Odd wiring.

[The Medway Handyman]

Doing various jobs at a lady's house, one of which was to replace the pull cord switch in her en suite. Like for like, should have been simple.

Three story town house, en suite and common bathroom on the same floor.

One extractor fan vents both bathrooms via trunking.

The switch had failed mechanically as pull cords often do, but this one was a weirdo.

Two cables coming in, both three core & earth, so red, yellow, blue.

The switch (Tenby MG888) had 4 terminals + earth.

Top left = COM, top right = N, bottom left = 1 WAY, bottom right = 2 WAY.

Never seen one of these before.

Cable 1 wired yellow to COM, red to 1 WAY, blue joined to blue in Cable 2.

Cable 2 wired yellow to COM, red to 1 WAY, blue joined to blue from Cable 1.

Terminals 1 WAY and 2 WAY are linked by a red cable.

I assume it's wired so that the switch in either bathroom triggers the fan (which is on a timer).

Three visits to electrical wholesalers & a web search doesn't find a Tenby MG 888 switch, so I've e mailed the manufacturers.

Not knowing how the switch 'switches' I can't figure out how it would work or what alternative I can use if I can't locate a replacement switch.

This has even caused the knowledgeable & helpful Mr Wadsworth to scratch his head!

Any thoughts?

[Roger Mills]

Odd! Were the two blue wires connected to the neutral terminal, or just joined together in fresh air? Was *anything* connected to the N terminal?

Does the switch have a neon light, which glows when it's 'on'? If so, that might account for the need for a neutral.

Having terminals marked Com, 1-way and 2-way suggests that it's a change-over - with Com connected to 1-way in one position, changing to Com to 2-way when you toggle it. In that case, it's *very* odd to join

1-way and 2-way together, because that means that the switch in *on* in *both* positions, so that toggling it has now effect!

Are you sure you have reported the wiring correctly? What, according, to the owner, is it *supposed* to do, and what is the perceived problem which caused her to ask for it to be replaced?

[Brian Gaff]

Two switches, take the other one that works off and test it?

Brian

[ARWadsworth]

That is something we discussed over the phone.But Dave was not on site at the time.

[The Medway Handyman]

Joined as in fresh air :-) Chocky block.

Nope.

My thoughts exactly!

Pretty sure - I'll post a photo somewhere. The switch failed mechanically & the light wouldn't come on - or the fan.

[ARWadsworth]

I have to say that I still believe it is what I suggested when you phoned me. It's a double pole pullcord switch. The reds have been linked up to give a permanent live to the fan (not that that link is needed), the yellows are the switched live and the blues in the strip connector are the neutrals.

[Owain]

Should be wired using a double pole switch.

-------------- SWa Pole 1----------- LIGHT -- Neutral | |-- SWa Pole 2----- | | -- SHARED -- Neutral -- FAN | | |-- SWb Pole 2----- | LIVE -------------- SWb Pole 1 ---------- LIGHT -- Neutral

if a timer fan then you will have an unswitched live to the fan as well.

Owain

[Owain]

SHARED -- Neutral

Double pole pull switch MK 3151 requires mounting block

[Owain]

live to the right-hand yellow switched live.

Owain

[Roger Mills]

> LIVE -------------- SWa Pole 1----------- LIGHT -- Neutral

That makes perfect sense! But, in that case, I wouldn't expect the 4 poles to be labelled Com, 1-way, 2-way and N [1]. Has TMH misead them?

[1] I'm not sure what I *would* expect to see, but not that!

[The Medway Handyman]

> LIVE -------------- SWa Pole 1----------- LIGHT -- Neutral

Ta. So how does that translate to wiring colours?

[Owain]

Red - perm live in, perm live to fan Yellow - switched live to light, switched live to fan Blue - neutral in, neutral to fan

RED -------------- SWa Pole 1-------YLW1---- LIGHT -- (neutral not present at switch) | |-- SWa Pole 2----YLW2-----| (sw live to trigger) | | |-----------------RED----SHARED (perm live to fan) FAN | BLUE ------------------CHOCKY-------BLUE-----| (neutral to fan)

Owain

[Owain]

Slightly amended so as not to linewrap. Still requires fixed font. Note the N to the light is not present at the switch

RED ----------- SWa Pole 1----YLW1---LIGHT--> N. | |-- SWa Pole 2----YLW2-----| (sw live to trigger) | | |-----------------RED----SHARED (perm L to fan) FAN | BLUE-------------CHOCKY-------BLUE-----| (neutral to fan)

Owain

[jgharston]

(snip Owain's diagram)

This is exactly why I wire up so there's exactly one unambiguous cable at each switch/outlet/whatever and do all the voodoo in junction boxes. Even tho' it's depreciated, I've had too many calls from people who've taken a switch or ceiling rose off and can't get any further.

Or worse, "I joined all the reds, and all the blacks, and all the greens, but when I try to turn the light off the fuse blows"

JGH

[ARWadsworth]

number 0611 30

[Owain]

Is that momentary or latching?

Owain

[ARWadsworth]

I cannot see anything that suggests that is a momentary switch.

[Owain]

My error, I forgot this application requires a latching switch.

Owain

[The Medway Handyman]

OK, I have located the switch Owain suggested.

It has L & N Supply at the top and L & N Load at the bottom.

So, do I wire it;

2 x reds to L Load, link to N Load, blues together, yellows to L & N Supply?

[Owain]

No, you put the supply in the Supply side and the load in the Load side :-)

RED ---------|--SUPPLY 1 LOAD---YLW1 | RED ---------|--SUPPLY 2 LOAD---YLW2

BLUE --------| | BLEU --------|

Owain