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Ferroli Optima Honeywell VMF7 PCB Relay Fault

Discussion in 'Plumbing and Central Heating' started by Helli, 27 Mar 2010.

  1. Helli

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    My Ferroli Optima Boiler struggles to ignite due to a buzzing/chattering Relay. Apparently this is a fairly common fault and a new PCB costs about £180.

    The chattering Relay is the one to the far right of the PCB and often looks burnt due to the sparks caused as it chatters. After much searching and testing I've managed to cure this fault for about £6.

    The chattering relay is actually caused by a breakdown in the small blue capacitor located close to it. This can be replaced for about 20p with a 10uF 100v (or bigger) electrolytic Cap. Don't worry if the replacement is physically bigger, just bend the legs. This may cure the fault; if not and the relay's knackered, replace the relay with a 48vDC 8A double pole one. The SCHRACK original seems difficult to locate in the UK but I got a similar spec one off ebay for £5 and it works great.

    Thanks to Mr Bardwell on Abbeydale Rd Sheffield & Hartley Electrical Repairs on London Rd Sheffield for diagnosing the capacitor as the cause of the problem. Saved me £'s! :D
     
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  2. JohnBD

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    Hi,
    I appreciate this is a relatively old post, but I have just encountered the same problem on my boiler and wondered if you could give me a bit more detail on the location of the relay and how to remove the PCB etc. It looks quite straight forward but worried in case there are any hidden screws etc. Many thanks
     
  3. Helli

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    Hi John,
    I'm no heating engineer but it's a pretty straight forward repair. Assuming you've got to the PCB by unscrewing the front, switch off the power and take some good photos of which wires go to which connections - label them if need be. Pull off all the wires, unscrew the PCB and take it out. Unsolder the capacitor next to the chattering relay and replace with the one I've detailed. You'll get one from any electronics place, Maplins etc. Note it has to be an 'electrolytic' type (I'm told). If the relay doesn't look to bad i.e. Not all black and case melted, I'd try it with just then replaced capacitor as it's that that causes the chattering in the first place not a faulty relay. If it doesn't work you'll have to take it out and replace the relay which I found on ebay. I've buggered about with this fault for ages and it's a common fault with these boards, so i was dead chuffed when Messrs, Bardwell and Hartley got to the bottom of it and saved me about £170. Let us know how you get on.
     
  4. Agile

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    You dont say what that firm charged you! I dont imagine they did it free!

    Whilst I dont encourage DIY repairs on PCBs that is an option for someone with a good understanding of electronics.

    But its not quite as simple as the OP says!

    Electrolytic capacitors are polarised. That means the have a + and a - connection and have to be fitted the correct way round.

    If thats not done then it could damage another part of the PCB or even create a dangerous condition as the PCB controls the gas valve and thus has a safety aspect.

    Replacing a relay which operates the gas valve with another make would create a modification to the PCB which has not approved by the manufacturers and could have safety implications.

    Schrack and Finder relays are better quality and probably chosen because they are far less likely to jam on and create a dangerous condition than cheap chinese relays you might find on ebay.

    Tony
     
  5. Helli

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    Quite right last poster, the capacitor does have a + & - leg which I was just logging on to re-post this info. So just check which way round before you desolder the original. Alternatively, you could get a heating engineer out to put you a complete new PCB in. I just posted the info so people know that a 20p component is the cause of the fault that I suspect often results in an expensive replacement. Entirely up to you which route you take. All the best with it.
     
  6. JohnBD

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    sorry, very new to the forum, and thanks to all for your help and advice. I should have said that I am en electronics engineer, although I haven't done this kind of stuff for many years. I just wanted to get as much info as possible from someone who had already done this job, and double check the location of the troublesome relay and capacitor on the PCB, If you could point me in the direction of the relay seller on ebay that would be very useful. I have found near but not exact equivelents on ebay and at Farnell and CPC.
     
  7. Helli

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    John, sorry I can't trace the ebay seller as it was some time ago but item 130364321191 looks like the one from my memory. Obviously you'll need to check the spec against the one one the board, DPCO etc but I think that's the one. As I said before though, unless yours has been chattering away for a while it might be fine when you fit the new capacitor. From what I remember Mr Hartley saying, the cap holds the voltage for a split second whilst the relay kicks in and then holds itself on. When the cap is shot, the relay can't do this and starts chattering. It seemed to make sense at the time but I'm sure will make more sense to you being an electrical engineer! I'd be interested to know how you get on. All the best.
     
  8. MickH71

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    Dear Helli My son is an excellent Electrician and I am an old -very old Commercial Heating Engineer. I hate combis for the fact that they always go faulty -usually at the wrong time but this Ferolli 700 Optima was probably the very best of all combis ever made for it's reliability. My son's combi has the same fault you mention and he replaced the two relays that appeared burnt (one was chattering) and not 'pulling in' as you mention. The board was put back in still same symptoms. He replaced three capacitors to no avail(the board is marked pos +neg so the observant won't make a mistake. Please may I ask if the folks in Sheffield you know of will repair this board.
    Incidentally there was a 'working' second hand one available on eb so this has been a good temporary measure. This second hand board works. But it would be very interesting to know if a line drawing is available for this PCB ???? P.S. 16 years old & still good -can't be bad ! !
     
  9. Helli

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