Drayton SCR and RF 2 fault finding

March 6, 2013 at 5:57 pm (house) (, , , , , )

We’ve been having some issues with our central heating.  A couple of weeks ago it stopped coming on completely.

A bit of debugging seemed to be showing that the thermostat had stopped asking the heating to come on.  Sure enough, when I bypassed the thermostat by adding a loop wire back into our boiler (as per the manufacturers default ‘as delivered’ state) I was able to control the heating manually, so I knew the boiler was fine.  So what to do about the thermostat?

Well I could go out and buy a new radio thermostat for £100-150, but thought I must be able to do better.  We have a Drayton SCR receiver and a RF 2 controller unit.  It all looked like it was working.  The green light came on when the override was pressed, but the heating wasn’t triggered.  I could also see the red light flashing when the controller was asking for the heating to trigger – but still no signal to the boiler.

Eventually, after trying the ‘learning’ mode and commissioning sequence as per the manual, manufacturers troubleshooting guide, and general Internet wisdom, I eventually found a site that said that the SCR units can develop a fault over time where the large capacitor on the circuit board degrades and can’t maintain the voltage required to actually switch the boiler.  That sounded promising so I found a replacement capacitor on eBay for £4, waited and when it arrived got my soldering iron out.

That did the trick!  All working perfectly then for around two weeks.  Then I had a different problem.  This time the red alarm led was always on.  Again I went through the commissioning sequence but no luck.  I reset the controller as per Internet comments – removing battery draws, etc, still no good.  I tried new batteries too, but still no good.

Then I found a note that the last hand battery drawer was the display and the right hand drawer was the transmission circuits.  So as the display was all fine, I wondered if there could be a fault with the radio side.  The contacts looked a bit dirty, so I got the polish and a cotton bug out and gave them a clean.  That did it!  Even though official fault finding seemed to say the unit would be faulty, it was just dirty contacts in the battery drawer.

So, with a bit of logic, Internet support and willingness to think the problem through, our heating is all fine again now and so far (fingers crossed) I’ve not had to spent £100 plus to replace a thermostat that has otherwise worked fine for around 10 years.



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Low-power household electrical standard?

April 20, 2007 at 9:08 pm (computers, house, moan) (, , )

Why is it that there are so many different power adaptors with different current ratings, different voltages and different connectors?

I’ve just spent about half an hour sorting through a drawer full of adaptors for mobile phones, MP3 players, gameboys, digital cameras, battery chargers, etc – they are all different! And these are just the ones that recharge things. If I factor in the different ones we have that power novelty lights, computer peripherals, musical items, AV equipment, etc, our house must have hundreds of different power adaptors!

Just when you think you’ve got it sorted with a multi-voltage, multi-connector, multi-adaptor, you find something that needs 4.34V precisely!

Isn’t it about time we had a common UK standard for low-voltage devices? Do we really need all these different voltage levels and connectors? Is it beyond the wit of man to come up with a new plug and wiring system to sit alongside our 240V supply? We have a starting point, with the 12V car cigarette lighter standard (sort of). Shouldn’t be too hard. Really. Should it?

In the mean time, I’ll keep that drawer space reserved.


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