worcester problem

Discussion in 'Plumbers' Talk' started by keitheboy, Oct 1, 2014.

  1. keitheboy

    keitheboy Member

    hi,i have a worcester gravity fed boiler and when i have the ce on and the boiler stops, water gets thrown up the expansion pipe into the small tank in the loft yet with the hot water on and the ce it runs perfectly and with the hot water on its own no problem at all, can anyone suggest a fix for this please?

    keith
     
  2. Dave does Gas

    Dave does Gas Screwfix Select

    OK lets start at the beginning, You say a gravity fed Worcester, doubt it as I can't remember the last Worcester boiler suitable for a gravity system, but assuming you do, do you mean gravity water system and pumped heating? Or in your airing cupboard is there either one or two motorised valves just after your pump? Have you had a look at the water in your F&E tank, thats the small one is it clean or is it full of crud? What Im suspecting is a partial blockage somewhere in your heating system which is being by-passed when the water is on thereby allowing full flow. If as you say its an old gravity system is the pump running when you put a demand on it, IE call for heat?

    Incidentally which worcester is it, are you oil or gas?
     
  3. keitheboy

    keitheboy Member

    hi dave,
    the boiler is a 14/19 cbi gas boiler about 10 year old there is one motorised valve with the pump above this the water in the fe tank is clean and the pump is running fine when the hopt water and ce are on its running beutifly and if the hot water is on its own fine its just when the ce is on its own it plays up ie noise in the pipe in the airing cupboard and the vent pipe gets hot from the water going up to the tank.had bg comwe and service the boiler about two weeks ago and he said it was fine but could not explain why it was doing this
     
  4. Dave does Gas

    Dave does Gas Screwfix Select

    Sounds like a Y plan System. Could be Air in the heating system although this would move when the system runs, just out of interest what speed has the pump been set on? And how many rads on the system? Do you have a BG contract? if you do get them out after all thats what your paying them for. My feeling is that there is an obstruction somewhere in the CH system, maybe around the cold feed open vent area. You can test this with a magnet. Run it over the area of the cold feed open vent it may stick, if it does theres your problem.
     
  5. Keith, is this a recent issue? When/how did you become aware of it? And are you sure it hasn't always been like this?

    The motorised valve - I assume that's a 3-port jobbie? Could this not be opening fully on the CH side? (Is it possible for the 'bung' to not move fully even tho' the microswitch goes 'click' at the end of travel? I just don't know.)
     
  6. keitheboy

    keitheboy Member

     
  7. keitheboy

    keitheboy Member

    hi dave,
    the pump is on no2 setting i dont have a bg contract i just had them out to service the boiler has they were doing it for £39! i will try the magnet test it did stick on the connecter to the 22mm to 15 mm connector so i changed it but it was not blocked and made no difference,but i also put in a isolater valve from the cold feed fe tank so i dont have much to drain oiff the fe tank will get back to you once checked the magnet theory,thank you for your help so far
     
  8. keitheboy

    keitheboy Member

    hi, i have always wondered about this valve but wasent sure if i had to drain the hot water tank has this comes through the valve?let me give you a rundown of what has been happening over the last ten years here goes i had the boiler put in by a friend who is a corgi reistered plumber the old boiler was a back boiler baxi in the fire place downstairs this was in there for 20 years and no trouble and was not serviced hardly at all the new worcester boiler was put in the airing cupboard up stairs in the beroom and a gas fire put in the dowstairs place of the boiler it ran for a year with no problem then the boiler started to leak water out came a worcester engineer and replaced the heat exchanger and charged me ?240 to replace this has the boiler was just over a year old andf the warranty had expired. then the trouble started with the ce so i had insurance and a chap came out and replaced the board to no avail so i took all the rads off and flused the system out which was pretty black i also installed a manatec filter and replaced the three port valve solienoid then was told it could be the pump so replaced this and had to alter the pipe bwork has the new pump was a slightly different size my fisrt go at soldering which i thought was quiet good even the chap who did the service said it was neat anyway by now i am getting the thought that the boiler is a lemon but it works very well when the boiler hot water and ce are running together and it does not seem to use anymore gas! i also used fernox flushing compound to clear out the system for 24 hours sorry to babble on but to me its a mystery and the wife says dont worry just use both the ce and hot water on but i hate not curring the prob just thought someone might have had the same problem

