vaillant ecotec 824 overpressurising

[newbie1]

went to boiler with leaking prv checked expansion vessel as pressure was in the red
water in expansion came out of valve so replaced expansion vessel and replaced prv
lots of gunk in prv
boiler worked fine for 2 days but is now going into red again and activating prv
also boiler needs to be at 1.7bar or it wont work and shows f75 from memory which means no rise in pressure
tenant has nasty habit of playing with filling loop as when i got there it had been left open
any ideas why boiler is going into red again as first port of call the expansion vessel has been replaced

 

[Puddle]

Could be rubbish in he small tube to the expansion vessel,or tenant messing with filling loop,as with 1.75 bar required maybe faulty gauge or rubbish also in sensor,

 

[Billy Bob Bob]

went to boiler with leaking prv checked expansion vessel as pressure was in the red
water in expansion came out of valve so replaced expansion vessel and replaced prv
lots of gunk in prv
boiler worked fine for 2 days but is now going into red again and activating prv
also boiler needs to be at 1.7bar or it wont work and shows f75 from memory which means no rise in pressure
tenant has nasty habit of playing with filling loop as when i got there it had been left open
any ideas why boiler is going into red again as first port of call the expansion vessel has been replaced

remove the braided loop if not integral,bloody tenants!!!

 

[LIFES A GAS]

I think "F75" is due to CH pressure sensor part No: 253595, drain boiler, remove sensor and clean out or replace, refit, refill, did you check air pressure of new expansion vessel before fitting? The filling loop is built in so not easy to disconnect.
Martin

 

[newbie1]

customer never called back so either sorted or got someone else as when he told me i could only get access after 2045 at night i said that was no good to me
i suspect the crap i found in the old prv is also in the heating pressure sensor as well
must say didnt check new expansion as i assumed they would have pressurised it at factory and system was working fine for 2 days after i fitted it

 

[LIFES A GAS]

I know what you mean, who needs customers like that anyway, 9am to 4pm Mon - Fri if they want it fixed incase any parts are needed are my rules.
Martin.

 

[RoryD]

The only other things I can think of is the filling loop / section is passing or more likely, because of the gunge, the plate to plate is leaking internally