boiler water pressure for a 3 storey house

pieroabcd

The radiators with thermostatic valves are working very well

ThisIsWeird

To try and dispel any confusion, you said "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."

The supply to the taps and showers (DHW) are completely independent to that for the radiators (CH). They should have no bearing on one another.

Doodling has explained the requirements for the CH side; each floor should have adequate pressure, and the suggested 1.5bar (at boiler level - presume ground floor?) should be perfectly fine in your case.

Q - When you 'bled' the upstairs rads, did the water come out the bleed valve with reasonable force?

Read the instruction book for your boiler/check the display - you will likely find that a pressure up to around 2bar is 'ok', so if you wish to try increasing this as an experiment, then go ahead. (Keep an eye on the pressures as the system heats up, tho', and make sure it doesn't climb much above 2 bar). If you find, as is likely, that increasing the pressure up to 2 bar makes no difference, then back it down again to a more comfy ~1.5.

That smooth round valve on the rad looks like a 'lockshield' type, so is the valve that is designed to 'balance' the rad, and not adjust its output. Could you show us what's on the other end?

(Every rad should have a control valve - ideally a TRV - and a 'lockshield'. You should not touch the l/s without first noting exactly its position, so you can always return it to that setting after playing about with it! Usually only 'tweaks' - quarter or half-turns) of the l/s will ever be required, so a good method is to remove the cap and tape a paper 'flag', pointing to - say - the wall, to the spindle before adjusting it. Note down any adjustment you have made so it can be returned to this if needed.)

In general, if one rad doesn't heat up, the issue will be with that one rad. If more than one rad doesn't heat up - like the whole of your top floor - it could be to a more general lack of system balance. If, for example, that loft was added with its new rads, but the lower floor rads were kept at their original l/s settings, then it would be no great surprise that the loft was receiving an inadequate flow as it's last on the chain. The quick test of this would be to close off most of the rads on the first or ground floor using their TRVs, and then seeing if the loft heated up ok. If it does, then clearly the loft is capable of getting an ok flow - so the plumbing is fine - but the whole house's rad system needs balancing in order to reduce the flow to the lower floors, so boosting it to the top. 

If you find your system - the upstairs rads in particular - need constant bleeding, then you may have an issue. One could be internal corrosion - if the 'air' coming out is actually hydrogen. Check your system's 'inhibitor' level. If air keeps needing to be expelled, then it's clearly being drawn in somewhere, and this could be due to a lack of pressure at the top level. But that would still be very unusual with a sealed system like yours.

pieroabcd

ThisIsWeird said:

Q - When you 'bled' the upstairs rads, did the water come out the bleed valve with reasonable force?

Read the instruction book for your boiler/check the display - you will likely find that a pressure up to around 2bar is 'ok', so if you wish to try increasing this as an experiment, then go ahead. (Keep an eye on the pressures as the system heats up, tho', and make sure it doesn't climb much above 2 bar). If you find, as is likely, that increasing the pressure up to 2 bar makes no difference, then back it down again to a more comfy ~1.5.

That smooth round valve on the rad looks like a 'lockshield' type, so is the valve that is designed to 'balance' the rad, and not adjust its output. Could you show us what's on the other end?

(Every rad should have a control valve - ideally a TRV - and a 'lockshield'. You should not touch the l/s without first noting exactly its position, so you can always return it to that setting after playing about with it! Usually only 'tweaks' - quarter or half-turns) of the l/s will ever be required, so a good method is to remove the cap and tape a paper 'flag', pointing to - say - the wall, to the spindle before adjusting it. Note down any adjustment you have made so it can be returned to this if needed.)

In general, if one rad doesn't heat up, the issue will be with that one rad. If more than one rad doesn't heat up - like the whole of your top floor - it could be to a more general lack of system balance. If, for example, that loft was added with its new rads, but the lower floor rads were kept at their original l/s settings, then it would be no great surprise that the loft was receiving an inadequate flow as it's last on the chain. The quick test of this would be to close off most of the rads on the first or ground floor using their TRVs, and then seeing if the loft heated up ok. If it does, then clearly the loft is capable of getting an ok flow - so the plumbing is fine - but the whole house's rad system needs balancing in order to reduce the flow to the lower floors, so boosting it to the top. 

If you find your system - the upstairs rads in particular - need constant bleeding, then you may have an issue. One could be internal corrosion - if the 'air' coming out is actually hydrogen. Check your system's 'inhibitor' level. If air keeps needing to be expelled, then it's clearly being drawn in somewhere, and this could be due to a lack of pressure at the top level. But that would still be very unusual with a sealed system like yours.

