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Poor flow

Discussion in 'Plumbing and Central Heating' started by Buffy330, 11 Aug 2021.

  1. Buffy330

    Buffy330

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    Hi

    my really old large house used to be a real mess in terms of several old heating systems that were cobbled together and extensions to it.
    Not to mentions redundant pipework from Back boilers and a Rayburn/Aga style device in the kitchen.

    Now - I have the original gravity fed Potterton Kingfisher2 floorstander - and Im happy with this .
    22mm flow/return from the boiler to the rest of the system - all new , but a lot of long runs.
    Downstairs - I have 22mm feeding 3 radiators off the flow / return.
    Upstairs , I now have a new 22mm single run of flow/return with no spurs , just feeds to upstairs radiators and drops to the remaining downstairs radiators.

    Total number of radiators is 18 !!!

    The system is pumped by a Grundfos UPS 15-60 130 pump.

    The only 15mm copper is is from the flow/return to the radiators.

    Now I have bought a thermo gun ( Bosch ) to measure the temps of each radiator in order to balance them , but my problem is what seems to be a lack of flow.
    At no point does the drop in temp across the flow and return pipes mirror what is acceptable , therefore I am suspecting poor flow.
    In fact the return is pretty close to cold !!!

    All new pipes , new valves , new radiators and a filter ***.. but sometimes when I open a bleed screw , all I get is slight dribble.

    Any pointers please ?
    The pump is only a couple of years old and I bled that too

    Many thanks for reading this

    Steve

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  3. cross thread

    cross thread

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    Are any rads getting hot ? Possibly balancing issue ,boiler undersized,design issue
     
  4. Elkato531

    Elkato531

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    Could be blockage at the cold feed/vent connections from the F&E cistern. This is common on open vented systems and in some cases can reduce circulation to almost zero. If the cold feed is blocked (again common), the system will be difficult to fill and radiators will not vent properly.

    Find the cold feed/vent connection and see if a magnet is attracted to the pipes. The copper pipes are not magnetic but the iron oxide crud that builds up is. Only remedy will be to cut out the blocked sections, clean and/or replace.
     
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  5. Buffy330

    Buffy330

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    Sir - I truly appreciate your wisdom

    Well , I got the magnet out , and the part of the pipe highlighted by the yellow arrow is indeed magnetic,
    This pipe is fed from the small tank in the loft , so I am guessing I have the correct pipe.
    No other sign of magnetism to date

    Is cutting this section out the only solution ?

    Blockage.jpg
     
  6. Elkato531

    Elkato531

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    Yes, cutting out and replacing is the best course of action. The build up tends to be pretty solid and it won't really be shifted by chemicals or flushing. Its clearly low down in the system so will probably need a full drain down. Often the feed/vent connection is high in the system which makes the job much easier. Sadly this doesn't look like the case here. The good news is that the blockage is likely to be limited to this small area as this is where the system water can become oxygenated.
     
    Last edited: 15 Aug 2021
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  7. Buffy330

    Buffy330

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    I have literally just downed tools after removing the blockage , and adding a good quality filter.


    Result , ALL rads are so hot I can barely touch them.

    I have installed a couple of litres of X400 system clean , and will drain down again in a week or so , flush out than add X100 inhibitor.

    The system is now also silent.


    Then I will balance the system and fingers crossed can say good bye to a problem that has plagued me for years.


    Thank you


    Steve
     
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  8. Elkato531

    Elkato531

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    Nice one. Happy to have helped.(y)
     
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