hello Anyone come across this one before? Recently put in a Worcester cdi combi having converted from a open vent conventional system. customer phoned me 3 weeks later saying prv was dripping...told him to leave heating off so i could return to check system pressure. when i got there pressure was upto 3 bar, straight away thought customer had been messing. I let to let some water out got everything running and left. 3 weeks past and he phones me ...same thing again.. pressure upto about 3 bar and he also said upstairs rads were not getting hot. I checked the rads and all 4 were virtually full of air. I released the air and pressure returned to normal about 1 bar... Therefore a very large amount of air had entered the sealed system therefore pushing the pressure up. started scratching my head... the only conclusion i can come to is a build up of nitrogen due to corrosion.. but this is a lot of nitrogen in all 4 rads. system appears in good nick not as though its 40 years old. anyone else had this problem???? thanks
hi check the filling loop is not letting by.. the air?, maybe just in the system and collecting upstairs. regards peter
its a Worcester removable filling key..system fully vented..going to go back & put a flame to air when venting to see if its nitrogen. its doing my head in
Could the diaphragm in the exp vessel have ruptured? That would be a ready supply of compressed air . Or, internal system corrosion - but unlikely.
far to much air to come from expansion vessel...never had anything like this before...1st time would have put money on customer had drained down for some reason then topped up by too much, not knowing that rads needed venting..but when it happened again im stumped???????????????????
Well, there is something obvious being overlooked . This system is under pressure - much greater than atmospheric - so there is no way air is getting in from outside. These rads had refilled with 'gas' after only 3 weeks? After having done this before after the recent install? Surely no way that could be as a result of internal corrosion - and you would have added inhibitor anyway? I cannot think of any other way 'air' can get into a system. So, let's discount 'air being drawn in' and 'gas from corrosion'. What do we have left? The exp vessel. Dare I suggest that when you say that the 'rads were full of air', that they weren't really 'full' of air - it just took a seemingly long time to bleed them? A fairly small amount of air can do this - you sit there for a couple of minutes going ssssssssssssssss. There can be a surprising amount of air in an exp vessel - don't forget it is 'compressed' air too. A pin-hole in your diaphragm would - I think - tick the boxes here, so surely worth a look (see if the Shrader valve goes 'pssssssss' or go 'psssssshhrrrpppsshhhrrrrrp' as water squirts out.) And lack of air in the exp vessel would cause silly pressure increases when the system is turned on too.
thanks all i can do is wait for him to phone me again saying thers a problem....if the vessels gone then all the air should have expelled by now...resulting in pressure increase when hot... worcesters are not as good as people think.
Almost certainly the expansion vessel. Press the valve down when you get there, probably get water coming out. And the gas by-product of the corrosion process is hydrogen, not nitrogen. I don't fit worcesters, they are ok but expensive with lots of plastic inside in my view.
just been back to this job , vented the rads & put a flame to it...nearly burnt my arm off!!!! so the rads must be corroded..first time i have come across this, this bad all upstairs rads were full of gas..converted systems to combi in many old houses with very old rads & not had this problem. look like i will be changing all the rads...no prob with expansion vessel............
Well put it this way,there's no way on earth that corrosion would be happening that quick,even if it's an old system,bearing in mind new boiler,flushed out system ,new inhibitor. Sums don't add up.
Kbs, did you add inhibitor to the system after you converted it? Yes? Good. In which case that ain't no corrosion. Oh, you didn't add inhibitor?! In which I'd still be bludy astonished if that was corrosion at that level - it chust don't add up, man.
The only thing that's flammable here is your imagination... You converted a system to 'sealed' and 3 weeks later all the upstairs rads had filled with hydrogen? Cough. If that is really the case, I hope you'll be replacing these rads FOC?
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