Ideal boiler

May888

Need some advice. I have an ideal boiler he15 icos and the heating and hot water is off but the boiler it displays C and it keeps firing up like it’s on continually. What does that mean. Whatever I switched on last ie if I put the heating on for an hour, the heating is still on after an hour and boiler keeps firing up even though it’s off. Not sure if it’s to do with anything, but recently changed the pcb 🤷‍♀️. 

southcoastrgi

Something is telling the boiler to carry on working, I'd be looking at a sticking/faulty mid pos valve or programmer 

dori2o

Could it be due to the cold weather?

I know my boiler will fire if the temperature falls below a certain level to prevent damage from freezing.

Jeepers_Creepers

I doubt it - your house can't be freezing! 'C' I think means that it is firing - it thinks it's being asked for heat.

What does the white 'burner' light do during this? If it's steady, the burner is on. If it flashes, it means that the boiler is being 'asked' for heat (from DHW or CH), but is already heating more than it can get rid off - so it 'pauses' the actual burning, whilst still actively running. Ie, everything is 'hot', and it's in 'keeping it topped up' mode. I think.

What level of testing are you up for? Do you know how to wield a test screwdriver or multimeter? If so, you could check for a 'trigger' voltage on the input socket of the boiler. That will tell you if the boiler is actually being 'asked' for heat or whether the boiler is acting on its own as a rogue...

Page 30: https://library.plumbase.co.uk/flipbooks/RE/idiche15_22390_t/mobile/index.html#p=30 If you can test the voltage at L2, that will tell you if it's the boiler or something else that's at fault. Ie, if your boiler is running with NO mains voltage at L2, then your boiler is confused. If L2 is getting a mains voltage when it shouldn't - when prog and stats aren't calling for heat - then it's a faulty something else , the prog and valve being the most likely culprits.

Worth trying this first, tho' - get a helper who will turn the programmer on and off whilst you observe the 3-port valve, pump and hot cylinder.

Ok, turn your boiler's mains supply wall switch 'OFF'.  

1) Go to your hot tank and note where the cylinder stat is set - around 65oC? Now adjust the cylinder stat up and down. Does the stat audibly 'click' at roughly the water temp (60oC or so if it's hot)? Does it click reliably going both ways (it will be a few degrees out, but roughly click in the same place)? Cool. Ok, turn it down to min. for the moment.

2) Does the room stat 'click' reliably at the approx room temp when turning it both ways? Cool. Ok, turn that down to min. too.

3) Have a look at the lever on the 3-port valve; is it tight against the 'auto' side, on the left? Cool.

4) Get someone to turn back on the wall switch for your system. Ask them to set the programmer to 'on' 24hrs for both CH and DHW. Nothing should happen in the wee cupboard you are in, since neither the cylinder nor room stats are calling for heat (you've turned them both down to min)

5) Ok, turn up the cylinder stat until it 'clicks'. The pump should come on, and so should the boiler - ask your helper to confirm. The valve shouldn't move. After a minute, it should be obvious that the inlet to the valve is getting hot and so should the pipe coming out of Port B (going to the cylinder). Cool. Now turn the cylinder stat back down until it clicks off - does the pump and boiler stop? Cool.

6) Shout at yer mate to go to the room stat and turn it up until it clicks. The 3-port valve should whirrrr smoothly for around 2 seconds and then make an audible 'click'. The pump and boiler should start, and after 30-odd seconds you should find the inlet and Port A to be hot. You should also find that the valve's lever is completely loose from one end to the other. Cool. Now turn the room stat back down until it clicks - the pump and boiler should turn off (the valve will probably stay where it is, tho'.)

7) Turn the cylinder stat back up - the valve should whirrr to its original starting position and the pump and boiler fire up. Port B should become hot again. The lever should feel tight against the 'auto' side again.

8) Now turn the room stat up too - the valve should give a short whirrr and both ports A and B should become hot. The lever will be loose, but not easily pushable all the way to 'manual' end.

9) Ok, have a play with the cylinder and room stats... Cylinder stat ONLY turned up should have the valve whirr until the lever is tight and port B only should be hot. Room stat ONLY turned up should have the valve whirrr until the lever is completely loose and Port A becomes hot. BOTH stats on should have the valve doing a SHORT whirrr from either of the previous end positions, and the lever should be partly loose for most, but not all, of its travel. Turning off the room stat should have the valve short-whirrirng back to 'auto'-lever end. Etc etc. Turning both stats down should have the pump and boiler stopping. Turning both stats UP but then turning the programmer OFF should have the pump and boiler stopping.

Have a play, and see if you can draw conclusions.

Why did you change the PCB? Because of this behaviour? Did you fit the correct jumpers?!