Angela
I couldn't find the clip on thermometers anywhere, so I bought the digital thermometer recommended here from CPC (part number IN0229366) at £30
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and followed the advice on balancing at the FAQ ..
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Firstly I found huge variations in temperature across the radiators, some were 2-3 degrees (indicating very fast water flow) and some 25 degrees. The boiler pipes showed a 20 degree drop until I switched the (Grundfos 15/50) pump to it's maximum speed.
I could get readings easily from the radiator pipes as they were all painted, but the brass/copper fittings of the boiler in/outs made it hard to get a stable reading (the non contact thermometer doesn't like shiny surfaces). I sprayed a blob of matt black paint onto the pipes and solved that problem.
I went around the house carefully setting everything, and as indicated in the FAQ, nothing really happens to the flow rates until the valve is wound down less than half. My valves had two and a quarter turns lock to lock and I found the radiators that had the lowest drops needed to be wound to about
1/3 or 1/2 turn from closed to have any effect.
Once the 3-4 radiators with low drops were restricted down, the other slow radiators started coming closer to the 11 degree drop. As the valves were getting close to their final settings, I found the boiler drop was down to
6-7 degrees and I could set the pump back to "2".
Finally I found some other useful comments on the
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site here
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The comments here about the operation of the thermostatic valves has made me think about replacing my pump with the Grundfos Alpha + which electronically modifies the flow to suit demand as the thermostatic valves open and close. A few of my rooms are in irregular use, so I tend to leave them on minimum, this causes other valves (bedroom particularly) to whistle a little as they modulate the temperature. It might be the new pump could supply a lower pressure in this case (talking myself into another DIY task).
The only hassle I found was the house getting up to temperature (even with
25 on the stat!) or the boiler taking thermal rests after a couple of hours of running. You need to make sure the boiler has been supplying hot water to the rads for at least 5-10 mins before you take a reading. The digital thermometer was a much better way than waiting for clip on stats to stabilise.
Good luck. It looked a bag of worms when I started but to run round the house and see 10/12 degrees across all the rads and boiler was a job well done. Thanks to the group and faq for help.
Colin
PS Tiny URL was broken by the time I finished typing this, the Grundfos pump info is here:
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