Boiler pressure

May 16, 2007 3 Replies
G

I tried to look in old post but can't find any information so I am asking.



At this time of the year I am turning on the heating in my flat only for couple of hour's in the bath room. All the radiators in the flat are off.



The pressure on the boiler is low than normal about 0.7. I know that when the hating is on it needs to be around 1.5 but isn't the fact that only on radiator is on actually mean less hot water in the system and there for less extract which mean lower pressure ? If I top up the system and open more radiators the pressure goes very high



2.5.

Thank you for any information



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T

That OK in a flat: 0.7 is about 20ft head which is a lot more than you'd have with a header tank in the flat. Some boilers will cut out if the static pressure cold drops below 0.5/0.6

No, it will rise when the system heats up, but there is no minimum figure. If you had a big expansion vessel it might rise to 0.8 and that would be fine. In a flat the concern would be if was rising to 2 or more.

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R

From distilling numerous previous threads, the 'norm' seems to be 1 bar when cold and 2 bar when hot.

The pressure rise is due to the fact that the water in the system expands when it gets hot and compresses the gas in the expansion vessel, with a consequent increase in pressure. If only *some* of the water is getting hot (the remainder being in unheated radiators and pipes) the pressure rise will be lower. What you are experiencing seems fairly normal - except that 0.7 bar sounds a bit low. Is that cold or (partially) hot?

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