pressure loss

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21 Jun 2007
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Yorkshire
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United Kingdom
Hello everyone.
May I say from the start, thanks for reading this. Yes you!
Right, on with the show. I am having problems with our ARISTON Combi A 24 MFFI boiler. It has been losing pressure and cutting out. I have located a leak on one of the radiators and intend to replace it. However I did isolate the radiator, thinking that this was the cause of the pressure drop. Well at least I thought I did! I got up the next morning after turning off the valves to the offending rad the night previous, only to find that we had no heating and no hot water. One side of the rad has a TRV fitted. I assumed that when turned to the off position that this would turn the valve all the way down, totally cutting off water into the rad. Is this correct? Do these TRVs not always fully stop water flow? I thought that this action would stop the system losing pressure and cutting out, but apparently not.

This morning at 0700 I decided to experiment, much to my wifes disgust I switched off the central heating. I repressurized the boiler to the Ariston recommended pressure of 1.5 bar and endeavored to monitor the situation, not easy because the boiler is in our loft space. Approximately 8 hours later, with the heating off it has lost only around 0.25 bar. I did notice earlier though, that when my wife went in the shower that the pressure did drop around 0.25 bar when she turned on the shower. When she turned off the shower it increased to near enough the 1.5 that it started at.

I perhaps should add that yesterday after repressurizing the system I returned home to find the floor outside wet underneath the boilers overflow. I can only assume that this is some kind of pressure relief tube, it is made of copper. (I do not believe that it is the boilers condensate discharge because the installation requirements in the manual indicate that this should run into a plastic pipe). Like today, I increased the pressure to 1.5 bar, but on that occasion did not switch off the central heating. As mentioned I returned home to see the floor wet, so obviously water had been flowing from it. We left the heating on for the remainder of that night, however when we got up this morning the boiler had cut out, with an error reading E02, meaning 'Pump Protect'. This is the confusing part, If the system is losing pressure, why did the pressure relief valve open?
I'm really confused.
Any help would be much appreciated
Thanks DG
 
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A boiler has a Pressure Relief Valve, with a discharge pipe called a blow off, usually discharging outside in copper, and is turned back against the wall.

Is this constantly dripping even with the central heating off, or does it discharge rather suddenly when system is at 1.5 bar and turned on.

Possible causes could be your boiler is heating the water too hot, therefore the pressure builds up too much as the water is heated and is released out of the PRV, thus why you are losing pressure within the CH... or your PRV just needs replacing because it has become faulty and is slowly letting the water out thus also causing pressure loss.
 
hi jr
things that might cause pressure relief valve to release its self
build up of pressure obviously
causes
the fill loop might be letting by-try disconnecting and have a look to see if letting by
expansion vessel might need re pressurising
a tyre gauge will test this but boiler needs draining to get accurate reading
or the diaphragm might of failed- (split) take tyre cap off expansion vessel release air valve (same as any tyre valve)if no air just water it needs replacing
or hate to say - the heat exchanger might have a hole in it

when you top up heating when cold check pressure relief valve outside - if
it isn't running you shouldn't have to replace it-when these run for long periods they scale or it wears the seating down and need replacing
i hope this all make sense
 

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