Earthing Air Conditioning Pipes

[RobFurn]

MEB needs to connect from MET to where the service enters. 40m is pushing it resistance wise, what size service? 10mm is not necesserilly correct. The MEB needs to be sized minimum to table 54h which relates to the neutral of the supply - also consult the DNO as they can overrule this.

The thing is the Pipes fitted to the the compressor are bonded to the Earthing teminal in the compressor, I have done a continuity test. So in effect the supply cables earth when connected to the earthing terminal of the compressor is bonded to the pipes. So as long as the earth cable in the supply cable is large enough to satisfy Table 54H I think Im covered. Right?

20A Max BTW

 

[Spark123]

What size is the incoming supply? What size neutral?

 

[RobFurn]

What size is the incoming supply? What size neutral?

You talking about the incoming supply to the DB? if so I cant remember Im in the office but I guess your going to tell me that the MEB has to comply with table 54 H for PME i.e. 35mm or less then your MEB has to be 10mm . Between 35 and 50 it has to be 16mm and so on. Right?

 

[Spark123]

A MEB is sized according to the size of the incoming supply the the premises, in the case of TN-CS it is relative to the neutral conductor.

 

[RobFurn]

The things you learn on this site
Cheers 123. Bet this is the same in the Red book, havnt got mine yet.

Anway assuming the earth or SWA equivalent agrees with table 54H do you agree with my scenario regarding satisfying the bonding of the AC pipes via the supply cable earth?

 

[Spark123]

I'd need to know more about the installation, is the compressor housed in a separate building? What material and how are the pipes run into the main building? Is there a risk of the AC pipes introducing a potential different to that of the installation into either building?

 

[RobFurn]

The building is a largish warehouse with a few offices built inside. Its brand new and is metal clad inside and out with about 10" of insulation in-between, not a brick in sight (cheap). The compressor stands on a concrete pad outside in a cage. The supply cable comes from the plant room about 40m away (slightly less actually). The pipes will enter the building through the cladding. The pipes will then be suspended at a height until they meet the condenser units (3 of) in a large office.

 

[RF Lighting]

Is it a steel framed building?

If so is the structural steelwork bonded in accordance with table 54H (table 54.8 of the new regs)?

 

[Spark123]

I'd have thought as the compressor is sat on the general mass of earth outside it will probably be considered extraneous. Would it be correct to think this should be bonded as you would a separate building? - you'd need to enquire with the manufacturers/suppliers. TN-CS isn't the nicest one where you have big lumps of metal outside too.
I'm of the opinion that given the above, the pipework should be MEB'd where it enters the warehouse.

 

[RobFurn]

I'd have thought as the compressor is sat on the general mass of earth outside it will probably be considered extraneous. Would it be correct to think this should be bonded as you would a separate building? - you'd need to enquire with the manufacturers/suppliers. TN-CS isn't the nicest one where you have big lumps of metal outside too.
I'm of the opinion that given the above, the pipework should be MEB'd where it enters the warehouse.

So you would recommend running a seperate Earth to bond the pipes where they enter the building?

 

[RobFurn]

Is it a steel framed building?



If so is the structural steelwork bonded in accordance with table 54H (table 54.8 of the new regs)?

Yes its a steel frame building,

Dont know Im over ther in a bit I will take a look and I may take some pics, I know how you love pics. Could open a can of worms this one if every AC units pipes have to be main bonded. I would bet the vast majority installed are not.

 

[ColJack]

how large is this air con unit?
we make industrial ones and the compressor set, and pipework are not earthed, they sit on rubber AV mounts and the pipes are clamped in rubber pipe clips.. the only point of earthing is incidental where the condenser coil is mounted to the rest of the unit..

 

[r.bartlett]

Having been in the air con industry since 82 I have yet to see any copper pipes run between indoor/outdoor bonded. There have been many discussions on this on the refrigeration/ac boards.

I have also yet to receive a call from a customer who has had an a/c installation (our or not...) condemned by an electrical inspection due to lack of bonding on the refrigeration pipes

Cheers

Richard

 

[r.bartlett]

how large is this air con unit?
we make industrial ones and the compressor set, and pipework are not earthed, they sit on rubber AV mounts and the pipes are clamped in rubber pipe clips.. the only point of earthing is incidental where the condenser coil is mounted to the rest of the unit..

Isn't there some form of earthing done within the terminal box?

Cheers

Richard

PS what make are we talking about ?

 

[Spark123]

I'd have thought as the compressor is sat on the general mass of earth outside it will probably be considered extraneous. Would it be correct to think this should be bonded as you would a separate building? - you'd need to enquire with the manufacturers/suppliers. TN-CS isn't the nicest one where you have big lumps of metal outside too.
I'm of the opinion that given the above, the pipework should be MEB'd where it enters the warehouse.

So you would recommend running a seperate Earth to bond the pipes where they enter the building?

Reading between the lines I'd have thought the pipes should be Main Equipotentially Bonded where they enter.