Combi Boiler pipe noise

wingman83

Hi

We live in a town house (three story - Ground, first and second floor).

We were using Warm Air Unit (WAU) for central heating. We recently removed it and installed vaillant combi boiler (vaillant ecotec exclusive green iq 843). This boiler is installed in loft (technically third floor). The radiators / pipes and everything is new (as WAU runs with ducting and blows hot air).

Since the boiler is installed, we hear pipe rumbling noise whenever we turn the heating on.

The boiler engineer said that
1. It was due to air in the system. So he bled the system and tried again, but no luck.
2. He then looked for any leak - but there is no visible leak
3. He then added pipe insulation as he thought the pipes were bruising each other - but no luck
4. He then installed automatic air vent - but no luck
5. He then installed air separator RV2 (SpiroVent RV2)- but no luck
6. He then used Sentinel x200 chemical - but no luck
7. He is now thinking that the boiler is not able to pump enough as its in loft (3rd floor) and this might build up the air on the system. Therefore he now thinks that installing additional water circulation pump between 1st and Ground floor might help the boiler to push the air through return pipe.

Apart from air rumbling noise,
1. When the boiler is running I can hear water discharging on the right most while waste pipe under the boiler (is it called condensate pipe).

2. We have also noticed that the boiler pressure rapidly increases when the heating is switched on. After few days the boiler goes to low pressure and switches off (as it might be discharging the water through outflow pipe).

3. Most importantly; Once we flush out the system, remove all the air, pressure the system again and switch on the heating - Bang! the rumbling noise!!! How can the air enter the system that quickly.

4. I googled and found something about vessel pressurising - but the engineer thinks that its a new boiler and this shouldn't be the case.

This has been a nightmare. We spent lot of money to move away from WAU an installed this boiler. I'm tired of bleeding the radiators for every 2 days.

Any help / thoughts will really be a life saver for us.

Thank you in advance.

bris

Time to get the warranty into play. The expansion vessel needs checked so claim it's faulty out the box.


Give Valliant a call.

Alex1983

How many radiators, possibly too big a system for the boilers internal expansion vessel and a additional one is required.

Also the valiant ecotec boilers had a setting on the boiler to change the pump from variable speed to fixed speed, might be worth seeing if the green iq has the same setting and setting it too fixed speed.

JimmyChanga

4. I googled and found something about vessel pressurising - but the engineer thinks that its a new boiler and this shouldn't be the case.

Doesn't matter if it's new. Would take nothing for him to check instead of assuming.

P.S. Condensate water trickling out of the condensate pipe is normal. Pressure relief valve water is not. Has the PRV been plumbed into the condensate pipe outlet or does it have it's own external discharge pipe?

southcoastrgi

Your engineer seems to do a lot of thinking & not much knowing.
Why has he put X200 in a brand new boiler ?
You must use loads of hot water to need such a big boiler,
Has a auto bypass been fitted ?
Has the internal bypass been adjusted for your system ?
The internal expansion vessel is almost certainly not big enough
How is fitting an external pump going to help with the air noise & you having to bleed the rads ?

wingman83

Alex1983 wrote: »

How many radiators, possibly too big a system for the boilers internal expansion vessel and a additional one is required.

Also the valiant ecotec boilers had a setting on the boiler to change the pump from variable speed to fixed speed, might be worth seeing if the green iq has the same setting and setting it too fixed speed.

Thanks for your respone, Alex.
We've the below radiators in place.

BTU
Second Floor
Radiator1: 9727
Radiator2: 6532
Radiator3: 7186
First Floor
Radiator1: 5836
Radiator2: 11345
Radiator3: 3404
Ground Floor
Radiator1: 10452
Radiator2: 5350
Radiator3: 6532

He has balanced the boiler today, i.e. reduced the thermostat level in second and first floor. And set the ground floor radiators to maximum.He also reduced the pump speed on the boiler.

Since then I can see the boiler holding up the pressure, however the air still rumbling in all the pipes. We are unable to get rid of them. He drains the system and fills it again, but the air is coming along when he pressurise the boiler.

wingman83

JimmyChanga wrote: »

Doesn't matter if it's new. Would take nothing for him to check instead of assuming.

P.S. Condensate water trickling out of the condensate pipe is normal. Pressure relief valve water is not. Has the PRV been plumbed into the condensate pipe outlet or does it have it's own external discharge pipe?

Hi Jimmy - I've insisted him to check the vessel.

Re PRV,it has its own external discharge pipe.

wingman83

southcoastrgi wrote: »

Your engineer seems to do a lot of thinking & not much knowing.
Why has he put X200 in a brand new boiler ?
You must use loads of hot water to need such a big boiler,
Has a auto bypass been fitted ?
Has the internal bypass been adjusted for your system ?
The internal expansion vessel is almost certainly not big enough
How is fitting an external pump going to help with the air noise & you having to bleed the rads ?

Hi

Thanks for your reply.
I will ask him about auto by pass / internal bypass. I don't quite understand these terms.
Re internal vessel;I've listed list of radiators in one of my reply above. If the internal expansion vessel is not enough, should we go for an external one?
I've said no to fitting the external pump.
"You must use loads of hot water to need such a big boiler,"- Sorry, but I dont understand this point. Should we check the water goes into the boiler?

southcoastrgi

A combination boiler is sized on the amount of hot water you use combined with the flow rate you have on the incoming mains, your boiler will give you around 17 ltrs/min but if you are only getting 15 ltrs/min on the incoming cold for example then the boiler is oversized, your heating requirements are less than 50% of the power of your boiler so for heating it will need to modulate down a lot so if you don't use much hot water then your boiler is way over spec'd

southcoastrgi

He will need to have a rough guess at the capacity of your heating system & then can work out the correct size of expansion vessel you need, you can't increase the one in your boiler so yes it would need to be fitted externally normally on the heating return as close to the boiler as possible

wingman83

southcoastrgi wrote: »

A combination boiler is sized on the amount of hot water you use combined with the flow rate you have on the incoming mains, your boiler will give you around 17 ltrs/min but if you are only getting 15 ltrs/min on the incoming cold for example then the boiler is oversized, your heating requirements are less than 50% of the power of your boiler so for heating it will need to modulate down a lot so if you don't use much hot water then your boiler is way over spec'd

Thanks for the explanation. It's 43kw boiler and we have 11 radiators as mentioned above and one bathroom.

Hoping we can still continuing using this boiler and If the incoming flow rate is low, what is the remediation. Did u mean to say fitting an external vessel is an remediation.

And does the oversized boiler cause / allow air into the system as it couldn't find enough incoming water?

Thanks again for all your suggestions.