What does this valve do?

[damorad]

My central heating system is a closed system with an expansion tank.
There is a filler valve on the mains side of the expansion tank that allows me to top up/pressurise the system to the recommended 1 bar.

The connection from the expansion tank to the is a braided pipe with a valve on it.
What does this valve do?
My first thought were it is a non-return valve but then isn't the expansion tank supposed to take excess pressure from the system.

Should I have a non return valve on the mains side of the expansion tank.

Thanks for all the help and advice offered...
Damo

 

[bab]

the expansion tank should have a permanent connection onto the heating system the non return valve used to be on the heating system & the top up valve used to be on the water main .It has just changed. the non return with an isolation is now on the water main with an isolater on the heating system.

 

[damorad]

This is my current arrangement.
For clarity I've left out the pressure gauge which sits on top of the expansion tank...

Am I right in thinking I should have a non return valve to the right of the mains feed. And I should remove any valves between the expansion tank and the system?
TIA

 

[meldrew's_mate]

Just to add to bab's comment, there MUST NEVER be any valve between the expansion vessel and the heat source (boiler). The valves you both refer to should be between the mains water supply and the heating pipework.

 

[Paul Barker]

Either you have drawn it wrongly or the installer was a cowboy and you are in great danger.

 

[bab]

Refresh ma memory damorad hav u a cracked exchanger on a suprima & rads gonin down like flys.

 

[damorad]

Refresh ma memory damorad hav u a cracked exchanger on a suprima & rads gonin down like flys.

I used to have ...

I'm up and running again,'nice and warm'

I have not made any mistakes with the drawing...

So I can assume from what is being said that I should remove the valve, (coloured blue) and install it on the mains side of the feeder.

 

[bab]

canot believe any body capable of fitting ya system would fit this valve where they have get um to read this forum theve lots to learn. lucky ya boilers still hung on the wall. Dont account for them wroting rads.

 

[Paul Barker]

Yep, then your heat exchanger will last the normal life everyone elses is, you radiators will stop turning into rugby balls and you life will be preserved.

I was once present when a radiator exploded, every rivet popped, it turned into a rugby ball shape and then filled the room from top to toe with black ink. My boss at the time had never seen that in 25 years, I considered myself quite lucky to have seen it.

Lucky it wasn't my fault I would have got the sack!

The guy who did that ows you a boiler and some rads.

 

[Agile]

I can understand that an installer MIGHT fit an isolating valve in the position shown to enable maintenance or replacement of the expansion vessel. Its not correct though!

More interesting is that with no non return valve on the mains feed, IF the mains feed valve was left open then the pressure would be at the incoming mains and as that fluctuates the system water would flow in and out bringing new oxygen in and corroding the rads!!! The resultant sludge would congregate in the boiler HE and cause it to crack!

I assume he has now replaced the boiler's HE without power flushing the system.

Tempting fate I fear!

Tony

 

[bab]

thats a very could point Tony. r u good at cluedo.once went to an optima with the complaint of cold rads, wet wall & large gas & water bills. The installer left the combi loop open in an area with 2 bar pressure cause they had a small leak he couldnt find .he fitted approx 32kw of rads to this office unit & left the relief in the cavity cause it was on a boundry. it was up to 3 bar all day for 6months when i arrived steam was coming out the facia on the flat roof.

 

[Paul Barker]

I was doing a job last week and mains water pressure was 2 bar at the time, imagine the effect on the drinking water of your scenario?

 

[bab]

I was doing a job last week and mains water pressure was 2 bar at the time, imagine the effect on the drinking water of your scenario?

gota go workin soon.

 

[Paul Barker]

It all hit the fan here yesterday, they sat on their problems over the holidays and all rang together yesterday.

I'm starting to feel like a GP's receptionist.

 

[damorad]

Just moved the non-return valve to mains side and used an isolating valve to bridge the connection between the flexihose from expansion tank and heating system.

Thanks for the help. I appreciate the advice I have been given by you all...


PS I know I shouldn't have anything between the expansion tank and the system but I will label it "LEAVE OPEN except whilst carrying out maintenance on the expansion tank."
I promise...
Thanks again...