help with adding another expansion vessell to 240x

[deeuk]

i sold a pc to a central heating engineer and i helped him out with a few problems with his laptop and computer. In return he serviced my boiler alpha 240x.

recently the pressure gauge started to raise well above the parameters. I called him in and he diagnosed it as the expansion vessel had gone.
He told me that you can fit an additional expansion vessel but as he has moved away, i need to contact some to carry out the job. Any ideas of what sort of costs i face. I am very short of cash at the moment and would appreciate some guidance.

many thanks

 

[chrishutt]

You can DIY. you should be able to get an 8 litre expansion vessel from say Toolstation or similar for maybe £30 including bracket. Then you need to partially drain the heating system so that you can make a connection to the return pipe near the boiler.

There's probably an existing 15mm branch off the 22mm run for the filling loop connection. You could use a 15mm compression tee to add your expansion vessel connection to this. Then run a length of 15mm copper to the vessel where you'll need a 15mm x ¾" female connector. If the angles involved are awkward you could use a flexible tap connector (¾" x 15mm).

 

[bengasman]

and check that the vessel is precharged at about 0.75 bar

 

[billy bob]

The expansion pre-charge will depend on the system cold feed pressure and system head, but in domestic situations 0.2bar below the cold fill pressure of the system is usually sufficient.

 

[bengasman]

The expansion pre-charge will depend on the system cold feed pressure and system head, but in domestic situations 0.2bar below the cold fill pressure of the system is usually sufficient.

cold feed pressure is totally irrelevant.

as it is a sealed system, it does not give head

 

[mrgas]

Have you tried repressurising the existing expansion vessel at back of boiler?

 

[chrishutt]

Surely the pre-charge pressure isn't that critical. If it was 0.5 bar and the system pressure was 1.0 bar then the air volume in the EV would be compressed to 50% of its original volume at 2.0 bar and to 37% at 3.0 bar, so it would be operating within a reasonable range.

If the pre-charge was set higher, at say 1.0 bar, and the system pressure still set at 1.0 bar then the air volume would be compressed to 67% at 2.0 bar and to 50% at 3.0 bar, so still operating within range, but of course once the system pressure fell below 1.0 bar it would drop rapidly towards 0 bar with any further pressure loss. However with a higher system pressure of say 1.5 bar it would operate well within its capabilities.

 

[billy bob]

The expansion pre-charge will depend on the system cold feed pressure and system head, but in domestic situations 0.2bar below the cold fill pressure of the system is usually sufficient.

cold feed pressure is totally irrelevant.

as it is a sealed system, it does not give head

Cold fill pressure is relevant, some systems require a 1bar cold fill, others require a 1.5bar cold fill, so each system will require the vessel to be set to different pressures, as for the static head of the system, this is relevant, I know it is a sealed system, but if the vessel was at the bottom of a 4 storey house, it will make a difference to the pre-charge pressure than if it were at the top of the system

 

[deeuk]

hay many thanks for the replys, i would dread tackling it myself, i will source a local plumber to fix it

thanks

 

[deeuk]

any chance of a rough price on this type of job please?

 

[deeuk]

Hi
sorry i rang up a local firm and they said you need the vessel in the boiler to be working before you add an additional one. The adiditional one is if you have a lot of water in your heating system.
Is that the case as the guy who diagnosed the issue was confident that to aviod taking off the bioler from the wall you can add an additional one.
thanks

 

[chrishutt]

i rang up a local firm and they said you need the vessel in the boiler to be working before you add an additional one. The adiditional one is if you have a lot of water in your heating system.

bo11ocks.

 

[bengasman]

Additional one will replace the broken vessel, in function that is. No need to fix the broken one first

 

[deeuk]

Additional one will replace the broken vessel, in function that is. No need to fix the broken one first

many thanks for your advise, much appreciated

 

[ChrisR]

Unless I missed it there's no evidence that you need a new expansion vessel. First try pumping yours up. Easy to DIY, see the FAQ Pressure Problems section. 100 need pumping up for every one which needs replacing.
Of the ones which do need replacing, a good number would leak water externaly or from the valve itself, to indicate it.