Boiler at 3 BAR - bleed rad to reduce pressure?

dunroving

I think this is a simple question, but wanted to check before proceeding. I've bulleted things for simplicity.

Boiler details - Biasi Garda combi, about 10 years old.

I bled two of the rads because they have been cold at the top (top half for the small bathroom rad, top third for large bedroom rad). Although I didn't feel like I let out much air, when I bled the second rad, the pressure seemed to drop (i.e., no more air coming out).

Boiler pressure was at 0 BAR, so I climbed into the airing cupboard, and refilled the system using the control valve, back to 1 BAR.

I finished bleeding the bedroom rad (a bit more air came out), and pressure at boiler seemed to be still at 1 BAR

All seemed OK, hot water working, etc. (CH currently off until 4 pm).

About 30 mins later, I noticed the pressure was at 2 BAR, and then it went to 3 BAR within a few minutes.

Although I couldn't hear any refilling sounds, I figured maybe there was a trickle so I re-adjusted the control valve and now, about 15 mins later, seems the pressure has stopped going up. I'm guessing that when I finished bleeding the bedroom rad, the reason the boiler pressure seemed to stay at 1 BAR is probably that it had gone up without me noticing, and bleeding the rad brought it back down to 1 BAR.

Questions:

(a) is a pressure of 3 BAR way too high/dangerous for the system? The CH won't be coming back on for 4 hrs so not worried at the moment. The boiler manual states the normal filling pressure is 1 BAR, but I have read online (I know, I know) that it can be higher than this without too many problems.
(b) if I need to reduce pressure, can I just do this by bleeding water out of the system, from the bathroom rad?

Norman_Castle

if I need to reduce pressure, can I just do this by bleeding water out of the system, from the bathroom rad?

yes........

dunroving

Norman_Castle wrote: »

yes........

Thanks. Simple(ish) question, simple answer!

neilmcl

Bear in mind the pressure will increase when the boiler is on so you need to check what the pressure is with the boiler off and system cooled.

bris

If the pressure went up to 3 bar from 1 then it may indicate the expansion vessel is either faulty or needing recharged.


When the heating is back on keep an eye on it.

Grey_Critic

When you heat water it expands. You have a sealed system so obviously the pressure increases. 3 Bar does seeem a little high but if that is all then bleeding radiators to remove the air it should be fine. Do you not have it serviced each year?

dunroving

Thanks, all. I probably should have given more detail, but I wanted to keep the initial post fairly simple.

I am new to the boiler, having moved into the house in early July. At that point, most of the rads had been taken off to facilitate decoration. The gas engineer who had serviced the boiler annually since about 2006 flushed and replaced the rads, add rust inhibitor, fitted the rads, bled them and serviced the boiler.

He set it up at 1.0 BAR, where it has stayed for about 4 months until I bled the rads this morning.

The pressure hasn't changed since I made my first post, so I think everything is OK, and I will bleed the bathroom rad to drop back down to 1.0 BAR or thereabouts.

p.s. Everything I described earlier was done with CH off and rads warm.

[ETA: Have now bled about a litre or two of water from the bathroom rad, bit by bit, and the pressure is back at 1 BAR and everything seems to be working fine.]