Greenhouse socket supply

[mcm]

Just wanted to see if the following is the correct way to supply a socket in a greenhouse.

Firstly the supply is tn-s and the customer wants a socket in the greenhouse for a heater. Now the supply to the greenhouse would come from the shed supply as it’s on a separate circuit. I was thinking of:

Run 2 core 2.5mm swa from shed cu to greenhouse using armour as earth in supply cable.
Terminated cable into ip rated double socket.
Insulate gland at greenhouse end and fit earth rod to give an earth due to bonding to the greenhouse.
Fit rod and run 10mm earth into socket and also bond greenhouse at same time.

Is this acceptable in regards to the bonding?
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[mcm]

Any suggestions?

 

[Engineer54]

You first need to check if the greenhouse frame is an extraneous earth (under 23,000 ohms). You wouldn't need an earth rod in either instance. Hopefully the socket will be RCD protected at the shed supply?? If you do want to bond or earth this steel/allum' frame, run in a 3 core SWA and use the third core!! Bit different if it was a TNC-S, but as you say, this is a TN-S system!!