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Ideal Mini C28, occasional hot water issues unless CH is on

Discussion in 'Plumbing and Central Heating' started by john_1981, 15 May 2017.

  1. john_1981

    john_1981

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    Hi

    I have an Ideal Mini C28 / re-badged Biasi boiler. There is an intermittent issue whereby at random points I get no hot water from the boiler, unless the central heating is on.

    I have read through the diagnostics section of the manual and located the dipswitch to aid in fault diagnosis. The boiler appears to be the older type, with two PCBs and 3 LEDs and when the boiler is in the fault condition, the LED on the left is blinking green very fast, the middle LED is solid red and the LED on the right is off. The manual states the following error code:

    Faulty primary circuit
    (no water or absence of flow)

    As soon as the CH is called and the room thermostat kicks in, the boiler fires up. The hot water then works without issue, until the next time, usually at some point in the next few days or typically in the evening when I want a shower. Even if I switch the CH off as soon as the boiler has fired up, the hot water will generally function for the rest of the day without the CH being on.

    The pressure in the system when cold is 1.5 bar and remains steady and all radiators have been bled of air when the CH has been on for a good while.

    I have had one heating engineer out to service the boiler who identified an issue with the Ignition PCB which was a hairline crack and visible electricity/plasma in that hairline crack so that has been replaced. Unfortunately, the issue is persisting and due to timing, I have so far been out of luck with the issue happening when a heating engineer is not otherwise engaged on another job.

    I have been told that the pump appears to be strong so should not be causing the problem. I have also been told that it may be worth flushing the CH system with a chemical and then refilling and also using an inhibitor as it could be caused by sludge in the system. I have also been told it could be the "primary flow switch", however I see no mention of a primary flow switch on this boiler, just a CH and DHW switch. I appreciate these suggestions may fix the problem (I am certainly not an expert), but after spending on the Ignition PCB, I really want to only spend on what is highly likely to be the problem.

    I have read various other posts on the forum but they do not appear to be as infrequent and unpredictable as the issue I am facing. I would be happy to pay for a new boiler, after all it is a good 15 years old now, however I have recently sold my house, before this problem started and the price for the house does not factor in a brand new boiler.

    I have also read some mixed responses regarding the divertor valve, does this sound like the culprit?

    If anyone has experienced this problem before I would greatly welcome your comments

    Cheers
     
  2. Agile

    Agile

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    Any experienced engineer will be aware that on this particular model there is a tendency for the primary flow switch to not operate reliably when DHE is called for.

    The proper cure is to chemically clean inside the boiler including the plate HE.

    Unfortunately there are lesser bodge cures which many bodgers like to apply!

    It is a relatively simple fault. But I am surprised that the engineer you called was apparently not aware of the problem and did not seem to want to find out either!
     
  3. DP

    DP

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    Oh really?
    I thought that component was designed that way.
     
  4. john_1981

    john_1981

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    The issue is not present on the replacement part so I assume it isn't designed that way :) If it was then I have been ripped off...

    In that case, I will speak to the heating engineer regarding chemically cleaning the system and book him in. I believe he recommended cleaning via a chemical that could be added via a towel rad inlet etc. Is that all you are referring to, or are you suggesting removing components for cleaning?
     
  5. DP

    DP

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    John, the some PCBs are fitted with said component that shows the spark when the electrodes are passing ht, other pcbs might not have that component.
    The PCBs are not made by the manufacturers, only run to criteria laid down by them. It is not uncommon to see component layout, and setup change as pcb designs is revised. Different PCB manufacturers will have different ideas on layout and component selection.
     
  6. HootingOwl

    HootingOwl

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    You need someone to clean the boiler internals properly. Adding chemicals into a towel radiator is unlikely to do the job. Both heat exchangers need to come out for acid cleaning. You will need new O rings for both exchangers otherwise it will probably leak. Possibly a new diaphragm and a clean of the flow proving assembly.
    I have had this problem on the Biasi derivative more than once.
     
  7. Agile

    Agile

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    I normally clean this model to cure this problem without dismantling anything at all.

    By coincidence went to one of them today with just that same fault.

    Tony
     
  8. Craig Beal

    Craig Beal

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  9. Craig Beal

    Craig Beal

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    I’m relation to this what’s the best way to clean the boiler?
     
  10. DP

    DP

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    My money is on weak pump
     
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  11. dilalio

    dilalio

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    2 year old thread :)
     
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