

I know where your coming from...

Sine and Trip...This is a definite grey area....

Your boiler quite often has the gas main directly under it, as mine is.

You have the 10mm main bond "Electrical" connection to this pipe which goes directly to the boiler...

Is this not then Exposed conductive part.?

Now part of the electrical installation due to "safety electrical connection do not remove"

ppe

PS what size cross bonding of the pipes is Ok in the above situation. I always used 6mm. Last year went the napit route and was told 10mm needed ? ...you what..

 

As you've understood the simple requirement for the boiler, treat the kitchen sink just the same. There is no need to continue the link to a socket outlet.

You can then inform your mortgage company that the installation has been upgraded (or downgraded, depending on the point of view)to the previous (15th) edition of the Wiring Regs. . . . .

Pb

 

As you've understood the simple requirement for the
boiler, treat the kitchen sink just the same. There
is no need to continue the link to a socket outlet.

All the extraneous conductive parts should be connected to the exposed conductive parts through the MET and the equipotential reference point is at the MET. Local crossbonding of extraneous conductive parts serves no purpose unless it is also connected locally to the earthing system, ie: to the earth terminal of the circuits in the area of cross bonding. This provides an additional and shorter low resistance parallel path between the simultaeously accesible exposed and conductive parts. The equipotential reference point is brought to local connection to the earthing system and the result is a lower touch voltage.

In other words, if you want any benefit (very small) from the bonding in the kitchen connect it to the earth terminals of the circuits which might cause any of the bonded parts to become live during the disconnection time. For an electric cooker, and any other appliance fed from its own circuit that is likely to be 5 sec.

 

The purpose of supplementary equipotential bonding is to ensure all conductive parts (and circuit earths) remain at an equal potential (hopefully zero volts). In this way there is no chance of having 240 volts at the hot tap, reaching for a towel on the radiator at zero volts thus completing the circuit. Even if the bonding brought the radiator up to 240 volts at least they would be at the same voltage and the only path would be through the floor which is a lot better than straight to earth through a metal radiator. Thats how I understand it works anyway.

 

can do. It looks pretty if nothing else.

 

OSG pages 23 -26 i think.
no requirement to do any cross bonding other than in bathrooms(except for metal waste pipes which should be main bonded to MET.

 

no, not the same.
check 7671 Part 2. for definitions.
regards