cancel
Showing results for 
Search instead for 
Did you mean: 

Boiler running at 3 bar, is that normal?

bmc
Pro
Posts: 828
Thanks: 162
Fixes: 6
Registered: 28-02-2017

Re: Boiler running at 3 bar, is that normal?

You could always try the old adage....

 

When all else fails read the .... manual!!!

 

Brian

Community Veteran
Posts: 5,237
Thanks: 1,321
Fixes: 31
Registered: 16-10-2014

Re: Boiler running at 3 bar, is that normal?

@nozzer, there was no air in any radiators, not even the towel rails that are the highest point in the system! But with that said on checking the pressure's dropped to 2.5bar.

Community Veteran
Posts: 5,237
Thanks: 1,321
Fixes: 31
Registered: 16-10-2014

Re: Boiler running at 3 bar, is that normal?

@bmc Are you actually serious! Wink

Jonpe
Aspiring Champion
Posts: 1,742
Thanks: 468
Fixes: 4
Registered: 05-09-2016

Re: Boiler running at 3 bar, is that normal?

The instructions for my Vaillant combi boiler says that it should run at one bar, and be topped up when the pressure drops below 0.8.  The service engineer usually tops it up to about 1.4 when he's finished, and there is a red line on the gauge at 3 bars.

Highlighted
RichardB
Pro
Posts: 353
Thanks: 117
Fixes: 4
Registered: 19-11-2008

Re: Boiler running at 3 bar, is that normal?

The Worcester bosch advice on sealed system pressure is https://www.worcester-bosch.co.uk/support/troubleshooting/faqs/home-heating-faqs/how-often-should-i-...

 

Last year my boiler system pressure was exceeding 2.5 bar when hot and 1 bar when cold.

I had recently had the boiler serviced and had assumed the service included a check of the pressure vessel...

The pressure vessel is inside the back of the boiler. To replace it would require total removal of the boiler!

 

Taking matters into my own hands:

1) I isolated the feed and return valves on the boiler

2) drained the boiler using its drain valve (not the pressure releif valve)

3) The pressure vessel has a car tyre schrader valve on the air side, I put my foot pump on the valve and inflated the pressure vessel to 0.8 bar. This forced out 4 litres of water from the boiler. Through the open drain valve.

4) close drain valve and open the feed and return valves.

 

Boiler pressure is now 1 bar cold and 1.5 bar when hot :-)

 

Over time the air had slowly leaked from the pressure vessel reducing the air volume.

 

More info on sealed systems can be found at:

http://wiki.diyfaq.org.uk/index.php/Sealed_system_FAQ#I_suspect_the_expansion_vessel_is_faulty.2C_ho...

harrym1byt
Rising Star
Posts: 181
Thanks: 24
Registered: 15-10-2016

Re: Boiler running at 3 bar, is that normal?

That time of year again, so....

 

Aim for 1bar when the system is cold. The pressure may rise a bit as the system heats up and the water expands, but the pressure vessel, if working properly, should take care of much of that expansion. The PV has a flexible diaphragm inside it, water on one side, air pressure on the other. If air pressure is lost, or the diaphragm fails, the boiler water pressure in the system can exceed safe limits, where upon the relief valve should open. If that happens (or you have some other water loss from your system) you will find your self constantly having to top up the water pressure. If water appears out of the Schrader valve when the pin is pushed in, the diaphragm has split.

If a boiler has a built in failed PV which is difficult to change, or source a replacement - a quick easy fix, is to install a PV in the system somewhere external to the boiler, leaving the failed one in situ.

Small, slow leaks in the system can be very difficult to find. If all else fails to find the source of a leak, a last resort to trace it might be to drain the system and add air pressure. Air escapes more easily than water and is noisier, making the leak much easier to find. . 

 An easy way to check if a relief valve is passing water, is to fix a plastic food bag over the pipe end with an elastic band. If water appears in the bag, the valve is either passing water or opening under excess pressure.

Some boilers needed a special plastic key to enable them to be topped up - make sure if your boiler is one of those, that you have that essential key to hand.

 

Infinity
Seasoned Pro
Posts: 5,928
Thanks: 232
Fixes: 3
Registered: 19-06-2011

Re: Boiler running at 3 bar, is that normal?


RichardB wrote:

 

I had recently had the boiler serviced and had assumed the service included a check of the pressure vessel...

The pressure vessel is inside the back of the boiler. To replace it would require total removal of the boiler!

 


My pressure kept dropping to zero after topping up to 1 bar.

The Service Engineer confirmed a leaking Pressure Vessel.

 

10 years since installation.

 

Luckily, replacement did not involve dismantling the boiler, just a bit of nifty easing of the PV out.

 

The PV had a split in it.

Replaced, everything is fine now...

 

Expansion vessel (the same thing ?) noted as being changed also

 

Community Veteran
Posts: 5,602
Thanks: 620
Fixes: 1
Registered: 21-03-2011

Re: Boiler running at 3 bar, is that normal?

I had problems with water pressure when I had a loose joint.

Now Zen, but a +Net residue.
RichardB
Pro
Posts: 353
Thanks: 117
Fixes: 4
Registered: 19-11-2008

Re: Boiler running at 3 bar, is that normal?


Infinity wrote:


 

Luckily, replacement did not involve dismantling the boiler, just a bit of nifty easing of the PV out.

 


 

That seems like good design if the PV can be eased out and replaced.

The recommendation for my boiler is to fit an external PV and hope the failed one in the back of the boiler does not leak :-(

However, as the boiler is an 11 years old Baxi/Potterton condensing boiler it will probably need replacing sooner rather than later :-(

Richard