Sd30e pressure rising and falling. Still got problems .

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Hi all
Once again another problem with our SD30e combi boiler.
Brief history of the problem :-

4wks ago noticed boiler pressure very low so topped up CH system with filling loop, but like an idiot the system was warm when l did it, which l know is a no no.

PRV started leaking, so let out some pressure from a rad. After a couple of days of this constant problem l realised that the filling loop had not turned off properly in the first place due to plastic lever being cracked and not turning fully off. ( I know the filling loop should not be always connected but it has been ever since installation 9yrs ago with no problems until now. )

Sorted filling loop problem out and fitted new PRV.
Problem now is system looses pressure,- top it up to 1bar and when CH is on the pressure goes up to 3bar and PRV opens again letting out water and hence pressure goes down and tripping out the boiler .
Did a search on this forum and decided to check pressure in expansion vessel which was zero, so following instructions on here l repressurized the EV, and put 10psi in it as recommended.

But to no avail, the pressure still keeps going up and down when CH on. No pressure loss etc ,when system not on.

Could there be another well known problem ?

Any help greatly appreciated.
 
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Chances are you havent let all the pressure out of the ch system before you recharged the expansion vessel and/or the rubber membrane has ruptured.
 
.Hi.
When repressurizing the EV, l used the CH drain cock below the boiler.
When the water had stopped dribbling out l pressurized the EV to 10psi.
Also no water came out of the valve on the EV when messing with it.

How can you tell if all the water is out from the EV and stabalised before repressurizing ??
 
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Did you leave the drain cock open as you pumped up the exv? and you should put 14 psi in the vessel.
 
Did you leave the drain cock open as you pumped up the exv? and you should put 14 psi in the vessel.

Hi Picasso,
No l kept the drain cock closed each time l pumped up the EV, as mentioned in the 'how to' section. and reopened it once the pressure was up to 10psi and the water just dribbled out and not spurt out. I did this several times until no more water dribbled out. Then left Ev with 10psi in it.
Should l try again but this time put 14psi in ??
 
try again with the drain cock open, if that does not work you may have a blockage on the pipe that connects the exv to the boiler, put in 14 psi.
 
Thanks picasso will try that and see what happens.
But how will l know when all of the water is out of the EV?
 
Help please.

I'm in the middle of repressurising the expansion vessel following the 'how to post'
Question is, l've drained 10 litres of water from the CH drain cock below the boiler and theres no sign of the water stopping coming out. Do l now close the drain cock and pump up the EV, or leave it open whilst pumping it up ??? Or leave it to drain some more until it stops ??

Much appreciated for a quick reply.
 
I drained off 12 litres of water in the end and the water never stopped coming out of the drain cock.
Decided to close the drain cock and pressurize the EV.

5 or 6 times l pressurized and then drained the system a little, until the pressure in the EV remained the same at 1 bar/14psi.

I then topped up the CH system with the filling loop, but had to bleed the rads several times before the pressure built up to about 0.8bar in the CH system.

Before turning on CH system to check it ,l decided to recheck the pressure in the EV which had dropped to 0.7bar.
Is this normal ????

Fired up the CH system and all looked well. Then after about 10 mins of being on, the pressure in the CH system had gone up to 3bar triggering the PRV, so now back to square one !!

Any ideas/help very much appreciated.
Thanks.
 
Is there a silver braided hose connecting the EV to the boiler as these are can quite often block up. Bit of a tip for you ......... let the air pressure out of the EV before removing the hose or sh*tty black water will spray out everywhere.
 
Is there a silver braided hose connecting the EV to the boiler as these are can quite often block up. Bit of a tip for you ......... let the air pressure out of the EV before removing the hose or sh*tty black water will spray out everywhere.

Hi, there's a small copper pipe coming off the EV at the bottom but can't work out where it terminates. There's a small copper pipe going to the PRV will this be the other end of the EV pipe??

Also on the right hand block there's a white crusty sediment that looks like its leaked from the top of what l think is the automatic air vent.

Is this normal ??
Could it be the AAV thats giving me my problems as above ^^ ???

Many thanks in anticipation.
 
You cant repressurise the ev with water in the boiler, open the drain cock and wait till the water stops running then do as before close the drain and pump up the ev then open the drain and repeat till the water stops,

the ev will then be empty of water, leave the drain open and put 14psi then refill the boiler , bleed the rads and it should be ok if not either the ev is knackered (membrane split) or there is a blockage in the connecting pipe.
 
Small up date - l've tried again this morning to recharge the EV putting in 14 psi. Within 25 mins of the CH being on the pressure has again gone up to 3bar and PRV started leaking. :evil: :cry: :cry:
 
You cant repressurise the ev with water in the boiler, open the drain cock and wait till the water stops running then do as before close the drain and pump up the ev then open the drain and repeat till the water stops,

the ev will then be empty of water, leave the drain open and put 14psi then refill the boiler , bleed the rads and it should be ok if not either the ev is knackered (membrane split) or there is a blockage in the connecting pipe.

Many thanks for response picasso. I tried what you 've said last night, but after draining 12 litres l closed the drain cock and tried the recharge etc. Seemed like l was draining the entire CH system.
So l just keep emptying the system until ALL the water stops coming out the drain cock ??

Just to make sure, the drain cock l'm using is at the bottom of the CH return piping.
Should l be using this one or is there a drain cock on the boiler itself ??
 

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