I failed my amateur electrician exam

[Timothy Murphy]

Yesterday I had a near-disaster when replacing a faulty immersion heater switch.

I connected Lin and Nin to the mains, and Lout and Nout to the immersion heater. The effect of this was that the immersion heater never went off (when the Bath switch was on). The water in the cistern boiled, the immersion heater burned out, and started leaking.

My wife cast doubts on my DIY competence, but the plumber I called did not say a word of criticism, even telling me "these new switches are very complicated".

I may say I had read the 1-page "instructions" (in tiny script) which came with the switch, but these did not mention connections. I'd also googled for "immersion heater switch wiring" without coming across anything useful.

The plumber only charged me ?75 (£63) including the new heater, so the lesson was not unduly expensive.

[DerbyBorn]

Timothy Murphy wrote in news:kn4t6h$cun$1@dont- email.me:

I don't understand what you did wrong. What is the "Bath Switch"

Why didn't the thermostat in the immersion heater prevent the water from boiling - had you wired directly to the element - and not through the thermostat?

[whisky-dave]

From what I read I think he put the immersion heater direct to the live and nueutral rather than going through the thermostat.

[The Natural Philosopher]

Only surpassed by my FILS 'simplephone' a mobile stripped of all gadgetry and with large buttons for the visually challenged.... ...and an instruction manual that even I could not read without scanning at 1200DPI and blowing up to A4.

[John Rumm]

So far so good...

Also sounds ok...

That sounds odd for two reasons: First the stat in the heater should prevent it from boiling in the first place, secondly the overheat cutout should have tripped.

Sounds more like you had a knackered immersion heater in the first place.

Where was it leaking from?

Chances are if the exiting heater was defective, you would have needed to pay £15 - £25 of that anyway for a new heater.

[Tim Watts]

On Friday 17 May 2013 10:31 Timothy Murphy wrote in uk.d-i-y:

The lesson here is to make sure to fit a decent replacement immersion with integral thermostat *and* failsafe thermal fuse - belt and braces :)

[whisky-dave]

Tried that and my trousers fell down ;-)

[John Rumm]

thus revealing your thermal fuse? ;-)

[Andy Champ]

Did you mean exiting, existing or possibly even exciting? :)

[John Rumm]

Erm the middle one, but either of the others work ;-)

[The Medway Handyman]

I didn't think you could buy anything else?

[newshound]

I *think* some industrial ones don't come with a thermostat, even though they have a pocket. Whereabouts is the thermal fuse? Can't say I have ever spotted an obvious one.

[Archibald Tarquin Blenkinsopp]

Cistern? Boiling?

Are you for real?

Is this your first post incidentally? Anyone inserting contact details into a post display's an almost childlike innocense of this medium, or like your electrical description suggests that you are not "up front".

AB

[Mathew Newton]

Why? That's how it's meant to be wired up.

More information required - there's something you're not telling us (perhaps unknowingly).

Mathew

[Timothy Murphy]

I've checked now how the plumber correctly wired the switch.

First of all, there are 10 terminals on the switch:

4 at the top, 4 at the bottom, and one on each side. The last two are connected together, and are wired to the earth (green/yellow) from the heater and the mains earth.

There are 4 wires coming from the heater: earth, black, brown and blue.

The 4 terminals on the bottom are labelled Nin, Lin, L2, L1. Lin/Nin are connected to the mains live/neutral. L1 is connected to the black wire from the heater, and L2 to the brown wire from the heater.

The first 3 terminals on the top are labelled Nout, Lout, Common. The fourth terminal is not labelled and is not used. Nout is connected to the blue wire from the heater. Lout is connected (by the plumber) to the Common terminal.

Through the brass cap on the top of the immersion heater, where a small hole had been created by the burn-out of the heater.

The plumber said he paid ?35 for the heater, and charged ?40 for the call.

[dennis]

I take it the switch has hot water, off, and bath positions and that there are two different elements in the heater, one to heat the top and one to heat the rest. Where is the thermostat or is there more than one?

[Grimly Curmudgeon]

Complicated by the twin-element nature of immmersion heaters that are common in Ireland, you should have taken heed of the fact that the thermostatic switch is in fact on the Neutral leg at the immersion. You likely wired up the load side of the switch directly to the Bath (full length) and Sink (short one) elements without the 'stat in circuit. What you actually had was a series of two heaters on at the same time, with no 'stat.

I don't think much of your poetry, though.

[newshound]

Thanks for the explanation. I'd like to think I wouldn't leave the stat out of the circuit, but putting it in the neutral is certainly one way to confuse!

[Jim K]

er... boiled? accidento bizarro?

Jim K

[jgharston]

Scorchio!

JGH