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

 

[Deleted member 120897]

The photos look like they’re pressure reducing valves. There’s generally no pressure on an open vented system, think you may have an unvented cylinder? What boiler is it?

 

[PeterMoonsock]

The photos look like they’re pressure reducing valves. There’s generally no pressure on an open vented system, think you may have an unvented cylinder? What boiler is it?

atag Q25S - Maybe I'm wrong in what I said. I have some water coming out of the pressure relief valve on the boiler so assumed the pressure is the issue

 

[Deleted member 120897]

atag Q25S - Maybe I'm wrong in what I said. I have some water coming out of the pressure relief valve on the boiler so assumed the pressure is the issue

Ok, yes, that’s a system boiler, which does use pressure, and 2.9 is high, and prv seeping water is a telltale sign. So if it’s only high when the heating has been on for 10 minutes or so, and then returns to a ”normal” pressure or loses pressure altogether, then you have an expansion/possible prv fault. If it’s high without the heating being on, then it’s been over pressurised. If it’s the latter, you could drain some water from a radiator, ensuring, that the filling loop is closed.

 

[John.g]

It looks possibly the top PRV (pressure reducing valve) is the supply to the boiler (topping up) If just shut the red lever valve and the boiler pressure will/should fall, this PRV should be set to 1.5 bar and only opened if the boiler pressure falls to ~ 1 bar cold.
Can you take a close up of the Wilo Fluid Control pump before closing anything.

 

[PeterMoonsock]

Ok, yes, that’s a system boiler, which does use pressure, and 2.9 is high, and prv seeping water is a telltale sign. So if it’s only high when the heating has been on for 10 minutes or so, and then returns to a ”normal” pressure or loses pressure altogether, then you have an expansion/possible prv fault. If it’s high without the heating being on, then it’s been over pressurised. If it’s the latter, you could drain some water from a radiator, ensuring, that the filling loop is closed.

The pressure is high without heating. I spent yesterday trying to do this but without success, when draining the pressure goes down but then fills back up when stopped. I tried finding a filling loop but couldn't, also have a water tank in my attic if that gives you any further information.

 

[Deleted member 120897]

The tank will be to feed the hot water cylinder. Looks like John may have given you the solution?

 

[PeterMoonsock]

It looks possibly the top PRV (pressure reducing valve) is the supply to the boiler (topping up) If just shut the red lever valve and the boiler pressure will/should fall, this PRV should be set to 1.5 bar and only opened if the boiler pressure falls to ~ 1 bar cold.
Can you take a close up of the Wilo Fluid Control pump before closing anything.

This pump is switched off on the wall and hasn't been used for a long time from what I can see. I did try turning off the red lever yesterday and bleeding the radiator for awhile without any luck. Wanted to make sure I wasn't stopping flow to the cylinder too

 

[John.g]

Both those PRVs which are set to 4 bar may have one reducing the mains pressure for the cold water supply and the other may be reducing the mains pressure for the cold water supply to HW cylinder and maybe just flowing through the stopped (free wheeling) pump now.
You might see a braided hose somewhere on the supply to the boiler or system with isolation valves.

Even though you did shut that red lever valve maybe check out the indicated 15mm T off.

Edit. Or thy the other indicated one in ....rev1

 

[PeterMoonsock]

Both those PRVs which are set to 4 bar may have one reducing the mains pressure for the cold water supply and the other may be reducing the mains pressure for the cold water supply to HW cylinder and maybe just flowing through the stopped (free wheeling) pump now.
You might see a braided hose somewhere on the supply to the boiler or system with isolation valves.

Even though you did shut that red lever valve maybe check out the indicated 15mm T off.

Edit. Or thy the other indicated one in ....rev1

The pipe in your 2nd pic seems to go into the cylinder

Those pipes in my original post are the only ones going into the boiler. Can't find a braided hose anywhere

 

[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