Combi pressure debate

[darren7]

I have posted this on another thread, but would like your views.

my system sits at 1.5 bar cold and rises to 2.6 hot.

some have said that this is to much of a rise, the Ideal hotline says this is ok, I did not really trust the hotline that much, as he kept stalling on me.

some have stated that it should only rise 0.3 bar hot-cold,

Views please

ideal isar new system

 

[oilman]

Have a look at the posts around October 2003. Theres lots of them to do with this there.

 

[ChrisR]

How do you find those posts - search on "combi pressure" doesn't help a lot!
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Check the expansion pressure vessel air precharge. Ie let the pressure off the system, then put a tyre pressure gauge on the tyre-valve looking thing in the PV to measure it. Should be about 0.7 - 1 bar.

Refil system with water through the loop to 1 bar.

(If you have a lot of water in your system - lots of large capacity rads, your pressure vessel might be a bit small. That gives large pressure rise on heat-up.)

 

[MANDATE]

Had a combi system fitted in a terraced house ( 5 rads ) year ago.
Pressure rise is 1 bar. Was 1.5 to 2.5 but I have changed this slightly now 1.2 to 2.2. I understand 1 bar rise is about right, any large rises are due to the 'pressure vessel' being undersized, faulty or incorrectly charged prior to use.

 

[ChrisR]

Have generally found some problem if the rise is as much as 1 bar - usually its about .5 .