I have an 8 year old Worcester Greenstar Heatslave 18/25 oil-fired boiler
which has been misbehaving lately. Whereas previously the pressure gauge
only moved over a very limited range during the course of day in which
heating and hot water were required, over the last few months that range
has got wider and wider, from zero first thing in the morning before it
fires up, to about 2.5 a few hours later. IIRC, if it gets to 3 it will
activate a pressure relief valve and dump water all over the floor, which
I'd really like to avoid obviously.
What's the most likely cause of the problem?
thanks.

In article ,
Al wrote:

I have an 8 year old Worcester Greenstar Heatslave 18/25 oil-fired boiler
which has been misbehaving lately. Whereas previously the pressure gauge
only moved over a very limited range during the course of day in which
heating and hot water were required, over the last few months that range
has got wider and wider, from zero first thing in the morning before it
fires up, to about 2.5 a few hours later. IIRC, if it gets to 3 it will
activate a pressure relief valve and dump water all over the floor, which
I'd really like to avoid obviously.
What's the most likely cause of the problem?
thanks.

Sounds to be like the pressure vessel has failed. If's basically a
diaphragm in a sealed box with water one side and pressurised gas on the
other. Which moves to accommodate the increase in pressure in a sealed
system as the water heats up and expands. Depending on boiler design, may
not be difficult to replace.

--
*Why is 'abbreviation' such a long word?

Dave Plowman London SW
To e-mail, change noise into sound.

Al formulated the question :
I have an 8 year old Worcester Greenstar Heatslave 18/25 oil-fired boiler
which has been misbehaving lately. Whereas previously the pressure gauge
only moved over a very limited range during the course of day in which
heating and hot water were required, over the last few months that range
has got wider and wider, from zero first thing in the morning before it
fires up, to about 2.5 a few hours later. IIRC, if it gets to 3 it will
activate a pressure relief valve and dump water all over the floor, which
I'd really like to avoid obviously.
What's the most likely cause of the problem?
thanks.

The expansion vessel diaphragm has either failed, or needs air pumping
in via the scrader(sp?)scrader(sp?) valve.

On 18/05/2019 13:37, Al wrote:

I have an 8 year old Worcester Greenstar Heatslave 18/25 oil-fired boiler
which has been misbehaving lately. Whereas previously the pressure gauge
only moved over a very limited range during the course of day in which
heating and hot water were required, over the last few months that range
has got wider and wider, from zero first thing in the morning before it
fires up, to about 2.5 a few hours later. IIRC, if it gets to 3 it will
activate a pressure relief valve and dump water all over the floor, which
I'd really like to avoid obviously.
What's the most likely cause of the problem?

Yup, what they said...

Find the pressure vessel, and look for the car tyre style valve. Give
the pip in the middle a push. If nothing comes out, then it needs
re-inflating. If water comes out, then it needs replacing.

To inflate, with the system off, drop the pressure in the system by
bleeding off a bit of water. Then pump up to 1 to 1.5 bar. Repressurise
the wet side and you should be done.

If its leaking, then you can either replace the failed one, or simply
abandon it, and add another expansion vessel elsewhere where it might be
easier to get at (some boiler makers like Vaillant make them nice and
easy to get at - slipped into the side of the case. Others seem to adopt
the lets build it right into the back of the case and stick *everything*
else in front of it, so you can't get at it without taking the whole
boiler apart!):

e.g. Pressure vessel is the sliver thing on the right with the inflation
valve looking straight at you:

http://wiki.diyfaq.org.uk/index.php/...cotec824HE.png


(if you need a way to keep a system running for a bit with a failed
vessel, then partially drain a rad so that there is an air pocket in the
top of it)



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 18/05/2019 13:37, Al wrote:

I have an 8 year old Worcester Greenstar Heatslave 18/25 oil-fired boiler
which has been misbehaving lately. Whereas previously the pressure gauge
only moved over a very limited range during the course of day in which
heating and hot water were required, over the last few months that range
has got wider and wider, from zero first thing in the morning before it
fires up, to about 2.5 a few hours later. IIRC, if it gets to 3 it will
activate a pressure relief valve and dump water all over the floor, which
I'd really like to avoid obviously.
What's the most likely cause of the problem?
thanks.


We have the 20/25 version of this boiler in a bungalow. Before we bought
the property where it is located, I think the expansion vessel leaked
and the water also destroyed the control box which is below.


