Boiler suddenly humming

pieroabcd

ThisIsWeird said:

If it's a Hive (like mine), then it doesn't make sense that the noise occurs if you turn it up by more than one degree, because - as you say - 'on' is 'on'. It ain't any more on.
Going up to 1.9 or 2 when hot is ok. Much more than this wouldn't be. 
If the pump bearings are worn enough to be noisy, then I can well imagine a scenario that increased pressure will affect it. The bearings tend to be 'plain' types, just a smooth sleeve to support the spinning shaft. What lubricates it is the system water, so that pressure will be 'pushing' on the bearing in some way, possibly moving the whole spinning part more in one direction = changing the contact point = more noise.
An experiment could be to reduce the cold pressure to 1 or even 0.9 - just release via a rad bleed screw.

I was thinking that a higher demand on the ambient temperature cause more pressure buildup in the heating circuit because the boiler heats water for longer and that somehow there may be a bond between this higher pressure and that noise.
I remember that when i heard the noise the pressure was at 2.7, but on the other hand I've heard the same noise even at 2.0 and most of the time at 2.0 the boiler works silently.

FreeBear

ThisIsWeird said:  However, there are some boilers which have more sophist controls, and this might make a difference; one degree might tell the boiler, "Come on, but you are close, so only come on gently..."

Vaillant Ecotec 837 is a fairly modern boiler that will modulate the heat output down. With a flow temperature of 60°C it will modulate from a maximum of 28KW down to 12.3KW - Pretty poor compared to the latest offering from most manufacturers (some will go down to less than 3KW). But if it is anything like my boiler, it should automatically modulate down to match the heat demand from the radiators. Although, with a minimum output of ~12KW, it will probably be short cycling regardless of how smart the thermostat is.

ThisIsWeird

pieroabcd said:

ThisIsWeird said:

If it's a Hive (like mine), then it doesn't make sense that the noise occurs if you turn it up by more than one degree, because - as you say - 'on' is 'on'. It ain't any more on.
Going up to 1.9 or 2 when hot is ok. Much more than this wouldn't be. 
If the pump bearings are worn enough to be noisy, then I can well imagine a scenario that increased pressure will affect it. The bearings tend to be 'plain' types, just a smooth sleeve to support the spinning shaft. What lubricates it is the system water, so that pressure will be 'pushing' on the bearing in some way, possibly moving the whole spinning part more in one direction = changing the contact point = more noise.
An experiment could be to reduce the cold pressure to 1 or even 0.9 - just release via a rad bleed screw.

I was thinking that a higher demand on the ambient temperature cause more pressure buildup in the heating circuit because the boiler heats water for longer and that somehow there may be a bond between this higher pressure and that noise.
I remember that when i heard the noise the pressure was at 2.7, but on the other hand I've heard the same noise even at 2.0 and most of the time at 2.0 the boiler works silently.

It isn't so much a higher demand, but a longer one. You turn the 'stat up one degree, and the boiler comes on at whatever rate the boiler output control is set for, and stays on for however long it takes to lift the house temp one degree. You turn it up three degrees, and the boiler comes on at whatever rate the boiler output control is set for, and stays on for however long it takes to lift the house temp three degrees, which will be a whole lot longer, but for the boiler not hotter.

Unless, of course, when you set it up just one degree, that temp rise might be obtained before the boiler gets up to max temp.

Anyhoo, your boiler pressure... 2.7 is yay too high. It might not be affecting your pump, but it's simply yaaay too high. Any higher - and it may have already reached this - it'll blow the safety release valve, dump excess water, and you'll find the pressure is waaaay down when it cools, necessitating a top-up.

lemondrops69

Maybe its humming as it doesnt know the words?

ThisIsWeird

Drrrrrrrrr-cheeeessssh!

pieroabcd

pieroabcd said:

Another strange thing happened, too 
When I rebalanced the system one month ago and when the boiler was serviced one week ago the pressure at cold (in the morning, before turning on) was 1.3 bar 
This morning at cold it was 1.6, even though the refill taps have been perfectly close all along.
How can the pressure have raised on its own accord?

Hi,
I observed this strange behaviour (pressure 0.2 higher than the previous day in early morning, after several hours with the boiler completely inactive) two more times.
The second time I bled again the valves to take the pressure back from 1.5 to 1.3. I noticed that the water didn't flow with a lot of pressure, definitely much less than the other times. When I turned on the heating the system the boiled reported "F75, water shortage", so I refilled again to 1.4 and everything worked.
This morning again, from 1.4 of the previous morning to 1.5. I didn't touch it this time.
It goes without saying that the refill valves under the boiler are completely closed.

I've called the gas engineer to give a look. I suspect that the pressure sensor may be defective and that the actual pressure is lower.
Is this sensor just a passive reader that doesn't affect the safety of the boiler or does it also command the release mechanism when the pressure is too high?


Thanks,

ThisIsWeird

pieroabcd said:

pieroabcd said:

Another strange thing happened, too 
When I rebalanced the system one month ago and when the boiler was serviced one week ago the pressure at cold (in the morning, before turning on) was 1.3 bar 
This morning at cold it was 1.6, even though the refill taps have been perfectly close all along.
How can the pressure have raised on its own accord?

