C.heating coming on despite being turned off in 3 places!

[Cohen]

I have an Alpha boiler and since yesterday it's been exhibiting the following strange behaviour...

We had the central heating on in the evening and it seemed to be working fine. A few hours in and I notice that the boiler seem to come on more often to check radiator water temp before heating it up. I find that normally it would do this every 5mins but now it was doing it every 15 seconds. At this point the radiators became too hot to touch so it was heating them up every time it came on.

We have a digital control, instead of the analogue clock, to control when we want the CH on. I set it to the off position so that the CH should turn of. No luck, the CH was still doing it's 15 second thing. I then go downstairs and turn the thermostat to the 0degrees, same result as before. I then put the boilor in to domestic hot water only mode and still the CH comes on every 15 seconds!

I've tried using the reset function but that doesn't resolve it either. The only way to stop the CH coming on is to turn off its electric supply, which obviously means we don't get domestic hot water either.

So I left it completely off overnight thinking it might have been an over-heating issue. I try it again this morning and shortly after turning on the electric for the boiler the CH kicks in again despite still being disabled in the 3 places described above!

Anyone ever come across this kind of behaviour?

 

[OilLecky]

I don't do gas but I've had similar with an oil boiler system and I guess that the control systems are similar. It all depends on if you have any zone valves and how they are wired. In a couple of cases the wiring was incorrect but this had shown up only after the cylinder thermostat had failed so it was calling for hot water all the time. Try turning the cylinder thermostat and listen to hear it "click" .I've also had the cylinder thermostat hanging on its cable in space and not detecting when the water was hot. This also calls for hot water all the time. Has your beloved stuck a big pile of clothes near the hot water cylinder lately?

 

[Agile]

I expect this is a combi and the DHW flow switch has failed int eh DHW mode.

Common fault on this model!

Tony

 

[namsag]

either the pin on divertor has stuck out In HW position and activating the microswitch ,or you have faulty microswitch,

Which alpha do you have

 

[Cohen]

Thanks for the replies so far people

It's an HECB33, out of warrany by about 3-months.

I'll have to see if this can be repaired under Alpha's AfterCare package. That package seems almost too good to be true, especially since a couple of hours labour would easily cost as much. This is the first major fault the boiler has developed since getting it just over 3 years ago so I've not had to call on them to fix anything. Anyone have any experience of their service?

 

[gas4you]

They use a lot of local agents for service. Pot luck I'm afraid.

The agents in my area are totally carp

 

[Agile]

If you have the serial number and installation date and the card was returned then if you phone and are polite ( that means no swearing! ) then they MAY agree to cover the fault on a discretionary basis.

Some of their current boilers have a five year warrantee.

It sounds to me as if the DHW flow switch has failed which is only a simple DIY job IF thats the cause.

Tony

 

[Cohen]

Thanks for the replies gas4you and Agile.

I've looked around and it seems the flow switch is about £20ish inc vat so that's quite reasonable. However, given its name it sounds like it should only affect hot water from the taps, rather than persistent heating of the radiators despite the central heating side being disabled. Getting hot water from the taps wasn't the problem. Would that switch still affect the radiators?

 

[Agile]

Please dont try your own thinking!

Leave the thinking to the boiler experts!

I know that you think that we are "plumbers" and everyone knows that "plumbers" leave school at 14 are are totally thick and have no ability at all to think or to understand something as simple as a gas boiler.

Its that public perception that stops me from being a plumber!

Tony

 

[Cohen]

My apologies Tony if my query came across as offensive with regards to your knowledge, that was certainly not my intention

I'm assuming then that your stance is that I should not take the DIY approach. As such, I think I will let Alpha inspect and repair as needed when I arrange for them to visit.

 

[Agile]

Changing the DHW flow switch is a simple DIY job now that we have identified it as a possible cause of your problem.

However, first identify it and disconnect the leads from it and see if that stops the boiler from running and heating the radiators.

Then reconnect the leads and remove the switch. If the boiler then does not run then it implies that the switch is OK but its not being deactivated. Thats a much more involved repair and not very suited to any but the most persistent DIYers.

If the switch is faulty then its a simple and cheapish part which you can easily replace yourself. However, deciding if its the switch which is faulty or its not being actuated can be more difficult and many would change it on test to see the effect. We keep them in stock in case!

Of course there are other things which could cause that fault but its the simple and cheap possibilities which should be checked first.

Tony