Wet Underfloor Heating noise when on

[wallaceoc]

Hi all,

I have a 3 zone wet underfloor heating system and I started to use it over the past few days after the summer. I've noticed that when the heating is on I can hear what I assume is water running through the pipes in the area where it's on (it's not near the boiler or the manifold) so the noise must be coming from the ufh pipes. This only happens for one of the three zones.

The noise is like a gushing noise (not hammering, tapping or clicking) and the best/only way I can describe it is like the sound of water running through pipes when a toilet cistern is filling (or similar to the noise of an areoplane flying in the distance). The system has been installed for 6 years and this is the first time I've noticed it. Over the summer all I've had done is had the boiler serviced and the burner seal replaced on the boiler. The system isn't losing any pressure and all zones are heating up as expected so I'm a bit at a loss as to what might be causing it.

Any sugguestions would be very welcome!!

Thanks

 

[Rodders53]

Possibly some air in that loop. Most UFH manifolds have auto air vents. Check those are not sealed down so trapped air cannot escape?

Some have see-through flow meters -check if any bubbles are visible - especially for that circuit?

Even with no air, maybe that circuit needs flow rate reduced a tad, or the UFH pump slowed a little to reduce the noise?

Might the service have disturbed the UFH pump speed setting?

 

[wallaceoc]

Thanks Rodders53.

I checked the auto air vent and it was open so that looks fine and I also do not see any bubbles in the flow meters. I did notice that the circuits were not "balanced" and the flow rate (4L / min) was the same for zones 1 and 3, even though zone 1 is just a small study while zone 3 is at least 4 times the size (main living / kitchen are). I don't know the circuit lengths of any of the zones unfortunately.

The most interesting thing is the zone with the issue (zone 2) is roughly 2 times the size of zone 1 and had a flow rate of 2L / min. When I tried to open the flow meter to increase it, I could not get it to rise above 2L / min.

I've never really looked at this in detail before but I'm thinking now that the system may never have been correctly calibrated for the circuit lengths etc but after 6 years of no issues only zone 2 is now giving me trouble (albeit just a noise).

 

[Rodders53]

Oooerrr... not an expert on this (but do have UFH that I wish we did not - it's a right uncontrollable pita).

You can probably guesstimate the loop lengths from the room dimensions and 200mm pipe centres, plus the distance to/from the manifold (and assume than no pipes are under kitchen units etc.,.)
Flow should be around loop length (in m) / 40 as litres/min one site tells me. Another reckons all zones should run at around 1.5 to 2 l/min. Go figure!

Odd that a) it has just started to be noisy nd b) no change to flow rate as it's not the longest loop (assuming main area is) when you try to alter it. Also the flow rate is lower than the other two - and faster usually means noisier.

Let's hope one of the resident experts comes along shortly with a better idea?

 

[Madrab]

Shut off all the other zones and up to the pump to max and run the noisy one at full flow, may be enough if there is air in the system.

The other possibility is the system is starting to fur up and you are now getting turbulence. Is the system water clean? Do you have clear pipework?

 

[wallaceoc]

Hi Madrab, I will try your suggestion and update on here.

The water looks clean through the flow valve, I get the boiler serviced every year and inhibitor is added. Unfortunately there was a period of a few months where there wasn't enough inhibotor in the system as a plumber changed one of my 2 port valves and din't top up the inhibitor. That got rectified a few months later with my next service.