Can the flow on this pump be turned up or is it automatic

Discussion in 'Plumbers' Talk' started by fred812, Sep 4, 2017.

  1. fred812

    fred812 Screwfix Select

    Its in a Worcester Bosch 30CDi all works fine except that a couple of rads at the far end don't get as hot as they used to with the previous manually adjustable Grundfos that I had in my old Baxi back boiler.
     

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  2. The Teach

    The Teach Screwfix Select

    From the information supplied.The pump pictured has 2 speeds and there is no user adjustment,its a 'modulating pump' and will run on the lower speed when the system has reached a set high temperature. Something to do with not having to circulate fast so just maintaining temperature and it saves some electricity.

    The pump is factory set but during installation it can be set to suit the the heating load.

    Depending on your system it could be out of balance so look up balancing central heating systems,its diy.

    good luck.
     
  3. fred812

    fred812 Screwfix Select

    Thanks Teach, the boiler reaches temperature pretty quick, 10 minutes if just the hot water circuit, 20 mins if the heating too, so pretty much will run at the low speed the whole time. Bit low perhaps for 12 radiators, 3 underfloor heating zones and the HW circuit.
     
  4. kitfit1

    kitfit1 Screwfix Select

    As Teach has said, this may be down to balancing. With 3 underfloor heating zones and 12 rads that's quite a large call on any heating system. Don't forget, during any heat up period those underfloor zones are a very large call and a very large loss of heat until up to temp.
     
  5. fred812

    fred812 Screwfix Select

    Its a pretty powerful boiler and reaches temp quite quickly, far quicker than the old Baxi it replaced. UFH zones are all balanced and go through a thermostatic mixer to keep the temp down and thermal actuators that are calibrated as per the design. This was all professionally installed and balanced, but I will have a look. The big rad in the lounge is wide open on the lockshield but never seems to get as hot as it did and it has been replaced with a new one. I have some verticals which need a lot of flow but these are on TRV4's and close down after a bit.
    Thanks for the advice.
     
  6. kitfit1

    kitfit1 Screwfix Select

    I know it's a powerful boiler :D, thats why balancing will almost certainly sort out the last couple of rads. As an example, it might be worth turning the first rads Lockshield in the system 2 turns down and then turning all the others a 1/4 turn less in turn and leaving the last 2 fully open. Cost's nothing and you will notice any improvement straight away. If there is an improvement you can then go back and fine tune it.
     
    Last edited: Sep 5, 2017
  7. fred812

    fred812 Screwfix Select

    Ok, will do. Thinking about it the radiator side of the system has never been "properly balanced" which I assume needs clip on thermometers on the pipes in and out of the rad's. Its always been a bit sort of, if its hot then turn the l/s down half a turn, if it isn't hot open it half a turn.
     
  8. Tricky Dicky

    Tricky Dicky Screwfix Select

    Hi, Fred's suggestion looks good. Make a note of the number of turns that you adjust each rad, in case you need to reverse your actions. Small single rads can often be turned down quite a lot, but large double rads perhaps left alone. 2 pipe thermometers just £10 from fleabay, or cheaper if you wait for a delivery from China. Had quite a bit of educational using a 'hand held infrared gun thermometer' from fleabay, for less than a tenner (via China) looking for cold spots in my mother-in-laws house. Regards.
     

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