Pressure too high in open vented system

[PeterMoonsock]

Hi Guys,

Hopefully someone can help me out - the pressure reading on my boiler and in the hot press seems too high. Just wondering how can this be adjusted?


Hot Press:

Downstairs boiler:

Any help would be greatly appreciated

 

[John.g]

A bit unusual to have mains direct to a HW cylinder, except that you have a heat store?, where the boiler heats and circulates the water around the cylinder and the hot water is supplied via a coil in the cylinder, can you see what type of system you have got, it's strange but the top PRV has a marker needle on the pressure gauge which may be a clue to something?.
If the system is like I described then the boiler pressure will be the same as the (unvented) store pressure.

 

[PeterMoonsock]

A bit unusual to have mains direct to a HW cylinder, except that you have a heat store?, where the boiler heats and circulates the water around the cylinder and the hot water is supplied via a coil in the cylinder, can you see what type of system you have got, it's strange but the top PRV has a marker needle on the pressure gauge which may be a clue to something?.
If the system is like I described then the boiler pressure will be the same as the (unvented) store pressure.

Really appreciate your help! I've just turned on the hot water which also does the radiators upstairs and these pipes are hot which lead into the cylinder:

Boiler:

 

[PeterMoonsock]

Hopefully those videos are useful

 

[John.g]

Well, I can see that the bottom PG is now showing ~ 6 bar, it was 4 bar in your original photo, so something amiss there like a failed expansion vessel. Can you take a photo of the label on your cylinder also (sometime) a few "still" photos of all the connections on the cylinder.

 

[PeterMoonsock]

Well, I can see that the bottom PG is now showing ~ 6 bar, it was 4 bar in your original photo, so something amiss there like a failed expansion vessel. Can you take a photo of the label on your cylinder also (sometime) a few "still" photos of all the connections on the cylinder.

^^^^
This pipe is the same type as this one here

 

[John.g]

Sorry Peter but really can't make much sense of that system, others on here may, I saw actually that both pressure gauges went to 6 bar with boiler on, if they fall back when boiler off or some hot water used then definitely points to a expansion vessel problem, although even at 4bar if connected to the boiler then the boiler PRV (safety valve) should be continuously passing as it should be a 3 bar PRV. If it is only passing at 6 bar but not at 4 bar then something seriously amiss IMO.
It looks as if the house system was originally pumped from the tank in your attic and converted to a mains only supplied system, do you recall any mods being made in your time there?.
There should also be a T&P PRV on the cylinder which opens at 90C or 7bar pressure, also a expansion valve on the cold water supply to the cylinder which opens at 6bar in the event of expansion vessel failure. If this cylinder is a store then safety devices may be different as not familar with them.

Some boilers (mainly combi I think) have a automatic top up system with the mains permanently connected, these are known to cause over pressure problems as well.

 

[ShaunCorbs]

What happens if you turn the water mains off ?

Also please put the boiler case back on as it’s important

 

[PeterMoonsock]

What happens if you turn the water mains off ?

Also please put the boiler case back on as it’s important

Is it safe to turn the mains water off then try bleed the system?

 

[ShaunCorbs]

Yes just make sure boiler isn’t heating the system