Central Heating Problem Pump & 3 Way Valve Not Working??

Discussion in 'Plumbing and Central Heating' started by smarty, 3 Oct 2008.

  1. smarty

    smarty

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    My heating is currently not working properly, the hot water is working fine though. It is quite an old system, Thorn EMI back boiler, with hot water cylinder upstairs and header tank in the loft. It has a 3 way Honeywell divertor valve. The boiler is firing up when heating is selected on the programmer. I had a similar problem last year and I replaced the syncron motor on the valve and it fixed it. I could not replace the valve head as it is an old valve. The thing is this time I am not sure if the pump is actually operating. We have these pumps on hot water systems at work and you can feel vibration when they are running, mine just appears to be doing nothing. To make it worse I do not think that it has isolation valves either side of it. Although it does have small protuding heads on the fittings on each side of the pump that may require some kind of key, but I am not so sure that they are valves. Has anybody got any ideas how to check the pump please, or any other pointers. Any help would be greatly appreciated ;)
     
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  3. John506

    John506

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    If you have no service valves, Drain system.

    Unscrew pump head (big flat headed screw)

    check it for sludge or corrosion, give it a good old clean.

    Put the pump head back on, fill system, and see if it works.


    You sure you don't just have air in all the upstairs rads?
     
  4. smarty

    smarty

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    I am not sure that I have air in the system John, I just thought that I would of been able to tell if the pump was running or not. It just seems dead. Thanks for the good advice though.
     
  5. smarty

    smarty

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    I am sure that this is an electrical problem. I was messing about trying a spare old thermostat that I had and the heating came on for a while, i.e the valve opened and I could tell the pump was running and all radiators got hot. I then switched the electric off again to refit the thermostat into it's housing and it would not work after this. Is there a way to link the thermostat out by any chance? If so which wires would I link together. It has a red, blue and yellow wires connected to different points. I am assuming that thermostat not only starts the boiler but operates the valve and pump, it would appear this way anyway. Please help.
     
  6. cjb1971

    cjb1971

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    Power goes from timer/clock to thermostat,then onto 3 port valve which will then open and send power to the boiler and pump,b4 changing the pump make sure there is 240 volt going to it.usually on the thermostat if its been wired in correctly linking the red and yellow wires will by pass it and system will work if the stat was at fault,im asuming u are talking about a room stat on the wall.
     
  7. countryboy20

    countryboy20

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    Hi

    if the room stat is faulty, then it won't make the connections (to call for heat) and there will be no power to the white wire in the 3 port valve and therefore the pump and boiler will also then start up.
     
  8. smarty

    smarty

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    Thanks for the replies guys. The stat is a room stat on the wall it is an old Honeywell T6160B. It has three wires going to it a red, yellow and blue. I am hoping that it is wired correctly as I knocked it off the wall a while ago and got a replacement dirt cheap off ebay and wired it the same way. I also made sure the heating was working at the time which it was. Currently it is wired Red to pin 1, Yellow to pin 4, Blue to pin 2. So I will try linking pins 1 and 4. Thanks ;)
     
  9. smarty

    smarty

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    Thanks Cjb1971 linking out the yellow and red wires has got the system working. I obviously need a new stat, I was wondering if fitting a digital one will be easy? Have I got enough wires for one of these stats and what are these wires for please? It has a Red, Yellow, and Blue wire. Or am I better off getting the same stat again, the only good thing about that is that they are cheaper. Thanks again though mate and all the other great advice from other posters :)
     
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  11. mahmot72

    mahmot72

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    It is rare for a system to clog up, if your pump is not chattering, rubbing, grindng, excessively noisy, or vibrating then it will be OK, a pump should last at least five years, so if it is that old change it anyway, because it will fail at anytime beyond that age, and it is a very simple job if you have the right tools. If the radiators all bleed OK then suspect that the header tank has not filled up to the required level. The small tank is always the highest component in the system and if it has dropped below the feed pipe level it will result in the pump pulling in a mixture of air and water, this will lead to and air lock at the pump. There are two ways to detect this. 1 you will hear the pump washing as the impeller churns up the air water mixture.2 You will hear the water gurgling through the pipes and the raditors nearest the pump. If you have the symtoms of pump running OK but washing, and gurgling pipes, and the pipes on either side of the pump being cold, or hot above the pump and cold below the pump then you header tank is very low or empty. Think of it like a hose pipe connected in a loop with a pump inserted in the loop, if the loop of pipe has a section filled with air the pump will move the water until the air comes round then it will stop pumping water, it will not move air, centifugal impellers do not move air.

    The cure is simple, and really it should never have happened because the ball cock valve should have opened as soon as the water level dropped in the top-up storage tank. The reason this usually happens is because the valve sticks shut. This tank is used so rarely that it can stick shut, the water level can drop so low until you have lost the head of water, it is like flushing a toilet with no water in the cistern. The plastic floats are so light that they do not have enough weight to fall and open the valve to refill the tank. Just push it down and lift it a couple of times to loosen it off.
     
  12. seco services

    seco services

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    rubbish

    rubbish as well.
    mine 24 yrs old best i get one of the van then.
    what is that load of jumble ? we surpose to read that. :rolleyes:
     
  13. mahmot72

    mahmot72

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    I might have saved someone a lot of cash mate. Or are you one of these rip-off Heating Engineers who charge people £200or £300 by telling them they need parts when all you do is bang the pump with a hammer?
     
  14. seco services

    seco services

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    tell me since when if a pump last 5 yrs its due to be changed ?

    not my fault you don't know what a paragraph is.
    don't get the sulks and start slacking people off.
     
  15. gaspro1981

    gaspro1981

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    no offence dude but wot a load of tish tosh :rolleyes:
     
  16. davebgas

    davebgas

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    Good grief.......
    What next, will we be discussing water vortices in pipework?


    You might also have caused him more problems and had him chasing the proverbial wild goose 'mate'.
    Did the OP's clue about an electrical problem with the room thermostat not spark your attention?

    And as for 5 years for a pump.... I suggest you ring Grundfos and explain to them that they could be making a killing what with all these lousy long life pumps out there.

    There's also no need to start accusing people of being rip off's or con men.... if all the people on here who give advice were as you accuse, con men, why the hell are they giving FREE advice to people?
    How about we all go away and leave it to obvious qualified engineers like yourself.
     
  17. kitesrus

    kitesrus

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    LOL just stumbled across this topic whilst looking for ideas as to why my system is only working on C/H thanks for the tips i will change this today

    But i cant believe what i have read, my pump is still running without any obvious signs of problems and is around 9 years old, i guess if you buy a cheap pump then maybe it wont last long.

    I am no heating engineer but i am an engineer and understand how things are manufactured and what makes things last is high quality and precision. Sometimes a little knowledge is dangerous and people really need to keep their mouth closed.

    As for con men, surely they would have been advising him to change the pump yet it was the one calling others con men advising the OP to change the pump?

    Ho hum, thanks for the tips guys and will be back if i get stuck
     
  18. DIYnot Local

    DIYnot Local

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