Posting a message to the forum will remove the above advertisement

Discuss New Central heating but problems, Please help in the Central Heating Forum area at UKPlumbersForums.co.uk.

  1. Dale Sanders

    Dale Sanders New Member

    Hi.

    hopefully someone can help me here.

    I have a recently had a new gas central heating system consisting of 7 rads and a Worchester 36cdi compact located in the lofty controlled by the wave thermostat.

    I used to have electric storage rads and the electric controlled heating with were on tanks.
    after install i have a drop in hot water pressure. if the cold is on then the hot drops and even running the bath takes forever.

    any ideas?
    i want to make sure i have all my facts straight before speaking to the plumber who installed as he did come arounf measureing pressure and said it was about average on the set up up i requested.
    the main in pressure was 3 bar and the flow was 14l/m with the hot being 10l/m.
    thanks for your help in advance
     
  2. jtsplumbing

    jtsplumbing Plumber GSR

    You need to call back the installer to check water flow your about 3Ltr per min short on hot water delivery,
     
  3. Scott_1979

    Scott_1979 Member

    Main stop tap fully opened? Isolaters under the boiler fully open?
     
  4. Dale Sanders

    Dale Sanders New Member

    He checked flow when I was present.
    Everything is open.
    I have 15mm that enter house that run in the loft but then goes to 22mm. Would it help to increase to 22mm from 15mm pipe.
    The flow seems fairly quick on top taps on sinks but very poor on bath.
     
  5. sammathias

    sammathias GSR

    All your outlets are 15mm to the hots but on your bath i presume its still old 22mm probably delievers the same litres per minute just seems slower.
     
  6. Dale Sanders

    Dale Sanders New Member

    Yes.
    Is the set up correct? How i can I increase flow?
    What seems to be the problem?
     
  7. sammathias

    sammathias GSR

    The flow on your boiler will be preset. Im not 100% familiar with your boiler but id say 12litres per minute. Thus cant be adjusted.
    As for the 22mm to the bath. Ideally it should be 15mm from a combi...you may find you have to draw off alot more water before it becomes hot.
     
  8. AWheating

    AWheating Trusted Plumber GSR

    Tbh it's sounds like there's not much wrong. Your water main is giving 14lpm. Your getting a little less once the flow has been restricted by your pipe work and boiler. If you open the cold then it is sharing the 14lpm with your boiler, probably have less restriction than your boiler it gets more of the share.
     
  9. Dale Sanders

    Dale Sanders New Member

    So if I am getting 14lpm and it enters the boiler at 14lpm why isn't it coming out at 14 or even 13lpm.
    Sure it shouldn't drop 4lpm.
     
  10. steadyon

    steadyon Active Member

    1. Your boiler will provide 13 lpm at a 40 degree temperature rise, plus or minus 15%. If you're unlucky, and its minus 15%, the maximum hot flow rate will be about 11 lpm. Also, the Compact ERP version has a flow restrictor to limit the flow necessary to ensure that 40 degree, which may also reduce the flow rate.

    2. The hot (and cold) flow rate at the bath outlet will be lower than an open pipe immediately after the boiler, as it has to navigate the pipework and fittings / bends. Friction in the system will reduce the rate of flow.

    3. With a tank system, the hot and cold flow rates are largely independent as both come from large stores of water, usually (in the case of a bath) via 22mm pipes. With a combi, the cold comes off the mains via 15mm pipe, and the hot also comes off the mains via the boiler, again with (usually) 15mm pipe.

    4. It would help to know what the cold mains flow rate is at the point of entry to your property. This would give you the maximum possible flow rate for both hot and cold. Measuring separately at the bath taps doesn't give you a full picture.
     
  11. Dale Sanders

    Dale Sanders New Member

    Thanks for this.

    I have measured all taps and the all cold measured around 14-15 Lpm and all hot is around 9-10lpm. The mains in is on 15mm until it gets to the loft transferring to 22mm it then runs the length of the loft to other side to where the boiler is situated.
    Should I be lose 4-5lpm on flow just going via the boiler?
     