--
Michael Chare

Al wrote:

I have an 8 year old Worcester Greenstar Heatslave 18/25 oil-fired boiler
which has been misbehaving lately. Whereas previously the pressure gauge
only moved over a very limited range during the course of day in which
heating and hot water were required, over the last few months that range
has got wider and wider, from zero first thing in the morning before it
fires up, to about 2.5 a few hours later. IIRC, if it gets to 3 it will
activate a pressure relief valve and dump water all over the floor, which
I'd really like to avoid obviously.
What's the most likely cause of the problem?

As others have said, its caused by insufficient expansion space for the
water. That said, unless your boiler was installed by a complete cowboy,
it shouldnt dump water on the floor. The pressure relief valve should be
plumbed in to carry the overflow into a drain or outside somewhere.

Tim


--
Please don't feed the trolls

I'm amazed that a boiler is not fitted with a suitable bit of plumbing to
dump water somewhere appropriate, not on the floor, though!
Brian

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"Dave Plowman (News)" wrote in message
...
In article ,
Al wrote:

I have an 8 year old Worcester Greenstar Heatslave 18/25 oil-fired boiler
which has been misbehaving lately. Whereas previously the pressure gauge
only moved over a very limited range during the course of day in which
heating and hot water were required, over the last few months that range
has got wider and wider, from zero first thing in the morning before it
fires up, to about 2.5 a few hours later. IIRC, if it gets to 3 it will
activate a pressure relief valve and dump water all over the floor, which
I'd really like to avoid obviously.
What's the most likely cause of the problem?
thanks.

Sounds to be like the pressure vessel has failed. If's basically a
diaphragm in a sealed box with water one side and pressurised gas on the
other. Which moves to accommodate the increase in pressure in a sealed
system as the water heats up and expands. Depending on boiler design, may
not be difficult to replace.

--
*Why is 'abbreviation' such a long word?

Dave Plowman London SW
To e-mail, change noise into sound.

Many thanks for all your constructive replies, guys.

I did manage to get access to the valve that looks and behaves like a
bycicle one. I pushed the needle in the middle and there was a *very*
weak puff of air came out. Seems the membrane hasn't become porous after
all. The heating engineer who did the last service told me the whole tank
needed replacing and offered to do it for me on the cheap. I managed to
get some more air into it via a car tyre footpump and the range of
movement has certainly decreased. Trouble is, the maker's recommended
pressure is only 0.5 bar and I can't find an air pressure gauge that
reads such low pressure! I'll take a look on Ebay and see what's what. So
ATM it's just guesswork on my part. Still, at least there's more air in
it than there was!

Thanks again, gents.

On 22/05/2019 01:14, Al wrote:
Many thanks for all your constructive replies, guys.

I did manage to get access to the valve that looks and behaves like a
bycicle one. I pushed the needle in the middle and there was a *very*
weak puff of air came out. Seems the membrane hasn't become porous after
all. The heating engineer who did the last service told me the whole tank
needed replacing and offered to do it for me on the cheap. I managed to
get some more air into it via a car tyre footpump and the range of
movement has certainly decreased. Trouble is, the maker's recommended
pressure is only 0.5 bar and I can't find an air pressure gauge that
reads such low pressure! I'll take a look on Ebay and see what's what. So
ATM it's just guesswork on my part. Still, at least there's more air in
it than there was!

you want about 1 bar in there.

Thanks again, gents.




--
€œThe ultimate result of shielding men from the effects of folly is to
fill the world with fools.€�

Herbert Spencer

On Wed, 22 May 2019 07:55:02 +0100, The Natural Philosopher wrote:

you want about 1 bar in there.

Absolute tops.

On 22/05/2019 01:14, Al wrote:
Many thanks for all your constructive replies, guys.

I did manage to get access to the valve that looks and behaves like a
bycicle one. I pushed the needle in the middle and there was a *very*
weak puff of air came out. Seems the membrane hasn't become porous after
all. The heating engineer who did the last service told me the whole tank
needed replacing and offered to do it for me on the cheap. I managed to
get some more air into it via a car tyre footpump and the range of
movement has certainly decreased. Trouble is, the maker's recommended
pressure is only 0.5 bar and I can't find an air pressure gauge that
reads such low pressure! I'll take a look on Ebay and see what's what. So
ATM it's just guesswork on my part. Still, at least there's more air in
it than there was!

Thanks again, gents.



I'd go for 10PSI - which is about 0.7 bar. Your gauge can probably
measure that.
--
Cheers,
Roger
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