High pressure in boiler

mel.b

I lost mains water on xmas day and then the tank emptied on the 26th. I got my waterr back this morning after melting a load of ice on the stopcock yesterday.

I have a baxi 35/80 boiler and yesterday i noticed the pressure was at .5. I didn't use the heating at all yesterday as the fire was enough. When the water came back and started to fill the tank i noticed the pressure on the boiler was back up to close to 1. I turned on the heating and it quickly skyrocketed to 3.5 in the space of about 15min. Because the pressure was so high i shut it down. It has been off for around 40min now and has dropped back to 1.1.

Am i ok to turn it back on when needed? Why did the pressure get so high? Was it a matter of getting flowing through the system or something...sorry, i really have no idea how they work i did read the manual and kt just said to call someone if the pressure went over 3.

Thanks
Mel.b

Buford T Justice

Pressure should have been released by the releif valve if it went above 3 bar.

You may have heating pipes frozen. When you had the heating on, did any rads get warm?

mel.b

I only felt one of the rads, but yes, it was hot

mullingar

The system should blow off water at 3bar +/- 10%. If it was 3.5 bar, something is VERY wrong.

If one rad is hot then you have a full circle of flow to/from the boiler. I wonder what your expansion vessel is like? ie did it blow its internal air diaphram.

mel.b

Ok, that post just made me suitably paranoid! I've had the heating on for the past 1.5hours. Pressure is sitting at 2.3. All rads are equally warm (i just wenr and checked)

What is the expansion vessel and can i check the internal air diaphram myself?

mullingar

The expansion vessel has a sealed bag of air inside under pressure @1 bar. This vessel absorbs the expansion of the water as water expands when hot.

The correct way to test a vessel is to remove it from the system, pressurise it to 1-2 bars, leave overnight, re-measure the pressure to see a zero drop.

But for a quick test to see if its not blown, find the air valve, its identical to a car tyre, press the valve inner and blow off a TINY amount of air. If there is no air, get it replaced/checked ASAP.

Also, best to drop the water pressure down to around 1.5bars (NEVER VIA THE AIR VALVE)

Buford T Justice

Is it at 2.3 when hot, and about 1.5 when cold?

mel.b

It is currently sitting at .6 cold.

The second time it was on yesterday it got to 2.3 when hot.

cram1971

Similar thread a couple of days ago worth a look

mel.b

cram1971 wrote: »

Similar thread a couple of days ago worth a look

Do you have the link / know the thread name? I've had a lok back thriugh and can't see anything similar.

Cheers

mullingar

mel.b wrote: »

It is currently sitting at .6 cold.

The second time it was on yesterday it got to 2.3 when hot.

Thats a very large pressure difference!!

My money is on the expansion vessel is blown internally.

Also, did you bleed the rads recently? If you did, the air pockets in the rads acted as expansion vessels and now that you removed the air, there is nowhere for the water to expand into.

mel.b

That .6 was measured after it had been off all night - don' know if that makes a difference?

I haven't bled the rads as i don't know how.

I had a quick look for that valve you mentioned above but couldn't see it. Anyhow i don't think i should be playing around with it and will get the landlord onto it as it seems serious.

mullingar

mel.b wrote: »

That .6 was measured after it had been off all night - don' know if that makes a difference?

Yes, it should only be around 0.3 bar difference. You have a 1.7 bar.

I haven't bled the rads as i don't know how.

If you cant bleed a rad, dont touch anything on your system. But thank yourself that you did find a problem with the pressure.

Anyhow i don't think i should be playing around with it and will get the landlord onto it as it seems serious.

Yes, Let the landlord pay for the plumber as its their problem.





Mod request; Time to close the thread?

mel.b

Just following up on this in case anyone has the same problem in the future.

just had the plumber out. First he thought the problem was that the council had increased the pressure in the mains and that was the reason for the high pressure readings. When we questioned him, saying that the council are highly unlikely to increase the pressure at the moment, he then thought that the pressure meter reader was probably out by at least 1/2 bar, but he said he'd check a couple of things just in case.

Sure enough, a problem was found with the expansion vessel as suggested above. He did something to it and has said to keep an eye on the pressure over the next few days and if it starts to flucatate then it will need replacing.

thanks again for the help,
mel.b

mullingar

€20 this way please!

The plumber probably re-pressurised the air in the vessel to the required 1.0bar. If its leaking, it needs to be replaced.

Also, the mains water should never be left connected to your heating. It should be isolated by means of a pressure regulator or a simple removable filling loop.