HW but no CH

Discussion in 'Plumbers' Talk' started by Randolfus, Oct 15, 2019.

  1. Randolfus

    Randolfus New Member

    Problem = HW but no CH

    System = Vaillant ECOTech Condensing Boiler; OSO Unvented Cylinder; Grässlin QE2 Programmer; Honeywell stat; Honeywell 2-way Port Valve (HW); Generic [cheap] 2-way Port Valve (CH)

    Hi all,

    Hope you can throw some light on this for me – my regular heating engineer is away and before I call someone else I’d like an idea of what may have gone wrong, having been fleeced in the past out of ignorance. I can do the simple electrical side (other than resistance testings) but I’m struggling to fathom it today.

    Heating hasn’t been on since April. I put the CH and HW on (Constant setting via the programmer). Both initially came on fine, but after about 20 minutes, the CH stopped (even though the light on the programmer was still active), so I am assuming something on the system has possibly seized/burned out.

    What have I checked so far?

    1. When the CH is set to Constant at the programmer, with room stat at 30 degrees, there is now no boiler activity.

    2. When the CH is set to Constant at the programmer, with room stat at 30 degrees, there is resistance at the lever on the CH 2-way port valve. I can put it into the MAN OPEN position but there is still no boiler activity.

    3. With the CH 2-way port valve lever initially set at AUTO, and the HW setting active on the programmer, the HW works fine, (lever on the HW 2-way port-valve is slack) and the cold water in the 22mm pipe leading into the CH 2-way port valve quickly flows hot once I manually open the CH 2-way port valve…not sure if that is relevant, but it suggests that there’s nothing stuck on closed in the CH 2-way port valve.
    I can’t locate a physical pump anywhere (I am assuming it must be integral in the Vaillant boiler).

    I’ve got a flame, because the HW works fine.

    There’s power to the programmer (although one curious thing was a spider emerged from behind the programmer during this fault-finding, and quickly curled up dead!!)

    I can change the synchron motor easily enough (I always keep a spare) if I am convinced this is the problem. There is no dimple on the silver casing over the CH 2-way port-valve, so I am assuming if the motor inside is burned out, it’s a complete valve replacement (A Honeywell, this time…not a cheapo £20 one off Ebay!)

    I’m happy to get someone in to do the wet-work once I have a general consensus of opinion from you good gentlemen on here.

    Thanks in advance.
     
  2. Mike83

    Mike83 Screwfix Select

    Sounds like the heating thermostat or the motor has went faulty
     
  3. Randolfus

    Randolfus New Member

    Hi Mike, thanks for your fast reply. I suspect the motorised valve has failed as it was a cheap replacement item two years ago, but in the past when I force the lever to the open position (MAN OPEN), and set the CH to Constant, it has worked whilst waiting for a new part....but no such luck this time... I may change the synchron as I have nothing to lose and if that doesn't work, I know I have to budget for either a decent new 2-way port valve or a new room stat. Cheers,
     
  4. Mike83

    Mike83 Screwfix Select

    Just check if your getting 240v at the brown on the zone valve.
    If yes then change the motor.
    If no check the room stat.

    a simple test would be to link the room stat out.
     
  5. MGW

    MGW Screwfix Select

    I will guess 6 wires on the two port valve.
    Green/Yellow earth.
    Blue neutral.
    Brown feed to valve.
    Grey N/O
    White N/C
    Orange Com this normally feeds boiler.
    So since the bleed leaver has resistance it would seem either Blue is not connected to neutral or Brown is not connected to line, not really worried about other wires at this stage, if valve not open you don't want boiler to run. So if you have power between Brown and Blue fault is valve. Don't need a meter, a standard lamp connected to line and neutral (Brown and Blue) will show if there is power there.

    If no power then is a neon screwdriver on the brown, if it lights then fault is neutral if not fault is no line.

    If no line then looking at thermostat and programmer, normally programmer comes first, so at thermostat does the neon screwdriver light, often no neutral at the thermostat so neon screwdriver is likely best option.

    If no power at thermostat then programmer, must be power in as hot water works, so likely if thermostat and valve showing not supply then contacts burnt in programmer.

    I am assuming from what you have said your no idiot and will ensure all done safely.
     
  6. Randolfus

    Randolfus New Member

    Hi MGW, many thanks for your comprehensive step by step suggestion. Yes, I have exactly that cable set-up (photo attached showing the cables at the connecting box end).
    I think I'll whip the programmer off the wall first and see if there is anything obvious (e.g. if the spider that got in there has fried something!!), then work through as you have kindly suggested, with full safety..
    Thanks again. I'll pop back on here tomorrow with an update.

    Cheers,
     

    Attached Files:

  7. Boilerdoktor

    Boilerdoktor New Member

    There is no such thing as safety with what that idiot MGW has suggested. Please don’t follow his stupid advice unless you are prepared to kill your self. Unbelievable that MGW can suggest fault finding with a neon pen ***!
     
  8. Randolfus

    Randolfus New Member

    Evening all,
    Well, it seems that the programmer could be the culprit after all (although the fried spider could have been a red-herring as nothing inside looks charred) - I've put it all back on the wall and now I have no HW or CH call to the boiler. I can't believe I've knackered both 2 way port-valves by testing them on bypass (MAN OPEN) but both have lever resistance when the programmer shows both are ON. These Grässlin Towerchron QE2 programmers do seem to be a bit flakey...this is the third one I'll be on now. Time to spend a few quid on decent gear I reckon.
     

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