Faulty Programmer/Timer?

[Fireskull]

Hi All,

After a bit of advice please, the problem I have is the boiler fires up to heat the hot water cylinder regardless of the timer being set for it to come on or not.
I can set the timer to OFF and the boiler is still going, if I go upstairs and turn down the cylinder thermostat that turns the boiler off.
Central heating is fine, programmer is set to always on as my Tado controls thats, and that turns off and on the heating fine.

Drayton Programmer/Timer
Drayton 3 Port Valve
Old Potterton Prima Boiler

Does this sound like a faulty programmer? or something worse?
Thanks!

 

[stem]

The programmer would be my first port of call. Provided that the system has been working correctly in its current state, i.e. without anything (wiring etc) being changed. If the problem only occurred for example after the Tado was installed, then it may be something else.

Also, if you have blown a fuse that is part of the heating control, that can often weld the programmer contacts together and prevent it switching off.

You don't give the model of the Drayton programmer, but if it is a dual channel programmer (separate control for hot water and heating) and has a backplate like this,.....

.....and has wires in terminals N, L, 1, 3, 4, there is a test that can be done. But only do it if you can do so safely. If in any doubt don't proceed, if you are unsure about anything, or have any questions ask.

Isolate the electrical supply & remove the programmer from the backplate. Then move the wire from terminal 3 and isolate it safely out of the way so that it's not touching anything. Move the wire from terminal 1 to the L terminal (note carefully which one it is so that you can put it back afterwards) and replace the programmer. If the Hot water doesn't come on now then the programmer is faulty. If it does the fault is elsewhere.

 

[Fireskull]

Hi Stem,

Thanks for your reply, the problem was there before the Tado, and I 'think' it was there before this but the only other thing I have changed was the 3 port valve, but that was like for like, but again should have RTFM as the wiring could have changed, I didn't think it was this as it all works apart from the Hot water... famous last words.

The Programmer has a backplate like the picture, I will isolate the sytem and check the fuse tonight and have a go at the wiring swapover and report back! thanks!

 

[stem]

No need to check the fuse if everything is working, the fuse won't be blown now.

My question was just in case something had happened in the past that had blown it. When too much current is drawn through the switch contacts, they can become welded together inside the programmer. But if you are not aware of that happening then don't worry about it.

When you say:

Thanks for your reply, the problem was there before the Tado, and I 'think' it was there before this but the only other thing I have changed was the 3 port valve

I guess I was really asking has it worked properly at sometime? or that it has it never worked properly? If it has never worked properly then it might have been incorrectly wired up from the start.

Anyway, I look forward to hearing what happens after the test. Remember that it is just a test though, not a solution to the problem, so it will have to be put back afterwards. Basically you are hardwiring the hot water in the off position and bypassing the programmer.

 

[Fireskull]

I guess I was really asking has it worked properly at sometime? or that it has it never worked properly? If it has never worked properly then it might have been incorrectly wired up from the start.

Anyway, I look forward to hearing what happens after the test. Remember that it is just a test though, not a solution to the problem, so it will have to be put back afterwards. Basically you are hardwiring the hot water in the off position and bypassing the programmer.

A tricky one, the more I think about it the more I think has it ever worked properly, I am more concious of it now I know there is a problem so I notice when the boiler fires up at random times etc.
I have only been in the property a few years I bought it off my parents so I could ask if they have any idea but I think the answer will be 'Don't know!'.

So if the above test works then it looks like a faulty programmer? and if not it's something else.
I see Screwfix has the Drayton LP722 on sale so could pick one of those up to replace!

 

[stem]

So if the above test works then it looks like a faulty programmer? and if not it's something else.

That's the idea. like I said, you will be hardwiring the system to simulate what would happen when hot water is set to be 'off' at the programmer. So if the hot water does continue to operate during the test, then the programmer is not responsible for it.

I forgot to say, that as part of the test the hot water cylinder thermostat should be 'calling for heat' ie 'on' [but the boiler still shouldn't come on. Remember because of the wiring mod it's effectively set to be 'off' at the programmer]

Nothing will change with regard to the central heating. But to avoid confusion that should be set to be 'off' during the test, so that the central heating doesn't start the boiler.

 

[Fireskull]

That's the idea. like I said, you will be hardwiring the system to simulate what would happen when hot water is set to be 'off' at the programmer. So if the hot water does continue to operate during the test, then the programmer is not responsible for it.

I forgot to say, that as part of the test the hot water cylinder thermostat should be 'calling for heat' ie 'on' [but the boiler still shouldn't come on. Remember because of the wiring mod it's effectively set to be 'off' at the programmer]

Nothing will change with regard to the central heating. But to avoid confusion that should be set to be 'off' during the test, so that the central heating doesn't start the boiler.

Tested what you suggested above and no hot water! I will pick up a new one tomorrow, thank you very much for your help Stem!