Unvented central heating losing pressure only in winter

[Selvara]

Update : So, I got gas engineer to check the pressure of the expansion vessel.
He checked and confirmed pressure of the expansion vessel is fine and put fernox leak sealer.

But still today the pressure went down close to zero when system was cold and no usage around 3pm

however when i start heating or hot water with out topping up, the pressure goes to 1 bar without topping up.
is still this a problem? is the water leaking?

when pressure automatically goes to 1 bar without topping up during hot water or heating running.

 

[Harry Bloomfield]

Update : So, I got gas engineer to check the pressure of the expansion vessel.
He checked and confirmed pressure of the expansion vessel is fine and put fernox leak sealer.

But still today the pressure went down close to zero when system was cold and no usage around 3pm

You still have an issue, your 'engineer' has failed to properly investigate it and resolve it.

 

[Selvara]

What is the issue please ?
Is the water leaking somewhere?
Or is it ab issue with pressure expansion vessel?

 

[Harry Bloomfield]

What is the issue please ?
Is the water leaking somewhere?
Or is it ab issue with pressure expansion vessel?

You have had all of this explained to over the past three pages.

 

[Laurieo]

As already mentioned your pressure relief/temp valve from your cylinder is not connected correctly,(photo one) it should go to a tundish then be piped outside to a drain .Yours looks like it goes back into your heating system.

 

[Selvara]

Thank you Everyone.
I have attached my picture of my cylinder temp&pressure relief value connected to tundish.
Sir, Please can you have a look at the picture and let me know if this still not correct I will get a gas engineer to look at it.

 

[Selvara]

Another clear picture attached

 

[Selvara]

Thank you

 

[Selvara]

Thank you

 

[Laurieo]

Thanks for the better picture .
The temp/PRV set up is ok .

 

[Selvara]

So water could be escaping somewhere under the floor (tiles) because I have been having this low pressure problem for one year especially during winter:
Should I then get leak detect engineer to detect leak under floor ?
Do they trace the leak with central heating pipe?

Can you advise

 

[Selvara]

When the unvented hot water mega system is ideal/cold, the pressure goes to zero on gauge at the unvented system.
but when i start the central heating with out topping up, the pressure automatically goes to 1 bar.
is this normal or any issues? i wonder how pressure goes to 1 bar with out topping up.

 

[Harry Bloomfield]

When the unvented hot water mega system is ideal/cold, the pressure goes to zero on gauge at the unvented system.
but when i start the central heating with out topping up, the pressure automatically goes to 1 bar.
is this normal or any issues? i wonder how pressure goes to 1 bar with out topping up.

Warm/hot water, occupies a larger volume, than cold water.

 

[Selvara]

is this an issue? do i need to get leak detection to look into ?

========
When the unvented hot water mega system is ideal/cold, the pressure goes to zero on gauge at the unvented system.
but when i start the central heating with out topping up, the pressure automatically goes to 1 bar.
is this normal or any issues? i wonder how pressure goes to 1 bar with out topping up.

 

[Harry Bloomfield]

do i need to get leak detection to look into ?

You need to get someone who knows and understands how such basic things work, to investigate it, rather than asking endless questions here - when you do not comprehend the answers you are given.