Generator installation and earthing arrangements

[Tony Way]

Hi.

Father-in-law has arranged for his local bowls club to have a generator to supply power to club house, as DNO wanted mega bucks. Genarator bought privately and they want to do all of the prep work themselves before more local than me sparks installs cu etc.

Generator will be in separate garage 15m away from building. Fed via underground SWA. Only fired up when people using facility.

He asked me what the earthing arrangements should be. I looked at section 551 and still have some questions.

Does the genset need its own TT connection at the SWA termination so that an RCD can be used to protect SWA?
Assuming that terapin (it's and ex school temporary classroom) needs RCD protection to circuits it should have a separate TT rod and also bonding to all maetal framework underneath, as it is on piles and metalwork is easily accessable. - Would that count as structural metalwork?

Many thanks

Tony

 

[Guest123]

What size is the geney you have?, 10, 20 KVA etc

 

[Tony Way]

Not sure Lenny. I would think knowing their lack of willingness to spend money, it would be in the <=10 KVA

 

[Guest123]

The size af the geney makes a difference to my advice.

Larger geneys (usually above 10KVA) will have N&E joined at the alternator box providing you with a TN-C-S connection which obviously changes the earthing and bonding arrangements.

Smaller units are generally TN-S configured (star point connected to chassis) as you are running a 3rd wire in your sub-main, this is where additional earth rods are needed to reference the framework to earth. If you cant get rods in due to ground conditions etc, you need to alter the connection to provide a TN-C-S connection to make the geney's RCD work.

Like I said depending on the size of the geney it may already be done.

My usual method is to install a rod at the geney, and an additinal rod at the CU at the end of the sub main.

And yes all steelwork should be bonded.

 

[Tony Way]

Thanks Lenny, most helpful