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Altered thermostat behaviour
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Ivan D. Reid
Nov 24, 2012, 12:50:08 PM11/24/12
to
Sometime last winter I noticed that my CH thermostat had changed
its behaviour. Instead of being on for ~10 minutes and off for ~20, it
would run the heating for ~40 seconds, then off for ~2 minutes. It was as
if it somehow lost its hysteresis. Given that it's an all-electronic
system (Drayton RTS1) I suppose it's possible that, e.g., an electrolytic
capacitor has dried out (or leaked). Is this a common problem?
I'm not that worried as it seems that the RTS1 is still available
cheaply and as it clips into the backing plate I'll not have to put
screwdriver to connector, just plug new gubbins onto old plate. If I can
get the old one out... It hangs on the upper-right corner; I suspect the
old chap who used to live here, and was a bit less proficient at DIY than
he seemed to think, put conduit over the wire after it was in place and
didn't leave enough room to lift the body off its locating lugs. We'll
see when I get a new one to compare.
There was a moment of panic when I apparently didn't get it
plugged back in correctly after trying to prise it loose, and the
thermostat didn't switch on at all. Fortunately a second attempt got it
working again so I won't have to spend the next few days wrapped up
warmly.
--
Ivan Reid, School of Engineering & Design, _____________ CMS Collaboration,
Brunel University. Ivan.Reid@[brunel.ac.uk|cern.ch] Room 40-1-B12, CERN
KotPT -- "for stupidity above and beyond the call of duty".
its behaviour. Instead of being on for ~10 minutes and off for ~20, it
would run the heating for ~40 seconds, then off for ~2 minutes. It was as
if it somehow lost its hysteresis. Given that it's an all-electronic
system (Drayton RTS1) I suppose it's possible that, e.g., an electrolytic
capacitor has dried out (or leaked). Is this a common problem?
I'm not that worried as it seems that the RTS1 is still available
cheaply and as it clips into the backing plate I'll not have to put
screwdriver to connector, just plug new gubbins onto old plate. If I can
get the old one out... It hangs on the upper-right corner; I suspect the
old chap who used to live here, and was a bit less proficient at DIY than
he seemed to think, put conduit over the wire after it was in place and
didn't leave enough room to lift the body off its locating lugs. We'll
see when I get a new one to compare.
There was a moment of panic when I apparently didn't get it
plugged back in correctly after trying to prise it loose, and the
thermostat didn't switch on at all. Fortunately a second attempt got it
working again so I won't have to spend the next few days wrapped up
warmly.
--
Ivan Reid, School of Engineering & Design, _____________ CMS Collaboration,
Brunel University. Ivan.Reid@[brunel.ac.uk|cern.ch] Room 40-1-B12, CERN
KotPT -- "for stupidity above and beyond the call of duty".
Ivan D. Reid
Nov 24, 2012, 3:26:22 PM11/24/12
to
On Sat, 24 Nov 2012 19:36:51 +0000, Graham <m...@privacy.net.invalid>
wrote in <7b72b851jkqn1m0q8...@4ax.com>:
> Despite having a thermistor for a sensor rather than a bimetal strip,
> it would appear that the electronics in these thermostats is very
> rudimentary, and they use a resistor as an accelerator heater to
> counter the hysteresis just like bimetal ones.
> Has the neutral connection gone O.C?
Hmm, interesting, I'll have to check if it's still short-changing.
The most logical place for neutral to go o/c would be where the controller
plugs into the backplate, and I broke and re-made that connection several
times this afternoon.
> On a conventional thermostat, the only purpose the neutral serves is a
> return for the anti hysteresis heater.
OTOH, the manual talks about it being double-insulated and it
needs to get a return path for the live current to power the electronics
(and activate the relay).
> I am aware you are complaining of *too little* hysteresis so I am
> probably barking up the wrong tree as usual.
It's all hypothesis until I fit a replacement.
> PDF manual here:
> http://snipurl.com/25ovkml
Thanks; I already had that but can't find anything more detailed
as regards circuit information and mechanical details.
> Ed. note.
> Forte Agent spell checker insists hysteresis is spelled "shysters".
