CH/DHW design flaw?

Discussion in 'Plumbers' Talk' started by screwfox, Nov 1, 2008.

  1. screwfox

    screwfox New Member

    Some advice please.

    My boiler (a recent Worcester Bosch system boiler) is more or less next to the hot water cylinder (about 3 feet of pipe). The system is an S plan, the CH is in 28mm to the first branch (upstairs/downstairs) then 22mm then 15 etc. The hot water is in 22mm to the cylinder, the 22mm return is tee'd into the CH 28mm return.

    The problem is, when the hot water demands then the return from the cylinder is too hot, causing the boiler to shut down, then start, then shut down and so on (cycling?). This causes the CH to not work effectively.

    Is there a simple solution? (someone suggested putting 15mm between the cylinder return and the common return to throttle it?)

  2. heatyman

    heatyman Well-Known Member

    Is there a simple solution? (someone suggested
    Put in a gate valve and experiment with throttling back the cylinder flow.
  3. Measure2cut1

    Measure2cut1 New Member

    What happened when it was hot water only and no heat in the summer?
  4. rome60

    rome60 New Member

    Ideally the domestic return is best run back to the boiler.Is the cylinder stat set at 60/65 cent,& is the stat fixed securely in bottom third of cylinder.Do you get reverse circulation to any rads when hot water only is on.
  5. Ryluer

    Ryluer Well-Known Member

    If HW demand boiler cycling is causing problems with the CH then its not plumbed/wired correctly. :(
  6. doitall

    doitall New Member

    Agree with Ryluer ;)

    Probably an old gravity primary system that's been converted.

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