Strange Heating Droning Noise

[BobSpoons]

Hi
Could anyone please suggest a reason for the noise in my heating.

Basically when its turned on its quiet for about 30mins and then it starts droning. The drone gets louder and then stays for the duration of the heating being on. Its a kind of constant drone.

Ive listened at the pump and the pump sounds to be quiet. Ive also adjusted the pump speed and it doesnt seem to affect the noise.

The motorized valve has recently been replaced (on a seperate issue) and this didnt seem to have an affect on the noise. Weve also had a new hot water cylinder in the last year and that didnt affect things.

The pipes are all plastic if that makes any difference??

Also weve just had the boiler services and so thats all okay.


What seems odd is that when we turned the TRV in the bedroom up from 3 to 5 the noise went away (suggesting maybe less pressure or more flow through the system) and came back if we lowered it back to 3.
BUT when we then left the bedroom on 5 and lowered the hallway rad from 4 to 3 the noise came back???
So we left them on the settings where it was quiet and then after about 15mins the noise started coming back of its own accord.

The noise also seems to alter a bit in pitch if we alter it between heating/water/both.

We have a sealed system off of a standard non-combi boiler. The pressure is set generally at about 1.7bar.
We do seem to loose about 0.1bar about every 6-8 weeks or so.

Another odditty is that the loop radiator (with no TRV) always seems to need a tiny bit of bleeding on it no matter how many times we have done it. Its only ever a tiny tiny amount but seems odd that in a pressurised system im not sure where the air is coming from, surely it would all be out of the system after refilling at about third week after bleeding every 4 days or so??


Anyway, after all that lot, I do hope that somebody can offer any thoughts as to what could be the cause. The drone is annoying during the day but in the morning it actually wakes us up which is awfull.

Many thanks for all who take the time to read this and also many thanks for any thoughts that may be able to help.

Cheers

Bobspoons

 

[Softus]

Regarding the droning, it sounds like the TRVs are the cause.

Do you possibly have uni-directional TRVs fitted on the return instead of the flow?

Or you might have dirt in the system? Talking of which, the repeated introduction of air/gas and the loss of pressure are also symptoms of a corroding system.

What's the history? When was it all installed? Was the system cleaned out? Was a chemical inhibitor added?

 

[bster]

Further more, I have found that my TRV's although bi directional make a whistling noise as they are closing down (this is gradual as they dont snap shut) if i turn them up or take the heads off thee noise stops due to the reduction of the rtestriction of a half open valve.


BTW - My TRV's are Peglar Bulldogs

 

[Softus]

Further more...

I'm confused. Are you also BobSpoons?

 

[bster]

No - it was meant to be a contribution to the OP's prob - but i just read it back (my post) and yes its not very well worded is it

what i'm saying is that the TRV's could be the prob regardless of their bi or omini directionalitity (nice word bster )

 

[Agile]

It sounds like the OPs TRVs making the noise as they are closing.

That "fault" is probably that there is no auto bypass fitted !

By the way, bster can always edit his badly worded postings!

Tony

 

[ACOperson]

The only real bi-directional TRV's are the Danfoss ones with the rotating shaft head.

I've heard water-hammer from others which claim to be bi-directional, including the current Honeywell & Siemens ones.

 

[bster]

we (the company) always install the Dabfoss Ras-C/d's TRV's- and they seem to work a treat. I've always had a theory that wax capsule types are not as good as the liquid type - is this in my mind or actually a fact?

BTW - if its a new boiler etc Mr ponder did they install an Auto or manual by-pass?

 

[Agile]

As Bster has pointed out a TRV being bidirectional or not is not the issue.

They can all chatter when almost closed if there is not an auto bypass to prevent the pump pressure from increasing.

Alternatively that a constant pressure pump like the Grunfoss Alpha is fitted.

Tony Glazier

 

[bster]

we (the company) always install the Danfoss Ras-C/D's TRV's- and they seem to work a treat. I've always had a theory that wax capsule types are not as good as the liquid type - is this in my mind or actually a fact?

 

[Softus]

It sounds like the OPs TRVs making the noise as they are closing.

What a revolutionary idea! Wish I'd thought of that.

That "fault" is probably that there is no auto bypass fitted !

Certainly possible, although your assessment of probability is as mysterious as it is spurious.

By the way, bster can always edit his badly worded postings!

Yup, just like you do, with the result that the topic would make as much sense as your garbled and random insistence on the use of the ® symbol.

...a TRV being bidirectional or not is not the issue.

Hm. Not now that we know they're bidirectional.

 

[Gasguru]

I've had complaints of noise from customers with Danfoss Ras C2 valves.

On one system half the valves had TRV's but no bypass fitted.

On another half the valves were TRV'd with a bypass in the combi.

I think a proper bypass valves may have sorted both but both customers didn't want to spend the money.

 

[Agile]

On another half the valves were TRV'd with a bypass in the combi.

I think a proper bypass valves may have sorted both but both customers didn't want to spend the money.

The bypass inside the combi is always stated to be for the protection of the boiler and an external bypass is required.

Customers will spend thousands on their fancy cars but baulk at £30 on a heating part.

Tony

 

[BobSpoons]

Hi
Thanks for all the thoughts folks.

The only wierd thing is that the droning noise is not coming from the TRVs. Its coming from the airing cupboard where the motorised valve and hot water cylinder is located. (Theres also a hole in the floor in the airing cupboard leading under the landing which is where there is the most of the heating pipe junction/connections).
If you put your ear or a screwdriver to the TRVs the sound dosent seem to come from them at all im afraid.

We have noisy TRVs at my work and the noise is similar I suppose but not the same.

My valves are Danfoss but im not sure which.

The system is only 5.5 years old, all the pipes are plastic so corrosion would probably only be from radiators which I would have said are quite new still at 5.5yrs. The system has been drained and refilled about 5 times within the time period (Though never actually cleaned) and I know at present it has inhibitor in it.

To be honest though, the noise has been with us for about 4 years so the system was only 1.5yrs old when it first appeared.

(PS: We had a major fall-out with the installer who was a family friend, hence the reason for him not being back to fix anything. The installer was corgi registered)

Not sure if theres an auto-bypass fitted, if the TRVs are fine, would lack of an auto-bypass cause pressure variations within the system as TRVs are opened and closed?


Any further advice would be really great folks, thanks.

BobSpoons

 

[Agile]

"""We had a major fall-out with the installer who was a family friend, hence the reason for him not being back to fix anything. The installer was corgi registered)

Not sure if theres an auto-bypass fitted, if the TRVs are fine, would lack of an auto-bypass cause pressure variations within the system as TRVs are opened and closed?"""

If you dont say why you fell out with a family friend then we will fear the worst! Thats when people dont discuss the cost first and the "friend" presents a bill for the normal cost of the work and the customer doesn't want to pay because he thought the "friend" was doing it for free!

Of course if the TRVs are closing and there is no bypass then the pump pressure rises from about 0.5 Bar to 5.5 Bar and is likely to cause them to chatter.

In your case if its not the TRVs then its likely to be a sharp change in direction of the pipework causing a resonance. You did not actually say that it was not coming from the motor valve but I will assume its not.

Tony