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Default boiler pressure

my ideal isar he35 has been fine for the last 6 weeks since fitting
until this week, i noticed the pressure had dropped to 0.75 bar from
the usual 1 bar (recomended when cold) i topped it back up to 1 bar and
it held this until the central heating had been on again, when it had
again dropped to 0.75 bar. This has continued all week it never drops
below 0.75 and works o.k. i can see no apparent leaks and the pressure
release valve has not discharged any water, the maximum pressure
reached when running is 2 bar. The only mention in the handbook of 0.75
bar is the pressure at which the expansion tank is pre pressurised at.
has anyone any ideas

thanks in advance

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andrewpreece
 
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"Set Square" wrote in message
...
In an earlier contribution to this discussion,
wrote:

my ideal isar he35 has been fine for the last 6 weeks since fitting
until this week, i noticed the pressure had dropped to 0.75 bar from
the usual 1 bar (recomended when cold) i topped it back up to 1 bar
and it held this until the central heating had been on again, when it
had again dropped to 0.75 bar. This has continued all week it never
drops below 0.75 and works o.k. i can see no apparent leaks and the
pressure release valve has not discharged any water, the maximum
pressure reached when running is 2 bar. The only mention in the
handbook of 0.75 bar is the pressure at which the expansion tank is
pre pressurised at. has anyone any ideas

thanks in advance


Stick a pot or something under your overpressure relief pipe, and see if it
fills up with water. If your expansion vessel is buggered then upon firing
up, the pressure will rise, the expansion vessel will not accomodate that
pressure rise and the overpressure relief valve will operate ( at about 2.5
to 3 bar ) dumping water out of the 15mm pipe that presumably emerges
outside your house wall somewhere. Then belatedly you look at the system
pressure and find it's dropped down to 0.75 bar.

That's one possibility anyway. If you keep filling up the system with mains
water to repressurise it eventually all the inhibitor in your system will be
flushed away and your boiler and radiators will start to corrode etc.

Andy


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[news]
 
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wrote in message
oups.com...
my ideal isar he35 has been fine for the last 6 weeks since fitting
until this week, i noticed the pressure had dropped to 0.75 bar from
the usual 1 bar (recomended when cold) i topped it back up to 1 bar and
it held this until the central heating had been on again, when it had
again dropped to 0.75 bar. This has continued all week it never drops
below 0.75 and works o.k. i can see no apparent leaks and the pressure
release valve has not discharged any water, the maximum pressure
reached when running is 2 bar. The only mention in the handbook of 0.75
bar is the pressure at which the expansion tank is pre pressurised at.
has anyone any ideas

thanks in advance


diaphragm in expansion vessel ?


RT


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Ed Sirett
 
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On Sat, 11 Dec 2004 18:45:50 -0800, andrewd90 wrote:

my ideal isar he35 has been fine for the last 6 weeks since fitting
until this week, i noticed the pressure had dropped to 0.75 bar from
the usual 1 bar (recomended when cold) i topped it back up to 1 bar and
it held this until the central heating had been on again, when it had
again dropped to 0.75 bar. This has continued all week it never drops
below 0.75 and works o.k. i can see no apparent leaks and the pressure
release valve has not discharged any water, the maximum pressure
reached when running is 2 bar. The only mention in the handbook of 0.75
bar is the pressure at which the expansion tank is pre pressurised at.
has anyone any ideas


See FAQ. 1.25 bar pressure rise is rather large and may indicate a
partially failed (or just possibly undersized) expansion vessel.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at 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




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John Rumm
 
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wrote:

my ideal isar he35 has been fine for the last 6 weeks since fitting
until this week, i noticed the pressure had dropped to 0.75 bar from
the usual 1 bar (recomended when cold) i topped it back up to 1 bar and
it held this until the central heating had been on again, when it had
again dropped to 0.75 bar. This has continued all week it never drops
below 0.75 and works o.k. i can see no apparent leaks and the pressure
release valve has not discharged any water, the maximum pressure
reached when running is 2 bar. The only mention in the handbook of 0.75
bar is the pressure at which the expansion tank is pre pressurised at.
has anyone any ideas


How many rads is it running?

My HE35 only registers a pressure rise of approx 0.8 bar going from cold
to hot. That is with 10 rads.

I tend to find that my system will slowly loose a little pressure over a
couple of weeks or so if you top it up to 1 bar, it takes the addition
of the equivilent of a couple of cups full of water to go back to 1 bar.
If you leave it, then it stabilises at about 0.8 bar. The difficulty
finding such a low volume loss, is that it will probably evaporate
rather than ever appear as water anyware.

On my system many of my rads are pretty old and I don't totaly trust all
the valves either (I am sure the previous house owner must have cobbled
together some of the collection of rads by raiding skips! - there are
about three different designs). I was half expecting lots of things to
start dribbling when I converted it to a sealed system, but so far
nothing has actually sprung a noticable leak.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd -
http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/
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Christian McArdle
 
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my ideal isar he35 has been fine for the last 6 weeks since fitting
until this week, i noticed the pressure had dropped to 0.75 bar from
the usual 1 bar (recomended when cold)


Probably a dodgy or undersized expansion vessel, or simply not inflated to
the correct pressure before filling the system. With a pressure rise of at
least 1.25 bar, you are quite likely to run into problems.

Given the new installation, it could be either a manufacturing fault,
installation fault (not checking charge pressure), or a design fault by the
installing engineer who didn't calculate the capacity of the system and
relied on the inbuilt vessel to accommodate expansion, when it was not up to
the task and should have had an additional external vessel fitted.

Do you have a large house by any chance?

Christian.


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Christian McArdle wrote:
my ideal isar he35 has been fine for the last 6 weeks since fitting
until this week, i noticed the pressure had dropped to 0.75 bar

from
the usual 1 bar (recomended when cold)


Thanks for all the replies they have certainly given me some ideas,

my house isnt particularly big more unusual 60' deep by 18' across, the
boiler supplies 13 radiators + 1 towel rad. I fitted the boiler myself
and was concerned at the expansion vessel section however i was assured
it 'should' be o.k. my old system had 28mm flow and return pipes
running to the old tank in the centre of the house 30' each i utilised
these when fitting the combi boiler
i intend removing them and connecting into the 22mm pipes. I think it
will be best to fit an expansion vessel at the same time, just a couple
of questions, can the vessel be fitted anywhere on the system,? can you
recomend any particular make? would i create another problem by
oversizing an expansion vessel?

Whilst i am asking, when i fitted the boiler i installed trv's
upstairs, when doing the above i will probably fit an automatic bypass,
what is the ideal location to fit one of these

thanks again

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Christian McArdle
 
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i intend removing them and connecting into the 22mm pipes. I think it
will be best to fit an expansion vessel at the same time, just a couple
of questions, can the vessel be fitted anywhere on the system,? can you
recomend any particular make? would i create another problem by
oversizing an expansion vessel?


Some boiler manufacturers state locations for the expansion vessel. However,
as this is an additional one anyway, you can put it anywhere on the system
that can't be valved off from the boiler. You can't (within reason) oversize
an expansion vessel. I would probably calculate for a 0.5 bar rise, which
gives loads of headroom.

Christian.


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