gland swa at both ends?

JohnS888 · Oct 22, 2020

Just wondering if others make off their armoured glands at both ends has have worked with sparks previously and seem to have different takes on it. My thoughts are that if glanded and so earthed at origin is acceptable so if for example supplying a sub board in garage a plastic gland at the board is fine and SWA glanded at origin of supply so house board is fine?

derek · Oct 22, 2020

A gland at both ends provides additional cable restraint that a stuffing gland won't to the same level. Should always gland the supply side as a minimum in my opinion. Personally I would always gland both ends, even into a plastic db. Obviously if the armour is also used as CPC then there must be continuity somehow.

ipf · Oct 22, 2020

I'd call that disgraceful, sub standard work. 134.1.1 for starters.

Grant1987 · Oct 22, 2020

ipf said:
I'd call that disgraceful, sub standard work. 134.1.1 for starters.

Should always gland both ends. Poor workmanship with plastic stuffers

cliffed · Oct 23, 2020

Yea should gland both ends,only exemption is if it’s a TT system,to separate the Earthing.

littlespark · Oct 23, 2020

Why do you think swa glands come in packs of 2?

the right tools for the right job.

pc1966 · Oct 23, 2020

As above, plastic glands for TT isolation purposes.

Maybe other odd cases, such as small 3-core SWA in to an outdoor light where they did not really expect a metal gland or provide adequate space for one.

ferg · Oct 23, 2020

Regulation wise my memory tells me that the SWA should be glanded / earthed at at least one end and preferably the supply end.

I think this is why some people think that glanding at only one end is acceptable.

JohnS888 · Oct 23, 2020

ferg said:
Regulation wise my memory tells me that the SWA should be glanded / earthed at at least one end and preferably the supply end.

I think this is why some people think that glanding at only one end is acceptable.

That's my point Ferg. I possibly understand the use of SWA gland for adding support to cable or using the SWA for earthing but in terms of an actual shock risk if cable aupported i fail to see one. A live conductor needs to come in contact with the steel sheathing and if this is earthed at supply end all good.

JohnS888 · Oct 23, 2020

littlespark said:
Why do you think swa glands come in packs of 2?

the right tools for the right job.

You've not actually explained the logical reason why though if cable supported and not using SWA for earthing?

pc1966 · Oct 23, 2020

Even if you have a CPC core it is still better to gland both ends so the armour is providing a CPC path. Not just in cases where the armour may not meet adiabatic limits, but just as it reduces the risk of an open CPC if you have parallel paths.

JohnS888 · Oct 23, 2020

pc1966 said:
Even if you have a CPC core it is still better to gland both ends so the armour is providing a CPC path. Not just in cases where the armour may not meet adiabatic limits, but just as it reduces the risk of an open CPC if you have parallel paths.

Now that explanation and reasoning I can go with ?

pc1966 · Oct 23, 2020

While it is not a common electrical requirement as such, if you correctly terminate the outer screen to the metal work where a cable enters by a gland or connector providing 360 deg contact as you get much better screening of high frequency noise from a EMC perspective.

In power systems this is only likely to be lightning surges, but it is a far more critical requirement for coax cable where taking the braid/shield in as a "pig tail" is very bad news from a radio screening and constant-impedance perspective.