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Manifold sizing for radiator flow and return

  • 15-01-2016 10:32pm
    #1
    sparks3000
    Registered Users, Registered Users 2 Posts: 46 ✭


    Hi was inside a new house today that has a 1 inch manifold for flow and return for radiators upstairs . It supplies 7 radiators. When I looked at the other manifolds for downstairs radiators they were 3/4 inch , which also supplies 7 radiators which are bigger than the radiators upstairs. My question is why are the manifolds different sizes . The radiators are fed from 15mm pipe from all manifolds. I'm not a plumber just a curious person


Comments

  • #2
    sparks3000
    Registered Users, Registered Users 2 Posts: 46 ✭sparks3000


    Does anyone know or is more information needed or is it down to the individual installers


  • #3
    sparks3000
    Registered Users, Registered Users 2 Posts: 46 ✭sparks3000


    sparks3000 wrote: »
    Does anyone know or is more information needed or is it down to the individual installers

    I calculated the total watts of the downstairs radiators to be 11kw and total of upstairs to be 9kw . After googling I came across a rule of thumb that a 3/4 inch manifold would supply up to 8kw and a 1 inch manifold would be required for anything over 8 kw
    Is this correct . Any help or advice would be greatly appreciated


  • #4
    Dtp1979
    Registered Users, Registered Users 2 Posts: 12,870 ✭✭✭✭Dtp1979


    sparks3000 wrote: »
    Hi was inside a new house today that has a 1 inch manifold for flow and return for radiators upstairs . It supplies 7 radiators. When I looked at the other manifolds for downstairs radiators they were 3/4 inch , which also supplies 7 radiators which are bigger than the radiators upstairs. My question is why are the manifolds different sizes . The radiators are fed from 15mm pipe from all manifolds. I'm not a plumber just a curious person

    They're different sizes cause that's probably what heat merchants gave the plumber on the day. Me personally I'd always use 1" but for 7 rads it's not gonna matter too much tbh


  • #5
    sparks3000
    Registered Users, Registered Users 2 Posts: 46 ✭sparks3000


    Dtp1979 wrote: »
    They're different sizes cause that's probably what heat merchants gave the plumber on the day. Me personally I'd always use 1" but for 7 rads it's not gonna matter too much tbh

    That makes sense but it got me thinking that the manifold should be sized on flow rates .
    If six radiators have a flow rate of 0.04 litres/sec and one radiator has a flow rate of 0.08 litres /sec.
    Would that give a total flow rate of 0.32 litres/sec .
    If this was correct what flow rate would a one inch and 3/4 inch brass manifold be rated for ?


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