Yes, the water bled with reasonable pressure in all floors.
After closing all radiators at floors 0 and 1, those at floor 2 started ti heat up full force  very quickly.  Turning on again the radiators at the ground floor made those at the second floor definitely cooler.
This system is obviously imbalanced. Will I have some chance to rebalance it by limiting the inflow of water at the ground and first floor playing only with the valves? Or do I need a plumber? There are 3 radiators that look horrible and old, I could take the chance to replace them with column-style aluminium ones.

The other side of the lockstep radiator is identical, twin brothers! 

Regaridng the hydrogen corrosion (very concerning), I'm wondering if all this push to adopt hydrogen instead of gas isn't counterproductive? That Hydrogen makes pipes brittle seems to be a well known fact. That water steam contributes massively to greenhouse effect is another very well known fact, so what's the rationale?

ThisIsWeird

Ok, nicely forceful bleeding from even the top floor rads would make it highly unlikely that the issue is down to lack of system pressure, so I'd keep it at no more than 1.5bar.

And, yes, the fact that the upstairs can be made to work ok by reducing the demand from the lower floors, again suggests the actual plumbing is fine. So, it'll likely be a case of rebalancing the system.

Best have a look at a few vids on YouTube about this, and decide whether it's DIYable for you. In any event, before touching a lock shield, make sure you can return it to its starting point if it all goes pear-shaped.

I mentioned the paper 'flag'? That's ok for small tweaks either way, but if you actually want to know 'where' the l/s is 'set', then you fit the flag and then close the valve down fully, counting the number of full and part turns this takes. Note this down for each rad.

Rads closest to the boiler will likely be only a half-turn or so open from the fully closed position. But, you'll see what it is with yours.

That nice rad with the shiny valves, where is it located? The two valves are probably both 'manual' valves, so both will likely control the rad, even tho' one should be 'set' (the l/s) and only the other used. What I would do is first check that they do move the valve - they should be nicely firm to turn, and not just loose caps. If one is just a loose cap, then pull it off to expose the spindle below - that'll be your l/s. Then, for both, shut them off fully (clockwise), counting what it takes to do this. Return them to their original settings, and let us know what they are.

ThisIsWeird

Oh, and if it is hydrogen in your rads, this will be as a result of corrosion, and not its cause.

What colour are the bled water samples? Do you have a magnetic filter fitter? Where was the corrosion inhibitor last checked/topped up?

pieroabcd

ThisIsWeird said:

Ok, nicely forceful bleeding from even the top floor rads would make it highly unlikely that the issue is down to lack of system pressure, so I'd keep it at no more than 1.5bar.

And, yes, the fact that the upstairs can be made to work ok by reducing the demand from the lower floors, again suggests the actual plumbing is fine. So, it'll likely be a case of rebalancing the system.

Best have a look at a few vids on YouTube about this, and decide whether it's DIYable for you. In any event, before touching a lock shield, make sure you can return it to its starting point if it all goes pear-shaped.

I mentioned the paper 'flag'? That's ok for small tweaks either way, but if you actually want to know 'where' the l/s is 'set', then you fit the flag and then close the valve down fully, counting the number of full and part turns this takes. Note this down for each rad.

Rads closest to the boiler will likely be only a half-turn or so open from the fully closed position. But, you'll see what it is with yours.

That nice rad with the shiny valves, where is it located? The two valves are probably both 'manual' valves, so both will likely control the rad, even tho' one should be 'set' (the l/s) and only the other used. What I would do is first check that they do move the valve - they should be nicely firm to turn, and not just loose caps. If one is just a loose cap, then pull it off to expose the spindle below - that'll be your l/s. Then, for both, shut them off fully (clockwise), counting what it takes to do this. Return them to their original settings, and let us know what they are.

The pressure is 1.5 when cold, but it gets to 1.9 - 2 when the heating is on. Is it ok?
I'm afraid that I've already rotates the lock shields several times before posting, not knowing that they behave differently from thermostatic valves. Of course I didn't keep track of the initial positions.

The new shiny radiator is at the second floor, exactly the one that didn't work well initially. The knobs are firm to turn and now they are fully open (counter-clockwise). There's nothing to remove, they are  single blocks, no spindle exposed.

pieroabcd

ThisIsWeird said:

Oh, and if it is hydrogen in your rads, this will be as a result of corrosion, and not its cause.

