Pressure too high in boiler - how do you release it?

[TheJockey]

My husband bled the bathroom radiator yesterday and it's affected our boiler. We noticed the pressure was well below 1bar so he opened the pressure valve to get this up. Now it's reading 3.3 so I've turned the heating off to see if it will drop. What's the best advice - other than calling a plumber which we can't afford because it's Sunday rate! Can we do anything ourselves to get this pressure down and why would bleeding the radiator make it drop so much in the first place?

 

[ianmcd]

Bleeding the radiator caused the pressure to drop because it is a sealed system and removing air causes pressure loss, to drop the pressure back down first make sure that the filling valve is definately closed properly, then take a container , a bowl or pot or something to a convenient radiator and just like bleeding the radiator open the air point an release the water into the container until the pressure guage reads correctly

 

[xr4x4]

The PRV should of popped by now, but as been said...

Just make sure the filling loop is turned off and bleed some air/water out some rads to get the pressure down to 1 bar cold.

What pressure does the gauge get to when the system is hot?

 

[TheJockey]

Thanks both

We bled one of rads, as suggested, and got the pressure down to below 2 but when we put the heating on it shot up again, however not to 3.3 as it was before. We're cooling it down again and will continue to bleed it later. We'll take it to 1 bar and see what happens after that.

I turned the heating off when it 3.3 before as I didn't want to damage anything, so I suppose I need to keep it off if it shoots up again later and get a plumber out tomorrow?

 

[Gas2Air]

If fill loop is shut and not passing. By bleeding the radiator you've took expansion out of the system, which the expansion vessel would cope with, it needs looking at.

Sunday rates? What would you do if it was an emergency?

 

[xr4x4]

But also the prv should release the pressure at 3 bar, do you have any pipes outside that are dripping?

 

[MIGEM]

We bled one of rads, as suggested, and got the pressure down to below 2 but when we put the heating on it shot up again

When you heat water, it expands.
Manufactures compesate for this by installing an expansion vessel within the boiler casing, normally on the back of the boiler, but that varies with each manufacturer.

Because water cant compress to absorb the pressure, the expansion vessel is filled on one side, with air and seperated from the water by a diaphragm. Water heats, it expands and compresses the air.
Water cools, volume reduces, as does the system pressure.

If your expansion vessel does not have sufficient air, the expanding water increases in pressure rapidly.

Either the tube to the EV is blocked or the air needs recharging.

Isolate the boiler by closing the flow and return valves underneath. Drain the boiler, but not through the PRV. Check the pressure on the EV (car tyre type schrader valve)
Charge to the manufactures guide or label, (allowing for system volume) while keeping the drain valve open to allow water to run out.
You should have pressure in the EV, but nothing on the boiler gauge.

Open the F&R valves, pressurise to 1 bar and turn the heating on.

If you get water from the schrader valve, or you cant pressurise it, your diaphragm is split.

 

[xr4x4]

That's if the expansion vessel is in the boiler, it could be in the airing cupboard, or beside the boiler. Big red thing.