Radiator 'whooshing noise'

[kpat16]

Hi, I was hoping someone could help with some insights please.

Set-up:
- Vaillant System boiler (with built-in pump inside boiler)
- x2 zones (x1 underfloor in the kitchen; x1 central heating rest of house)
- x10 radiators (x8 wall rads each with dreyton TRVs/lockshields that are all newly installed; x2 bathroom towel rads).
- Automatic bypass value installed (current setting is 3).

Current Status:
- All of the radiators heat up fully with no issues

Issue:
- 2 radiators downstairs make a noticeable 'whooshing' noise when the central heating first starts. After 1.5hrs ( heating still on) this noise becomes even more louder. All of the other 6 wall rads are fine and silent. On the 2 noisy radiators, If I turn the TRV setting down from 6 to 5 the noise reduces but this is because the valve closes and it means the radiator starts to cool down, which then means it takes longer to reached the desired temperature. Surely I should be able to keep the TRV on 6 without any noticeable noise. All the radiators heat up full (upstairs and downstairs) so I am keen not to mess around too much given it is cold right now but the whooshing noise does annoy me (must be my OCD!)

Question:
- Could it be the automatic bypass valve, should I raise this up from '3' to either 4 or 5? or given all the other rads are fine it cannot be this?
- Could it be the lockshield valve and if yes, do I open them more (turning anti-clockwise) or do I close them (turning clockwise)? How many turns should I make?
- Could it be the TRV even though these are new?

 

[Johntheo5]

A TRV setting of 6 and even 5 should correspond to a room temperature well over 25C so seems as if they are full open execept you have exceptionally warm rooms, what model Draytons?. I have my 8 (EPH) set between 2 and 2.8 to give ~ 17C to 20C room temps.

What exact model Vaillant boiler do you have, all of these have user pump settings, you can see its present setting and maybe reduce the pump head although you probably still need 3.0/3.5M pump head with those 10 rads.

Should also have asked if these are mechanical type TRVs, which the look like with those settings, and do not have motorized actuators which I believe can be problematic.

 

[Dereekoo]

Try fully opening the lockshield valve? Take note of how far its opened at the moment so if it upsets the balancing of the system you can always turn it back down to the original setting.

 

[kpat16]

A TRV setting of 6 and even 5 should correspond to a room temperature well over 25C so seems as if they are full open execept you have exceptionally warm rooms, what model Draytons?. I have my 8 (EPH) set between 2 and 2.8 to give ~ 17C to 20C room temps.

What exact model Vaillant boiler do you have, all of these have user pump settings, you can see its present setting and maybe reduce the pump head although you probably still need 3.0/3.5M pump head with those 10 rads.

Should also have asked if these are mechanical type TRVs, which the look like with those settings, and do not have motorized actuators which I believe can be problematic.

Thanks for coming back on this, very kind and much appreciated. Answers to your questions below:

TRVs - Drayton RT212
Vaillant Boiler - EcoTecPlus 637 system boiler.

The boiler was installed back in 2012 but the pump was replaced last year (2024). It was replaced just shortly after all the rads had their TRV/lockshield replaced and a new auto bypass valve was installed. Given all of this was done around the same time it's difficult to know what exactly is the cause but the whooshing noise definitely wasn't there before.

I should also add, I have 4 rads downstairs. 3 large and 1 small. The 3 large ones are the ones making the noise. I also noticed that on one of them, when the TRV is set to 5, after an hour or so you can hear some very gently whistle noises that only stop if I move the TRV setting up or down.

Re the boiler pump, the engineer installed it so I don't know what setting he left it on but my guess is 'Auto'.

If the pump is set to 'auto' should the pump not regulate itself? Or do you think even under 'Auto' there can be cases where it needs to be manually set?

Do you think it could be the auto bypass valve? The boiler itself runs fine and doesn't make much noise at all.

 

[kpat16]

Try fully opening the lockshield valve? Take note of how far its opened at the moment so if it upsets the balancing of the system you can always turn it back down to the original setting.

Thanks. Should I do this as the heating comes on or wait a short while and then do this?

 

[Dereekoo]

Thanks. Should I do this as the heating comes on or wait a short while and then do this?

Any time, its just to see if its the gap within the valve thats creating the whoosing noise

 

[Johntheo5]

Thanks for coming back on this, very kind and much appreciated. Answers to your questions below:

TRVs - Drayton RT212
Vaillant Boiler - EcoTecPlus 637 system boiler.

The boiler was installed back in 2012 but the pump was replaced last year (2024). It was replaced just shortly after all the rads had their TRV/lockshield replaced and a new auto bypass valve was installed. Given all of this was done around the same time it's difficult to know what exactly is the cause but the whooshing noise definitely wasn't there before.

I should also add, I have 4 rads downstairs. 3 large and 1 small. The 3 large ones are the ones making the noise. I also noticed that on one of them, when the TRV is set to 5, after an hour or so you can hear some very gently whistle noises that only stop if I move the TRV setting up or down.

Re the boiler pump, the engineer installed it so I don't know what setting he left it on but my guess is 'Auto'.

If the pump is set to 'auto' should the pump not regulate itself? Or do you think even under 'Auto' there can be cases where it needs to be manually set?

Do you think it could be the auto bypass valve? The boiler itself runs fine and doesn't make much noise at all.

The Drayton RT212 do have a bit of a reputation for noisy operation, how true this is, I don't know

Anyhow check out your pump data. If its on Auto, then yes, one would expect it to be controlled by the boiler output so it will be interesting to see what D.015 reads, if, for eaxmple, it reads say 85% and assuming a 7M pump then that pump is effectively a, 7*0.85*0.85, 5.1M pump or a 4.4M pump if a 6M pump, if the speed is anything around 70% (3.4M) then wouldn't expect much noise but the internal bypass will still be open (partially) if set to its default of 2.5M.

If your boiler is......
637 (VU GB 376/5‑5 A) ecoTEC plus 0010018538 41-044-85, then you can check the target pump speed D.014 and the actual pump speed D.015

This boiler also has a adjustable bypass settable between 170mB and 350mB, default setting 250mB = 2.5M, even the max setting of 350mB, 3.5M always seemed quite low to me because this is before the boiler heat exchanger, some MIs also state that you don't require any ABV even with all TRVd rads, so I would set this to say index 4 for now, piping should be cold downstream of it (ABV).

 

[johnny2007]

A couple of mine do this because the lock shield is only a quarter turn open.
Doesn't bother me but the balance is perfect.
If I open it more it stops the noise.