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lopp0man

Good afternoon,


I'm new to this forum, I'm not a professional, more a DIYer but, as usual, many jobs are outwith the ability of someone like myself so it's interesting and revealing to read through the wealth of information that the forum contains. Very useful place - well done!


I have the Potterton Titanium 33 condensing boiler, professionally fitted new just over a year ago. I live in a bungalow in Glasgow - the boiler is located in the attic (it's a nuisance having to regularly climb the loft ladder to get access to re-pressurise). All the radiators, sinks, showers are on the ground floor. It is generally acknowledged that our water is of the "soft" variety, i.e. lathers easily.


The installation manual suggests that if the boiler is fitted at the highest point, it should include an automatic air vent. I assume this is not referring to the AAV fitted on the pump but is an additional component. The only AAV is on the pump and the vent is closed off.


All the radiators are heating up OK, there is no evidence of trapped air anywhere and so it would appear that everything is working well. Nevertheless, the pressure drops about 0.5 bar/week. The PRV outlet is bone dry. I've inspected all I can and there is no sign of any leaks. The boiler CH is set at about 65 degrees and the cold pressure at 1-1.5 bar.

I'm aware that water expands when heated and that is the reason for the expansion vessel. However, in my case, there's no visible increase in pressure. I don't understand that - there should be.
When the boiler starts CH, there's a decrease in pressure. When the CH stops and the pump overrun stops, the pressure increases back to where it was. I'm told elsewhere that the pump, because it's in the return line, causes this drop in pressure. Don't know if that's true.
Generally, the pressure is lowest when the pump runs. When the boiler starts HW, the pressure increases slightly and then drops back when the HW is off.


As the PRV is dry, and I keep putting more water into the system, where is all that water going?


I realise that there are probably numerous reasons for the pressure drop but maybe someone can suggest something I haven't thought of.


Thanks anyway.
 
Hello.
Welcome to the forum.
If you are loosing pressure, the most common causes would be a leak or the PRV passing or opening to release pressure due to a fault.
Have you any pipe work that is out of sight ( under floors for e.g.) ?

Not all Boilers show a big increase in pressure, it depends on the size of system you have. If it's only fairly small then you may not notice much of a rise. It would normally be around or 1/23 in expansion ( sometimes less dependant upon temperature ).

If it's only 1 year old, why not get the installer round to look at it for you?
 
I think that you ought to get the installer back to check the expansion vessel as I have had this problem several times and it always turns out to be the XVn that either got a split in the diaphragm, or it's not been set at the correct pressure.
 
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