Help me fix my central heating timer please!
Discussion
I have a combi boiler in my flat, and there's a timer alongside that seems to have a mains feed in that connects on to the boiler to control when the central heating comes on. It looks like this:
Timer by kiteless, on Flickr
The clock goes around as you'd expect but it doesn't do anything - it just stays on all the time. Turning the dial in the top-right doesn't do anything either.
I undid the screws and took it off the wall, revealing the following:
IMG_0235 by kiteless, on Flickr
IMG_0237 by kiteless, on Flickr
The back of the timer - I cleaned up the contacts and checked there was a connection between the two plates when it clicks to the on position:
IMG_0239 by kiteless, on Flickr
...but it still doesn't work. Help! Can anyone identify the unit (it says TR20 on the front, but there's about a billion things that aren't timers that are called that!), suggest anything else I could check or a replacement that I could easily DIY fit?
Thanks!
Simon
Timer by kiteless, on Flickr
The clock goes around as you'd expect but it doesn't do anything - it just stays on all the time. Turning the dial in the top-right doesn't do anything either.
I undid the screws and took it off the wall, revealing the following:
IMG_0235 by kiteless, on Flickr
IMG_0237 by kiteless, on Flickr
The back of the timer - I cleaned up the contacts and checked there was a connection between the two plates when it clicks to the on position:
IMG_0239 by kiteless, on Flickr
...but it still doesn't work. Help! Can anyone identify the unit (it says TR20 on the front, but there's about a billion things that aren't timers that are called that!), suggest anything else I could check or a replacement that I could easily DIY fit?
Thanks!
Simon
Tiberius said:
That looks Suspiciously like an immersion heater timer and nowt to do with the combi bolier
Especially as in this picture;
...the terminals have the words 'Immersion Heater' on them. Looks like someone's re-used the immersion timer when they fitted a combi.
I would start by looking at whether the unit is compatible with your boiler at all. In fact, are you absolutely sure it's connected and there isn't another timer elsewhere?
Are you sure you have a boiler 
That's the immersion heater timer, one of those wires is the mains input and the output goes to the immersion heater coil in the side of your hot water tank. Sliding those segments in or out decides whether the water heater will be on or off at any particular time of day.
That's the immersion heater timer, one of those wires is the mains input and the output goes to the immersion heater coil in the side of your hot water tank. Sliding those segments in or out decides whether the water heater will be on or off at any particular time of day.
From what I can see, the boiler has a permanent 240v (so that water is heated on demand) then a switched 240v one to control whether the heating is on or not. The latter seems to be going via this timer. An immersion timer needs to do the same thing, so it makes sense it would be used for this.
The wheel should have pegs, which turns clockwise and pushes the dial in the top-right around to switch it on and off. Except that the dial clicking around has no effect - the output ends up live regardless.
The wheel should have pegs, which turns clockwise and pushes the dial in the top-right around to switch it on and off. Except that the dial clicking around has no effect - the output ends up live regardless.
You have to move one of the outer segments, it looks like you pull them away from the centre for OFF, or it could be that you lift them up, or push them down. Right now, they're all in the ON position.
Once you've moved one, rotate the dial past it, it will click OFF and then back ON again when it hits the next peg.
Once you've moved one, rotate the dial past it, it will click OFF and then back ON again when it hits the next peg.
sjg said:
The back of the timer - I cleaned up the contacts and checked there was a connection between the two plates when it clicks to the on position:
OK, but you know it stays on. More importantly, did you check if there's a disconnection between the two contacts when it's supposed to be off?Does the system have a room thermostat? Most combis these days are controlled by programmable room thermostats. The boiler stays powered all the time and the 'stat turns it on and off if the room temp falls below what ever value is prgrammed in for that time of day.
If there is a room stat it's easy to convert it to a programmable one.
Have you got a a better picture of the bottom of the terminals where the wires go in?
Reason I ask is that it looks to me as though there are two lives going into terminal 4. If this is the case the installer has re-used the terminals of the wall clock rather than fitting a fused spur. A combi is designed to be left on all the time so you can get hot water on demand. If the clock did work it would cut all power to the combi meaning you could only get hot water when the the heating was on.
Reason I ask is that it looks to me as though there are two lives going into terminal 4. If this is the case the installer has re-used the terminals of the wall clock rather than fitting a fused spur. A combi is designed to be left on all the time so you can get hot water on demand. If the clock did work it would cut all power to the combi meaning you could only get hot water when the the heating was on.
Yep, clicking the dial around means the contacts go between closed and open.
Boiler is a Valliant VCW-sine 18 T3WFH according to plate inside - on googling, it seems one of the earliest combi boilers. No thermostat (or at least I've not found one in 6 months!). I was wrong about the power - looks like a single cable goes in there, killing the power that goes to the switch means no hot water either. Could have been bodged at some point to just stay on all the time, as per what Simon_m says - which would make sense I guess.
Looks like I'll be manually switching the heating on and off then. Thanks anyway all!
Boiler is a Valliant VCW-sine 18 T3WFH according to plate inside - on googling, it seems one of the earliest combi boilers. No thermostat (or at least I've not found one in 6 months!). I was wrong about the power - looks like a single cable goes in there, killing the power that goes to the switch means no hot water either. Could have been bodged at some point to just stay on all the time, as per what Simon_m says - which would make sense I guess.
Looks like I'll be manually switching the heating on and off then. Thanks anyway all!
sjg said:
Yep, clicking the dial around means the contacts go between closed and open.
Boiler is a Valliant VCW-sine 18 T3WFH according to plate inside - on googling, it seems one of the earliest combi boilers. No thermostat (or at least I've not found one in 6 months!). I was wrong about the power - looks like a single cable goes in there, killing the power that goes to the switch means no hot water either. Could have been bodged at some point to just stay on all the time, as per what Simon_m says - which would make sense I guess.
Looks like I'll be manually switching the heating on and off then. Thanks anyway all!
All is not lost Boiler is a Valliant VCW-sine 18 T3WFH according to plate inside - on googling, it seems one of the earliest combi boilers. No thermostat (or at least I've not found one in 6 months!). I was wrong about the power - looks like a single cable goes in there, killing the power that goes to the switch means no hot water either. Could have been bodged at some point to just stay on all the time, as per what Simon_m says - which would make sense I guess.
Looks like I'll be manually switching the heating on and off then. Thanks anyway all!
You could fit one of these http://www.plumbingandheating-solutions.co.uk/Wire... or if you're not up to it get a sparky to do it.Edited to add: this would be better as it is programmable http://www.plumbingandheating-solutions.co.uk/epag...
Edited by Simon_m on Tuesday 25th October 20:36
Without seeing what's connected to the terminals on the wall, it looks like the pins on the unit with the timer don't match up with what is on the diagram in the wall-mounted unit.
Check that the pins on the unit match up to what the diagram says, because it looks like someone's bodged a wire between pins 1 and 4 which shouldn't be there (and then drawn something to that effect on the diagram).
If pin 1 goes to the boiler, that might be your problem.
Personally, I'd buy a dedicated c/h timer and be done with it.
Check that the pins on the unit match up to what the diagram says, because it looks like someone's bodged a wire between pins 1 and 4 which shouldn't be there (and then drawn something to that effect on the diagram).
If pin 1 goes to the boiler, that might be your problem.
Personally, I'd buy a dedicated c/h timer and be done with it.
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