Help with exp. vessel please.

[outinthestix]

Hi, I am about to replace an expansion vessel on a Grant 50/70 oil fired system boiler.The old one is leaking water at the schrader valve.
Can anyone offer help on the following issues ?
Is it just a matter of swapping the vessel and topping up the water to 1 bar ?
How do I bleed the vessel of air from the water side of the diaphram ?
How do you replenish the system with inhibitor ?
All help greatly appreciated in advance.

 

[oilman]

Hi, I am about to replace an expansion vessel on a Grant 50/70 oil fired system boiler.The old one is leaking water at the schrader valve.
Can anyone offer help on the following issues ?
Is it just a matter of swapping the vessel and topping up the water to 1 bar ?

No. You have to set the vellel air pressure first.

How do I bleed the vessel of air from the water side of the diaphram ?

Dont bother.

How do you replenish the system with inhibitor ?
All help greatly appreciated in advance.

Unless you do something unnecessary like draining the boiler, you dont need to.

If you have to, buy a cartridge you inject into a radiator.

 

[outinthestix]

Great, that doesn't sound too difficult. Thanks for that .I was under the impression the vessel came pre-charged but you say this is not so. What pressure should it be ?

 

[Agile]

He did NOT say that the vessel did not come precharged. They usually do!

But before fitting you check and set to your required pressure. There is no space for air on the water side when its pressurised.

Tony

 

[outinthestix]

O.K. . I think I've got the idea. But at the risk of annoying you with details, am i right in thinking that the vessel needs charging to the same pressure as the water in the system, i.e. 1 bar, or does the air pressure need to be greater ?

 

[Agile]

It would take too long for me to explain why on Christmas Eve's Eve!

Howerer if you intend to pressurise the system to the recommended 1.5 Bar cold then I suggest you set the vessel air pressure to 0.8 Bar.

Tony Glazier

 

[ChrisR]

Precharge pressure isn't critical. If it starts at 0.75bar and your system pressure is 1.5, the vessel will be half water and half gas at 1.5bar.

 

[Agile]

Yes, but thats cold!

My recommended precharge pressure of 0.8 or 0.9 bar ensures that when hot the vessel is still 50% air and water, thus giving more capability to absorb any over heating pressure increases.

Must go to bed now, jobs to do tomorrow! And wrapping the presents too!

Tony

 

[ChrisR]

What I rote, stands. Explanation not recommendation.
Hot or cold. Pressure goes up when system is hot of course.

Do people still buy Christmas presents? Whatever for? I thought that went out of fashion in the 80's. I shan't be buying anything. Is it a "children" thing?

 

[Agile]

I have a present from a boiler manufacturer, one from the owner of the kosher plumbing firm we do some boiler repairs for and several from customers!

As far as I am aware present giving is on the increase! I have more this year that I can remember ever before!

Even my dog gets a present!

Happy Christmas to everyone!

Tony Glazier

 

[outinthestix]

thanks for all your help and a very Happy Christmas.