Expansion vessel replacement on Worcester Bosch Greenstar boiler

melb

hi there, our boiler pressure was going between 3 and 4 so we called an engineer round who said this was probably caused by a problem with the expansion vessel.
He removed it, showed that it was leaking and replaced with a new one.
When I was researching high boiler pressure before his visit, faulty expansion vessels were only mentioned when people were losing pressure on their boiler which would make sense if the pressure was too low.
Have we been misled?

HumberFlyer

No...you haven't been mislead. Increased pressure in the system would push against air in the expansion vessel. If yours had leaked into the air chamber it would be pushing against water (no resistance).... hence, High pressure

melb

thanks HumbleFlyer i feel better now, although I must say the pressure is still regularly reaching 3 so don't know if there could be something else going on

Lorian

what's the pressure showing first thing in the morning before the heat starts for the day?

Mr.Generous

Expect a bill that includes WB washer kit (s) and a pressure release valve if its blown. The boiler has to come off the wall on a Greenstar I think.

rob7475

You say the pressure was getting high. When it got over 3 bar, did it then drop back down quickly? That is the usual tell tale sign of the expansion vessel failing. If the vessel isn't holding air, it fills with water. As the system heats up, the pressure increases until it reaches around 3.5 bar before the PRV kicks in and releases some water out of the system to relieve the pressure. You would find that you are regularly topping up the water in the system.

Did he replace the expansion vessel or just try pumping it back up? With most greenstars, it's a boiler off the wall job as the expansion vessel slides out of the top and there's not usually enough room above to get it out. When our expansion vessel failed, I just fitted an external one next to the boiler which cost me about £40 and took about an hour to drain down the system, fit and refill.

Albermarle

Did he replace the expansion vessel or just try pumping it back up? With most greenstars, it's a boiler off the wall job as the expansion vessel slides out of the top and there's not usually enough room above to get it out. When our expansion vessel failed, I just fitted an external one next to the boiler which cost me about £40 and took about an hour to drain down the system, fit and refill.

I have a Greenstar R1 18, which is 8 years old.

The expansion tank is separate/external.

Sounds easier to deal with, but we have had three problems with it. It fell off the wall due to the weak bracket supplied + the pipe split and sprayed water everywhere ( luckily we caught it early or could have flooded the house) + it failed and had to be replaced.

I guess the first two items would not have happened if it had been internal to the boiler.

Phil4432

Sounds right, same thing happened to me last weekend,  Pressure went up to 3, then the vessel started leaking.  Worcester also.

Pressure shouldn't be going that high, you need to check with the engineer.

melb

thanks all for your comments.  The engineer said it doesn't sound right and he is coming back on Monday to investigate. I will have a look first thing before it fires up.  I have looked during the day when the boiler isn't fired up and it is regularly at 3

Phil4432

melb said:

thanks all for your comments.  The engineer said it doesn't sound right and he is coming back on Monday to investigate. I will have a look first thing before it fires up.  I have looked during the day when the boiler isn't fired up and it is regularly at 3

If you drain the system slightly and when cold, does the pressure go down?

melb

sorry Phil4432 only just seen your reply.  No I haven't but he's coming back tomorrow so will wait for him to have a look