Appropriate Pressure for unvented CH in 3 storey house

[yorskshirebob]

Hello,

There are similar posts online - but nothing that answers my specific question - so here goes...

Recently moved into a 3 storey house with:
(a) Megaflo Cylinder in Cellar (for water)
(b) Keston C40 boiler on Ground Floor (for water and CH)
(c) Two separate CH loops (1st feeding ground floor rads, 2nd feeding 1st and 2nd Floor rads) including Orange Pressure vessel.

I noticed that a couple of the radiators were weeping and sorted them out and then noticed the pressure on the pressure vessel was about 3 bar. I found that the filling loop was connected and although the tap was closed it was leaking into the system and causing a pressure rise. So I disconnected the filling loop, changed the leaking tap and then vented some pressure back to about 1.5bar. Pressure obviously not going up anymore (and I've left the filling loop disconnected now) but it now seems to be losing a tiny amount (about 0.1bar per two weeks) but I've checked for leaks when the system is cold and found none.

However, on the top floor I'm bleeding a few seconds of air out of the highest radiator every couple of days. I've read online this can be caused by too low a pressure - but since I'm at 1.5bar I can't believe its that. Then I read that with a 3 storey house I might need more pressure (seen somewhere you lose 1/3 bar each floor) so I'm wondering whether to raise the pressure to 2bar, but since most recommend 1-1.5 I'm worried that 2bar will be too high and cause more radiator leaks (and more air!).

Appreciate any help anyone can give,
Thanks.

 

[Agile]

If you are bleeding air OUT of a rad then the pressure inside is obviously higher!

You have not said where your gauge and the expansion vessel is located!

Generally you need about 0.5 Bar in the top floor rads so add 0.33 Bar for each floor down to the gauge!

But increased if necessary to ensure there is at least 1.0 Bar at the boiler.

It might be theoretically necessary to increase th air charge in the EXV depending on where that is located!

Air continues to come out of the water for several days if you have reduced the pressure.

Tony

 

[yorskshirebob]

Hi Agile,
Thanks for the reply.

Pressure Gauge is in the cellar with the expansion vessel. So if pressure required on 2nd floor is 0.5bar, then it's 0.83 on 1st, 1.16 on ground (which is where boiler is) and 1.5 in cellar - which is what I've got. So that sounds ok as it is.

How can I tell if I need to pressurise the air in the Pressure vessel (in the cellar)?

Thanks again.

 

[Agile]

Pressure should be set at 1.5 Bar with system cold.

If the EXV is correctly sized and air pressured then the pressure will not increase by more than about 0.3 Bar when the rads are hot.

I doubt that you need to worrry!

Tony

 

[yorskshirebob]

One thing I have noticed is that the pressure doesn't seem to change at all between cold and hot - can you tell me what this indicates?

Thanks.