Post installation failure

[targaid]

We've just had our loft floor raised to cover new insulation.

Since the installers finished we've had trouble with the shower. It became a bit temperamental having to be switched on and off a couple of times before it would work. Tonight it's totally failing to operate.

When we switch on the mains power outside the bathroom the light in the switch lights up, but when we switch on the shower the light in the mains switch goes off. I've had a look in the loft for damaged cables but I can't see anything obvious. Can anyone advise what might be causing this problem and how to sort it, please?

 

[EFLImpudence]

Check the connections in the switch.

 

[targaid]

Check the connections in the switch.

No sign of an issue, though I'd have been surprised if it had. It was working fine the morning the work was started and playing up afterwards. It could be a coincidence but it doesn't seem likely. I can't find any evidence of damage in the loft but it's a bit of a rats' nest of cabling and I'm not sure where they all go. Apart from recently discovering that whoever wired it had left an exposed live wire connected to the hall light with the other end wrapped around a joist in the loft.

 

[BlueLoo]

As a wide guess, they haven't buried the shower cable in insulation so that it has overheated?

(Depends on size of wire, rating of shower, etc,etc) but it could be like mine which is a 6mm2 wire on the edge of its rating and sat on top of the insulation which does get warm when in use and which i will upgrade to 10mm2 as soon as i do what you are doing.

Edit: also, they might have pulled the cable on either end leading to a loose connection...

 

[targaid]

I don't think that's an issue, Blue as it's immediate so no time for anything to be heating up and cutting out. I assume your edit is the more likely option. I'm just hoping not to have to lift the newly laid flooring lol

 

[BlueLoo]

If you lift the flooring, wear rubber boots and use insulated tools....... !

 

[targaid]

The installer has 'strongly' recommended I not attempt to lift the floor. Apparently it can be 'tight' and 'difficult to do' without experience.

 

[delmel]

Check the wiring and for loose terminals in the Switch and the shower, they may have had a good tug on them creating a loose connection.

 

[plugwash]

The fact that the light on the switch is going out when load is applied indicates that there is a high resistance, either in the switch or upstream of the switch.

An overheated cable is unlikely to cause this, when cables overheat it's generally the insulation that melts not the conductors itself.

I would be inspecting the connections in the switch and at the consumer unit, if they all seem good then I would suggest replacing the switch is the next step.

I guess it's possible there is a joint burried in the loft somewhere that has been disturbed by the insulation work, but afaik such joints in shower circuits are pretty unusual.