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Continuity question (Read 3536 times)
Gilly1am
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Continuity question
May 12th, 2013, 11:56pm
 
Hi, I have a 150w heated towel rail with an electronic timer (time guard FST117) which has stopped working. I assumed the timer had died as the over ride button no longer has a positive click when pressing on. Therefore bought a replacement to change like with like without changing any wiring. However, before changing decided to use my multimeter (kewtech 117) to make sure there were no voltages after turning off breaker switch then decided to checking the heating element continuity - I took the wiring of this out of circuit & connected it in series with the multimeter and am not getting the continuity buzzer sounding, however it does give a reading of 112 ohms. The buzzer sounds if I touch the meter probes together. So, my question is, is the problem with a bad heating element rather than the timer? Many thanks for help with this.
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thescruff
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Re: Continuity question
Reply #1 - May 13th, 2013, 12:14am
 
Why didn't you check the s/live from the timer
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woodsmith
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Re: Continuity question
Reply #2 - May 13th, 2013, 6:44am
 
With the Kewtech the buzzer only sounds if the resistance being measured is less than 100 ohms, as you are measuring 112ohms for the resistance of the heater element you wont get a buzz.
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Lectrician
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Re: Continuity question
Reply #3 - May 13th, 2013, 7:07am
 
Yep, most meters will only beep for continuity when it is low enough - 112Ω is not low.  It is the resistance of your element.

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Gilly1am
Re: Continuity question
Reply #4 - May 13th, 2013, 12:24pm
 
Thanks for your posts. I did wonder whether the 112 ohms was just the natural resistance of the heating element and as you say the MM wont sound unless resistance below 100.

With regards to the timer, I did check the voltages at the back of this. Firstly with mains box RCD switched off: L in- N in; L in-earth; N in -earth; L in - back plate; N in -back plate all no or tiny voltage. Repeated L in - N in with mains supply on (used fused leads from the MM) & showed 240v AC; whereas the timer's L out - N out showed 2.9v approx.

I was thinking of testing the timer using a simple lamp circuit with say a 60w bulb but I guess the above is giving me the answer & just need to now go ahead & change the timer box.
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Re: Continuity question
Reply #5 - May 13th, 2013, 1:13pm
 
I would still favour the stat.

Can't you link the timer out to test the heater is working.
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Gilly1am
Re: Continuity question
Reply #6 - May 13th, 2013, 1:29pm
 
Makes sense, will try taking in's & outs off back of timer & use temporary join with a block, thanks
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