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PostPosted: Mon Oct 06, 2003 8:50 pm 
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Joined: Tue Sep 09, 2003 2:25 pm
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Bit of a bid for help please... Recently moved into a flat with the above running 6 rads and the hot water. Water runs fine, but the heating will run for maybe an hour, then the pressure will suddenly rise quickly, vent the over pressure valve (spraying anyone in the wrong part of the garden) and shut the gas off. I have bled the rads and found no air in them. Could there still be some air trapped in the system causing this problem? If so how can I get it out?


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PostPosted: Mon Oct 06, 2003 9:09 pm 
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Joined: Sun Aug 10, 2003 5:45 pm
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Sounds very much as if your pressure vessal has gone, on the 9.24 its large red vessal above the controll panel or sitting on top of the boiler on early models,its suposed to basicaly cussion the expansion of the system water when heating up. on the vessel is a tyre valve if you depress it for a second you should get air out, if its water then its for the bin, simple to change and around £40. the pressure relief valve thats dichargeing the water should be replaced at the same time or it will probably drip when under pressure 9 out of 10 will at that age.


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PostPosted: Mon Oct 06, 2003 9:53 pm 
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Joined: Thu Jan 09, 2003 11:40 am
Posts: 3449
Location: NW London
Has anyone ever seen any performance curves for PRVs ?

I went to one where the EV had split due to filling loop being left open when the mains pressure was about 7 Bar and the PRV could not cope.

Tony Glazier

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PostPosted: Mon Oct 06, 2003 10:56 pm 
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One has to ask what happen to the pressure relief valve Tony.

scruff


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PostPosted: Mon Oct 06, 2003 11:19 pm 
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Joined: Tue May 13, 2003 10:37 pm
Posts: 268
Sounds to me as though your pressure vessel has lsot most of its air pressure. Being under-charged with air will give your symptoms. It should be pumped up to about 1 bar (15psi).

If yours has failed (water comes out of the Schroeder [spelling?] valve when you check the pressure) you could leave it in situ and fit another one externally. Sometimes easier to do than swapping a built-in vessel.

Cheers, Mike


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PostPosted: Wed Oct 08, 2003 9:21 pm 
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Joined: Tue Sep 09, 2003 2:25 pm
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Had a look at the pressure vessel.. only air coming out of the valve, so I upped the pressure by about 3/4 bar. Waiting to see what happens.... will let you know. Thanks as ever!

Scruff... could there be a prob with the PRV??


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PostPosted: Wed Oct 08, 2003 9:35 pm 
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Joined: Tue Sep 24, 2002 10:02 pm
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No Tonysmith.

My reply was to Tony argile, who had a 7bar mains pressure and the prv couldn't cope.

The valve should blow at 3 bar.

scruff



This message was edited by thescruff on 10-8-03 @ 10:41 PM


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PostPosted: Wed Oct 08, 2003 11:15 pm 
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Joined: Thu Jan 09, 2003 11:40 am
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Location: NW London
Went there a few days ago and at 4 Bar the PRV was only letting by about a litre per minute and was totally inadequate to protect the EV.

Another problem today on a Baxi Bahama. The pressure gauge was grossly inaccurate and varied widely as the inlet tube was moved.

The square EV was leaking water on the seams and found to be empty of air. On repressurising it the leak stopped. Does anyone know if it can be trusted or should be renewed ?

Tony Glazier

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PostPosted: Wed Oct 08, 2003 11:40 pm 
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Thats what I couldn't understand Tony, the EV should be protected with a Pressure relieve valve set at 3bar.

scruff


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