Boiler increasing pressure with filling loop disconnected, new boiler same problem.

[dilalio]

EV hose restricted?

 

[Johntheo5]

Pre heat is switched off and there is no other filling loop, as the Bosch had a filling loop above the boiler that was removed when the boiler was replaced.

What I am struggling to get my head around is why did I have the same issue last year after the first service that eventually cured itself and why did the same thing happen in 2009 with my Worcester boiler. Maybe a coincidence? The difference now is that for the first time I have isolated the CH today. My assumption is that if the boiler is faulty the pressure will now increase quickly as it is only pressurising the boiler and not the whole system.

Wasn't the Bosch filling loop permanently connected from the the cold mains into the boiler with a key/valve arrangement, did you break/disconnect that loop as well when trying to figure out the problem with that boiler? Your presnt problem does point to water ingress because when you drained off 1.4L the pressure fell fro 1.4bar to 1.0bar, consistent with a 10L EV precharged to 0.75bar.

 

[Ltnman]

The installer of the Worcester installed a Straight Braided Filling Loop with 2 valves that sat just above the old boiler. This was stripped out when the new boiler was installed as the new boiler was re piped.

Straight Braided Filling Loop - Part L

Braided flexible hose with CP isolating valve and CP isolating double check valve.

www.toolstation.com

​

 

[Ltnman]

I have removed 1.4 litres of water to get the boiler down to 1 bar again and have isolated the CH by turning the valve off allowing me to keep the hot water on. I will now play the waiting game and will report back if the pressure changes in the coming days.

So it is now 5 days later. The pressure gauge increased by 0.1bar, which might be the natural tolerance of the gauge. I then turned the two valves on at the bottom of the boiler to reconnect the CH flow and return. The gauge didn't flinch. This was after having to drain 1.4 litres from a radiator to maintain its normal off pressure the week before.

What I did notice with the CH isolated, was that when HW was called for, the pressure gauge would increase by around 0.3 bar while producing hot water.

I have now called for heat, which produced a major gurgling sound from the boiler, which lasted a good 60 seconds together with a whooshing sound. This sounded like the boiler was filling up with water even though it was not and reminded me of the boiler being filled for the first time on installation. The sound transferred or maybe it was duplicated to a downstairs radiator that also sounded like it was full of air. This was after bleeding the radiators before isolating the CH after adding another bottle of X100 on top off the original 2 bottles that was added when the system was installed in 2022 with an additional bottle added last year, as it was testing under strength.

So the questions are:

1/ Where did this 1.4 litres of water come from (see thread) that I drained last week, seeing the filling loop on the boiler is disconnected on one side and is it still an opinion that the expansion vessel could have a pin hole?

2/ Why did the boiler gurgle loudly after being isolated for 5 days?

3/ Why did I have to bleed the radiators again of a little air but not enough that stopped the tops of the radiators getting hot?

4/ Can air circulate that bleeding just doesn't remove, as I have had this gurgling last year in the same radiator that just stopped making a noise after a while.

5/ Is it normal for the boiler to show an increase in pressure with the CH isolated when the hot tap is run?

6/ Is there a link to my problem in 2009, as per my first post of this thread?

 

[Johntheo5]

In answering 5, the boiler pressure should increase by the pump head if the EV is teed in just before it, but should also increase by the same amount with CH on.
Have you been using the HW each day with the CH isolated??

 

[Ltnman]

Yes the HW has been used daily including for showers and yes the pressure increases as soon as the CH is turned on so at least this is normal behaviour.

 

[Ltnman]

This is a 20 second YouTube video of the noisy rad. When I bled it next to no air came out just water..