New fuseboard mounted on case of old metal clad board

[Dazza1976]

Hi all,

If replacing an old metal clad consumer unit with a new Plastic one, where the metal conduit is used as the CPC throughout the installation, is it acceptable to mount the new unit directly over the case of the old unit, linking the two with a length of 16mm earth, in order to keep the earth continuity ??

A friend of mine whos company has a contract with the council, says they always do it this way, because it can sometimes be a right pain and fairly time consuming disconnecting the conduit from the old consumer unit and reconnecting to a new metal clad one.

Has anyone else ever done it this way ?

 

[telectrix]

i would think that as long as the earthing and IP rating is satisfactory and test results are acceptable, no problem.

 

[malcolmsanford]

Is there a reason you want to pick up the continuity with a piece of 16mm^ ?

Have to admit I'm a little confused by how your going to fit this. Are you going to strip all the internals out of the old metal clad just leaving an empty box with conduits going into them.

If so how are you securing the new board onto the box.

 

[Dazza1976]

I havent said i was going to do this, its how my friend does it at the company he works for.

Yes thats correct he strips out all the internnals just leaving the box with the earth bar and conduits going into the box, he keeps the two screws from the cover of the old box and drills 2 new holes in the back of the new box the same distance apart as the ones for the old cover, and simply uses the old screws to secure it.

The 16mm main earth would go from the main earth bar to the new unit, and then another length of 16mm earth between the earth bar in the old unit and the new unit, not sure why you are querying about using 16mm ??

 

[BlueToBits]

I agree with Telex and malcom. The (empty) old board effectively becomes an adaptable box. Providing that the resulting 'enclosure' meets all the requirments of such, there should not be a problem. 16mm^ is possibly overkill as a means of providing earth continuity, and of course, the conduit should not be used as the main earth conductor without careful consideration.

 

[malcolmsanford]

Then to be honest I would not do this. Is the old DB flush or surface.

If it is surface, I would not want my CU secured by perhaps a couple of front cover screws to be honest. Also I would be worried about the IP situation, unless you get an exact fit you are surely going to have gaps that will need to be filled.

If it's a flush old mounted DB then you may get away with it.

 

[tonys]

If the conduits with the original Dis-board are surface mounted, then that's a lash job.

 

[High Tower]

Why are anything to do with council jobs such a pain in the arse?

Suppose this is the only method without destroying half of the wall!

 

[Engineer54]

If these are council properties then the conduits will be buried. I've seen this done many times the new CUs always being quite a bit larger than the buried Wylex box .....

 

[BlueToBits]

If the conduits with the original Dis-board are surface mounted, then that's a lash job.

It depends on the circumstances and many other factors. Just because it's unusual does't mean it's wrong or unprofessional. If it results in a safer and more usable installation at an affordable price it's far better than not doing it at all because it's too expensive.

 

[tonys]

If these are council properties then the conduits will be buried. I've seen this done many times the new CUs always being quite a bit larger than the buried Wylex box .....

Ive worked in excess of 2000 council properties and seen plenty with surface mounted metal Wylex Dis-Boards with metal conduits.

Now if someone is to lazy to use a bush spanner or pair of grips to release what, 6 bushes, then it just goes to show the industry is becoming full of semi skilled people.

Fitted plenty of skeleton kits in metal cabinets as well, not saying its clever to work on domestic properties, its the lowest skilled work with in the industry.

Not a pop at you engineer, cause your on in the upper league when its comes to electrics. But when people try and justify bullcrap about xyz it don't hold water.

Blue ToBits

If the old Dis-board is flush, then not an issue, but to piggy back a Dis-Board is a lash.

 

[Engineer54]

In fact, i've done something quite similar recently for a friend of mine over here. The buried conduits are not metal but standard PVC. Plus there were 2 such flush CU back boxes not just one.

Anyway here are a couple of pictures of what i did for him...

Before....

After....

The new CU was for a split load design, so had to later replace the neutral and ground bar arrangement for a standard non split one. So now all the individual circuit neutral and earth conductors have there own terminal connection...

 

[Engineer54]

Perhaps i should explain, one of the old CUs was from an unused heating/a/c supply, which i disconnected/removed from that supply at source. Basically then combined the 3 radial circuits from that CU to the general purpose new CU which gave my friend 3 extra double socket outlets that he didn't have use of before....

 

[tonys]

Well done.

Ones like that Ive found over here, were very old dual units (50 years old) fed by a 6mm 4 Core Heavy Duty MICC.

 

[malcolmsanford]

Ive worked in excess of 2000 council properties and seen plenty with surface mounted metal Wylex Dis-Boards with metal conduits.

Now if someone is to lazy to use a bush spanner or pair of grips to release what, 6 bushes, then it just goes to show the industry is becoming full of semi skilled people.

Fitted plenty of skeleton kits in metal cabinets as well, not saying its clever to work on domestic properties, its the lowest skilled work with in the industry.

Not a pop at you engineer, cause your on in the upper league when its comes to electrics. But when people try and justify bullcrap about xyz it don't hold water.

Blue ToBits

If the old Dis-board is flush, then not an issue, but to piggy back a Dis-Board is a lash.

Total agreement with you Tony if the board is flush as both of us suggest then yes you can get away fitting a surface mounted board over it.

If it's not a flush board again agree entirely anything other than removing it would be a total lash up.