    keith
     
  9. keitheboy

    keitheboy Member

    sorry dave the system has 6 rads on it
     
  10. keitheboy

    keitheboy Member

    hi dave have done the magnet test and nothing
     
  11. Hi Keith.

    Fitting the filter was a good move as was adding chemicals to clean your system. How often do you clean out the filter, and how much crud tends to be in there? Have you now added inhibitor to the system to prevent corrosion?

    Ok, here's my t'uppence worth as I'm not a plumber. I suspect the problem was caused by that boiler change you mentioned - moving the boiler from one floor to another shouldn't be a problem provided the pipework is fully modified to cope - especially the cold feed and expansion pipes wot go to that wee tank in t'loft.

    If you look at this: http://www.gasman.fsbusiness.co.uk/fully_pumped_systems.htm , you can hopefully see that when you turn on the pump, it is likely to draw down some of the the water which sits in the vent pipe (water would normally sit in that vent pipe at the same level as the water in the tank itself - ie, nearly at the top). The water level in that pipe will drop as the pump is running - in really severe cases (which yours isn't) it can even suck all the water down from that pipe and even draw air into the system. With all systems, there's bound to be a wee wobble in that level. At the same time, the same amount of water is pushed up into that tank from the cold feed, so the level inside that tank raises a tiny amount. So, you've unbalanced the levels there.

    Then you turn the CH off. What happens? The pumps stops running, the water in that tank drops again, and the low water in the expansion pipe shoots back up to its proper level. But, if it was really unbalanced, then it'll over-shoot and dump some water in the tank out the looped overflow.

    Why does this sometimes happen? Lots of possibilities; pump running too fast, too much restriction in your radiator system (that's probably why it doesn't happen on DHW - less friction to flow), some rads fitted in the upstairs floor so much closer to the expansion tank level, etc.

    I suspect in your case it's down to the boiler being moved, and possibly the expansion and cold feed pipes aren't best located any more. Can you tell us where these two pipes are in relation to the boiler and the hot cylinder? Photos would be good.

    How to solve? Ok, if it's down to a recently-created 'fault' such as a restriction in your rad system, then that should be sorted. Obviously. Or, if it's down to the pump running too fast for your system, then try turning it down to speed 1 and check that everything (rads and hot cylinder) still heat up quickly. However, if the furthest rads now take too long to heat, put it back to '2'.

    Assuming it's a boiler-swap issue - eg a slight design fault and not a 'real' fault - then you may be able to sort it (compensate) by; raising the whole expansion tank! Ok, you want it simple? Then just raise the height of that looping expansion pipe to another foot above the exp tank. That might do it.
     
    Last edited by a moderator: Oct 2, 2014
  12. That 'isolator valve' you fitted on the cold feed FE tank - what type is that? Hopefully full-bore? And no chance of anyone leaving it shut off...? :eek:
     
  13. Dave does Gas

    Dave does Gas Screwfix Select

    Too right there should not be an isolation valve on the cold feed. Not only does it fill the system but assists in taking up expansion when the system is hot. Be a very good idea to remove it soon as possible.

    Cant fault DA's post may help you understand what is going on. Have a look in the boiler book for the recommended heights from F&E tank to top of boiler and check yours
     
  14. keitheboy

    keitheboy Member

    hi dave,
    the isolater valve is just a normal valve with a screw fixing to turn it off and its by the fe tank in the loft so no one goes up there except me i simply did it to save draining the fe tank if i need to change anything in the airing cupboard.the height is 6 ft to the fe tank from the bottom of the boiler so that should be enough i think as there is another two feet where the expansion pipe goes. da seems to think it might be the three way valve and he admits he is no plumber so do you know if i replace the valve if i have to drain the hot cylinder has thgis passes the valve from the pipe?
     
  15. keitheboy

    keitheboy Member

    Fitting the filter was a good move as was adding chemicals to clean your system. How often do you clean out the filter, and how much crud tends to be in there? Have you now added inhibitor to the system to prevent corrosion?

