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Worcester Highflow 400. No central heating . Hot water ok.

Discussion in 'Plumbing and Central Heating' started by October, 18 Dec 2008.

  1. October

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    I have a Worcester Bosch Highflow 400.
    The pump seems to be working ok. I removed the head and the impellor is still attached and spinning freely. Both the inlet and the outlet from the pump heat up.
    I removed the diverter valve and part stripped it. There was a few bits of dirt in it but not much. The diaphragm at the back seems ok.
    I'm at a loss as to the reason so any help would be most appreciated.. Thanks.
     
  2. weargas

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    First you need to know if there's a demand for ch. Turn the ch to on at the timer and turn the dhw thermostat down as far as it will go. You need to access the PCB and look for connector X12, it's the one the timer plugs into. You need to have 240v AC across the top and bottom wires. If you aren't getting 240v AC and the red light on the front of the timer is on for ch then your timers gone. If you are getting 240v AC then you need to check whether you are getting 240v AC at plug X7 on the PCB. If you are getting 240 there then the problem isn't electrical. Lots of engineers even miss this one, there's a small copper pipe goes from the diverter valve to up behind the pump. Drain the boiler, remove the pipe and make sure it isn't choked up. You may also want to stick something into the holes it goes into on both sides to make sure they aren't choked either. Any blockage in this pipe will stop the diverter from going into ch mode. If all of the holes and the pipe is clear then I would say your diverter is gone.
     
  3. October

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    Thanks for the information. Tested ok for voltage at both test points.
    Any ideas as to what resistance should be through the divereter coil?
    This one reads 2 Meg Ohms which seems to me awfully high.
    There is a magnetic pull at the coil though.
    Thanks....
     
  4. superdupergasman

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    Easy way for this, switch everything off on the timeclock, put HW stat to zero and wait for the pump to stop over running.

    Switch on CH....does the pump run and the boiler fire for a short period, if so clock and external room stat is working.

    Diverters are problematic, never had the little tube choke although it is a known problem, after these if still not working then there is a filter in the top manifold that can block also.

    My money would be on the diverter valve.

    when replacing make sure you put the small thin o ring only on the first shoulder of the central plastic tube and not fully home.
     
  5. October

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    Thanks for the information folks.
    I've ordered a diverter valve so it's big jumpers and jackets time till it arrives.
    I'll let you know how it goes......
     
  6. October

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    Diverter valve arrived on 24th Dec. Fitted it and the heating started working. Woke up on 25th and it was back to the original problem.
    Went to Tenerife on 26th and just back today so i've beeen warm for a week at least.
    I've not tried to clean out the filter mentioned on an earlier post as I'm not sure exactly where it is.
    Again, any help would be gratefully appreciated. Cheers.
     
  7. weargas

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    when you had it drained down for changing the diverter did you check the little tube I mentioned in my post?
     
  8. October

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    Yes. The tube was fine.Took it out,blew it through ok and checked ports on either side.
     
  9. October

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    Ended up getting a heating engineer in today.
    Gave him the story so far, & he started checking things then eventually said he was stumped & reckoned the new diverter valve must be goosed.
    He fitted another new one & fingers crossed it's been ok now for 3hrs.
    Many thanks for your help weargas & superduper.
    Cheers.....
     
  10. JonR71

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    did you ever find out what was wrong? we have exactly the same problem. plenty of hot water, but no central heating. and no error messages. we had diverter replaced about 3 weeks ago - worked fine for a while, but back to the problem in past two days. any thoughts?
     

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