X3 isolator switches blown for zip inline water heater

[Jakegood]

Hi,

Got sent to a job today at student halls of residence. They have had 3 45 amp isolator switches blow in the last month for the zip inline water heater.
As shown in pictures, the water heater is being fed by a B40MCB and then in to a 45 amp isolation point above the door, then to the heater with 10mm.
The students keep the isolator switch on all the time, and have the setting on the heater at 55, the highest setting.
Would the fact that it’s bwing left on 24/7 through the isolator be the issue? Or is it just dodgy switches? The cable all looks fine and tests out ok. Just changed the switches and was fine. Just want to know if it being left on all the time would do this??

 

[chris gray]

What does ‘blow’ actually mean?
And what is it’s load?

 

[littlespark]

The students were probably playing with the switch.... Holding it at the half on- half off position listening for the crackle.

Looking online for those heaters, I think its the Zip Dex12 retailing at over £400.
Data specs show power rating at 11kW That could be the problem. Check the rating of the heater you have there.
I first found the Zip Dex…. which was rated at 27kW! Couldn't be that one

 

[Jakegood]

The switch is no longer functional. Need to have another look to find out if it is a DEX12 or DEX?

DEX12 rated current: 38/48
DEX: 26/39

Think it is possible that they have been playing around with the switches.

 

[Jakegood]

If it is 11KW would it be best to put the heater on a 50 amp mcb with a 50 amp isolator?

 

[Toneyz]

I take it you mean the actual switch mechinisum and not the cable at the termination screws.

 

[Jakegood]

Correct.

 

[123]

What size of cable is being used?

 

[Jakegood]

10mm

 

[Strima]

Does it need an isolator?

 

[snowhead]

Have the cable ends at the 45a isolator been cut back to clean copper before reterminating?

 

[suffolkspark]

Hager.... I just sicked in my mouth

 

[richy3333]

Those Hager switches are rated at 50A. Speak to Hager technical?

 

[Wilko]

The switch is no longer functional...Think it is possible that they have been playing around with the switches.

Looking at the switch it seems to be 50A rated, but mechanically they may not be teenager rated.
Edit - just read @richy3333