Central heating circulation problems

Discussion in 'Plumbers' Talk' started by Jasperoni, Jan 12, 2013.

  1. Jasperoni

    Jasperoni New Member

    We have a gravity fed ch system approx 15 years old.w
    Three rads on a loop downstairs have suddenly stopped working whilst all upstairs and another rad downstairs (on a separate loop) are working.
    I have checked the stop cock in the loft which is working.
    I have checked downstairs rads to see if they need bleeding and they are all full.
    I have opened up a downstairs drain plug and run water through till it went hot but it didn't circulate beyond drain valve, it goes into a rad after drain valve so I guess there could be a blockage in ad or trv.
    The expansion tank in loft is full of hot water but I'm guessing this is because the upstairs water is overheating.
    Pump is noisy but it does sound as though water is flowing, I have also turned the bleed screw to ensure there is no air in pump, and I have bled upstairs rads to ensure no airlock.
    I'm guessing it is either a blocked rad or a failed pump, my question is, how do you know for sure it is pump before replacing? Likewise with rads, is there an easy way of ruling these out?
    Is there anything else I should try such as flushing?
     
  2. tom.plum

    tom.plum Screwfix Select

    change the pump,
     
  3. Jasperoni

    Jasperoni New Member

    Right, I turned the pump up to 3 and turned all the trv's down and now have circulation downstairs.
    I have turned the pump back to 2 and it is staying warm downstairs.
    Next step is to start turning trv's back on one by one upstairs to see what happens.
    Pump does sound noisy, especially on 3.
    I also drained some water off and went to the expansion tank to see if tank drained down, which it did, although stop cock only trickling so I will probably have to replace that at some point.
     
  4. Jasperoni

    Jasperoni New Member

    Also, how do you top up inhibitor?
     
  5. petertheplumber

    petertheplumber New Member

    A week ago I posted an article on balancing radiators, if you read it or copy and past it it may help with your present problem.
     
  6. Jasperoni

    Jasperoni New Member

    Cheers pete.
     
  7. Captain Leaky

    Captain Leaky New Member

    Fit a new pump as advised.
     
  8. petertheplumber

    petertheplumber New Member

    Yes, Yes, Yes. As C leaky says, fit a new pump before that one dies probably on a Saturday night when you cant get a replacement. BNecause it won't last the rest of the winter with any degree of a guaranty.
     
  9. Jasperoni

    Jasperoni New Member

    Either side of the pump I have got valves, so presumably I don't need to drain the whole system down to replace the pump?
     
  10. Jasperoni

    Jasperoni New Member

  11. petertheplumber

    petertheplumber New Member

    I prefer grunfoss, wilo are always fitted to cheap combi boilers, grundfoss will last 5-8yrs on fully pumped or 10-20 years on gravity hot pumped heating systems.
     
  12. Your call, Jasperoni. I know nothing about these pumps, but - as you say - the reviews are pretty good and it does have a 5-year warranty. If it's really a third of the price of a Grundfos, I know which one I'd go for (hint - I'm Scottish).

    As you say, you just isolate the pump using the valves either side. I presume the Wilo is identical so will need no modifications to the pipes/valves, but I don't know (can pros confirm?)

    The easiest way to introduce inhibitor is, I think, to shut off the expansion tank valve (or just the mains stop cock), drain off the system until the water level in the tank is about to uncover the supply pipe near the bottom (have someone downstairs ready to shut off the drain cock as soon as you shout from t'loft...), add the inhibitor and drain off another small amount from downstairs so's most of the inhibitor goes down t'pipe and into the system (but it won't get anywhere near the downstairs drain cock so won't be lost), and then refill the tank (keeping an eye on how the ball valve behaves).

    Or, just drain off half the tank and chuck the inhib into it. It'll make it's way into the system in a couple of weeks (the tank partially fills and empties each time the heating goes on).

    And look closely at the drained water - put some in a cup and check the colour. If it's clearly yucky, you may wish to flsuh out the whole system - there's avid on PooTube from our own Mr Tom Plum
     
  13. petertheplumber

    petertheplumber New Member

    Nothing wrong with being a reputed skinflint scot, but I can get a 15/50 grundfoss selectric pump for under £90 that is NOT 3 times the price of a wilo. Never take too much notice of price comparisons they will go for the cheapest of theirs and most expensive of the others, with most products, not just pumps.
     
  14. Jasperoni

    Jasperoni New Member

    Excellent, thanks for all the help everyone.
     
  15. tom.plum

    tom.plum Screwfix Select

    as mr devs has said, I have a channel on utube, there you will find' how to free a pump'  and ' how to add inhibitor' I know you're not freeing a pump, but its close enough to changing,;)
    go to youtube and from the search box type 'TheTomplum',
     
  16. Jasperoni

    Jasperoni New Member

    Thanks for the advice, I now have the old pump off and about to replace with a new shiny green one (decided to risk a wilo) my next question is the original pump was positioned upside down so flow goes downwards, is this correct? Or doesn't it matter.
    System worked before so I'm guessing it is fine but seems counter intuitive to fit something upside down, if it helps the pump is located in upstairs cupboard so it is currently configured, feed/expansion > pump > 3 port valve > immersion loop > rads > boiler ?
     
  17. petertheplumber

    petertheplumber New Member

    There is an arrow telling you which way the pump goes, the arrow has to be such that the flow is going towards the motorised valve. If the pump is horizontal then the motor should be on the top of the pipe not under it.
     
  18. Jasperoni

    Jasperoni New Member

    Pump is vertical and above 3 port valve, flow is going towards 3 port valve so all good.
     
  19. Jasperoni

    Jasperoni New Member

    Having replaced the new pump the downstairs rads are heating up but occasionally i have to turn upstairs rads down before they start getting warm.
    Also when the heating is on there is constant hot water going into the expansion tank is this just a balancing issue or something else?
     
  20. petertheplumber

    petertheplumber New Member

    I suspect the cold feed and vent are in the wrong places on the airing cupboard plumbing. You need the air vent teeing off vertically from the flow from boiler before the pump. then the pump tees off from the pipe and goes into the valve or valves. The cold feed should then feed into the vent within 150mm of the pump supply from it. It is very difficult to describe a plumbing layout unfortunately.
     

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