Any central heating guys out there I need a bit of advice.

[Streetluge Chris]

Any central heating guys out there I need a bit of advice.
I have pretty old boiler fitted 1992 yes that old it's done well lasting this long.
Any way the water pressure is not holding in the system I would top it up once a year but now I'm having to do it every couple of days.
It's dropping from 1.5bar to near nothing in couple of days I can't find any leaks on the radiators last time I checked the pipes under the floor there was no leaks.

Could it be the heat exchanger in the boiler or is it something else?
Hoping I don't have to change it at the moment as money is tight but if I do anyone in North West fancy fitting new one?

[trexamanic]

check your pressure relief pipe outside.
probably a flat expansion vessel on the boiler. what model is it

[Rctintin]

Hi, I am a gas engineer. Sounds like your pressure relief valve is letting by. There should be a pipe outside, behind the boiler, is that dripping?

With your system water cold, set the pressure to 1bar. Now put the heating on, and watch the needle. Does it climb fairly quickly to 3bar, then the pressure drops? If so, your expansion vessel is knackered. Easy to repair, you can cut into any flow and return pipe and fit an external pressure vessel. The Pressure relief valve will need to be replaced, but they are cheap, around £15-20

Let me know, and I will keep an eye on this thread for you.

[Dan22]

yes, sounds like the expansion vessel has lost the pressure. you can re pressurise it using a foot pump but it's probably goosed. I by passed my vessel and added a larger external one.

Dan :peaceful:

[Rctintin]

Let me know what boiler it is. If you can identify the expansion vessel (usually behind the boiler accessible from the top by the flue) there will be a screw on cap just like a car tyre valve. Remove the cap, and press the valve in (like you would to remove pressure from a tyre) If you get water coming out rather than compressed air, for sure you need a new expansion vessel. You can get on from Screwfix like this [url=http://www.screwfix.com/p/expansion-vessel-12ltr/46517]Expansion Vessel 12Ltr | Screwfix.com[/url] and a fixing kit like this [url=http://www.screwfix.com/p/expansion-vessel-mounting-bracket/86194]Expansion Vessel Mounting Bracket | Screwfix.com[/url]# then just fit a 'T' into a heating pipe anywhere in the system, and connect this vessel with a flexi tap connector like this [url=http://www.screwfix.com/p/flexible-tap-connector-22mm-x-x-300mm/15015]Flexible Tap Connector 22mm x ¾" x 300mm | Screwfix.com[/url]

If only air comes out of the valve, it can be re pressurised with a car foot pump. To do this, you have to first relieve all pressure from the heating water, them pump the vessel up with 1bar of air. The needle on the boiler pressure gauge should not raise at all, if it does, again relieve the water pressure. Now check air is 1bar, and refill heating to 1bar. Dont forget to replace the PRV though, because once disturbed at that age, it will never reseat, and will continue to drip.

[Streetluge Chris]

The boiler is Myson Midas B I have found all the info on the model and lucky for me it shows all the bits.

[url=http://85.189.44.185/Baxi/System/DATA/Dx/DS1/installation/2514/I19-2514/I19-2514.htm]Midas - B - Installation and Servicing Instructions[/url]

Hi, I am a gas engineer. Sounds like your pressure relief valve is letting by. There should be a pipe outside, behind the boiler, is that dripping?

With your system water cold, set the pressure to 1bar. Now put the heating on, and watch the needle. Does it climb fairly quickly to 3bar, then the pressure drops? If so, your expansion vessel is knackered. Easy to repair, you can cut into any flow and return pipe and fit an external pressure vessel. The Pressure relief valve will need to be replaced, but they are cheap, around £15-20

I have checked the above and the over flow is not leaking and the water pressure always stays the same I have never noticed it rise?

Thanks for you help .

[Rctintin]

Your Exp Vessel is no 75 in the diagram at the rear of the linked instructions, and your PRV is no 78. Look around the edge of the square tank for the valve, and follow the advise I listed above.

[trexamanic]

the vessell will probably not be knackered.
You can quite easily pump it back up with a foot pump.

This is a common issue and easily fixed in most cases with little expense

[trexamanic]

That amount of water has to be going somewhere.
are you confident you checked the correct pipe outside?

[Rctintin]

True, but at 20 yrs old, I bet it has perished inside. As I said above, check if water is coming from the valve, if it is, new vessel required.

[Streetluge Chris]

I've had a quick look at it the expansion tank at the back is hidden at the back I can not see a valve on the tank.
There is a valve on this below

[ATTACH=CONFIG]50435[/ATTACH]

I did find slight leak on 102 automatic air vent.

[ATTACH=CONFIG]50436[/ATTACH]

General pic of inside.

[ATTACH=CONFIG]50437[/ATTACH]

I think if it is the expansion tank I'm in trouble.

Your fantastic bunch of gents thanks again for help.

[trexamanic]

It is normal for the auto air vents to spit out a bit of water but as long as its not coming out steady then leave it alone.
there must be a schraeder valve somewhere that is accesible on the big red exp vessel on the back. obviously do not take any combustion doors off or go anywhere you aint supposed to go ;)
if you do find the cap then f you attach a foot pump to it you can check if its flat or not.
If it was then you would need to open the ch system by either draining it off from a radiator or you can use the prv(the red valve in the middle of pic 3) You turn it and it discharges the water through the prv pipe. the trick is to turn the valve until it stays open. then you start pumping and you may think its just going out the wall but keep at it as it can take a while to get the pressure into the vessel. if it does pressurise then pump it to 1 bar(average) then remove the foot pump. you would then start to refill the water in the central heating. whilst doing this twist the prv valve a couple of times till it clunks back into place as it normally passes once its been opened.
i really cant see that the water is going anywhere else unless you have a leaking rad or pipe. It is normally very obvious if the vessel is flat by touching the end of the 15mm copper pipe going through the wall to the outside.
when the vessel is flat and you top up the sys press to 1 bar it heats up expands and discharges through the prv. this cycle continues until the pressure drops.
Please take extreme care not to do any work on your boiler that you are not qualified to do mate.
If you are really stuck then you can get on contract and have a first fix first visit with british gas for £99 then a monthly homecare contract of your choice.
Personally if it was me i would be swapping that boiler for a worcester greenstar combi.