Heating leaking

[John D v2.0]

Hi Terry thanks for replying, I was struggling to find any info online

Justvone if the points I was trying to make above is that if your system loses water it will be replaced by air at the highest point of the system

Not if there is water in the vessel and the pressure is higher than the height of the system. The water will be replaced by water from the vessel.

When I go to a system and replace an expansion vessel in a boiler on the ground foot I drop the pressure out of the system, disconnect the vessel, the system now has no vessel let alone an incorrectly charged vessel

My rads on the top floor do not suddenly become dry ? They are still full of system water

Of course, that's why I said if the system loses any water. In your case you didn't so it was ok, but if you lost 1l of water there would have been 1l of air at the top of your upstairs rads.
If your ev is present and has 2l of water in, losing 1l of water causes the ev to have 1l left but the system will still be full (assuming sufficient size ev and correct pressurisation)

 

[Terry lambert]

You open a drain point and drain water to drop the pressure

As I said I’m busy fixing boilers and havnt the time to go through this

 

[John D v2.0]

You open a drain point and drain water to drop the pressure

Is that while the ev is connected, so you're dropping water from the ev?

As I said I’m busy fixing boilers and havnt the time t

That's no problem, I appreciate your time, I'm always happy to learn! Maybe someone else understands as well as you on here and has time?

 

[Terry lambert]

Is that while the ev is connected, so you're dropping water from the ev?

That's no problem, I appreciate your time, I'm always happy to learn! Maybe someone else understands as well as you on here and has time?

My initial statements were to get you to think about it, I’ll have a read again later

 

[cdbe]

Thanks for your assistance (although I don't think I'm fully understanding the discussion), if it makes a difference the vessel is at the highest point of the system (along with an aav on the cylinder return).

I've pressed the valve on the top of the vessel and for what it's worth air hissed out. When I get chance I will drain the vessel and check the air pressure.
My own simplistic "logic” for thinking that the air pressure in the vessel should be slightly higher than the (cold) system pressure was that otherwise the water will compress all the air and there won't be any capacity left for when the water gets hot. However, what I think you're saying is that when the water is cold it should be partially compressing the air so there's a bit of ”spare” water in the system but still room for expansion when hot. In my case a small water loss is resulting in a large pressure loss.

Sooo - if I try the air at 0.8 and the water at 1 it should (till the remaining older and suspect parts of the system are replaced) take longer for the little bit of water loss to affect the system pressure?

 

[Hot&Cold]

It loses about a quarter of its 1 bar pressure over a few weeks. Only needs.a one second burst from the filling loop to bring back to 1 bar so not much loss. No visible leaks. It's ex open vented, now sealed, with a megaflo. Rads and pipework are a mix of new rads with new plastic pipework and 40 year old copper pipe and rads. I am repiping and replacing the old stuff as I work round the house but in the meantime is it likely that I'm losing a bit from the old parts and it's evaporating off?

Learn some fecking manners,or call in an approved installer


K un t omer from hell.com

 

[Hot&Cold]

Thanks for your assistance (although I don't think I'm fully understanding the discussion), if it makes a difference the vessel is at the highest point of the system (along with an aav on the cylinder return).
View attachment 134003

I've pressed the valve on the top of the vessel and for what it's worth air hissed out. When I get chance I will drain the vessel and check the air pressure.
My own simplistic "logic” for thinking that the air pressure in the vessel should be slightly higher than the (cold) system pressure was that otherwise the water will compress all the air and there won't be any capacity left for when the water gets hot. However, what I think you're saying is that when the water is cold it should be partially compressing the air so there's a bit of ”spare” water in the system but still room for expansion when hot. In my case a small water loss is resulting in a large pressure loss.

Sooo - if I try the air at 0.8 and the water at 1 it should (till the remaining older and suspect parts of the system are replaced) take longer for the little bit of water loss to affect the system pressure?

FFs hope the remainder of the installation is better,even a maze is designed better View attachment 134022

 

[cdbe]

Hi and thanks for your advice. I'm sorry if my posts come across as lacking in manners. Unfortunately as I'm not particularly knowledgeable in this subject area even writing the basic details of my problem seem to result in quite lengthy posts so I have tried not to make them worse by filling them with platitudes, but this does not mean I am not extremely grateful for any advice from members of the forum.

Regarding the ”maze”, it honestly doesn't look as bad in the flesh, or didn't until I put all the insulation on it, and it is all squashed into a very small space.

 

[Wildcat1961]

That's no problem, I appreciate your time, I'm always happy to learn!

It doesn't take a genius to copy and paste from the Internet , being in the trade day in and day out is the way to gain experience which would be the correct way to learn.
Quoting from the Internet is a far cry from actually carrying out the works first hand.
An armchair 'googler' will always trip themselves up due to the terminology used (chaff from the wheat).
Were you referring to vessel 'Pre-charge' pressure?

 

[John D v2.0]

It doesn't take a genius to copy and paste

Hi wildcat thanks for replying, I am certainly not trying to copy and paste, in fact no one seems to discuss this matter anywhere that I can find on the internet. So I couldn't copy and paste even if I wanted to.

Quoting from the Internet is a far cry from actually carrying out the works first hand.

Of course if I'm carrying out the works I just fill it up according to the instructions ie just below system pressure. I'm not disagreeing that it should be so, the debate is about why it has to be just below rather than just above cold system pressure. Perhaps you can enlighten us?

Were you referring to vessel 'Pre-charge' pressure?

I'm referring to the pressure in the vessel relative to atmospheric pressure, when atmospheric pressure is acting on the wet side of the diaphragm.

An armchair 'googler' will always trip themselves up

I'm not claiming to know everything or pretending anything, so if I've tripped up let me know and I'll learn something new. Maybe you're mixing me up with someone else?

 

[Wildcat1961]

Of course if I'm carrying out the works I just fill it up according to the instructions ie just below system pressure. I'm not disagreeing that it should be so, the debate is about why it has to be just below rather than just above cold system pressure. Perhaps you can enlighten us?

It gets a tad more involved when commissioning PU's in relation to..
PRV lift pressure
Vessel pre-charge pressure.
System cold fill pressure.
System working pressure.
Static head.
Etc etc.

 

[John D v2.0]

why it has to be just below rather than just above cold system pressure. Perhaps you can enlighten us?

It gets a tad more involved when commissioning PU's in relation to..
PRV lift pressure
Vessel pre-charge pressure.
System cold fill pressure.
System working pressure.
Static head.
Etc etc.

Was that an answer to the above?
Most of those factors are more relevant to sizing the vessel or deciding the cold fill pressure not to the pre charge pressure. Only cold fill pressure would be directly relevant, but that was my question

 

[Wildcat1961]

Was that an answer to the above?
Most of those factors are more relevant to sizing the vessel or deciding the cold fill pressure not to the pre charge pressure. Only cold fill pressure would be directly relevant, but that was my question

Really?
I suggest you read it again and hopefully you will 'learn' that 'cold fill pressure' is not the only factor involved whan commissioning heating systems.

 

[John D v2.0]

Really?
I suggest you read it again and hopefully you will 'learn' that 'cold fill pressure' is not the only factor involved whan commissioning heating systems.

I'm not asking about commissioning the whole thing otherwise this thread will never end, my question is specifically why should the pre charge pressure be slightly lower than cold fill pressure, rather than higher.

 

[Wildcat1961]

my question is specifically why should the pre charge pressure be slightly lower than cold fill pressure, rather than higher.

It was you that mentioned it so hopefully you could shed some light on the matter?
Keep in mind the guys that actually do this for a living poke their heads in here from time to time.