TT advise

[PS Electrics]

Nobody is saying it's not a good idea or that it's not good practice, but it's not mandatory.

OK

My take on the precautions to implement when omitting an up front RCD on a TT system. Tails Clamp seems an absolute necessity in my view.

There wasn't a switch to strictly use a metal consumer unit, but one made of non-combustible material.
You could still use a plastic Cu, in fact, plastic ones are preferred in some locations.

Just quoting what the article said.

Just because you may have double insulated Swa isn't a good enough reason to omit the upfront Rcd that's being used for fault protection.

The suggestion of double insulated SWA was to avoid the joint that would be required to double insulated tails not as a reason to avoid RCD protection. Omission of up front RCD protection can be considered if the tails are fully protected (from contact to the earthing system) up to the point of termination. My point was that I wouldn't consider a joint as meeting that requirement.

PS Electrics said:
Should we NOT be earthing the armoring in this case if doing away with the RCD protection? On a TT we won't meet the disconnection time requirement for an earth fault and so if the SWA is earthed and such a fault occurred we have just made the whole installations earthing live!


The Swa armour Must be earthed, otherwise a penetration of the armour could cause fatal electrocution.

My point was if we have an SWA with no RCD protection then connecting the SWA armour to the Installations earthing arrangement would be a bad idea.

As I said installing an up front time delay RCD avoids all the above issues.

 

[mainline]

OK

My take on the precautions to implement when omitting an up front RCD on a TT system. Tails Clamp seems an absolute necessity in my view.

It is not mandatory to fit consumer unit tails clamps, it's an option.

Omission of up front RCD protection can be considered if the tails are fully protected (from contact to the earthing system) up to the point of termination. My point was that I wouldn't consider a joint as meeting that requirement.

What should be considered is the requirement for that sub main swa to meet the requirements of bs7671.
If the swa isn’t capable of meeting the requirements then it shouldn’t be connected at all.

My point was if we have an SWA with no RCD protection then connecting the SWA armour to the Installations earthing arrangement would be a bad idea.

You didn’t actually say “the installation “.

 

[PS Electrics]

You are talking about tails not about the swa which is what the Op is asking about.

Treating this as the same scenario as a consumer unit located more than 3m from the intake.

Lots of complications which is why I recommended an upfront 100mA RCD at the intake.

You didn’t actually say “the installation “.

I didn't but respondent said the SWA should be earthed with no RCD and there is only one earthing arrangement and that would be the installations.

If the swa isn’t capable of meeting the requirements then it shouldn’t be connected at all simple.

Agree I was just pointing out it would be a bad idea.

 

[mainline]

Treating this as the same scenario as a consumer unit located more than 3m from the intake.

It's not the same scenario, though.

Tails more than 3mtrs can be overcome by using a fused switch and rcd board, whether the earthing system is TN or TT.

In the case of the OP the sub main swa is TT so you haven't got that benefit.