Problem With 2-Way Heater Switch Setup

[four_engines]

Hello everyone!
 
Need as much advice as I can get. This issue has stumbled a few certified electricians. Hopefully, with the wealth of knowledge here, a solution to this can be found.
 
I'm a homeowner and a fairly competent DIYer.
 
My home was meant to be set up to have 2 points of 2-way (aka 3-way in the US?) heater switches connected to a conventional storage-type water heater placed in the roof area during a renovation, which was completed about 3 years ago. However, every year of so since, one or both of the switches would malfunction. Upon inspection, one of the parts on the inside would be melted.
 
At each of the point, there are 3 sets of E, N and L wires coming out of the wall. Totalling of 9 wires per point. Unfortunately, I don't have the wiring diagram. I would like to assume that they are wired "correctly" between each of the 2 points and the water heater.
 
I'm using Schneider Electric's Vivace series KB31D20NE_2, which is described as "20A 250V 1 Gang 2 Way Double Pole Switch with Neon and Earth", for both. I assume they are DPDT switches.
 
The back of each switch looks like this.
 
o L1   o L2   o L3   o NEON
o N1   o N2   o N3   o NEON
o E
 
How should the switches be wired so that they will not melt and still allow me to turn on the heater from either of the 2 points, complete with neon light indication.
 
F/E
​

 

[ProDave]

It's not a question of "how to wire it so it won't burn out" but to check the heater rating.

In this case you have a 20A switch.  what;s the rating of the heater?

 

[Blue Duck]

what rating (watts) are the heater(s)?

edit: curse you prodave

 

[four_engines]

It's rated at 3kW 240V 50Hz

 

[kerching]

When i googled that part number there was no mention of 2 way....just double pole with neon

 

[Andy™]

When i googled that part number there was no mention of 2 way....just double pole with neon

you didnt look hard enough... i did find a 20a DP 2 way switch.... full part number is KB31D20NE_2_WE_G11

as for wiring, fairly simple, just dont get the strappers wrong. 2nd switch neon can easily be done, but i cant see an easy way to get neon to work on first switch without taking SL's from seconds switch back to first...

 

[ProDave]

I found this http://www.gumtree.sg/a-building-trades/orchard-holland-d09+10/electrical-lighting-switch-kb31d20ne-2-20a-250v-1-gang-2-way/1001344396690910677424209

Which does suggest it is indeed 2 way.

that's a first for me, never seen a 20A 2 pole changeover switch like that before.

 

[kerching]

-1 to me then!

Curse Mr Shiraz and his 14% ness

 

[Andy™]

that's a first for me, never seen a 20A 2 pole changeover switch like that before.

Ive never seen one either

 

[Phoenix]

It just seems like the current set up is asking for trouble. 3x 2.5mm terminated in a plate switch (with terminals which probably are not great) with multiple cables per terminal carrying 13A for hours on end after it has been forced back into a box

I think if I was asked to wire such an arrangement, it would end up as a feed straight to the water heater location from the board. Local DP isolation, then the load switched by a contactor, with the coil being operated by 2 way switching set up using ordinary light switches and protected by a 6A breaker fed off the supply coming into the contactor. If neons required then extra cores and a MK grid plus arrangement for the switches

I wonder how difficult it would be to convert the OPs set up to this

 

[ProDave]

Can I ask what the peculiar need is to have a heater 2 way switched?

I would try and engineer out the need for 2 way switching.  Every other heater I have seen works perfectly well switched from just one place.

 

[Sharpend]

Would the idea be like a boost button? So could be switched as needed from a more convenient position? Admittedly a single switch with time clock would suffice if really needed.

 

[Rob_the_rich]

can't see the point of double pole switching here, it is usually used to safely isolate an appliance for maintenance, but with a second remote switch capable of re-energising the heater, double pole seems pointless.

 

[SLIPSHOD & SLAPDASH]

The switch may or may not be used as double pole, its being used as its 20A. I think the 3rd set of cables is for the neon & the 2 way is wired with 2 x 2c & e. I personally would have just fitted a contactor and smaller cables.

I dont think anyone can give a wiring diagram based on what we have been told as we do not know where the cables run.