Worcester 24i Junior RSF, high pressure problem

[JohnBob1971]

Greetings people, my boiler was working fine until the heat exchanger developed an internal leak and allowed mains pressure into the sealed system, this also blew my pressure gauge.

I have since replaced the heat exchanger, fitted a new gauge, checked the expansion vessel (it was not letting water by but was a little low in pressure so was pumped up), replaced o rings and washers to anything that needed it and checked the filling loop. Then with joy in my heart I switched the heating on only to see the pressure steadily rise to 3.5bar.

The one thing that I did notice is that the pressure relief valve did not appear to open and since the pipe from the expansion vessel and the valve are at close proximity to each other I am wondering if there could be a blockage somewhere?

I will be taking a look at these later but will be out of ideas after that, are there any other reasons for this to happen?

Any help will be appreciated, thanks.

 

[plumbplumb]

Check for a blockage in the pipe to the expansion vessel.

Did your pressurise the vessel with an open end (i.e drain cock open)

 

[Gasguru]

Probably the hose to the vessel/PRV manifold blocked...replace it...and have fun getting it out the back of the pump.

It's a major design fault on these models and the reason the safety valve doesn't open.

 

[JohnBob1971]

Yes plumbplump the system was drained.

I know the hose you are talking about Gasguru, looks like another round of grazed knuckles is on the menu.

Thanks to both of you, I shall let you know what happens.

 

[JohnBob1971]

Gasguru, you are a genius!

Had to remove the pump assembly completely to remove hose and it was packed solid. Rather than wait for a replacement I cleaned it out with a wire coat hanger. Apart from a few weeps that should sort themselves out, the boiler is firing away happily at 2.5bar.

Thanks again people for the help.