    Ok, here's my t'uppence worth as I'm not a plumber. I suspect the problem was caused by that boiler change you mentioned - moving the boiler from one floor to another shouldn't be a problem provided the pipework is fully modified to cope - especially the cold feed and expansion pipes wot go to that wee tank in t'loft.

    If you look at this: http://www.gasman.fsbusiness.co.uk/fully_pumped_systems.htm , you can hopefully see that when you turn on the pump, it is likely to draw down some of the the water which sits in the vent pipe (water would normally sit in that vent pipe at the same level as the water in the tank itself - ie, nearly at the top). The water level in that pipe will drop as the pump is running - in really severe cases (which yours isn't) it can even suck all the water down from that pipe and even draw air into the system. With all systems, there's bound to be a wee wobble in that level. At the same time, the same amount of water is pushed up into that tank from the cold feed, so the level inside that tank raises a tiny amount. So, you've unbalanced the levels there.

    Then you turn the CH off. What happens? The pumps stops running, the water in that tank drops again, and the low water in the expansion pipe shoots back up to its proper level. But, if it was really unbalanced, then it'll over-shoot and dump some water in the tank out the looped overflow.

    Why does this sometimes happen? Lots of possibilities; pump running too fast, too much restriction in your radiator system (that's probably why it doesn't happen on DHW - less friction to flow), some rads fitted in the upstairs floor so much closer to the expansion tank level, etc.

    I suspect in your case it's down to the boiler being moved, and possibly the expansion and cold feed pipes aren't best located any more. Can you tell us where these two pipes are in relation to the boiler and the hot cylinder? Photos would be good.

    How to solve? Ok, if it's down to a recently-created 'fault' such as a restriction in your rad system, then that should be sorted. Obviously. Or, if it's down to the pump running too fast for your system, then try turning it down to speed 1 and check that everything (rads and hot cylinder) still heat up quickly. However, if the furthest rads now take too long to heat, put it back to '2'.

    Assuming it's a boiler-swap issue - eg a slight design fault and not a 'real' fault - then you may be able to sort it (compensate) by; raising the whole expansion tank! Ok, you want it simple? Then just raise the height of that looping expansion pipe to another foot above the exp tank. That might do it.[/QUOTE]
    hi,
    i clean the filter every two months and have fernox inhibitor in the fe tank and top up every year looked at the diagram which was useful so it looks like it is either the three port valve or rads even though i did flush them mind you they are very old 28 years to be exact but then would they not cause the problem when ths ce and boiler are on has the hot water must turn off when it reaches the required temp? i will take some photos and post asap
     
  16. How much crud do you remove from the filter each time?

    I'm not saying it's the 3-port valve or the radiator system, or blockage or anything. Because I have no way of telling.

    In fact, now that I think aboot it a bit more, it strikes me as very unlikely to be the 3-port valve because this would introduce a partial blockage on the flow from the pump so this would make it less likely for the pump to draw down water from the expansion pipe. But then, that would only be true if the pump were fitted as in that diagram - on the boiler 'flow'.

    We on here don't even know that much about your system!

    We need photos, man. Is the boiler close to the hot cylinder? Please provide photos of the boiler, cylinder and all the pumps and valves malarkey - and clearly showing the expansion and cold feed pipes to the FE tank....
     
  17. keitheboy

    keitheboy Member

    hi da,
    the amount of filings is small but they keep coming,enclosed is photos
     

    Attached Files:

  18. keitheboy

    keitheboy Member

    cant seem to send some has they say it is to big to upload?
     

    Attached Files:

  19. keitheboy

    keitheboy Member

    hi da,
    having trouble sending large files this way,have you an email address then i can compress them to you?

    keith
     
  20. Best to reduce them in size first and then get them on here so as many as possible can view. Take some photos from further away so's we can follow what the pipes are going. Where's the boiler?

    Do you have Windows Photo Gallery or Microsoft Picture It? If you open them in the former, you can email them to yourself in a reduced size. If you have the latter, you can open them and save them again, choosing what size you'd like them to be.
     

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