Hi,
I observed this strange behaviour (pressure 0.2 higher than the previous day in early morning, after several hours with the boiler completely inactive) two more times.
The second time I bled again the valves to take the pressure back from 1.5 to 1.3. I noticed that the water didn't flow with a lot of pressure, definitely much less than the other times. When I turned on the heating the system the boiled reported "F75, water shortage", so I refilled again to 1.4 and everything worked.
This morning again, from 1.4 of the previous morning to 1.5. I didn't touch it this time.
It goes without saying that the refill valves under the boiler are completely closed.

I've called the gas engineer to give a look. I suspect that the pressure sensor may be defective and that the actual pressure is lower.
Is this sensor just a passive reader that doesn't affect the safety of the boiler or does it also command the release mechanism when the pressure is too high?


Thanks,

Have we asked you for the make and model?

But... no boiler I know needs a pressure above, say, 1 bar, unless it's in a very tall house. So, if yours is shouting 'water shortage' when it's 'indicating' a pressure of 1.4, then the internal sensor must surely be at fault, as you surmise.

Boilers with analogue - needle - pressure gauges also have digital pressure sensors inside then to actually tell the boiler wot's going orn, and to shut down if the pressure ain't high enough.

The Pressure Release Valve is a purely physical device, and just blows open when the pressure reaches around 3bar. It is not controlled by anything else - just the physical system pressure.

Good chance you are on the right track - 'a' pressure sensor is faulty. Whether it's the analogue one reading too high, or the internal digital one reading low, who the hell knows!

pieroabcd

Have we asked you for the make and model?

But... no boiler I know needs a pressure above, say, 1 bar, unless it's in a very tall house. So, if yours is shouting 'water shortage' when it's 'indicating' a pressure of 1.4, then the internal sensor must surely be at fault, as you surmise.

Boilers with analogue - needle - pressure gauges also have digital pressure sensors inside then to actually tell the boiler wot's going orn, and to shut down if the pressure ain't high enough.

The Pressure Release Valve is a purely physical device, and just blows open when the pressure reaches around 3bar. It is not controlled by anything else - just the physical system pressure.

Good chance you are on the right track - 'a' pressure sensor is faulty. Whether it's the analogue one reading too high, or the internal digital one reading low, who the hell knows!

The model is Vailant ecotec plus 837

ThisIsWeird

IGNORE THIS. POSSIBLY FOR WRONG THREAD. But I don't want to delete it yet until I know.

Thanks.
Operating instructions, page 6, https://www.google.com/search?client=ms-android-google&sca_esv=583727050&sxsrf=AM9HkKmWrsh-lhnJmDpkUB_e_J_-HW8YkQ:1700379999471&q=vaillant ecotec plus 837 user manual&ved=2ahUKEwjO2-eOyc-CAxWvUkEAHWF_DLkQsKwBKAB6BAhoEAI&biw=393&bih=698&dpr=2.75 refer to a flashing radiator symbol as being: 'Anti-cycling mode active'.
'Cycling' generally means a boiler that is turning on and off repeatedly - 'cycling' - to meet a lower heat demand (say some rads are turned off), or  when the actual room temp demand has been met, so the boiler tries to maintain it.
A cycling boiler is considered wasteful, and also undergoing unnecessary wear on its bits, and much better is if the boiler can modulate its output right down to keep on running for longer, but with just enough 'flame' to meet the reduced demand. At some point, the room stat will say "I'm warm enough now", and the boiler will turn off for a while before being told to come back on again later, but it'll use Anti-cycling when it can.
I'm guessing in your case - since it's happening on start-up - that it means the boiler is operating in normal CH mode, but has possibly produced too much hot CH water for the flow to handle, ie for the rads to take, so it has temporarily turned off the burner whilst the current hot flow is used up. The pump is still running, and the boiler knows it's still being told there's a central heating demand, so it'll keep on running to satisfy that, turning the flame on and off to match demand. 
If so, I'm also guessing there's two possibilities with your boiler. One is that everything is fine and it's all normal behaviour, but the other is that your radiator lockshields in general are slightly too far closed, so that the overflow flow is a tad too restrictive, and the boiler is going into anti-cycle when it just shouldn't need to.
With cold rads, I'd have thought that anti-cycle would be minimal. I'd have thought it would mainly happen when the rads are fully up to temp.

ThisIsWeird

Ignore the above until I find out what I was actually replying to :-( is there a thread where someone mentioned a flashing radiator symbol?

Piero, there appears to be a few things going on with your boiler. There's the fluctuating and soaring pressures - according to the analogue gauge, and the 'lack of water' report which will be delivered by the boiler's built-in digital pressure sensor.
Then there's the humming noise. 
I'm thinking a fixed-price-repair would be a good option here, as they should replace everything that's faulty, and I'm guessing that could include the pump, one or both pressure gauges, possibly the EV... In essence, they will need to get the boiler 'working' correctly, with no risk of you calling them out again for at least three months.
Have you had anyone out yet?