Ideal ICOS HE15 will not turn off

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Hi,

I have an Ideal ICOS HE15 boiler which has been regularly serviced and worked fine for around 7 years. It still works fine its function as a water heater, however the central heating system as a whole has recently developed an odd quirk, namely that the boiler still continues to burn gas periodically even after the central heating controller/programmer has finished its cycle. The radiators go cold, suggesting the pump has correctly been turned off (which presumably means the external CH controller is not faulty), but the boiler continues to display 'C' and periodically fire up.

This happens most of the time (80%), but sometimes the boiler shuts down as expected and returns to '0'. When it doesn't shut down, I'm forced to turn the power off at the wall to prevent the boiler burning through gas unnecessarily.

I intend to call someone to inspect and fix this fault, however I would like to gain a rough idea of what is wrong just in case there is a simple fix, or in case the engineer suggests replacement of a part that is probably not at fault.

Thanks in advance, all comments welcome.
 
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What valves do you have controlling your heating and hot water? usually found in the airing cupboard near the hot water cylinder.
 
Do you have a Wireless thermostat? Such as a honeywell. If you do it could be that it’s gone into fail mode. If it has you will have a red light on the receiver box
 
What valves do you have controlling your heating and hot water? usually found in the airing cupboard near the hot water cylinder.

Hi there, many thanks for the response - appreciate it.

I was able to identify a Honeywell Stop Valve, part number 272848.

There was also a part made by a company called Danfoss, but I couldn't find a part number on that.
 
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Do you have a Wireless thermostat? Such as a honeywell. If you do it could be that it’s gone into fail mode. If it has you will have a red light on the receiver box

Hi,

Thanks for the reply snb.

The central heating thermostat is made by Danfoss. I couldn't see any red light. From a quick Google image search, the part appears to be as follows: RET230P

It is located in our hall, which is just outside of the kitchen where the programmer and boiler live. I guess it's wired through to the programmer.

Thanks
 
These are called zone valves and have a small switch called a micro switch, sometimes referred to as the end switch sounds like one of these is sticking, very common
 
These are called zone valves and have a small switch called a micro switch, sometimes referred to as the end switch sounds like one of these is sticking, very common

Thanks Ian - presumably there is no way to fix it through maintenance ... it's just a simple case of replacing it?
 
Have heard some saying that they have sorted them by spraying them with contact cleaner or WD 40 or the like but not a great believer in if that would work
 
Thanks. I'm going to give the area a general clean as it is full of dust. I've noticed that there is a lever on the back of the valve housing - I presume that this isn't a manual override but something else? And I should leave it be?
 
it is a manual override for when you are filling the system, the switches are inside the valve actuators so cleaning around them will not make any difference
 
Hi there,

Just a brief update. I've been monitoring my boiler/CH system over the last few days, and in particular listening to the zone valve. The system started working perfectly again about 3 days ago, with the boiler returning to '0' shortly after the programmer finishes its cycle.

And then the problem I initially re-appeared again today.

After Ian's advice, I decided to listen to the zone valve, and it sounds like it is working every time - I can hear the motor running for about 1.5 seconds, presumably to close the valve.

One final question I have is: does the zone valve control power to other components?

The thing is, when the system is misbehaving I can hear something else running near the zone valve, it sounds a bit like a pump or an electric motor but I can't put my finger on which item it is (my hearing has got worse in recent years).

When the system is behaving, everything shuts down and the boiler returns to '0' after a brief period.

There are two other Honeywell components near the Honeywell zone valve and I wonder whether those also perform valve or switch functions.

Thanks in advance.
 
You may need help doing the following if you are not electrically competent:
1. Turn off the power to the heating system.
2. On each zone valve, in turn, operate the lever fully to partially open the valve, listen to the noise it makes on returning. Without yanking it, operate the lever again, but a little faster so that it continues to open after the lever has reached its stop. Do you hear a click (as the microswitch operates inside the head), then a second click as it spring returns to the closed position?
3. Remove the metal lid of the valve head. Look inside, do you see evidence of wetness or damp around the waxy card insulator at one end of the valve head? If so it could be that a small leak from the valve is short circuiting the micro switch on one of the zone valves, giving the boiler an erroneous signal to run.

You may wish to use a hairdryer to dry up any dampness in this area before refitting the lid and restoring power. If this proves successful then you will need to repair or replace the valve body (but preferrably the whole valve) soon. If the clicks are not evident at step 2 above, and there is no evidence of dampness, then replacement of the valve head (actuator) is all that is needed.
 
Thanks Meldrewsmate, I appreciate the response and that is very helpful.

I didn't realize that I actually have two zone valves in my CH topology, and I wonder now whether it is the second (made by Danfoss) which is the problem. The Honeywell zone valve located above the pipework and it seems to me the chance of a leak short-circuiting the switch is perhaps lower than for the Danfoss zone valve, which is located to the side of the pipework, and it looks like a small leak could easily leach across into the housing and onto the micro-switch.

I considered following instructions 1, 2 and 3 above, however the work area of my plumbing is extremely compressed and constricted (it's a new-build house and everything seems to have been put together with little thought for maintenance). Indeed, there isn't even room for a regular screwdriver to remove the screws on the valves.

The CH service guy arrives on the 17th; thanks to the help of everyone here, I think I am now comfortable with what the problem is, and I will leave him to take care of the repairs. I'm still curious as to why the valves themselves make a demand on the boiler. I would have thought that this would have been the job of the thermostats alone and/or the CH programmer...

Cheers
surf_doc
 

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