...as one does...
wrote in <7b72b851jkqn1m0q8...@4ax.com>:
> On Sat, 24 Nov 2012 17:50:08 +0000 (UTC), "Ivan D. Reid"
><Ivan...@ivan.fsnet.co.uk> wrote:
>> Sometime last winter I noticed that my CH thermostat had changed
>>its behaviour. Instead of being on for ~10 minutes and off for ~20, it
>>would run the heating for ~40 seconds, then off for ~2 minutes. It was as
>>if it somehow lost its hysteresis. Given that it's an all-electronic
>>system (Drayton RTS1) I suppose it's possible that, e.g., an electrolytic
>>capacitor has dried out (or leaked). Is this a common problem?
> Hi Ivan.
><Ivan...@ivan.fsnet.co.uk> wrote:
>> Sometime last winter I noticed that my CH thermostat had changed
>>its behaviour. Instead of being on for ~10 minutes and off for ~20, it
>>would run the heating for ~40 seconds, then off for ~2 minutes. It was as
>>if it somehow lost its hysteresis. Given that it's an all-electronic
>>system (Drayton RTS1) I suppose it's possible that, e.g., an electrolytic
>>capacitor has dried out (or leaked). Is this a common problem?
> Despite having a thermistor for a sensor rather than a bimetal strip,
> it would appear that the electronics in these thermostats is very
> rudimentary, and they use a resistor as an accelerator heater to
> counter the hysteresis just like bimetal ones.
> Has the neutral connection gone O.C?
Hmm, interesting, I'll have to check if it's still short-changing.
The most logical place for neutral to go o/c would be where the controller
plugs into the backplate, and I broke and re-made that connection several
times this afternoon.
> On a conventional thermostat, the only purpose the neutral serves is a
> return for the anti hysteresis heater.
OTOH, the manual talks about it being double-insulated and it
needs to get a return path for the live current to power the electronics
(and activate the relay).
> I am aware you are complaining of *too little* hysteresis so I am
> probably barking up the wrong tree as usual.
It's all hypothesis until I fit a replacement.
> PDF manual here:
> http://snipurl.com/25ovkml
Thanks; I already had that but can't find anything more detailed
as regards circuit information and mechanical details.
> Ed. note.
> Forte Agent spell checker insists hysteresis is spelled "shysters".
...as one does...
Ivan D. Reid
Dec 3, 2012, 10:20:15 AM12/3/12
to
wrote in <slrnkb226g.i...@smtp.orangehome.co.uk>:
twelve new pence. There is a Plumb Centre down the other end of my road
and they had one in stock (must be a real hardware store; they close
Saturday afternoons and Sundays). The new gubbins didn't want to work
with the old baseplate (I suspect it was fouling the door jamb and not
fitting into place properly) so I gingerly removed all wires, swapped the
baseplate and rewired. Back to 10 minutes on, 20 off now. I think the
pump, etc., will have heaved a sigh of relief.
> Sometime last winter I noticed that my CH thermostat had changed
> its behaviour. Instead of being on for ~10 minutes and off for ~20, it
> would run the heating for ~40 seconds, then off for ~2 minutes. It was as
> if it somehow lost its hysteresis. Given that it's an all-electronic
> system (Drayton RTS1) I suppose it's possible that, e.g., an electrolytic
> capacitor has dried out (or leaked). Is this a common problem?
Solved now by the application of twenty of your British pounds and
> its behaviour. Instead of being on for ~10 minutes and off for ~20, it
> would run the heating for ~40 seconds, then off for ~2 minutes. It was as
> if it somehow lost its hysteresis. Given that it's an all-electronic
> system (Drayton RTS1) I suppose it's possible that, e.g., an electrolytic
> capacitor has dried out (or leaked). Is this a common problem?
twelve new pence. There is a Plumb Centre down the other end of my road
and they had one in stock (must be a real hardware store; they close
Saturday afternoons and Sundays). The new gubbins didn't want to work
with the old baseplate (I suspect it was fouling the door jamb and not
fitting into place properly) so I gingerly removed all wires, swapped the
baseplate and rewired. Back to 10 minutes on, 20 off now. I think the
pump, etc., will have heaved a sigh of relief.
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