Gurgling Sounds From My Boiler

[Andy B 23]

I have a Potterton Promax 12 SL, it is the original boiler, installed in 2011, it is in good order & has just been serviced with no issues found.

My system is S plan, I have a Grundfos alpha 2 pump which had been left on fixed speed 3, after some experimenting this has now been changed to PP2.

Pressure when system cold 1.0 bar, rising to around 1.6 when CH heating fully warmed up (12 rads in total), if only the HW is on the gauge rises to around 1.4/1.5 bar.

Many of the parts of the heating system are original so I have had the following parts replaced over the last couple of weeks:

18 Litre HW expansion vessel - partial drain down to install.

12 Litre CH expansion vessel, PRV & pressure gauge - partial drain down again but on a different day.

Automatic air vent - pressure just dropped enough to swap the vent, again on a different day.

2 leaking radiator bleed valves - individual radiators isolated at LS & TRV to enable the valves to be changed.

Radiators balanced.

Now when the boiler first starts you can hear the sound of running water inside the boiler, as the boiler fires the sound begins to fade, after around 20 (ish) seconds the sound has gone, other than this new noise the boiler is working as expected, the HW is being heated to temperature, the radiators are performing better than ever following the balancing, the boiler flow & return temperatures are consistent. When the boiler shuts down you can also hear the sound of water again, but only for a few seconds, the pump shuts off as soon as soon as the boiler goes off, the pump does not run on.

I have checked all the rads & they are free of air, I ran the HW & CH at the same time to create a full open circuit, I have tried cycling the pump through the various speeds while the system was warming up in a bid to try & dislodge any air in the system but so far no luck.

Any thoughts or suggestions?

Thanks in advance.

 

[Madrab]

If you've had your system drained and filled, drained and filled etc over a number of times over the last few weeks, then it wouldn't be unusual for a little air still to be travelling about the boiler/system working it's way out causing a little noise like that. As long as everything is performing properly then I wouldn't worry about it and It should eventually settle out

If your system is fully TRV'd then the pump shouldn't shut down when the boiler does. If it has been wired to the correct block in the boiler , the boiler should control the pump and allow it to overrun/anticycle when all the TRV's shut down. Maybe a wiring check needed there. Is it a Y or S plan? Does it have a bypass?

 

[Andy B 23]

Hi Madrab thanks for taking the time to respond.

The system is S plan with an unvented Santon Premier Plus 170 litre cylinder.

Manual bypass, LS valves fitted to both flow & return on rads in hallway & landing.

Manual bleed on on the common return in the airing cupboard, AAV on the flow above the pump, again in the airing cupboard.

Not much chance of the TRV's closing in my house, 10 TRV's in total, mostly set to position 5, the boss likes to be kept very warm & toasty & I have been told (sorry advised) not to change anything that will impact on the boss being warm!

I was looking at old posts on this forum & found one with a similar issue to me, not much detail in the post but the general idea was that they closed all the TRV's & let the system run, not sure if it was just the CH or just the HW circuits or both at the same time but they said it pushed the air through & resolved the issue.

Any thoughts on this plan?

 

[Mottie]

Gurgling sounds from boiler? Andy will be along soon…………..

 

[Madrab]

Any thoughts on this plan?

You could try it but TBH you will probably find that the system will eventually clear it itself as it goes through its heat cycles.

 

[Andy B 23]

Thanks Madrab, much appreciated.

 

[Agile]

Gurgling within s condensing boiler often means that the condensate is not completely draining away properly.

Sometimes as a result of insufficient fall ( slope ) close to the boiler.

 

[HERTS P&D]

Also, has the inhibitor being replaced when drained and re-filled?

Andy

 

[Andy B 23]

Hi Andy, thanks for taking the time to respond.

Due to the current demand from the boss for the heating to be available 24/7 I was not able to carry out the full drain down, mains flush & inhibitor re-fill, as soon as the weather/boss will allow I will fully drain down & re-fill adding X100.

 

[Madrab]

You don't need to, just drain the equivalent water out of one rad and then refill it with the inhibitor