Ask The Trades - Print Page

Ask The Trades
https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Plumbing Questions >> baxi 105e instant expansion tank repressurise https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1184186189 Message started by dd on Jul 11^th, 2007, 9:36pm

Title: baxi 105e instant expansion tank repressurise
Post by dd on Jul 11^th, 2007, 9:36pm

Hi, please can anyone explain how to check expansion tank pressure and recharge if neccessary, is this the same as pressurising via filling loop and using boilers gauge?

Title: Re: baxi 105e instant expansion tank repressurise
Post by thescruff on Jul 11^th, 2007, 10:51pm

The red expansion vessel has a car tyre valve on the top, you have to release the boiler pressure, then test with a car tyre gauge, if it wants more pressure you blow it up with a tyre pump.

If you have a problem please post it, otherwise I would leave well alone.

Title: Re: baxi 105e instant expansion tank repressurise
Post by dd on Jul 12^th, 2007, 5:23pm

Hi, thanks for the response, the reason for wanting to check the expansion tank pressure was because I thought that the pressure was getting very close if not into the red when central heating on and I read somewhere that if the? expansion tank pressure was not right it could cause this, can the expansion tank be checked in situ? Of course the gauge could be faulty I could remove it and check calibrate with known source.
cheers,
DD

Title: Re: baxi 105e instant expansion tank repressurise
Post by thescruff on Jul 12^th, 2007, 7:00pm

Several things could cause the pressure to rise.

As you said the vessel may be undercharged. or on the way out depending on age.

The vessel could be undersized for the system. (Common)

You could have a fault, plate heat exchanger (combi) or filler loop letting by.

The starting pressure is too high.

Title: Re: baxi 105e instant expansion tank repressurise
Post by dd on Jul 12^th, 2007, 8:59pm

Hi, what do you suggest I should try first, the boiler is about 5 years old,not indicating any neon faults and relief valve not lifting, cheating pressure sometimes reads 2.5 to nearly 3 bar ,rv set at 3 bar according to info.

Cheers
DD

Title: Re: baxi 105e instant expansion tank repressurise
Post by thescruff on Jul 12^th, 2007, 11:18pm

What is the cold pressure reading. It should be around 1.2 bar.

Is the filler loop disconnected and if not do so and check its sound.

To check the vessel, you drop the system/b oiler pressure down to zero, and using a car tyre gauge test the pressure at the valve on the top, it should be 0.5 min.

have you got the manual.

Title: Re: baxi 105e instant expansion tank repressurise
Post by dd on Jul 13^th, 2007, 6:23pm

Hi, thanks again for your help, already have filling loop disconnected ,got the manual that came with boiler but doesnt show expansion tank filling point or give procedure, so thanks again and I will give it a try.

Cheers,
DD

Title: Re: baxi 105e instant expansion tank repressurise
Post by thescruff on Jul 13^th, 2007, 6:50pm

If you look on page 33, 12.16 you can see the valve at the top on the expansion vessel.

If you need to replace it you would be advised to get an ```rgi in as you have to remove the boiler from the wall.

Title: Re: baxi 105e instant expansion tank repressurise
Post by dd on Sep 1^st, 2007, 5:22pm

Hi,
Checked expansion tank and pressure was lo , repressurised to 0.5 bar, tried central heating and pressure still goes above 2.5 nearly three at times, could the vent on the pump be faulty ( note rv not lifting or getting any boiler fault lights on)
cheers, DD

Title: Re: baxi 105e instant expansion tank repressurise
Post by thescruff on Sep 1^st, 2007, 9:57pm

Did the vessel hold the charge when you up it to 0.5.

If it did then the vessel is too small for the system.

How many radiators are on the system and what sizes, you need to work out the water content of the system, or just add another vessel thats remote from the boiler, say 10-12 litres, it can be cut into the heating pipework anywhere on the return, nearer the boiler is best.

If however the pressure rises when the boiler is off then you need to say.

Title: Re: baxi 105e instant expansion tank repressurise
Post by dd on Sep 18^th, 2007, 9:21pm

Hi,
Please could you explain what you mean about holding pressure and increasing to 0.5 bar , 12 rads, but dont recall having pressure problems when new.

Cheers,
DD

Title: Re: baxi 105e instant expansion tank repressurise
Post by thescruff on Sep 18^th, 2007, 10:36pm

The expansion vessel has a pre-charge and is set with the boiler and system on zero pressure.

You say you have set it at 0.5 bar does it stay at that over say 30 mins, also is 0.5 the right pre-charge pressure I would up it a tad to nearer 0.75.

Title: Re: baxi 105e instant expansion tank repressurise
Post by dd on Oct 7^th, 2007, 1:01pm

Hi,
set expansion tank to .75 bar, suspect leak from schrader valve itself can the internals of schrader valve be screwed out and replaced like normal car valve? Also where else could expansion pressure leak from ?
The drawing I have not very clear to identify all suspect/leak points.

Cheers,
DD

Title: Re: baxi 105e instant expansion tank repressurise
Post by thescruff on Oct 7^th, 2007, 1:33pm

Screw the dust cap down and it shouldn't leak, if the bladder in the vessel is sound air cannot get out.

You have typical signs of the expansion vessel being undersized for the system, has any rads been added from first install.

A simple solution is to add a second expansion vessel and tee it into the heating return.

Title: Re: baxi 105e instant expansion tank repressurise
Post by ianjk on Oct 3^rd, 2008, 4:50pm

Hi, can the expansion vessel be recharged in situ and is 0.75 bar maximum and what would this be in lbs my calculation is about 15 lbs is this about right
Thanks in advance Ian

Title: Re: baxi 105e instant expansion tank repressurise
Post by thescruff on Oct 4^th, 2008, 9:54am

wrote on Oct 3^rd, 2008, 4:50pm:

Hi, can the expansion vessel be recharged in situ and is 0.75 bar maximum
Thanks in advance Ian

Yes if you drain the boiler out.

The pre-charge pressure is in the manufacturers installation manual.

Title: Re: baxi 105e instant expansion tank repressurise
Post by Twobarrows on Oct 16^th, 2008, 11:30am

wrote on Oct 3^rd, 2008, 4:50pm:

Hi, can the expansion vessel be recharged in situ and is 0.75 bar maximum and what would this be in lbs my calculation is about 15 lbs is this about right
Thanks in advance Ian

Of the top of my head 0.75 bar is about 11 lb sq. in.