Vaillant 637 Ecotec plus - air bubbles in system

[DP]

This is the same boiler as yours but 31 kw output and has hot water components. Bathroom tall radiator is forever getting air in it.
Been in this house for 38 years, this boiler in no 3. Bathroom radiator has always entrained air be it open vented system or sealed like last two boilers

I also get ticking of pipes as these heat up and cool down especially with the type of controls I am using. Bedroom rad and bathroom switch at 6.30 am. It is like an alarm clock

 

[RK_London]

Thank you DP for your reply.

A filter does not need to know how boiler works, a misstep can creates issues like you have found

When you say a misstep what do you mean? I did ask the Vaillant engineer why I needed an external by pass when the boiler already had an internal bypass and he said the way the pipes were fitted to the boiler didn't provide enough by-pass and was probably why I was having problems with banging during pump over-run.

You are running the boiler at 15Kw- that would amount to a system with 10 radiators ( approximation) and no cylinder unless cylinder is ancient non insulated

I have 13 radiators but two I don't use all the time. I do have a new 300L cylinder.

I have managed to take out all the air from the vertical radiator. But took me almost 4 weeks.

 

[RK_London]

The sound I get is more banging than ticking. I've attached an audio in the previous post.

When the system switches on in the morning I get banging in the pipes. Because I thought initially problem was pipe expansion I reduced boiler setting to 15Kw so the house heats up slowly over 30 minutes.

The loudest banging is in pipes near an upstairs bath radiator ( not the vertical one - that is ok now). I've replaced the radiator so it's not the radiator. Will change one of the valves because it does leak if I open it too much. Every night I shut this radiator off and the pipe banging is less in the morning. There is also banging during the day particularly during pump over run.

So is the issue the boiler pump being more powerful than previous boilers?

 

[DP]

When you say a misstep what do you mean? I did ask the Vaillant engineer why I needed an external by pass when the boiler already had an internal bypass and he said the way the pipes were fitted to the boiler didn't provide enough by-pass and was probably why I was having problems with banging during pump over-run.

What I mean is, a fitter who is only interested in nailing the boiler on the wall, collecting money and never intends to come back will overlook finer details that make any boiler run better. To me these are missteps. An example that can be see widespread is installation of flues. The boiler manual details how the boiler should be trimmed but this step is missed and flue fitted that double as bird perch.

13 radiators, rule of thumb would suggest about 19kw for heat load. Your cylinder coil will berated at 24kw
Running the boiler at 15kw might be on the low side unless your house is super insulated.

Switch the hot water zone off, manually open the HW zone valve, set the boiler to 60 degree target temperature and wait for frost stat to kick in. See is the banging noise takes place

When your timer goes active for heating or hot water, is there a delay of some 20 seconds before the boiler sees a demand to run?

What type of TRVs do you have on the radiators.

 

[RK_London]

Thanks for the reply.
Unfortunately my experience of the fitter/plumber was exactly as you describe. He is a nice guy but wanted to (as you say) nail the boiler on the wall and leave. He later told me he got some kind of cashback from the manufacturers for fitting a certain volume of boilers. The flue was also incorrectly fitted and the boiler was shut down by a Vaillant engineer as dangerous. But to be fair to plumber he has come back to fix flue although I'm not sure how much he knows about the correct settings - I've got more from people on this site than I ever did out of the plumber.

I agree that 15KW might be low but idea was to try it out and then increase power if house and hot water not warming up enough. Insulation is very good so not had any problems with power setting.

How do I go about switching off hot water zone and opening hot water zone valve?

Yes I think there is a delay - I will double check this.

I have Myson TRVs on radiators

 

[DP]

On the motorised valve there will be a lever which is pushed to a park position that keep the valve open without power.

When you restore the hw function, valve will auto reset

Also try opening all the trvs to fully open.

Is the bang occurring at the start or end of demand.

 

[RK_London]

Thank you for your reply.
I can see on a valves there is a push lever to manual setting - I have 3 valves - one on the hot water cylinder, one from flow of house central heating and another valve on flow of underfloor heating - see picture below.
https://www.dropbox.com/s/ctvk0b4veujmp7d/2020-12-23 23.23.57.jpg?raw=1

How do I restore HW function?
All TRVs open - kept them open last few weeks to eliminate any TRV noises related issues.
Banging occurs at the start but also during the day particularly around pump over-run at end of cycle.

 

[DP]

Banging occurs at the start but also during the day particularly around pump over-run at end of cycle.

I wonder if the motorised valves are banging or slamming shut
Can you alter the times for each zone to pinpoint what zone is the culprit

 

[RK_London]

Thank you for your reply.
I was also thinking issue might be motorised valves. ..I can alter the times for each zone and let you know how it goes

 

[RK_London]

From past experience, had banging issues when under-floor heating switched off ( don't use it much as in new extension and insulation very good). I did test once switching on hot water about 30 mins before heating and had no problems with the hot water. Initially put banging down to expansion as water was already at target flow when heating started.

Will check valves again to confirm

 

[RK_London]

Heating zone causes the banging. So might be motorised valve but not sure how that links to why the noisy radiator bangs whenever I open it next day.

 

[ScottishGasMan]

Here's a recording of the noise in link below
https://www.dropbox.com/s/abd3p56poxub4s3/Bath Radiator- Turning on in morning.m4a?dl=0

Thats expansion noise pure and simple. No amount of replacing zone valves etc is going to make an ounce of difference. Could be the radiator its self (new does not equate to good), the bracket its hung on, does it have the little plastic movement lugs fitted to the braket to stop this exact noise when the radiator heats up? Are the pipes touching a joist where it goes under the floor? (few mm of difference when things are replaced/moved is all it takes to start that sort of issue) and might be worth closing the lockshield right down to just a trickle to slow how fast that radiator heats up

 

[BlueLoo]

Here's a recording of the noise in link below
https://www.dropbox.com/s/abd3p56poxub4s3/Bath Radiator- Turning on in morning.m4a?dl=0

Mechanical expansion.

So, you need to remember what you have changed in thinking its anything otherwise and reverse those before you rectify the expansion issue.

Expansion noise is stiction.
It's the phenomenon of something overcoming its static state to a dynamic state.
Solve that and you may have your answer.

Reducing friction on the sliding surfaces will help but if the expansion is large, you may need to free up some of the constrictions stopping the free movements.

 

[RK_London]

Thank you for your replies.
ScottishGasMan - I agree with you about mechanical expansion. Even though the radiator and pipework not touched by boiler installation, didn't understand why I have mechanical expansion issues now after 20yrs. I isolated vibration to pipework just beneath valve on the return under the floors. I also changed the 20yr old radiator to eliminate internal radiator issues. I have significantly reduced flow into radiator and control that further by adjusting the return side valve to a trickle ( Lockshield on the flow side ). None of this has made a difference. I thought there was a possibility of swapping the flow and return during boiler installation causing problems with the valves but this isn't the case.

So it is very possible issue is pipes rubbing against floorboards. But before I take up the floors which will be very expensive, I need to try to understand why I have the banging issue now and not before. I also need to figure why the radiator bangs in the morning when I turn a closed return valve just 1/16th of a turn when the heating comes on and the the flow temperature is barely 25C. And if the issue is expansion, why does the banging continue during the day when everything has warmed up.