Faulty light switch causes shower pump to start up

[sparkol]

Went to look at a job where the customer was complaining of his bathroom lights working intermittently and also that sometimes he was hearing ‘a loud noise like thunder’ when he turned his bathroom lights on.


Found that the connection in the light switch was ropey, and when the switch is partially open - i.e. when it is arcing across the contacts in the switch, the shower pump in the bathroom cupboard starts up for a couple of seconds!


My question for the kind users of this forum is… WTF?


The shower pump is on the same circuit as the bathroom lights but is obviously wired with permanent L+N (not into the switched L+N feeding the bathroom lights).


The shower pump is starting up for a couple of seconds even though the shower is not running. Otherwise the shower pump comes on with the shower when it should, and works fine.


There’s no RCD on the circuit as it’s an old Wylex. Megger values are fine. I checked for wires wrapped round pipes or anything like that and all looks fine.


Any ideas why this would happen? Should I just replace the light switch and not worry about it?


Thanks in anticipation.

 

[Plonker 3]

Well for whatever reason he couldn't carry out further investigations. Dillb jumping down his throat does no favours for other people looking for advice on the forum ... It just makes people feel uncomfortable and go elsewhere,

I haven't jumped down anyones throat, I asked for test results of the basic tests. Which weren't done.

Also why it takes 2 visits to diagnose a fault.

If people are paying for time the least they should be given is the above information, so they can at least make a decision on weather to repair it or not.

 

[GMES]

As above Sparkol, if your bored and just want a chat that's fine, if you don't know how to fault find with a test meter then just say so.
But to echo previous replies, you have got to at least do the basics before asking for other people to fix it for you.

 

[telectrix]

i'm just wondering what test might show why the pump is kicking in when it should not. seems as though the arcing of the faulty switch is the cause and a simple replacement would cure the fault. then again, i learnt my fault finding with a wind up megger and a test lamp.

 

[sparkol]

Dillb - I find the majority of faults tend to be resolvable within an hour, but a few can take much longer. When I have 2-3 weeks’ of work booked in ahead of me, and an employee who I have to pay whether we are working or not, then the practicalities of the job mean I can’t just leave a clear day, or even a clear morning, for what might turn out to be a 1-hour job. I find the best way is to tell the customer I’ll have time to come and have a ‘quick look’ and go from there. Are you a spark for a living, and if so how do you deal with this sort of problem? Don’t take that the wrong way - I’m genuinely interested to know how you and other people deal with fitting potentially open-ended fault-finding jobs into their schedule.



I appreciate what you say about ‘looking at the wiring’ vs testing, but looking takes 2 mins and felt it was worth it for the chance (however small) that I may have seen something helpful (even a plumbing issue given that we are talking about a shower pump here).



I fully appreciate that it is easier to comment when you have a full set of test results but one of the queries in my original post was whether it was even worth doing a full test given that, on the face of it, the problem was just a faulty switch. I also thought that, given the unusual and slightly amusing nature of the fault, people might find it interesting and perhaps even a little fun to venture ideas as to why a light switch would cause a shower pump to start up. It hasn’t turned out to be as fun as I expected.



I have to go out now, sorry, but will pick up later on.

 

[pjcomp]

I also thought that, given the unusual and slightly amusing nature of the fault, people might find it interesting and perhaps even a little fun to venture ideas as to why a light switch would cause a shower pump to start up.

Maybe it's only a light shower ... ?

 

[tony mc]

Have you had a look at the connections on the shower pump?

 

[UKMeterman]

Well,
A bad arcing light switch can act as a broadband radio transmitter, this can affect a badly designed or badly earthed shower pump. Replace the switch and also check earth loop impedance on the shower pump. If the earthing is good advise customer issue may reocour, and if customer needs fit external filter for the shower pump or advise customer to swap it.

 

[Lucien Nunes]

Well for my 2p I'd say there's an electronic timer / supervisory circuit in the pump control box that doesn't like spikes being shoved up its supply. Is the bathroom lighting ELV? If the switch is arcing in series with the primary of a transformer, at the end of a long thin circuit that the pump shares, it could be creating some hefty interference that causes the pump controller to go wobbly.

A high resistance connection upstream in the circuit could cause similar false triggering, as the voltage at the pump might sag on the lamp inrush.


E2A post collided with UKM's