Noisy lockshield valves after balancing

30 Nov 2020
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United Kingdom

I have just balanced the rads and there is now a high pitched noise coming from the lockshields when the heating is on. The house was built seven years ago and no surprises the CH was never balanced when commissioned. The noise will vary on how open the TRVs are set as well.

The TRVs are Myson 2-way, so I assume the lockshields are the same.

Could this be caused by there being too much sediment in the system, we live in Exeter which is not hard water but leaves red silt over time. If this is likely, would getting the rads flushed and some new additive be beneficial, or is this just a thing with a balanced system?
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It's an Ideal Logic Heat 24 - not a combi.

It is a pressurised central heating system.

Balancing was done from 1st rad to warm to last and set between 10 and 11 degrees difference between flow and return throughout.
The Logic Heat 24 is an open vent boiler, which is usually used with a Feed and Expansion tank in the loft. But they can be sealed and pressurised.

Are you sure it's not a System boiler?. The Heat version has an external pump; the System has the pump inside the boiler.

The boiler is designed to work with a 20C differential, not 10-11C.
It says Heat on the front of the boiler, so I assume that is what it is. We have an expansion vessel in the airing cupboard which is showing just under 1 bar of pressure which is where the filing loop is. We don't have a loft so everything is on mains pressure.
OK, so it has a separate pump, possibly a Grundfos and probably near the HW cylinder.

Can you confirm the make and model of the pump, and what speed setting it is on?
Sorry about not getting back sooner, work gets in the way :)

It is a Grundfos UPS 15-60 (130) set to position III.

1 bar with CH on and hot.

So looking at the manual for the pump online, I can see that the pump has been set at maximum and I doubt that it was set to I to see if this would heat the rads. So, as I have tried to balance the radiators with the pump possibly set too high, should I open the lockshields to full again, set the pump speed level correctly and when that is working, balance the rads again?
Set the pressure to 1 bar when the system is cold.

You should be able to balance the system with the pump on speed 2, or even on 1.

What balancing procedure are you following, and how are you measuring the rad temperatures?
Thanks for this, I will probably check the rads again - can't really go anywhere at the moment can we.

I balanced the rads by working from the quickest to heat up to the slowest. TRV open to max and lockshield off. Turn on heat and open lockshield 1/4 turn and then adjust as necessary. I have a digital thermometer with 2 heat sensors which I attach to the flow and return. The thermometer shows the difference between them. I then repeat this on each rad to the slowest to get warm.

Even with the noisy valves, they are all heating up at the same time, so with the pump set to 1 they should be quieter as this in my head explains the cause. It might be possible to get a bigger difference between the flow and return that you originally mentioned, though I understand that it is quite hard to achieve.
You seem to be going about balancing in the right way, though removing the TRV heads will eliminate any chance of them closing and messing things up. You could also try setting all LS valves to 1/4 turn open and checking all rad temperatures. This will tell you which ones need opening a bit and whch need closing. Adjustment is always very fine, say 1/12th turn or less at a time; and you need to leave a few minutes for the temperature to stabilize.

Setting the pump to 2, or even 1, will automatically increase the temperature differential as the flow rate will decrease.

Setting all radiators to the same temperature differential assumes that the radiators are sized exactly for the heat-loss of the room. In reality, this is never true; some may be undersized, but many are oversized. You can ccompensate for this by having a larger differential on an oversized radiator and smaller on an undersized. Just make sure the differential does not exceed 20C at the boiler.

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