Ideal ICOS HE12 - Firing when no heat called for?

[stroller133]

Hi

I have moved into a house in Apr 14 with an Ideal ICOS HE12 supplying heat for Central Heating and a Santon unvented water tank. There is a Drayton lifestyle programmable timer and a room stat in the hall.

Its worked fine over the summer with a timed 20 mins in the morning and 15 mins in the evening ensuring we always have enough hot water. Last week put the CH timer on to come on for an hour or so at 9pm and that seemed to be working.

However this evening at 9:45 I noticed the boiler had fired several times within about half an hour - all the rads were cold and the HW is timed to be off. The stat was set below actual room temp, but when I turned it up the valve in the airing cupboard could be heard moving and the rads got warm - when the temp was reached the valve closed again but the boiler the stayed on, not always burning, but always displaying C rather than zero. I then turned both HW and CH to off on the drayton controller but still the boiler was displaying C and firing every few mins.

I turned the boiler off, firstly for a minute and when turned on it went straight to C and not 0. I turned it off for about and hour and when turned on then it went to 0, but as soon as heat was demanded and then turned back to off on the controller the boiler would not shut down again.

I have turned the boiler off, for now as I don't like the thought of the boiler constantly heating the water tank.

What's the possible cause of this problem:

A loose wire to from the controller to the boiler
Faulty controller - although all appears fine, time displayed ok and "on" LED only on when On selected or at right times in timer mode.
Fault on the boiler PCB
A fault/loose wire with the valve/stat in the airing cupboard - but I thought valves and the stat could only call for heat via the controller which is not requiring heat

I am going to try and contact someone tomorrow to come and look, but would like some idea what might be wrong.

Thanks

 

[St0rmer66]

One of the valves (either heating or hot water) will be sticking on. Sounds like hot water one since your radiators don't constantly get hot. But could just be the switch inside one of the actuators and not the valve itself seized up. Won't be thermostats or programmer though, they can't bring the boiler on alone, they just control the actuators.

 

[stroller133]

I have 2 valves in airing cupboard the HW is a Honeywell and the CH a danfoss.

Had a look at wiring diagram online now and think I have a better understanding alongside reading the reply. The controller is not the device that calls for heat, the valve does? The controller and the stat should both be switched to activate the valve, but if this sticks (open?) then the junction box will be call for the boiler and pump to run.

Is there any possibility of moving the manual valve from Open to Auto to try and free it off, or do I need a new one?

 

[St0rmer66]

Correct. The valve must open fully to turn the pump and boiler on. The timer sends power to the stat... The stat sends power to the brown wire on the actuator motor. When the valve is open the grey wire (permanently live) is joined to the orange wire to give power to the boiler.

Most actuators (the plastic or metal part on top of the brass valve) can be removed without draining any water to check for the free movement of the spindle. Please turn off the power to the heating system before you do so, especially on the metal honeywell one! It could either be a seized spindle stopping it closing properly or just the actuator itself (easy to replace if you understand the wiring, the colours should all match up). A seized spindle can sometimes be freed off but often will seize again in the near future without complete replacement of the valve or a service kit fitted to it.

 

[stroller133]

It all makes sense now. I just realised that the pump was still running- I think this confirms a valve (most likely HW) is open or actuator faulty.

I may get someone in to do it for me, but fairly confident now that if they say I need a new boiler or a replacement flux capacitor they are having me on!

I think it might be a good job I spotted the pump and turned it off - that may have been pumping against a shut valve if the actuator is faulty?

Many Thanks

 

[St0rmer66]

It could be, the boiler you have doesn't require a bypass for such an occasion as there is no pump overrun after a demand; but sometimes installers who don't know this put one in anyway! (might have been a blessing in this case). If there is no bypass but the boiler hasn't gone to overheat lockout then that makes the case for a valve stuck open even more likely because the heat has been going somewhere!

 

[stroller133]

I've tried to arrange someone to look at it this morning but struggling. A few peolpe are busy and were 2-4 weeks before being able to come and look.

Might try British Gas as they offer quick appts but only offer 3 prices - £79 (which I have to pay even if they I don't go ahead with work) £199 or £409.

I doubt it would only be £79 as the valve is about £50+ and I imagine they won't have it on the van so it would beceome the next price up by default, but £199 sounds a bit high if its only the actuator and unless the job is lot more involved than I think then £409 would be ridicoulous!

I might try this evening to get the actuator off to see if valve moves. Unless the power is on the same fused switch I have a back up immersion heater and can probably manage until next week without heat

 

[St0rmer66]

They will definitely have a valve on the van. But it will take over half an hour (but not more than 2). The £79 slots are really just simple problems requiring no parts like changing settings, clearing air etc. £199 is really the standard price in reality.