  12. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    Check the instruction manual for the boiler. It will tell you roughly what flow rates to expect at what temps. But as stated above this is a rough guide only and may not be spot on.
     
  13. Dale Sanders

    Dale Sanders New Member

    Max flow on hot is 13lpm at 40 c + 15%.
    How can I increase flow as only getting 10lpm
     
  14. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Under sized pipes if it's run from the mains to the boiler in 15mm also all hot in 15mm
     
    • Like Like x 1
  15. Dale Sanders

    Dale Sanders New Member

    Most of hot is in 22mm but mains in is 15mm from floor to loft then transferred to 22mm
     
  16. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    All of this will have an effect.
     
  17. Dale Sanders

    Dale Sanders New Member

    What will be most effective to Do?
    My options are:
    Change 15mm main in to 22mm
    240litre Accumulator on hot
    Pump on the hot line
     
  18. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    change the 15mm to 22mm

    accumulator wont work nor a pump
     
  19. Dale Sanders

    Dale Sanders New Member

    I am being advised by the guy who installed the system an accumulator will give me the max pressure the boiler can cope as effectively it's a storage of water so I can fill 2 baths at max flow.
     
  20. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Combi boilers will never fill two baths they struggle with one
     
    • Agree Agree x 1
  21. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    In my opinion a combi will never run a bath and a shower at full rate together let alone 2 baths.
     
  22. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Think someone's been sold a dream :)
     
    • Like Like x 1
    • Agree Agree x 1
  23. Dale Sanders

    Dale Sanders New Member

    We all know a combi can't do this alone.
    But what about a accumulator tank
     
  24. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    No as the combi won't do over 14lpm
     
  25. Dale Sanders

    Dale Sanders New Member

    Yes I am aware of that but currently it's doing 10lpm so any more will be an advantage
     
  26. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    I would do 22mm to the boiler that should sort it unless your mains flow is 10lpm

    Any ISO valves on the hot pipework that arnt full bore get them changed as well
     
    • Agree Agree x 1
  27. Dale Sanders

    Dale Sanders New Member

    Mains flow is 14lpm.

    Do you think the 15mm is restricting it
     
  28. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    yea
     
  29. Dale Sanders

    Dale Sanders New Member

    Why don't you think an accumulator will benefit my system? Why won't it work
     
  30. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    because you will have 10lpm coming out, they dont increase the flow
     
    • Agree Agree x 1
  31. Dale Sanders

    Dale Sanders New Member

    Don't they store water so will push water at max flow through 22mm pipe as they compress?
     
  32. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    I see you logic here but upgrade the pipe and iso's
     
  33. Gasinspect

    Gasinspect Member

    Chap I work with always increases mains to combis in 22mm all the way. He doesn't win jobs on price, but gets a lot from recommendations.
    At home I only have 15mm but family have learned not to turn tap on when anyone the shower. Even thought of putting a solenoid valve on mains but managed so far. also we turn dishwasher and washing machine off. You learn to live with it. Worse at 7-8 in the morning when incoming pressure low. Might put in mains boost pump.
     
  34. Dale Sanders

    Dale Sanders New Member

    I am struggling to understand.
    I have spent 5 grand on a new combi boiler to control heating and water from electric storage rads and electric thermostat controlling the water in a cylinder. The hot flow was as good as the cold.
    I am prepared to spend more money to get the flow up but what is a guaranteed fix to improve flow on hot?
     
  35. Harvest Fields

    Harvest Fields Trusted Plumber GSR Top Contributor!!

    Upgrade pipe as stated before and as shauncorbs has said change ISO valves to full bore.
     
Loading...
Similar Threads - Central heating problems Forum Date
Central heating system loosing pressure Central Heating Forum Oct 12, 2017
Header tank for solid fuel open vented central heating Plumbing Forum Oct 9, 2017