Boiler pressure question

ploppy

pressure on my boiler has started to increase when it has been running for a while.
It always has increased slightly from 1.5 bar to between 2-2.5 bar depending how long it has been running. Now it is reaching 3 bar and opening the pressure relief valve.
Any ideas ?
Boiler is only 3 years old but radiators are a bit older, it is a Ferroli make.

Gaz_Hammer

Hi,
It could be something as simple as the filling point letting by i.e. not shutting water off completely.
Ideally the filling loop should, under water by-laws, not be left permanately connected.
If not, then its possible it is the expansion vessel which is generally located within the appliance casing which has either lost pressure on the expansion side through natural pressure loss or is faulty (split internally). The expansion vessel contains a rubber type diaphragm or pocket which is designed to absorb any increase in working pressure as system temperature rises.  It would either requires re-pressuring with a foot pump or replacing.  
Alternatively it could be a faulty thermostat (thermistor).

Unfortunately its impossible to be totally accurate as to the answer without seeing it but from my experience this is normally what causes the problem.

Try contacting the manufacturers http://www.ferroli.co.uk/index_main.html

Check the call-out charges first though!

Hope you get it sorted
Gaz

dreaddan

sorry to hi-jack the thread, but what would cause pressure loss?
IE, when running the boiler gets to about 3-4 and drops to around 1.5 when cool.
I keep having to fill the system to get the pressure back from 1 to 1.5
I dont seam to have any noticeable leaks.

dan

Rex_Mundi

Don't forget, when water gets hot it expands. This could explain why the pressure increases. Have you turned up the temperature on your heating recently? The hotter the heating gets, the more the pressure will build up.

I've known someone in the past to overfill the pressure on their heating. When the heating was switched on the pressure built up and the safety valve released the excess pressure. After this first time, the system was OK.

If you are topping up the water every time it gets cold, then when the water heats up the pressure will build up. The safety valves normally go off at 3 bar.

Saying this, for the pressure to build up so much from 1.5 to over 3 regularly does sound like there may be a problem with your system.

ploppy

Thanks for the replies, also got a friend to ask someone who works in this field (though he is too busy to come and see boiler) and he has suggested there may be a build up in the system (think he may mean sludge) as the radiators are a good few years older than the boiler, talking about flushing the system somehow.
Would this also be a possibility?
What would you recommend I do first?
By the Way I'm a Maintenance Engineer, so pretty used to stripping and re-building machinery.

beefster

Its air in the system. Bleed all your rads and see if it is as bad afterwards. It cured my similar problem.

After draining the system the new water will start corroding the system and gas is produced which builds up in your rads, normally at the highest point. Adding an inhibitor can stop corrosion and build up off said gasses.

If bleeding fails then move on to the pressure cylinder as mentioned.

robowen

sorry to hi-jack the thread, but what would cause pressure loss?
IE, when running the boiler gets to about 3-4 and drops to around 1.5 when cool.
I keep having to fill the system to get the pressure back from 1 to 1.5
I dont seam to have any noticeable leaks.

dan

The system is designed to "blow off" excess pressure at 3bar.
If your system shows 3-4 bar and hasn't  released pressure through the pressure relief valve, then I suspect your guage or your relief valve is faulty.
If it has released and you may not have noticed, then you have another fault.

ploppy

definitely not radiators needing bled, just drained down system to replace radiator then topped back up and bled all radiators in the system (problem was there before swapping radiator and no change afterwards). Will try out others.
Had a thought though, I did have a liquid inhibitor in the system, put in when the new boiler was installed, having drained the system down a couple of times in the last 2 years I dont suppose any would be left.
Anyway last question, whats the recommended order of action ie 1 bleed rads, 2 add inhibitor, 3 etc.. etc..
And once again thanks for the replies

robowen

Have a look at the pressure vessel.
Its quite often red and has a valve on it .... like a car tyre.
Some boilers you have to look over the top at the back of the boiler  to find it.

If you push the inside of the valve in and get nothing, then it needs repressurising. check in your booklet what pressure to pump it to. (foot pump will do). If you get air, its ok but you will have to replace what you let out.

If you release pressure and get water out of the vessel, then the vessel will need to be replaced as the diaphram inside is split.

dreaddan

The system is designed to "blow off" excess pressure at 3bar.
If your system shows 3-4 bar and hasn't released pressure through the pressure relief valve, then I suspect your guage or your relief valve is faulty.
If it has released and you may not have noticed, then you have another fault.

Ohps, it gets to 2-3 bar not 3-4 ::)

sorry.
dan

beefster

Its easiest to add inhibitor before filling. You can get a pump thet pumps it in when the system is pressurised but its easier (i find anyway) to remove the blank or the large nut containing the bleed screw at the top of a rad and using a funnel, pour it in.