Gran combi Boiler

[damsal in distress]

Hi, i hope somebody can help a damsel in distress.
I have a Grant conbi outside boiler, yesterday i was doing my usual yearly check to make sure all my radiators were working properly, i had to bleed a few, same ones as last year, however i checked my pressure on my boiler this morning and it was at 0, i toped it up to 1bar and ran the system to check it was all ok, but the pressure then went from 1 to hover between 2.5 and 3 bar. i let the boiler cool down and cheeked it again and it went back to 1 bar but im concerned as to why the pressure is rising so much, have i done something wrong, i had the same problem last year and had to called out an engineer who fixed it, i get my boiler serviced every year. i can't afford to get an engineer out again this year for the same problem.
pleas help

 

[Gasguru]

Read the faq's on expansion vessels.

 

[damsal in distress]

Hi gasguru, thanks for your reply, call me blond if you like but where do i find the FQA's on Expansion vessels??

 

[gas_man_gaz]

sounds like ya exspansion vessel is flat! if ya not any good at diy ya prob best just gettin sum1 in to do it ya

 

[damsal in distress]

Hi gas-man-gaz, its not that im not good at DIY, but i cant seem to find the FQA's that gasguru was talking about, i just relay wanted to know if i should be worrying about the rise and fall in pressure or will it rectify itself in time, would it help if i bleed the radiators again, or is there an easer way to release the the pressure??

 

[Gasguru]

http://www.diynot.com/forums/viewtopic.php?t=37170

 

[gas_man_gaz]

the pressure rise is the water which is exspanding as it warms up. ya exspanion vessel is filled with air and absorbs the exspansion of the water so prob needs pumping back up! n no it wont sort it self, wen ya put the heating on it will exspand up to 3bar then the pressure will be released via the prv and discharged outside. then wen it cools down the pressure will prob drop rite down to 0

 

[damsal in distress]

Thanks gasguru you are a star, as i only had my boiler serviced in July, is it likely to be undreinflated, this problem only happened after bleeding my radiators last night, i was wondering if i had done something wrong, as the boiler was fine till then??

 

[damsal in distress]

Hi Gas-man-gaz
Do you think i have probably had this problem for a while and only noticed it due to me cheeking my pressure after bleeding the radiators, or have i caused the problem by bleeding the radiators.

Also does this problem need urgent attention or can it wait a few months, the last time i had a problem with fluctuating pressure and no hot water, i was told i needed something( cant now remember what) to change over from heating to hot water, which i got fixed and whilst waiting for the new part i was told not to worry about the fluctuating pressure the new part took 2 weeks to arrive.

What do you think??

 

[Gasguru]

The expansion vessel contains presurised air that absorbs the extra volume of water as the radiators heat up. The air that was trapped in the top of the radiators served this purpose. You have now bleed the radiators but your expansion vessel has very little air within it.

Hence when the water heats up and expands in volume it has nowhere to go and the pressure rockets. Once it gets towards 3 bar the safety valve will open causing more problems.

As a temporary measure either turn some of the radiators off or turn down the temperature of the heating on the boiler (if you can), otherwise the expansion vessel needs re-charging as per the link.

 

[damsal in distress]

Thanks Gasguru, i will get it cheeked out by and engineer

 

[Agile]

It should be dealt with within a few days.

Tony