maintenance free junction boxes, who makes them? whats on offer?

[ericmark]

I first came across the maintenance free spring terminal in 1980, when working for a Dutch firm, by 2000 many panels were using maintenance free spring terminals and it seemed anything imported for Europe used them.

The vibration with any steel frame structure did result in screw terminals working loose, so it was an on going job to test terminals are tight, and it was included in the service schedule, however I have never seen a house serviced, even with an EICR I have not seen anything about checking screws for tightness.

So if the installation is not maintained, then it should be all or nothing, it does not matter if a sheet of plaster board needs removing to service the junction box, if even if the junction box is service mounted no one will ever check the terminals are tight.

But nearly every European control panel manufacturer makes a maintenance free version for the control cables, but every box I have opened the power cables still use screw terminals, so not really maintenance free, but reduced maintenance, one amp with a spring terminal is great, but as you go up in amps, service area of contact becomes important, so we move from the spring to the crimp.

So any box with cable restraint and crimp connectors is maintenance free, or when potted of course. I have used maintenance free cable joints using crimps all my working life, using epoxy lined shrink sleeve, and potted, although the old joints pre the shrink sleeve were around when I was an apprentice I never used them.

There seems to be an idea maintenance free is new, it is not, maybe not as old as the hills, but been around all my working life and now retired.

What has changed is type testing, when I started we did not need to look for BS 5733 or any other standard when using maintenance free joints. As @Risteard says if you change something with a type tested item then it loses its type tested status, so if you fit a non recommended door bell transformer into a consumer unit then it is no longer a consumer unit, it is just a distribution unit, I have seen people argue as such not covered by Part P, but that is really clutching at straws.

But it raises the question can or should we use non type tested equipment in the home? We saw so called socket protectors sold in nearly every supermarket, non had BS 1363 stamped on them, I would remove when I did an inspection and put in a carrier bag, and hand to some one on leaving for disposal, saying these do not comply with regulations, I would never bin them myself.

However I have seen the local council social services insist on their use, and although now banned in Welsh national health places they were at one time seen in every dentist and doctors waiting room.

So how important is type testing, and can we use non type tested components? I have used silicon sealant in a tube before now to make a cable joint, it takes a long time to completely go hard, but no water can get in and once hard it is better than original cable, same covering in silicon sealant then insulation tape, once sealant has gone off even if tape removed no access to live parts, there is no BS number for a DIY joint like that, but I knew where used it was safe.

Even a simple blue pre-insulated crimp is not to standard unless crimped with the crimp pliers supplied by the manufacturer of the crimp. Only GEC large steam turbines of all the firms I worked for calibrated the crimp pliers and insisted only one manufacturer of crimps used.

Let him without sin cast the first stone.

 

[ericmark]

I first came across the maintenance free spring terminal in 1980, when working for a Dutch firm, by 2000 many panels were using maintenance free spring terminals and it seemed anything imported for Europe used them.

The vibration with any steel frame structure did result in screw terminals working loose, so it was an on going job to test terminals are tight, and it was included in the service schedule, however I have never seen a house serviced, even with an EICR I have not seen anything about checking screws for tightness.

So if the installation is not maintained, then it should be all or nothing, it does not matter if a sheet of plaster board needs removing to service the junction box, if even if the junction box is service mounted no one will ever check the terminals are tight.

But nearly every European control panel manufacturer makes a maintenance free version for the control cables, but every box I have opened the power cables still use screw terminals, so not really maintenance free, but reduced maintenance, one amp with a spring terminal is great, but as you go up in amps, service area of contact becomes important, so we move from the spring to the crimp.

So any box with cable restraint and crimp connectors is maintenance free, or when potted of course. I have used maintenance free cable joints using crimps all my working life, using epoxy lined shrink sleeve, and potted, although the old joints pre the shrink sleeve were around when I was an apprentice I never used them.

There seems to be an idea maintenance free is new, it is not, maybe not as old as the hills, but been around all my working life and now retired.

What has changed is type testing, when I started we did not need to look for BS 5733 or any other standard when using maintenance free joints. As @Risteard says if you change something with a type tested item then it loses its type tested status, so if you fit a non recommended door bell transformer into a consumer unit then it is no longer a consumer unit, it is just a distribution unit, I have seen people argue as such not covered by Part P, but that is really clutching at straws.

