Ideal Elan 2 Boiler Short Cycling

Discussion in 'Plumbing and Central Heating' started by crazykong1972, 16 Aug 2011.

  1. crazykong1972

    crazykong1972

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    Hello All,

    I've done a search on this forum and this seems to be a bit of a common issue, but unclear what is going on with our ageing boiler.

    Moved into a house with a 17 yr old Ideal Elan boiler with short cycling issue. Now from what I can see some changes to system have been made including adding radiators over the years.

    These are the times the boiler takes to enter a short cycle when thermo dial is set to 5 on the boiler panel.

    HW - 8-9 minutes.
    HW & CH - About 50 mins.

    After a short cycle completes, it repeats after a few minutes on both HW/CH until the boiler is turned off. All rads do heat up and no problems with the HW either.

    The thermostat dial on the boiler is turned up to 5. If it is turned down lower the cycling starts to occur sooner. Just before the boiler shuts down you can hear slight boiling coming from the exchanger.

    Setup summary
    ------------------
    * Ideal Elan 2 Boiler.
    * Grundfos Pump - set to maximum pump flow.
    * About 18 rads.
    * TRVs on all rads - set to max open.
    * Wall thermostat (Danfoss) in hallway - functions correctly.
    * System drained, cleaned with Fernox cleaner, left for 6 weeks, drained again, refilled and Fernox F1 protector added in Jan 2011.
    * One rad removed to look for sludge - cleaned out - didn't appear to have that much sludge in it.
    * All airlocks removed from system using the bleed valves.
    * The above measures have had no effect on the short cycling timings or cured it, although the system is now cleaner. :)

    Now I have no idea where to go next to troubleshoot this, the pump appear to be fine, but I have some doubts about the various boiler thermostats and perhaps the water flow level speed into the boiler. For example would balancing the system improve the flow back to the boiler?

    I'll try to provide more info later (like model number), as I'm away from home at the moment, but if anyone has any good starting points, or has tackled a problem like this before, would be extremely grateful for your input. :D
     
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  3. mysteryman

    mysteryman

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    You have insufficient flowrate through the boiler. This needs fixing, as it may cause premature failure of the heat exchanger. Could be caused by a tired pump, sludge, system design made poor by random alterations. These were good boilers which needed competent installation.
     
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  4. crazykong1972

    crazykong1972

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    This is an old thread, but still an ongoing problem. Belated thanks for the feedback so far.

    I've returned to this on and off over the years and still have a flow problem/short cycling. Upon moving into the house it was clear the system had been neglected (sludged up and no inhibitor).

    Things done over the years to attempt to improve this...

    * New pump fitted (Grundfos Alpha 2L 15-60). Set to iii and not ppt2.
    * System drained, refilled, cleaned with fernox system cleaner twice.
    * Downstairs Rads taken off and blasted with water outside.
    * Hose attached to bleed plate of downstairs, whilst running flow and return valves out to the drain.
    * Run system with all rads shut except the problem ones.
    * System balancing performed.


    Despite all of the above, the basic problem appears to be the same, the boiler short cycles after 50mins.

    Going back to the flow problem theory, there appears to be a definite problem with the flow rate on some of the downstairs rads (about 3 large). The flow side seems OK, but the return seems be reluctant to take the water back. This evident in the flow being hot whilst the return is only warm when rads start getting back up to temp.

    I'm a bit stuck now at what else to try, not 100% sure there is a blockage as all downstairs rads flowed freely when using the hose and opening the return valves to the outside drain. So am I right in assuming no blockage?

    It almost seems to me that there appears to be some counter pressure or resistance on the return pipes which is restricting the flow to them. Could this happen? If so, would it be something to do with a bypass valve or something?

    This is a 15mm rad system, so no microbore. TRVs all on flow. Problem rads are on furthest circuit from boiler. Inherited system and it looks like a new radiator has been added in a new location (furthest away and one of the problem rads), but others remain in same place as when system was installed.

    Any advice on anything else to try would be appreciated. Next plan was to run mains water through the return valves whilst F&E is closely monitored, but still not convinced it is blocked since all return valves when opened flow outward freely (as tested with the hose to outside).

    Any more help, advice or assistance appreciated. :)
     
  5. DIYnot Local

    DIYnot Local

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