advice needed regarding potterton puma 100e combi boiler

[jimmac]

Hi all, need some advice regarding my boiler, its a potterton puma 100e, iv'e notice over last couple of weeks that pressure keeps dropping, had couple of frozen pipes which stopped couple of rads from working, but managed to get them thawed out, so suspected a burst pipe, but had no water damage in any area, so investigated today, and eventually discoved overflow from pressure relief vale was dripping. After a few attemps to get it sealed again by opening it up a few times, problem still was there, so I know i will have to replace it, question is whats the best way to do this, figured out thats its only held in place with couple of grub screws. Am i gonna give myself problems by undoing them and unscrewing overflow pipe, and removing the offending part, by being flooded out. And if so how do I stop that from happening, or is it just a case of superman speed needed lol to get new part in before i'm swimming out the kitchen, or do i have to drain boiler, and if so will i cause any additional problems once part is installed and topped system back up. I did notice that there are stop valves on ch outlet and return and also cold mains into unit.please help, don't want to give myself more problems than I already have. Sorry If post is long and winded, but really need advice and help with this, so thanks in advance for any given.

 

[grahamgas]

Hi
The best way to change the PRV is this:
Close iso valves on CH flow and return.
Relieve pressure through PRV.
Drain boiler from drain under pump body.
Disconnect PRV pipe and move to the side.
Undo grub screws on body ,where PRV goes.
Remove PRV.
Wipe out recess where PRV sits into.
Fit new PRV, ensuring the rubber o-seal is on.
Do up grub screws.
Refit drain under pump body.
Open iso valves, and recharge, whilst going around system bleeding out any air.

Hope this helps

Graham

 

[Puddle]

As Graham says however do not touch boiler isolation valves on flow and return,no need to,,if moved they have a good chance of leaking and we do'nt want that as then will have to replace them
Also if you or have or can get hold of a car foot pump,it would be good to pump up/re prime the expansion vessel while boiler drained down,as boiler this old,probably will need doing
Also remember to electrically isolate boiler before you open up and work on it

 

[stevetheplumber]

as puddle ses most iso valves will leak if used some times its possible to just change the head of the prv grip edge with pair of pump pliers i seem to recal the puma being a screwed in valve thats a pain to get out so head only might be the way to go obviously clean the seating if you go this way

 

[jimmac]

thanks guys for the promt advice, puddle, can you explain more about the car pump side of it, have read this on other posts thats the bit that kinda throws me putting air into system rather than bleeding it off, also when i remove the prv will i not get massive loss of water,and if so, and boiler is empty, is it just a case of topping it back up then bleeding air from the air release screw at top of boiler or should i use the old prv to take pressure down to zero first before replacing it, also read again that the grub screws can sometimes seize, and if they strip when trying to be removed i'm up **** creep without the perverbile paddle, any tips to prevent that from occuring, thought maybe applying some wd40 to them few days before removal to let it soak in, so they are easy to get out, cheers in advance again.
also is it worth doing a powerflush on it first, and is that easy,and how do i get it out afterwards, and then adding inhibitor, or go straight for the inhibitor, to prevent rust , doubt there is any left in it since being topped up so much
I know I can do this, even if my wife thinks otherwise lol

 

[Billy Bob Bob]

the expansion vessel is behind the boiler,from memory the shrader valve is on the top,or bottom of the expansion vessel its like a car tyre valve.wd40 would really help on the grub screws.whatever happens you need to change the safetyvalve but a expansion vessel thats low on air or failed will take it out anywayor of course your filling loop is passing.as puddle said isolate the mains first had a nasty unsuspecting shock off a puma in the week [and i should know better] on the plus side with a puma the expansion vessel is easy to change if the wall sleave is fitted[thats if its a horizontal flue]but you need to be gsr to do this as the flue has to be dissconected also when you drain and re-fill you need to be aware your auto air vent may be faulty that should be replaced as well its a standard calleffi 3/8 aav you will also need a 3/8 washer its located on the lh side top of heat exchanger

 

[stevetheplumber]

to avoid the grubscrew problems just change the head of the prv

 

[jimmac]

thanks gas man, when pumping up the expansion tank, how do i know if i have put enough air into it, total novice here, but dont mind getting hands dirty, but also don't wanna f**k it all up too, prv, looks easy job to dissasemble, and insert new one, what does expansion tank do, and would that have failed, as well as auto air release, i have boiler casing front and side off and have had a good look, to be honest, its still going strong,even after seeing numerous scottish gas vans in street cause other units have broken down lol and only the pressure dropping from leaking prv has caused me any serious problems ( if calling topping pressure up after every use a problem lol) hey i've even resoldered dry solder joints on pcb when they caused an issue. As i said, just a good diy'er, and will tackle most things in my life, but dont wanna bite off more than i can chew, so any basic layman advice is gratefully appreciated cheers in advance jimmac

to avoid the grubscrew problems just change the head of the prv

steve now your getting technical lol, how do ya manage thatthought the whole pvr was one component, see told ya total novice lol, give me a saw and spirit level, any day lol

steve, am assuming that you mean removing the red cap on the pvr and that would allow me access into the prv valve, i tried to get that off last yesterday, ended up releasing more water and pressure, there must be a knack

 

[jimmac]

steve, can you explain your forum post to me in greater depth, that a total idiot like me can understand lol