Fittings rated for continuous duty?

[vitoboy]

Hi all
So had some issues lately related to high current fittings .. dp switches mostly.
A number of electric boilers of various ratings .. from 7kw on up burning out their isolators .. the last one this week was a 7.5kw electric boiler running on a 6mm t&e cable 4m long from a 32A MCB .. 50A dp switch isolator.
No sign of cable overheating at the boiler (even though the terminal block is by the output pipe) . No sign of cable over heating at the consumer unit.. no tripping of the 32A mcb ..
So I understand the the cable is rated to carry over the 32.5 ish A which is max load .. mostly the boiler is modulating and no using anywhere near full power.
Now i know that there are issues with various 13A sockets that are not rated to supply 13A continuously 24 7 .. and these have caused problems with things like car charging.. we use all Hager fittings which I believe are all rated for continuous duty of there rated current... but many manufacturers sockets are not .. my question is are many dp switches and other fittings not rated for continuous duty at their started rating.. and this is causing them to fail at much lower loadings .. and if so how do I find out the continuous duty rating of such fittings.. I believe they should be published ..but a quick search tonight I can't turn up any ratings.
I know at the installation stage it's easy to over rate these things .. which I guess is why the installer for the 7.5kw boiler fitted a 50A dp switch .. but it still failed.

All thoughts greatfully accepted

Ta
Vito

 

[timhoward]

I prefer the Crabtree, they are easier to fit giving a little more room to maneuver 10mm cable into position. They also have a deeper feed in for the cable & if I remember correctly 2 securing screws per 'pin'. I would always prefer to fit a wall mounted isolator but few customers will (understandably) wear the additional cost of chasing, plastering etc.

I agree, Crabtree are the best. A further handy tip is that the Mk 50A isolator and Crabtree screwdriver positions are different by 90 degrees.
If some muppet has fitted either of them in a certain orientation right next to a wall it is almost impossible to tighten the back screws and it's always better to swap to the other brand.

 

[Lucien Nunes]

I don't fit showers or cookers so I haven't looked at switch offerings recently, but are there any where the switch mechanism fits into the box first and then a cover fits over the top, gridswitch style, like some of the 1960s / 70s types? Thinking back to the traditional MK portrait 2G cooker switch, you would put the cables into the terminals, seat the switch mechanism and then tighten from the front, so that once tightened it wouldn't be disturbed.

 

[Eddy Currents]

One thing I didn't mention and that is decreasing quality.

This is sometimes intentional and is called planned obsolescence, you don't see it as much with electrical accessories due to the safety aspect but some countries aren't as concerned with safety but either way they can still reduce quality even if keeping them safe

There is an interesting video which shows the history of the light bulb and the "Phoebus Cartel" where all manufacturers got together to reduce the lifespan of light bulbs to increase profits...

 

[vitoboy]

I don't fit showers or cookers so I haven't looked at switch offerings recently, but are there any where the switch mechanism fits into the box first and then a cover fits over the top, gridswitch style, like some of the 1960s / 70s types? Thinking back to the traditional MK portrait 2G cooker switch, you would put the cables into the terminals, seat the switch mechanism and then tighten from the front, so that once tightened it wouldn't be disturbed.

Nope

 

[vitoboy]

This is sometimes intentional and is called planned obsolescence, you don't see it as much with electrical accessories due to the safety aspect but some countries aren't as concerned with safety but either way they can still reduce quality even if keeping them safe

There is an interesting video which shows the history of the light bulb and the "Phoebus Cartel" where all manufacturers got together to reduce the lifespan of light bulbs to increase profits...

I don't think there is a conspiracy here .. but I do think 5he sort of loadings we are talking about with things like electric boilers and single phase car chargers have just never been seen before .. I was looking at a 14kw electric boiler today ..so 14000÷230=60.8A .. but the paperwork with it says must be installed with an 80A circuit.
If its a holiday house the tenant may well turn the heating on max for days .. after all its free for them.
Hell.. that's the size of a house supply these days .. let alone a flat at 60A probably.
These boilers are used where there is no gas .. so the property will likely be cooking on electricity also .. put on a kettle .. toaster .. boiling water tap ..coffee machine .. times that by 8 or 10 flats in a building even if they are on 80A supply and soon things are going ---- up so to speak..