Hello All My Boiler has been dropping pressure every few days and the hot taps were beginning to running lukewarm. Pressure was never great but was constant..3 floors up so only ever just over 1 bar. I called out the Gas Safe engineer who usually services the boiler and he said that the flat plate exchanger would most likely be scaled up (London area) and noticed the PRV overflow was leaking (damp patch on external wall when I switched on the central heating...so the pressure was dropping. He initial took out the exchanger and was going to replace the whole kit and caboodle but then suggested I descale it since I was going away for the day.. I had some phosphoric acid to hand so that got rid of the scale (which was a great saving on buying a fitting a new one so can't fault him there). Resumed the next day...exchanger descaled, cold flushed and refitted resulted in constant hot water/that job done. However he couldn’t get to the PRV to replace it (...he’d replaced a PRV on my OH's 16 year old W B 24i RSF..absolute doddle..and then saw that the Greenstar was a whole dfferent issue due to being at the back right hand side and the copper pipe leading to the PRV is threaded through the boiler framework so pipe seemingly cannot be simply dropped down (vertically) off of the first coupling point of the PRV in order to then be able to release the second ( horizontal/90 degree angle) coupling. The PRV seems wedged into place and to get to the horizontal coupling ...so much stuff needs to be dismantled and removed from the front of the boiler (pump, diverter valve motor etc) in order to get to the simple task of reaching in and replacing the PRV). So he said “not keen to do this..time and effort will be costly just to replace a 20 quid part (had new part in his hand..go check and see if your warranty was still in date"...Warranty is 6 months out of date. Darn. So no freebee Worcester Bosch engineer callout. By now he’d put the exchanger back and I’ve got hot water..result. But he seemed unsure about how to access the PRV...he thought he’d have to take out the pump and he wasn’t too sure what the green housing was that is attached to the righthand side of it (bit puzzled by what the green housing actually houses..I checked on youtube and is it the diverter valve motor??). So pressure is still dropping over a week esp if I run the CH. Questions 1) I thought it’s a PRV..a simple push fit item...must be an easy way of replacing it...so I googled and youtubed how to replace a PRV on a W B Greenstar 24i but nothing has come up....is it such a difficult job to replace the PRV on this model of boiler,,is there no ingenious shortcut to make things simple? 2) I’m guessing it’ll be scale build up on the PRV internal valve seat...will repeated flicking the lever remove the scale issue?...or is it possible to somehow unscrew the lever section and then clean the internal rubber seal and brass seat of the PRV without removing the pump etc in order to resolve the issue of limescale wedging the PRV slightly open. Finally..it's now a saga so had to laugh...also ended up with a spring circlip from somewhere...pointed it out to the engineer but he said not to worry. Switched the Central Heatng on after the GSR engineer had left and found out where the circlip should have been...it was one of the prv circlips..water pressure inevitably caused the prv to move due to not having circlip in place and boiler peed itself..water exited the joint (can see it by looking up from below) ended up on the floor. I hit the electrics switch to off, mopped up the water and called the GSR engineer...he's coming back Monday (so no hot water). Whenever stuff like this happens I think my dad and all his family used a tin bath and one lot of water...life is not instant custard. So any info on a simple method to access and replace PRV.. then I’d be grateful. Thanks in advance.
...just thought...is it even anything to do with the PRV?....is it an excess pressure problem due to a EV issue? (that the PRV is simply responding to).
LOL! I've no idea if that PRV is especially hard to swap - I simply don't know, but hopefully a WB fellow will be along to advise. Yes, something must have caused that PRV to open in the first place - scale won't have gotten on to the valve seat without it having been forced open first. So, yes, it's likely your EV needs checking and re-pressurising. (And if it's blown, then consider adding a remote one to your system instead as replacing the boiler's EV might be a pita.) As soon as you mentioned finding a left-over 'spring circlip', I was worried - and would have warned you about the inevitable had you not already had it happen... Bottom line - don't ever use this guy again - he is a twit. He clearly isn't au fait with WBs, and to not know what the 'green' bit was is incredible (ok, I don't know what it is either, but I'm not pretending to be a pro. And I bet I would know what it was if I actually saw it...) But, to not be concerned by a left over circlip is - jeepers, that's real bad. How about posting some photos to explain the awkwardness of the PRV location? Ah - looks like it's part of the Hydrobloc, so a bit of dismantling required file:///C:/Users/Dad/AppData/Local/Temp/Greenstar%2024-28%20i%20Junior%20Combi%20Installation%20and%20Servicing%20Instructions.pdf Having said that, if the guy was a WB specialist, then he could do this with his eyes shut - it's one of these jobs that is just a matter of fact when done a few times.
Hello All..Figure this out! So I get the GSR engineer back to put the circlip back to secure the PRV..He can't manage it! So i did it with him standing there! PRV is secure but still leaking so I suggest the EV but he's still fixated on the PRV...I suggest causal situation..PRV is a dumb on off device opening n response to pressure increase...He says PRV and wanders off..... You're going to like this next bit. I then switch off the boiler, take off the cover.... I look at the EV.... It's not even connected to the system...5 inch label attached to blanking end on boiler/EV connection point...`Please remove this plug ..Connect expansion hose and secure with clip`....Oh! No wonder the PRV leaks..That'll be because there's no expansion tank connected... I got the boiler fitted five years back..I lived in it and it's a warm flat..So never used the CH..Then i rented it for 3 years..Gas cert every year..The pressure was never right..Brother and wife stayed...Hot water went lukewarm...So plate expansion tank taken out, cleaned, replaced by GSR....Pipe is hanging down in plain view by exchanger..not connected...Label is in plain view! Unbelievable. I'm going to connect the expansion vessel... Question: if i open the PRV via the red lever,thereby depressurising the boiler...can i simply connect and circlip the EV then pressurise then boiler and the job is done?
Answer: yes. Don't, alas, be surprised if your PRV continues to leak as they are a sod like that - once opened, they rarely seal shut again. And, sorry I called your plumber a 'twit'. He is actually a lot worse...
The expansion vessel on these boilers is only intended to take up the expansion from the boiler. Many installers fit additional expansion vessels to large systems to prevent venting of water at the pressure release. My Bosch boiler was also gunged up so I cleaned both heat exchangers with phosphoric acid, it worked! Had to dismantle the boiler to do it, oops! what 'Gas Safe?'
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