Balancing Radiators!

[mattataa]

Hi
I recently moved into my first home and after spending the winter here, I wasn’t particularly happy with the performance of the heating. Shortly after we moved in we installed a Hive thermostat as the old one was broken. To save a bit of money I also invested in the hive TRVs.
After using the heating for a few months, some radiators were really hot and others lukewarm. I read about balancing so decided to give it a go. I opened all LS valves completely, ran around the house working out the order, which I then got but wasn’t spot on as some started heating at the same time. I tried for hours to achieve the 12 degree drop but was pretty unsuccessful in doing so, so I tried the old fashioned method of opening the first radiators 1/4 of a turn and gradually increasing this round the house. The heating isn’t really any better but I have noticed the heating is now really noisy with the sound of water ‘rushing’ through the radiators. The furthest radiator away is still not getting as hot as the others and fails to heat the room adequately. I’m not sure what to do now as it’s really noisy and I feel that the hive TRVs are not helping either (I took these off when balancing and for a few days after) any help would be greatly appreciated! I have a Worcester green star 24 boiler and flow temp is set at 61.

 

[Knappers]

Furthest rad may have a bit of a blockage if it's full open and still not very hot.
I'd recommend opening the valves a bit more to stop the noise.

 

[Timmy D]

Also bear in mind that typical/standard lockshield valves have poor “Valve authority”. This means that they do not adjust the flow through their complete working scale (from closed to fully open).

Typically it’s the first full rotation of the spindle from closed to one rotation open which has any meaningful impact.

So if you’ve open any rads by more than 1 revolution, it’s pretty much the same as having it fully open. If these rads are close to the boiler, they will steal the circulation before it gets to the last once, hence your colder than previous rad.

As a guesstimate, open the closest 1/4 of the rads, a 1/4 of a turn.
Then the next closest 1/4 of rads, 1/2 a turn.
Then the next closest quarter of rads, 3/4 of a turn.
Finally open the last 1/4 (remaining rads), 1 full turn.

That will likely get you pretty close. Fine adjustments from there.

Also bear in mind that recommended drop across rads is always difficult to achieve with the mix of old/new rads/standard/high efficiency boilers out there.

 

[Chuck]

What setting is the boiler pump on? The out-of-the-box factory setting is 'maximum', which is unnecessarily high for many systems. The manufacturer's instructions say something like 'set to the lowest value that gives satisfactory circulation' but some installers overlook this. I would try to reducing it to the 'medium' constant pressure mode setting, which will also probably make balancing a bit easier by reducing the interaction between radiators.

Everybody has their own method, mine is to imagine a clock face to judge angles and work in changes of no more than 'one hour'. My starting point for a from-scratch setup is to close the lock shields to the point turbulence becomes audible and then open by 15°, i.e. 'one hour'. Then visit each radiator in turn to tweak the temperature drops. In practice, anything between 10°C and 15°C is going to be okay as the highs and lows will average out. Expect to have to go round tweaking at least twice.

 

[mattataa]

Thanks all.
Any ideas on how to adjust the pump as from what I can see of the manual it doesn’t really tell you!

 

[Chuck]

Thanks all.
Any ideas on how to adjust the pump as from what I can see of the manual it doesn’t really tell you!

Assuming you have a Greenstar i 24 system boiler with an internal pump, there should be a section 'Available pump head' in the 'Pre-Installation' section of the 'Installation commissioning and servicing instructions' explaining the options. You select them using the 'Boiler Settings Menu' which is explained in the 'Commissioning' section.

If you've got an external pump you need to consult the manual for that pump. If it's old, it may not have a constant pressure option just three speeds.