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Discuss Compex Units course help and advice please in the Electrical Courses & Electrical NVQ's area at ElectriciansForums.net


EF Member

Recently done the 2019 Compex , the Velcro equipment board is an online assessment now with drop down menus and I failed the Ex01 part of this, is there anyone who can clarify the following for my knowledge please

Exd equipment can be used in zone 1 and 2 also
If I have a cable 3m long direct entry, IIC Gas group with any internal volume Exd box I use a barrier gland? , if the cable entry is more than 6mm thread I don't need an IP washer?

any help appredciated


Regular EF Member
Barrier gland is not required for Exe box. Exe by its very nature and design shall not contain sources of ignition. Barrier gland is required in this instance only for the light switch which must be Exd. IIc gas means you need the barrier only on the light switch in this case.

6mm thread will satisfy the minimum IP54 rating for Exe, but if the JB has a higher rating then you need to fit an IP washer to maintain the higher IP rating.

Metal JB with 6 threads - your CPC can double as earth. If it is non-metal and has an internal earthing plate then you need a lock ring, maybe a serrated washer. Non metal with no earthing plate then you need a banjo and IP.

Basically choose the JB or fitting to the gas group, the T class and the IP rating and then build each item up from there one by one.

Compex is based on minimum standards, as such your barrier gland will be a fail on Exe. Rule of thumb is use Universal gland for everything, barrier only where it is needed. Where a stuffing gland is needed then it must match the classification of the JB and the IP rating (dual Exe / Exd if it’s there).

What they used to tell you on the 5 day was to fit an IP to everything as it was not a fail, although it is a demerit on the refresher and could contribute to a fail!

Ps - I am basing this on the Velcro board refresher, 2018, if it has been changed since I know not.


EF Member

thanks for the reply, could you help me clarify the following please regarding Exd and barrier glands,

IIC Gas any internal volume Exd equipment needs a barrier yes
IIB and IIA greater than 2 litres needs a barrier
IIB and IIA less than 2 litres not required

Exde equipment does not need a barrier
What does the 3m cable rule mean

any help appreciated thanks


Regular EF Member
Based on the latest EEMUA toolbox guide your statements are correct.

The reason that Exde does not need a barrier is that the main protection of the equipment is Exd, but the cable entry is Exe. Basically you generally have a seperate Exe entry for the cables, using Exe terminals for the cable connections, which is sealed from the main part of the equipment which is Exd. Exe can not have sparking components, so negates the need for a barrier gland.

3 metre cable rule means that if the cable is >3m then you can use a standard Exd gland. <3m you need to use a barrier (IIa or IIb). IIc will need a barrier gland no matter what.

Refer pages 42, 43 on the toolbox guide for Exd gland selection.


EF Member
Thanks again for your info

Your reply refers solely to use of Exd quipment regarding barriers etc yes?

I’m thinking from memory that I had a 3m cable feeding a switch , can you remember if there was a requirement or situation presented where you had to use a barrier gland ? If I had a Exde switch I could eliminate the barrier yes

Just thinking here , it’s minimum standard


Regular EF Member
If the area is IIc and the equipment Exd, yes you need a barrier gland. If the cable is less than 3m in a IIa or or IIb zone then an Exd gland is NOT suitable. It has to be a barrier. Likewise if the volume on Exd is >2 litres you need a barrier.

The principle of Exde is that the cable termination is Exe whist the main protection of the equipment is Exd so a barrier is not required.


EF Member
What about serrated washers , would I fit these only on painted surfaces ? Or ..

On less than 6mm threaded entry’s or clearance holes on plastic boxes with an internal earthing plate

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