Boiler pressure question

[Ali]

Friend has just has some new radiators installed and they needed bleeding. She did so and used the filling loop to bring the pressure back up. After switching on the heating the pressure increased significantly. Tap at filling loop appears to be switched off. I used the pressure release valve to reduce the pressure, after which it then wouldn’t maintain pressure, but opening and closing a few times it was then ok.

Is the pressure increase normal?

Boiler is a Worcester 24i

 

[Ali]

I feel like this is a really daft question, it makes complete sense for the pressure to increase but I’m sure on my boiler the needle stays out whether the heating is on or off…

 

[gaz1]

its 1 bar or as marked with the black indicator 2 marks above 1 bar

the pressure will go up but if its reaching over 2 bars you are more like experiencing expansion vessel issues

where tank needs filling with air or a new one needs fitting as it will jet water out of the prv lowering the pressure again which needs constant filling due to you thinking theres no pressure

 

[dan treg]

pressure when sat normally about 1 bar running probably upto 2 running edit gaz beat me to it

 

[Ali]

The red is the indicator, the black is the pressure reading. It looks like as long as the operating pressure doesn’t exceed 2.6bar all is well. So the pressure should be set cold?

 

[gaz1]

one other thing if you have used that prv valve to drain water expect it needing a replacement

its what i hate about lazy plumbers who wont fit a drain taps on the system

there a swine for failing at best of time to use them to drain the system is a big no no

 

[gaz1]

The red is the indicator, the black is the pressure reading. It looks like as long as the operating pressure doesn’t exceed 2.6bar all is well. So the pressure should be set cold?

turn red up to 1.2 bars set between 1 bar and 1.2 bars always done cold

 

[Barking Mat]

Yep normal, our various boat central heating systems cold can be anything from 0 to 1 bar cold, 1 to 2 bars running at full tilt.

You got an expansion tank somewhere, rubber bladder, pressurised thing ? Checked the pressure, car tyre valve thingy ?

 

[Ali]

one other thing if you have used that prv valve to drain water expect it needing a replacement

its what i hate about lazy plumbers who wont fit a drain taps on the system

there a swine for failing at best of time to use them to drain the system is a big no no

In fairness the manual says to use the PRV, but fair enough I’ll drain off at a radiator if needed.

turn red up to 1.2 bars set between 1 bar and 1.2 bars always done cold

I’m inclined to leave the red where it is, if that’s how it’s always been running? Just monitoring now to see that it doesn’t exceed 2.6 bar

 

[Ali]

Yep normal, our various boat central heating systems cold can be anything from 0 to 1 bar cold, 1 to 2 bars running at full tilt.

You got an expansion tank somewhere, rubber bladder, pressurised thing ? Checked the pressure, car tyre valve thingy ?

Can’t see an expansion vessel anywhere

 

[Barking Mat]

Can’t see an expansion vessel anywhere

Some of our systems do, some don't, doesn't seem to make any difference.

 

[gaz1]

In fairness the manual says to use the PRV, but fair enough I’ll drain off at a radiator if needed.



I’m inclined to leave the red where it is, if that’s how it’s always been running? Just monitoring now to see that it doesn’t exceed 2.6 bar

at 30-70 a replacement too just fitting a quick bleed tap onto the system at 4.00 which way would you want that plumber to fit it

your expansion vesel is normally fitted at the rear of the system it would mean a full removal off the wall to replace it

its easier to fit an external exchanger than remove off the wall but if the customer wants it that way of coarse we will oblige them all at cost

 

[Barking Mat]

I feel like this is a really daft question, it makes complete sense for the pressure to increase but I’m sure on my boiler the needle stays out whether the heating is on or off…

It's not uncommon to find the needle gets stuck.

We've been caught out by that, you think there's pressure in the system, but no.

 

[daleyd]

Pressure rising significantly when the heating is on is usually a problem in the expansion vessel. Ours went over Xmas, every time the heating came on the pressure would go above 2 bar, when it went off it would be almost 0. Needed filling every morning!!

Replaced the expansion vessel and pumped it up and it’s now rock steady at 1 bar hot or cold (ours is baxi but the principle is the same). Pressure vessel may well be internal to the boiler, ours is and our old Worcester model was also.

 

[mtt.tr]

Expansion vessel could have failed.

Try the Schrader valve water may well come out of it

 

[Ali]

Yep normal, our various boat central heating systems cold can be anything from 0 to 1 bar cold, 1 to 2 bars running at full tilt.

You got an expansion tank somewhere, rubber bladder, pressurised thing ? Checked the pressure, car tyre valve thingy ?

Pressure rising significantly when the heating is on is usually a problem in the expansion vessel. Ours went over Xmas, every time the heating came on the pressure would go above 2 bar, when it went off it would be almost 0. Needed filling every morning!!

Replaced the expansion vessel and pumped it up and it’s now rock steady at 1 bar hot or cold (ours is baxi but the principle is the same). Pressure vessel may well be internal to the boiler, ours is and our old Worcester model was also.

Expansion vessel could have failed.

Try the Schrader valve water may well come out of it

Not sure I’m getting this fully, some systems the pressure will increase when hot and it’s normal, others stay static? The manual says design pressure should be up to 1.5 bar and pressure at max operating temp should be up to 2.6, so this type of boiler the increase is normal?

I set it cold and then ran it and it reached 2.1bar and stayed put for 30 mins.

 

[Wozzaaah]

As above, if the expansion vessel has failed that will cause the pressure to rise dramatically.
The air in the rads would have acted like an expansion vessel.

 

[Wozzaaah]

Not sure I’m getting this fully, some systems the pressure will increase when hot and it’s normal, others stay static? The manual says design pressure should be up to 1.5 bar and pressure at max operating temp should be up to 2.6, so this type of boiler the increase is normal?

I set it cold and then ran it and it reached 2.1bar and stayed put for 30 mins.

2.1 bar is a little higher than normal but should be fine.

 

[mtt.tr]

Not sure I’m getting this fully, some systems the pressure will increase when hot and it’s normal, others stay static? The manual says design pressure should be up to 1.5 bar and pressure at max operating temp should be up to 2.6, so this type of boiler the increase is normal?

I set it cold and then ran it and it reached 2.1bar and stayed put for 30 mins.

Your expansion vessel has a rubber diaphragm it's purpose is to take up the expansion

When they fail they will fill up with water removing any ability to asborb expansion which will rapidly increase the pressure in the system leading to it shutting down or pushing over the PRV.

It could be a failed diaphragm easily spotted as the shcrader valve will have water come out when pressed, or it could just be down on pressure

 

[Barking Mat]

Your expansion vessel has a rubber diaphragm it's purpose is to take up the expansion

When they fail they will fill up with water removing any ability to asborb expansion which will rapidly increase the pressure in the system leading to it shutting down or pushing over the PRV.

It could be a failed diaphragm easily spotted as the shcrader valve will have water come out when pressed, or it could just be down on pressure

Can’t see an expansion vessel anywhere