Boiler much more sensitive to pressure after Evohome?

[rotor]

Hi there,

I have recently installed Evohome, 9 x HR92, S-Plan. I ended up replacing all the TRVs as a couple were stuck (I did them all out of sense of completeness), and one thing I noticed afterwards (everything working, bled all the rads numerous times until no more air was coming out anywhere), is that the boiler's pressure gauge went much higher than it used (pre-Evohome).

Pre-Evohome:
When cold, the pressure gauge would show 1 bar, maybe 1.1. And at its hottest (72 degrees), it would show 1.5-1.6. I previously (a year ago) had the boiler pump replaced, so the system had to be topped up, so I've used the filling loop before and am comfortable with the lag in response from the boiler pressure gauge. In other words, when filling the cold system, my target was always 1.0 - 1.1 bar.

Post-Evohome:
After refilling it started at 1.1 bar, and very quickly went to 2 bar. After 3 days at 2 bar, I drained about a litre from the drain spigot, and this dropped the pressure down to 1.2-1.3 (warm -- it has been quite mild in London in the last few days).

I am quite suspicious that such a tiny amount of water would cause the pressure to go from 2 bar to 1.2-1.3. I'm also very suspicious that the pressure no longer seems to fluctuate (it should be low when it's cooler, high when it's hotter).

a) Did I break something when I drained and refilled?
b) Does the fact that a lot of rads are now closed off by the HR92s means that there is a lot less give and take in the pressure of the system, as it is barely more than the core loop?

Does this ring true to anyone else? Any ideas or suggestions?

Thanks!

[top brake]

you have air in your system

Hi there,

I have recently installed Evohome, 9 x HR92, S-Plan. I ended up replacing all the TRVs as a couple were stuck (I did them all out of sense of completeness), and one thing I noticed afterwards (everything working, bled all the rads numerous times until no more air was coming out anywhere), is that the boiler's pressure gauge went much higher than it used (pre-Evohome).

Pre-Evohome:
When cold, the pressure gauge would show 1 bar, maybe 1.1. And at its hottest (72 degrees), it would show 1.5-1.6. I previously (a year ago) had the boiler pump replaced, so the system had to be topped up, so I've used the filling loop before and am comfortable with the lag in response from the boiler pressure gauge. In other words, when filling the cold system, my target was always 1.0 - 1.1 bar.

Post-Evohome:
After refilling it started at 1.1 bar, and very quickly went to 2 bar. After 3 days at 2 bar, I drained about a litre from the drain spigot, and this dropped the pressure down to 1.2-1.3 (warm -- it has been quite mild in London in the last few days).

I am quite suspicious that such a tiny amount of water would cause the pressure to go from 2 bar to 1.2-1.3. I'm also very suspicious that the pressure no longer seems to fluctuate (it should be low when it's cooler, high when it's hotter).

a) Did I break something when I drained and refilled?
b) Does the fact that a lot of rads are now closed off by the HR92s means that there is a lot less give and take in the pressure of the system, as it is barely more than the core loop?

Does this ring true to anyone else? Any ideas or suggestions?

Thanks!

[rotor]

I've bled every rad. Anything else I need to be doing?

[top brake]

I've bled every rad. Anything else I need to be doing?

the boiler will likely have an air vent. or there will be an air vent at the highest point in the system, perhaps next to the cylinder

[rotor]

OK thanks, will investigate and report back.

[electronicsuk]

After refilling it started at 1.1 bar, and very quickly went to 2 bar. After 3 days at 2 bar, I drained about a litre from the drain spigot, and this dropped the pressure down to 1.2-1.3 (warm -- it has been quite mild in London in the last few days).

I am quite suspicious that such a tiny amount of water would cause the pressure to go from 2 bar to 1.2-1.3. I'm also very suspicious that the pressure no longer seems to fluctuate (it should be low when it's cooler, high when it's hotter).

I can't explain why your pressure isn't fluctuating any more, but I am not at all surprised that removing a litre of water dropped the pressure by about 0.8 bar. Remember that water isn't exactly compressible, therefore the expansion capacity in a sealed system comes, for the most part, from an expansion vessel (usually located inside the boiler). These generally hold something in the region of 8-10 litres in total, and that would be at the vessel's maximum designed operating pressure - i.e. more than 2 bar!