baxi 105e 3 bar pressure problem

[seanmfc]

hi all

i was told i would be back with a problem

about a month ago i was advised the ex vessel (which is charged to 1 bar) was knackered so fitted an external one t into the return pipe everything was running fine until i checked the pressure level then i topped it up to 1 bar then ran the ch watched the needle within 5 mins it was at 3 bar so i presume the prv kicked in looked outside confirmed this anyone any ideas

thanks

 

[oldplumber]

check the new expn vessel is charged to .75 bar when the system pressure is zero first.

 

[Billy Bob Bob]

yep sounds like the new ones flat

 

[Toddyplumb]

Did you top the expansion vessel to 1 bar or the heating system ?
Is your filling loop closed and disconnected ?

 

[ferret]

the vessel should be at the same pressure as you are intending to run the system at ie 1bar system pressure = 1bar vessel pressure ,you need to check it with 0 pressure in system then top up and as toddyplumb says disconnect the fill loop in case its letting by

 

[seanmfc]

sorry for the delay in getting back been away for a week

when fitting the new ev it was pre charged to 1 bar pressure then the water was pressurised to 1 bar also

i have now noticed that the needle does not go past 3 bar pressure when hot and also when cooled down the system stays at just over half bar pressure there are no leaks and the filling loop is not passing water more importantly there is no water comming out of the prv
shall i just leave it alone seeing as there is no leaks and no more loss of pressure

 

[Toddyplumb]

How many rads on the system ? What size exp vessel did you end up getting ?

 

[diesel_ltd]

very good point toddyplumb......

 

[seanmfc]

hi all

a 12l ev and there are 6 rads on the system

 

[Toddyplumb]

Are you sure that expansion vessel is charged . Just run through with us how you checked it

 

[seanmfc]

it said it came pre charged to 3 bar so we let the air out until it got to 1 bar

 

[Toddyplumb]

I have never had one charged above 1 bar . I am guessing you have let out the charge !.
Turn off the boiler . Release the central heating pressure (through a drain valve , safety valve if u must ! )
Get a tyre pressure guage on the expansion vessel . Get a bike pump and get the pressure to 1 bar

 

[seanmfc]

hi

done what you said any everything seems to be fine no leaks no loss of pressure and the needle stays just under the 3 mark when on hot well pleased

 

[seanmfc]

just when it was too goo to be true the pressure has started to rise above 3bar causing the prv to kick in and hence loss of pressure when cold im now at the point of getting a new boiler although this one has been rebuilt with nearly all new parts any one any more ideas

 

[Billy Bob Bob]

have you looked at basics? loop passing? you could have a faulty ev dont replace the boiler its a good un

 

[seanmfc]

the loop is deffo not passing water

 

[Billy Bob Bob]

would look like one of 2 problems then either the ev is faulty or the plate heat exchanger has failed

 

[seanmfc]

just my luck and both are brand new any way of testing either one

 

[Billy Bob Bob]

difficult one with the plate heat drain the system and check the ev pressure with a tyre type tester should be 1 bar when cold

 

[ferret]

A bit concerned that it was running just under 3bar when you finished messing with the expansion vessel ,,,,before you try anything else can you pick any radiator that wont be missed too much , isolate it both ends and drain it out , then with the air vent closed , reopen the valves and do not vent it at all , check the system pressure is at 1bar (if not adjust it) then run the heating , if the pressure remains under 2 bar then your vessel is either too small or you still have not got it charged correctly.

 

[seanmfc]

i have noticed that the boiler is running ok now there is no loss of pressure but the pressure is 0.65 on the ev and on the boiler the needle drops down to about the same as the ev im tempted to leave it alone seeing as its working ok would that be ok to do so or shall i top the ev up to 1 bar

 

[ferret]

you can leave it as is but keep an eye on it , ideally 1 and 1 when cold but there is no transducer on your boiler to cut it out at low pressure so will be ok

 

[seanmfc]

thanks for your help