ICOC HE 24 - Crazy Crazy problem.. got me foxed - upstairs zone issues ???

[clubsport911]

Hiya. First post.. please be gentle :wink5:

I've got an ICOS HE24 Boiler fitted to a Megaflo Cylinder. All about 6 years old. All - until recently - was in perfect working order. The problem I have is strange, so I'll jump straight in - please bear with me and read on.

1. Zoned system - up and downstairs.
2. I've replaced the boiler control board 3 years ago with the new V9 (it was failing to light) - all ok when it was installed.
3. All rad valves are thermostatic - 2 years old - perfect working order.
4. Until recently- All was well.
5. Hot water is still fine.
6. Downstairs is still fine - i.e. flick the 'stat over (orange light on the room 'stat is lit) and voila, the boiler lights - rads heat up
7. Upstairs - doesn't work - but hang on, it does.... bear with me.
8. If the downstairs is "on / working".. and the upstairs stat is then set to "on" then the upstairs rads warm up as usual until the temperature is reached upstairs.
9. However, if the downstairs zone is "off" , but the upstairs is "on" (orange light on) then the boiler doesn't light.
10. In other words... the only time upstairs rads get hot.. is when the downstairs circuit is working

I've:-

1. Mechanically checked all the zone valves in the airing cupboard. (the little qtr turn jobbies). Mechanically, they move well, no leaks
2. I've checked that downstairs room stat moves the zone valve OK
3. I've checked that the upstairs room stat moves the zone valve - A little sticky to return to normal... so in fact this is suspect, but manually operating has no effect on the fault.
4. There is another valve which operates the water to the hot water cylinder. This is wierd... even though hot water is fine, there appears to be a demand from "something" for hot water. In other words, with all circuits switched to OFF and HW on the timer to OFF, the boiler can light. ! Not sure what's going on here
5. I've tried my next door neighbours controller.. their sytem is by chance identical - no change.. I still have troubles.

Finally, there is another problem

Its the height of summer. All my room 'stats are "OFF" with the little switch on the side.However the rads are getting warm - downstairs only. This might be that dodgy valve ?

How does the room stat work ? I thought it sent a signal to the controller to spin the pump which then was seen as a low temperate water demand to the boiler which then said "boiler, please light"... I might have got this wrong.

Given that

a) The pump clearly works
b) The valves clearly work
c) The controller is clearly OK....

You can see I'm puzzled. Why does (all of a sudden) the upstairs demand for heating not result in a boiler light up ?

ALL THOUGHTS and OBVIOUS STUFF please welcome !..

Thanks

S

 

[Pipes Plumbing]

I would look at the upstairs zone valve, it sounds like the microswitch may have failed... When the valve motors open it should cause a microswitch to make and deliver 240v to the orange wire from the valve, asking the boiler to fire and the pump to run.
If you are comfortable testing electrics safely, make sure you hae a permanent 240v to the grey wire and 240v back out on the orange wire when the vale is motored open (has to be on the motor, not by pulling the manual lever) - assuming it's a honeywell valve.

Regarding your downstairs rads in summer it could either be the zone vale passing (check if flow is hot from the downstairs zone valve when the hot water is on but the heating off), or heat circulating through the downstairs rads via the returns, depending on how your system is piped up...

 

[erj]

I agree with pipes, check that there is power on the orange wire when upstairs calls for heat. make sure every thing eles is turnd off so you done get a false reading

 

[clubsport911]

Hiya pipes and thanks for the post / reply.

Hmm... that makes sense. The Zone valves are identical. DRAYTON ZA5. I ripped them apart to see if anything was amiss, and recall the colours you mentioned. Stupid question from me, are these colours (grey, orange etc) standard for zone valves ?

FYI - I'm a qualified power systems engineer so working on mains - even live - is something I've done many many times
(I used to work on TV's where the HT connection was 26kv).

I had completely forgotten about the microswitch inside the valve - DOH

I think the downstairs "leak" (the rads do not get that hot) is that sticky valve in Zone 1 (*downstairs). I cannot work out if the motor is just past it's sell by date (It opens well, but fails to close well enough) of perhaps the return spring is knackered ?

Again.. thanks. Any more thoughts or observations are most welcome

 

[clubsport911]

FIXED !!! FIXED....

Ripped Zone valve apart to find the microswitch had become detached from the platic housing. Cleaned up the surfaces and superglued back into it's correct position. Wedged in with some supporting plastic "just in case" and tested the valve to hear the reasurring "tick" of the microswitch operating.

Wired back up...

PERFECT !!.. Zone 2, we have lift off

Now to sort out the downstairs heating "leaking" on... I now suspect a dodgy spring

THANKS TO PIPES for helping - much beers.