But it raises the question can or should we use non type tested equipment in the home? We saw so called socket protectors sold in nearly every supermarket, non had BS 1363 stamped on them, I would remove when I did an inspection and put in a carrier bag, and hand to some one on leaving for disposal, saying these do not comply with regulations, I would never bin them myself.

However I have seen the local council social services insist on their use, and although now banned in Welsh national health places they were at one time seen in every dentist and doctors waiting room.

So how important is type testing, and can we use non type tested components? I have used silicon sealant in a tube before now to make a cable joint, it takes a long time to completely go hard, but no water can get in and once hard it is better than original cable, same covering in silicon sealant then insulation tape, once sealant has gone off even if tape removed no access to live parts, there is no BS number for a DIY joint like that, but I knew where used it was safe.

Even a simple blue pre-insulated crimp is not to standard unless crimped with the crimp pliers supplied by the manufacturer of the crimp. Only GEC large steam turbines of all the firms I worked for calibrated the crimp pliers and insisted only one manufacturer of crimps used.

Let him without sin cast the first stone.

 

[JohnW2]

They are Mf for life. After that you will have to replace it !

Quite so

They probably should be called "UM" ("Unmaintainable"), or something like that. With a traditional screw-terminal JB, if the connections ever loosen (not something I can personally recall ever having experienced), one can 'maintain' them by tightening the screws, but with a spring-terminal one, in such a situation there is no way to 'maintain', so one would have to 'throw away and replace'!

Kind Regards, John

 

[JohnW2]

The vibration with any steel frame structure did result in screw terminals working loose ...

Yes, one can see that in any environments subject to significant vibration, spring terminals certainly offer a theoretical advantage - but that does not apply to the fixed wiring of domestic (or commercial) electrical installations, and probably not even in many industrial ones. Situations within "things which move" (e.g. 'vehicles', in the widest sense) and things which contain motors or other moving parts (e.g. kitchen/utility appliances)seem to be the situations in which vibration needs to be considered.

... so it was an on going job to test terminals are tight, and it was included in the service schedule, however I have never seen a house serviced, even with an EICR I have not seen anything about checking screws for tightness.

Quite - and, even in the non-domestic environments, at least one could, if one so wished, check the tightness of terminal screws - whereas with spring terminals I'm not sure that there is any way of 'checking' them which doesn't carry a risk of damaging the connector or compromising the connection. I would also imagine that, in environments which have a vibration risk, one does all one can to avoid 'inaccessible' joints of any kind (and probably does them by soldering/welding {or maybe crimping} iuf they are unavoidable).

So if the installation is not maintained, then it should be all or nothing, it does not matter if a sheet of plaster board needs removing to service the junction box, if even if the junction box is service mounted no one will ever check the terminals are tight.

Again, quite so. As you say, if screw-terminal joints are considered unsafe if inaccessible, then they really should also be considered unsafe (i.e. 'banned') even if 'accessible' - since, as you say, it's very unlikley that anyone is ever going to 'check' most of them.

... I have used silicon sealant in a tube before now to make a cable joint, it takes a long time to completely go hard, but no water can get in and once hard it is better than original cable, same covering in silicon sealant then insulation tape, once sealant has gone off even if tape removed no access to live parts ...

Just to repeat a warning about that, relating to what I have learned by bitter experience .... standard silicone sealants (as bought in a DIY store or builder's merchant) give off acetic acid whilst curing (over a period of at least a few days) and, if it is used on bare conductors, that can be (again, bitter experience!!) increase it's conductivity enough to trip an RCD. All is fine (and IR very high) once it has fully cured, but one has to be prepared to wait for at least a few days before the cable/whatever can be energised without tripping an RCD.

Kind Regards, John

 

[ericmark]

Yes agree silicon sealant not best idea. However you have seen main point

Again, quite so. As you say, if screw-terminal joints are considered unsafe if inaccessible, then they really should also be considered unsafe (i.e. 'banned') even if 'accessible' - since, as you say, it's very unlikely that anyone is ever going to 'check' most of them.

And you can't get 100 amp maintenance free connectors on the main isolator, or even RCBO's with maintenance free connectors, so if nothing is tested for tightness what is the point in any maintenance free in a normal house?

Yes steel frame building with motors, but brick built house, pointless.

 

[JohnW2]

... And you can't get 100 amp maintenance free connectors on the main isolator, or even RCBO's with maintenance free connectors, so if nothing is tested for tightness what is the point in any maintenance free in a normal house? ... Yes steel frame building with motors, but brick built house, pointless.

As you will realise, I personally agree.

Kind Regards, John