Discuss Problem With 2-Way Heater Switch Setup in the DIY Electrical Advice area at ElectriciansForums.net

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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.
 

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A photo of the switch after melt down will help. What condition is the insulation in on the wire that went to the melt down point.
 
The parts melting is indication of a load too great for the accessory.
This could be because: the water heater is above 20A, the cable is too small for the load, the terminations of the cable in the switches is not secure, the switches are faulty.
Normally it is loose connections.
If you only have nine wires at each of the switches then there is no cable for having the neon operate at both switches, this would require another two core cable.

The wiring diagram you post should work OK.
 
Hello guys

Thanks for the replies.

Ifindoubtdont: Here's the picture. The melted plastic part is circled in red while an undamaged one is above it. Also, the wires connected to the melted part seem perfectly fine. Maybe the plastic took the brunt of it.

View attachment 29962

Richard:

The heater is rated at 3kW 240V 50Hz. This would mean that it is only drawing a max of 12.5A? Above the switch rating of 20A?

Of the few times I removed the switches after they malfunction, I didn't see any loose connections.

I have swapped 3-4 damaged switches for brand new ones so the likelihood of the switches being faulty would be rather low?

As for the neon, can I use the 2 E wires between the 2 switches?

F/E
 

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i'd say the switches weren't man enough for the load. seen several immersion heaters ( 13A ) with 20A switches burnt out. might be feasible to use a relay/contactor for the job.
 
Agree with Tel, that sort of damage is where there is a high resistance at the switch contacts causing the switch rocker contact to get hot and melt the pivot rod.
One thing that could be possible is if the wall is not flat and the switch twists once it is fixed to the wall the rocker contact can hit the stationary contact at an angle and provide a low contact area causing (usually a poor operation) heat build up as shown.

The other alternative is to try a different manufacturer of the switch and see if they are more forgiving.
 

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