boiler water pressure for a 3 storey house

pieroabcd

HI, I've just tested the heating system. The ground and first floor radiators worked beautifully, but those at the second floor didn't: I could feel some hot water in one of the pipes and that was it..
I've removed some air from the valves (there was some but not a lot) but the situation didn't improve.
The water pressure in this Vaillant boiler is currently 1.2. What's the right value for a 3 storey house? (it's the typical 40sqm per 2 floors + 30sqm in the kitchen extension + 20sqm in the loft extension+bathrom). It was 1.4 before removing the air. 
What's the right value for a house like mine?

Thanks

Ayr_Rage

As long as the pressure is within he recommended range (is there a green arc?) the boiler will work normally, it will not affect circulation.

However the boiler pump may struggle to deliver water to the highest floor, try turning off all the lower radiators and see the result.

pieroabcd

OK, I can do the test, but I forgot to add that the bathroom at the second floor receives hot  water for tap and shower without problems.

pieroabcd

With the water pressure at 1.5 and some more  water discharge (it was gurgling) I could make all of them work (with or without the first floor active), but for some reason the radiator at the second floor doesn't seem to be sending the water to the outflow pipe: it remains cold all the time.

doodling

Hi,

With a sealed central heating, you want to ensure that there is some pressure in all the radiators - I would want at least half a bar.

10m height if water is approximately 1 bar.  That means that you can subtract 1 bar from the pressure gauge to estimate the pressure in a radiator 10m vertically above it.

I'm going to guess that your highest rafiator is no more than 10m above your pressure gauge so a pressure of 1.5bar is probably about right (1 bar lost due to the height leaving 0.5bar at the highest radiator).

The height does not affect the ability of the pump to get water to the radiators - if you have a cold radiator then it is either full of air, the flow through it is blocked (sludge / dodgy valve / blocked pipe) or the system isn't sufficiently well balanced and all the water is finding it easier to pass through other radiators.

pieroabcd

1.5 is the current reading and it seems to work okish, even though it's clear that the second floor is less served. I'm  very surprised that the outflow pipes at the second floor remain cold.

doodling

Hi,

Assuming that your heating system isn't more than 10m tall and you have a pressure of 1.5bar towards the bottom of it then the pressure is not the issue.

The issue will be unrelated to height.  My guess is poor balancing so that the lower floors are getting most of the flow from the boiler but there may be other issues - if one radiator is a problem then are you sure that its valves are working correctly?

anselld

Is it a Thermostatic Valve?  Sometimes the operating pin inside gets stuck.  Take the head off and see if you can press the pin up and down with a small blunt object.  If not, wiggle it a bit and apply some wd40 to unstick it.

pieroabcd

doodling said:

Hi,

Assuming that your heating system isn't more than 10m tall and you have a pressure of 1.5bar towards the bottom of it then the pressure is not the issue.

The issue will be unrelated to height.  My guess is poor balancing so that the lower floors are getting most of the flow from the boiler but there may be other issues - if one radiator is a problem then are you sure that its valves are working correctly?

Uhm sure is a big word. I bought this house 20 days ago! 
The valves seem to be working correctly in all radiators, but i haven't tried all possible combinations.
I have the feeling that the loft room hasn't been inhabited at all (or they would have ruined like all the rest) hence the poor heating performance.

pieroabcd

anselld said:

Is it a Thermostatic Valve?  Someno, times the operating pin inside gets stuck.  Take the head off and see if you can press the pin up and down with a small blunt object.  If not, wiggle it a bit and apply some wd40 to unstick it.

No, not this one that is working poorly.
It's a cylinder with a knob, without any indication about the direction to turn to open and close

pieroabcd

This is it