I have an Ariston Genus 27 BFFI combination boiler with an integral 60l hot
water tank.

I have just replaced the heating expansion vessel, which was leaking, and
found that the hot water expansion vessel had also failed - water came out
of the valve when I tried check the pressure.

Does this matter?

If it does, is it urgent?


--
Chris Melluish

On Wed, 17 Dec 2008 17:22:26 +0000, Chris Melluish wrote:

I have an Ariston Genus 27 BFFI combination boiler with an integral 60l hot
water tank.

I have just replaced the heating expansion vessel, which was leaking, and
found that the hot water expansion vessel had also failed - water came out
of the valve when I tried check the pressure.

Does this matter?

Yes, when the system heats up and water expands the pressure will rise a
lot and blow open the PRV. Then when it cools down again the pressure
will drop to practically nothing and the boiler will probably refuse to
fire up again. You will need to either replace the expansion vessel or fit
an external one.

If it does, is it urgent?

You're not going to get much use out of the boiler until it's sorted.



--
John Stumbles -- http://yaph.co.uk

Time flies like an arrow
Fruit flies like a banana
Tits like coconuts

I dont understand why the pressure would drop to nothing. It is the hot
water expansion vessel, not the cenral heating one. The pressure in the hot
water tank cannot drop to below mains pressure. I will lose a bit of hot
water out of the overflow when it heats up, but is this a problem?

--
Chris Melluish

"YAPH" wrote in message
...
On Wed, 17 Dec 2008 17:22:26 +0000, Chris Melluish wrote:

I have an Ariston Genus 27 BFFI combination boiler with an integral 60l
hot
water tank.

I have just replaced the heating expansion vessel, which was leaking, and
found that the hot water expansion vessel had also failed - water came
out
of the valve when I tried check the pressure.

Does this matter?

Yes, when the system heats up and water expands the pressure will rise a
lot and blow open the PRV. Then when it cools down again the pressure
will drop to practically nothing and the boiler will probably refuse to
fire up again. You will need to either replace the expansion vessel or fit
an external one.

If it does, is it urgent?

You're not going to get much use out of the boiler until it's sorted.



--
John Stumbles -- http://yaph.co.uk

Time flies like an arrow
Fruit flies like a banana
Tits like coconuts

On Thu, 18 Dec 2008 13:35:52 +0000, Chris Melluish wrote:

I dont understand why the pressure would drop to nothing. It is the hot
water expansion vessel, not the cenral heating one. The pressure in the hot
water tank cannot drop to below mains pressure. I will lose a bit of hot
water out of the overflow when it heats up, but is this a problem?

D'oh! Read your post wrong. Sorry.



--
John Stumbles -- http://yaph.co.uk

A: Because it messes up the order in which people read text.
Q: Why is top-posting a bad thing?

On Thu, 18 Dec 2008 13:35:52 +0000, Chris Melluish wrote:

I dont understand why the pressure would drop to nothing. It is the hot
water expansion vessel, not the central heating one. The pressure in the
hot water tank cannot drop to below mains pressure. I will lose a bit of
hot water out of the overflow when it heats up, but is this a problem?

If this was a typical unvented external cylinder it would imply a fault
with the pressure guage and/or the pressure reduction valve.

However the integral unvented store may be a little different. So the
first thing is to check the manual and see how the whole thing works.

I have a manual for 47-116-11 is this your model? It is not clear to me
with a 10 minute look over the book where pressure guage that measures the
DHW is located?


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html