What colour are the bled water samples? Do you have a magnetic filter fitter? Where was the corrosion inhibitor last checked/topped up?

The water is fully clear, no dirt of strange colors.
I don't know about the magnetic filters, but I'll try to find out when the sellers did the last checks. I remember it wasn't that far.
I've lived in this house for ... 20 days!

ThisIsWeird

pieroabcd said:

ThisIsWeird said:

Oh, and if it is hydrogen in your rads, this will be as a result of corrosion, and not its cause.

What colour are the bled water samples? Do you have a magnetic filter fitter? Where was the corrosion inhibitor last checked/topped up?

The water is fully clear, no dirt of strange colors.
I don't know about the magnetic filters, but I'll try to find out when the sellers did the last checks. I remember it wasn't that far.
I've lived in this house for ... 20 days!

Hopefully it's just a bit of accumulated air, having come out of the system water. Just keep an eye on it, and hopefully future quants will be neglible.

If the boiler is recentish - say in the last 5-odd years - it should have a mag filter fitted on the return pipe to the boiler. This can be used to check the condition of the water, and also for adding chemicals as required.

ThisIsWeird

pieroabcd said:

ThisIsWeird said:

Ok, nicely forceful bleeding from even the top floor rads would make it highly unlikely that the issue is down to lack of system pressure, so I'd keep it at no more than 1.5bar.

And, yes, the fact that the upstairs can be made to work ok by reducing the demand from the lower floors, again suggests the actual plumbing is fine. So, it'll likely be a case of rebalancing the system.

Best have a look at a few vids on YouTube about this, and decide whether it's DIYable for you. In any event, before touching a lock shield, make sure you can return it to its starting point if it all goes pear-shaped.

I mentioned the paper 'flag'? That's ok for small tweaks either way, but if you actually want to know 'where' the l/s is 'set', then you fit the flag and then close the valve down fully, counting the number of full and part turns this takes. Note this down for each rad.

Rads closest to the boiler will likely be only a half-turn or so open from the fully closed position. But, you'll see what it is with yours.

That nice rad with the shiny valves, where is it located? The two valves are probably both 'manual' valves, so both will likely control the rad, even tho' one should be 'set' (the l/s) and only the other used. What I would do is first check that they do move the valve - they should be nicely firm to turn, and not just loose caps. If one is just a loose cap, then pull it off to expose the spindle below - that'll be your l/s. Then, for both, shut them off fully (clockwise), counting what it takes to do this. Return them to their original settings, and let us know what they are.

The pressure is 1.5 when cold, but it gets to 1.9 - 2 when the heating is on. Is it ok?
I'm afraid that I've already rotates the lock shields several times before posting, not knowing that they behave differently from thermostatic valves. Of course I didn't keep track of the initial positions.

The new shiny radiator is at the second floor, exactly the one that didn't work well initially. The knobs are firm to turn and now they are fully open (counter-clockwise). There's nothing to remove, they are  single blocks, no spindle exposed.

That amount of pressure increase is within 'normal', at least not 'unusual', and getting to 2bar, whilst not 'ideal', should be ok. Look up the manual for that boiler and see what pressure range it considers acceptable, or see if the guage has a shown acceptable range shown on it.

A larger pressure increase than that would suggest the boiler's expansion vessel needs attention, or - with a large rad system - a second one might need fitting; how many rads do you have? But, a sub-2bar pressure should be 'ok'. You could always reduce the cold pressure to, say, 1.2 to keep it all working fine, provided, of course, your upstairs rads still get enough pressure.

Re the shiny valves, with both valves fully open, the rad now works, yes?! I would personally now consider one valve to be the l/s and the other the control. (Follow the convention used with the other rads; if most TRVs are on the LH side, then make the LH one here the control one too).
So, turn the l/s fully closed, and then back open one full turn. See if the rad heats up fully with that. If so, use the other side to control the temp.

Two common reasons why a rad will not have a TRV when all the others do; it's a designer rad for which a nice-looking TRV is not available, or it could be it's a 'by-pass' rad designed to allow a constant minimum level of circulation for when all the other rads are off - the boiler might not have a built-in by-pass.

pieroabcd

After reading about rebalancing I've finally understood why the thermostatic  valves are put on the inflows rather than the outflows: to preserve the baancing! Otherwise people would meddle with it all the time and unbalance the system.
I thought that it was counterintuitive but it makes perfect sense.