System boiler pressure keeps rising, filler loop letting by?

[harrypotter]

Got a system boiler with unvented cylinder. Took out some water yesterday when the system was cold to lower the pressure from about 2.7 bar to 1 bar. Today it's back up to about 2.7 bar cold. I assume the filling loop might be leaking?

 

[Jurassicspark]

The filling loop most likely is letting water by. Disconnect the filling loop and see if the problem is resolves. Silly question, but have you turned off the valves on the filling loop? I've seen people accidentally forgetting to turn it off after refilling.

Does the pressure rise rapidly?

If the pressure still rises when cold (boiler not in use), then you may have a split DHW heat exchanger. You can check for this by isolating the cold water inlet to the boiler. What is the model of the boiler?

 

[xd400]

Is it a removable filling loop?

 

[harrypotter]

@Jurassicspark and @xd400 thanks for the replies.

I yesterday realised the expansion vessel for the unvented tank was basically deflated. No wetness from the valve, just seems like I need to replace the leaky valve core. I pumped it up to 3 bar and today after a heating cycle the boiler pressure has not risen.

But I'm a bit confused, isn't the expansion vessel on a different "circuit"? Looking at the pipe work (standard Y-plan) I don't fully understand how expansion vessel pressure can have an affect on boiler pressure.

 

[terryplumb]

If the expansion vessel is red it's part of the central heating circuit ,not the hot water cylinders expansion vessel. When you pumped up the EV pressure did you drop the system pressure and leave a drain cock open ? 3 bar pressure in the EV is too high.

 

[harrypotter]

If the expansion vessel is red it's part of the central heating circuit ,not the hot water cylinders expansion vessel. When you pumped up the EV pressure did you drop the system pressure and leave a drain cock open ? 3 bar pressure in the EV is too high.

No it's white, potable. I'm pretty sure it's on a different circuit so won't affect the boiler pressure. I guess it's just coincidence that I pumped that unvented cylinder expansion vessel back up to 3 bar and now the boiler pressure seems to have stabalised.