Worcester Greenstar Heatslave 18/25

Discussion in 'Engineers' Talk' started by Glenn13, Jan 24, 2020.

  1. Glenn13

    Glenn13 New Member

    I have a Worcester Greenstar Heatslave 18/25 which is providing hot water but no heat. The boiler is not showing locked out. Any suggestions as to anything I can do or what the likely cause is that I may try before contacting an engineer would be most grateful.

    Glenn
     
  2. billfromarran

    billfromarran Active Member

    Hi Glen, I think I can help with this. I had the exact same prob. with my boiler a couple of weeks ago (See my post below "hot water but no heating")
    The problem was caused by the three way valve, which could be seen moving as I turned the room stat on and off...this looked OK, but there is a microswitch at the end of its travel which switches the pump on, this M/S was not working with the result that the boiler would fire up, but without the pump moving the water through the system the boiler would overheat and switch off until it cooled down.
    Solution? ...fit a new actuator on the motorised valve. The actuator is the bit with the motor only, you don't need to change the valve. It only costs about £50-60 and is simple to replace,You don't need any tools,Follow the cable to where it plugs in to the PCB. Apparently this is a fairly common fault. Easily fixed though. Hope this helps.
     
  3. Glenn13

    Glenn13 New Member

    Hi Bill, thank you very much. I was a bit concerned about tinkering what with the way Worcester pack so much into a tight space. Cheers!
     
    ramseyman likes this.
  4. billfromarran

    billfromarran Active Member

    If the boiler is like mine, you will be able to easily access the actuator ,Take off the front panel and it is on the left hand side of the unit, near the top.
    It might have the Drayton name on it.
    ( I did try to post a photo in my original post, but failed miserably. )
    There is a bit in Youtube where a guy shows how to remove the actuator ,It has a small push in lever on the left hand side of the case.(all assuming it is the same one as mine!!) PS.. Switch off at main switch first!
     
  5. Glenn13

    Glenn13 New Member

    Thanks Bill, I'll update on my progress.
     
  6. MGW

    MGW Screwfix Select

    It seems there are a few flavours of the Worcester Greenstar Heatslave 18/25 but if like mine the pump runs for central heating but not for DHW so pump failure would stop central heating, with oil boilers normally all the control stuff is outside, pump, valves etc. Not built into boiler, but seems there are some where it is built in, the valves are often in airing cupboard not with boiler, mine are in a cupboard alongside the boiler.

    Pictures are good, if you can find the valve, there is often a bleeding lever on the side, you can try latching that on, some times that will allow it to work on a temp basis.
     
  7. billfromarran

    billfromarran Active Member

    Hello MGW, This particular boiler is oil fired as far as I know. Mine, the 12/18 has all the control stuff inside the cabinet, including the pump and 3 way valve .I assume the 18/25 boiler is the same.?
    When mine failed to run the heating,the pumpwas definitely not running, but the fault was not the pump itself, but the microswitch in the 3 way valve actuator which had failed to send the signal to the pump to start.
    On my boiler,the lever on the side of the valve that you mention is not for bleeding but to manually move the valve position from Hot water to heating.
    Hope this makes sense.:)
     
  8. MGW

    MGW Screwfix Select

    Mine same name it seems but pumps and valves in a cupboard at side of boiler. Maybe they were originally inside, but was in house when we bought it, and using C Plan.

    The three port valve can be either W Plan or Y Plan, the W Plan is normal when the storage tank is small, as DHW gets prioarty but Y Plan with large storage tanks.

    With any motorised valve you need a method to open valve for bleeding when there is no power, and the Y Plan valve has a centre position for this, although I know W Plan existed I have never worked on one, there is only two positions with W Plan so maybe it goes all the way over?

    Only talked about it as it may keep heating running while getting parts.
     
  9. Glenn13

    Glenn13 New Member

    Hi Bill, you're a star. I purchased a new Drayton actuator/valve control from Screwfix and then watched a detailed video on YT. It was really easy to fit, although the wiring had to be modified as the old one had a block attachment for the PCB board. I just cut it off and used a block connector. I'm glad to say the boiler fired up straight away and all is back up and running. Thanks again, buy yourself a pint from me.
     
  10. billfromarran

    billfromarran Active Member

    Brilliant! glad it worked!
     
    Glenn13 likes this.

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