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Back Boiler problem

  • 30-11-2007 10:43am
    #1
    karltimber
    Moderators, Home & Garden Moderators Posts: 1,928 Mod ✭✭✭✭


    HI,
    recently got the house renovated and put in a back boiler as we light a fire every now and then. Last winter all was fine. The system is fine when heated by oil - all rads are hot and no pitching.

    But we lite the fire last week and found the system "pitching", where hot rad water was coming out of the expansion pipe (as it is an open system).

    Why would this be happening. what can I check before I get the plumber back and as above it was working fine last winter.

    I have the upstairs rads all on, and the pump is kicking in also ??
    Could the flow thru the emmersion tank be an issue - ie too slow?

    Am I right in saying that the level of water would be the same in the expansion pipe as the header tank -ie water leveling off.
    If so, could the header tank be too high in the attic ? and the heated water has no-where to expand to ?

    just ranting here with ideas.

    Any suggestions would be great,

    Thx

    K


Comments

  • #2
    Avns1s
    Registered Users, Registered Users 2 Posts: 3,423 ✭✭✭Avns1s


    Is your circulation pump working?

    IMHO the most likely problem is that it has become seized after being unused for a while. A common problem. Unscrew the cover in the middle of the circulation pump and twist the shaft with a screwdriver.


  • #3
    karltimber
    Moderators, Home & Garden Moderators Posts: 1,928 Mod ✭✭✭✭karltimber


    Avns1s wrote: »
    Is your circulation working?

    IMHO the most likely problem is that it has become seized after being unused for a while. A common problem. Unscrew the cover in the middle of the circulation pump and twist the shaft with a screwdriver.

    Thx Avns1s,
    the 1st time I checked the pump it was hot and when I moved the speed dial 1/2/3 it started to vibrate which I though meant it was rotating.
    I will try what you say and open the front and physically check it's moving.

    Can these pumps (grundfos) stick after lying idle for 6 months?

    thx again,

    K


  • #4
    Avns1s
    Registered Users, Registered Users 2 Posts: 3,423 ✭✭✭Avns1s


    They absolutely can stick after a short time.

    When you unscrew the "cover", if you can look right into the pump, you should be able to see the shaft rotating if the pump is set to run.

    Let us know what you find. If it's not this, we'll have to think harder.


  • #5
    karltimber
    Moderators, Home & Garden Moderators Posts: 1,928 Mod ✭✭✭✭karltimber


    have only got to checking this today :rolleyes:

    Opened the pump and turned it on and the shaft is rotating.

    What temp should the thermostat be set at (hot water from the back boiler) and what setting should the pump be at -1,2 or 3?

    any other ideas or things to check.
    will light the fire again tomorrow and see if anything has changed.

    K


  • #6
    311
    Closed Accounts Posts: 5,332 ✭✭✭311


    Your cold feed is probably not done correctly ,the cold feed for the back boiler should be seperate and brought down to the cylinder or boiler.

    It also depends what way your cylinder was installed ,does it have two coils ?

    It can be akward to get it right sometimes ,so don't worry about it too much.

    You will be able to get it sorted ,if the worst comes to the worst you can extend the open vent in the attic ,to a greater height.


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  • #7
    JamesM
    Registered Users, Registered Users 2 Posts: 1,775 ✭✭✭JamesM


    karltimber wrote: »
    have only got to checking this today :rolleyes:

    Opened the pump and turned it on and the shaft is rotating.

    What temp should the thermostat be set at (hot water from the back boiler) and what setting should the pump be at -1,2 or 3?

    any other ideas or things to check.
    will light the fire again tomorrow and see if anything has changed.

    K

    Try setting the thermostat that controls the pump quite low, about 40c, then it will bring on the pump sooner. Also set the pump speed at number 2, in case it is just the power of the pump that is causing the pitching. If the water coming out the expansion, is just hot, it may be the pump. If it is boiling, it means that probably the pump was not switching on soon enough.
    Jim.


  • #8
    Sparkpea
    Registered Users, Registered Users 2 Posts: 1,118 ✭✭✭Sparkpea


    i'd always advise customers to keep the thermostat at 60degrees to bring the pump on, pump setting on most normal houses set to 2. the cold feed should be seperate for the back boiler, the expansion pipe should be at least 3/4 (22mm) or inch (28mm) pipe, the header tank should be as high as possible and the expansion pipe should be as high as possible even if it means looping it away across the roofspace and back, it could be that the pump is pumping too hard and throwing it over the expansion tank.


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