I sure I’ve seen plumbing/heating questions answered on here before so here goes.

The pressure reader is shooting up to 2.5/3 bar and cutting out then when cold drops back down to below 0.5 bar, I can press the cut out button and restart but it shoots back up on running hot water and cuts out again in about 10 seconds.

It’s a Worcester Bosch 230 if that helps been running OK for a while , got techie coming out on Monday but hoped there could be something I could do to limp through the week-end with at least some heating and hot water.

TIA.

Does it only come on when running the hot water and OK all the other times?

If not is the tap open on your filler loop (a little metal ccoiled hose under the boiler)?

Not sure I understand the first question, heating hasn’t been due to come on since it’s stopped working, but as soon as the hot water goes on the pressure jumps and cuts out, pressure then immediately drops.

Filler loop is closed.

Expansion Vessel needs recharging.

+1 for the expansion vessel.

Had similar symptoms myself a couple of weeks ago and it was this.

Is that DIYable?

If so how?

Track pump! There’s a flying saucer shaped thing (are they all the same shape?) with a schrader valve on it. Attach a pump and pump it up. If it sounds like blowing air into water, the diaphragm has split and you’ll need a new one. 0.5 bar rings a bell, I’ll check….

Nope, they can be different shapes, present boiler’s vessel is rectangular. 0.75 to 0.9 bar recommended for my boiler.

Double post.

Is that DIYable?
If so how?

Yes.

Look for your boilers recommended pressure and inflate to that pressure with a bike pump.

Dead easy once you have found out the pressure required (and what an expansion vessel looks like 😉 )

Dead easy – the only problem I had was actually getting my hand to the valve.

Deffo your expansion vessel.
Let your techie know now so he can turn with the part on Monday.
Don’t even bother trying to fix it.
Have you been filling the system with fresh water often? You may have leak, usually Pressure Relief Valve which should get changed with expansion vessel.

Don’t even bother trying to fix it.

Money to burn ?

I’ve recharged loads of Expansion Vessels that just needed the pressure sorting out.

Why replace without even trying ?

If your pressure is going up when using hot water it isn’t normally expansion vessel. You mention resetting the cut out? Probably the overheat device. Do you know how to repressurise/ top up pressure in boiler with filling loop as mentioned above? You need to repressurise to 1-1.5 bar first if still having pressure/overheat problems could be circulation problem ie pump has gone.

Water coming out of valve so guess it’s knackered.

Not always it can be condensation