Bonding oil supply to outside boiler

[Adam White]

Does the oil supply to a boiler which is outside the house need bonding since it doesn't actually enter the house and so is not an incoming supply?

[John Rumm]

If it does not enter the house, then its not capable of introducing a potential into the house's equipotential zone, so no.

(however the flow and return pipes presumably do, and they would constitute extraneous metalwork that should be bonded close to where they enter)

[Tim Watts]

I wonder if their are any addition oil regs that might want it bonded - or spiked to the ground.

The reason I say that is there used to be an LPG tank at my house - the pipe that went to that was bonded to a TT spike near the tank.

Now that's gas (spark risk of ignition) and not oil but just wondering...

[John Rumm]

Spike to the ground (i.e. earthed) is not the same as bonded though - a metallic connection to a local earth spike would not mitigate the need for bonding should there be a conductor from the tank to the house, since it could still introduce a (different) potential into the building via the fuel pipe than that say of the TN earth.

So if there is no connection from the tank to the house, then it can't bring in a potential into the house and hence there is no need for bonding into the house equipotential zone.

(even if the tank etc should itself be earthed for other reasons)

Indeed and there may be good reasons for doing that, and in the case of more elaborate systems supplementary EQ bonding all of the bits of it together (tanks, valves etc) as well.

The HSE have a bit to say on this:

Pg 31

"Bonding and earthing Static electricity

134 Static electricity is generated when movement separates charge which can then accumulate on plant and equipment, and on liquid surfaces. If the plant is not earthed or the liquid has a low electrical conductivity, then the charge may be generated faster than it can dissipate. Eventually, there may be an electrical discharge or spark. If this has sufficient energy it could ignite a flammable gas or vapour.

135 To minimise the accumulation of electrostatic charge and prevent incendive sparks, all metal parts of the storage installation should be bonded together and earthed. A maximum resistance to earth of 10 ohms is recommended. It should be possible to disconnect the earthing facilities for periodic test measurement.

Further advice on earthing and bonding is in BS 7430: 1991 Code of practice for earthing "

(in spite of the comment at the end, BS 7430 does not appear to have anything to say about fuel storage tanks)

Yup, you could also have requirements for lightening protection etc.

[ARW]

As the oil supply will propably be connectected to the cpc of the boilers power supply due to the copper pipework I would say it needs bonding.

[John Rumm]

I would bond the flow and return pipes where they enter the house... that ought to cover the requirement. (as you say the CPC to the boiler will also return to the MET - making the point rather moot)