Author Topic: column heater bleeding voltage from switch  (Read 458 times)

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Offline User895236

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column heater bleeding voltage from switch
« on: May 26, 2018, 06:07:50 pm »
I have a heater like this,

The timer dial was broken, so I opened up the heater, eliminated the dial from the wiring, and tested it.  Unfortunately there was some voltage registering at some places I didn't expect.  I labelled the following diagram:

F is the component no longer included.  C is a tipping-switch, working fine.  The dial-thermostat at E is working fine, the safety-thermostat at G is working fine.  But at D, there is a voltage at the side of the brown wire.  It should be 0, but it isn't.  D is a switch, giving 0, 1,2,3 as settings (see first piccy).  When this switch is set to 0, voltage at the brown wire connection to D is about 50V, but i thought it should be zero.  When the switch is set to 1, 2, or 3, the voltage at the brown wire reduces to about 23 volts.  BTW, I live in a 240 V country and the input voltage seems to measure fine.  Whatever voltage I read at the junction between D and the brown wire shows up also at A (the earth wire).

Here is a close-up of the switch.

I thought that any voltage appearing at earth was a problem.

There is one possible complication: many of the appliances in my house have 'live' casings, because I live in a dodgy country with very lows standards in electrics (Egypt).  For example, the macbook pro I am using right now , when I rest my hands on the keyboard, is generally around 20-50v (so I use a wireless keyboard!).  But it's not usually a problem unless I take my shoes off.

But I didn't think this could be the  full explanation, since the voltage to the heater measures zero all the way from the entry (B), through the tip-switch and thermostat; it is only at the switch (D) that voltage seems to be 'lost'.

Any ideas?

« Last Edit: May 27, 2018, 07:04:16 am by User895236 »

Offline LateLesley

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Re: picture
« Reply #1 on: May 26, 2018, 07:56:52 pm »
For the initial problem, I'd be checking the continuity of the power cable, checking the connections in the plug, And also metering out the 2 elements in the heater (A).  That brown wire should have the full 240V on it. You should get the full 240V just below point B where the brown wire connects. The switch D, has two outputs, which will switch on the black wire, white wire, or both together. You should see 240V on both of these when set to 3. setting 1 and 2 will switch on one or the other wire.

I'd check continuity with the power off, from the plug, right through to the elements. I'd then check the elements are not shorting to earth, although you may read a low value resistance. (55ohms on one, and maybe about 28-30ohms on the other.) any less than 20 ohms, i'd say the elements are faulty.

It may be worth checking the socket you are plugging into as well. It's not unknown for the socket terminals to loosen over time. So it may be worth turning off the power to the house, and checking the socket on the wall.

Also you say you have earthing problems too - would it be worth looking into installing a grounding rod? You could then bond the house earth system to this, to give you a proper ground reference. All it is is a piece of copper or metal rod, driven deep into the ground, and then a wire clamped from that to the earthing point in your home. It would give you a stable ground, and maybe stop you getting "tingles" off the mains. :-) ( )
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Offline User895236

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Re: column heater bleeding voltage from switch
« Reply #2 on: May 27, 2018, 07:07:17 am »
Thank you so much.  Your suggestions are very specific, I will get to them right away. Thank you for giving me your time!

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