elderly neighbours boiler overheating

my neighbour is in her 80s and living on her own, ive just found out her heating is cutting out, shes had a new boiler put in 2 years ago, then a new cylinder 2 months ago after the old one leaked, then some guy serviced the boiler on the cheap because of overheating, which only temperarily fixed the prob.
so yesterday she called me in to look at it, now i love diying but leave plumbing to the experts so am going to call my plumber in and explain whats going on for her, she gets confused explaining it.
i dont want to leave anything out so any pointers would be hugley apreciated.

details
boiler - baxi solo 3 pfl 60 link
on a closed system (was open with old boiler)
cylinder - vented
40 year old gun barrel pipes in between
controls : none that i could see

symtoms
prv - dripping, reading zero bar
expansion vessel - holding air but i have no idea how much it was inflated.
pump - sounds like its turning including on the overrun cycle
filling loop - cant find one, but i did find the old header tank in the attic has a new plastic return pipe on it with what i think is a non return valve on it and then a gate valve (open), the pipe then goes under the floor boards so it might be capped or it might be for filling.

boiler - cutting out, overheat light on, when left on for half an hour, requires manual reset.

i turned down the boilers thermostat and it overheated after an hour and an old AAV a few meters away on the flow started spewing air.

whole system gurgles and seems to me way too hot, she lives downstairs so only uses a max of 3 rads now they are either off or piping hot, also system probably has no bypass.

from reading the forum im guessing its 1 or more of these
1) to much gas flow
2) dodgey thermostat
3) dodgey pump
4) dirty HE
5) leak

and ontop of whats needed to fix the problem she will need
(a) room control thermostat and (b) new prv.
and maybe also
(c) radiator valves (d) filling loop and (e) bypass.

am i guessing right? and more importantly

is it safe to turn on the heating till the plumber comes?

(sorry for the long post, and thanks for any help)

Firstof all repressurise the system to the minimum recommended by the instructions.

though it sounds as if you may have a tank fed sealed system if you cannot find a filling loop, .so you may have a sticky check valve.

But if the PRV is dripping the system has overpressurised due to expansion vessel depressurising or something.

I'm not much help am I?

your help is most welcome bster.

is the sticky check valve you mentioned, the valve i called a "non return valve" or the prv?

if its the prv, the gauge seems to be working a bit, (again a guess on my part) i did notice after the overheat and AAV expulsion that the pressure had gone up to 0.2 bar.

if its what i called a "non return" then at least i learn a new term

i have a felling the present setup is a bit of gunter or even double-guntered job just to get it up and running. how can i tell if the prv has been reseated? would it gush instead of drip if it wasnt?

anyway, i called my plumber today and hes coming around tommorrow, ill keep you informed.

All of this is pretty irrelevant unless the system is pressurised to about 1.5 Bar and the performance checked.

Hopefully your plumber will be able to decide if its pressurised or not.

Tony

thanks tony, ive read alot of your posts, helped me sort out my own system already ill keep you informed

do you think she should add a filling loop near the boiler? theres a cold mains supply close by.

It would be sensible to have the filling loop in view of the pressure gauge!
SOunds like the loop in the loft might be the filling loop , but the gate valve has failed. Does the wheel head keep turning? If so it's bust, and jammed shut.
There's a pic or two of a f-l in the faq section - some do have plastic instead of a metal braid.

In an emergency you can fill a system from the garden hose, jubilee clipped onto a drain cock. Inclined to leak while you do it, but hey.

thanks chrisr, the gate valve was about 1/2 turn from fully open and it did seem to turn to a point that was fully open and fully closed.

her boilers btu is similar to mine and the thermostats on both boilers are set low, so today i did a quick estimate of what her gas meter usage was compared to mine, she was burning gas at about 3 times the rate of me.

(not sure if this is relevent, but her reading was taken from a cold start, and mine from a restart after the system was off for an hour, still seems like a big discrepancy)

So you have water in her system??
Don't use it without!
Your boiler may have turned itself down as it's warm.
A GATE VALVE shouldn't be used on the mains at all - they "let by". Needs a stop cock or normal filling loop.
Hope you visiting plumber fixes it.

hi chrisr, plumber never came today, hopefully i can catch him tommorrow.

the gate valve is off the return of the header w/ ballcock in the attic.

So you have water in her system??

Click to expand...

do you mean is totaly dry? or is there a point where to much air becomes unsafe?

the prv is dripping when the boiler is on, and i bleed the pump and water dripped out, the aav was wet after it let off air/steam, and the whole system gurgles intermitantly like there is air being pushed around.

is this safe?

i told her to use the emersion for water and a electric for heat, and seen as it was overheating after 1/2hr to 1hr depending on the setting of the thermostat of the boiler, i set it to overheat after 1hr and said if she is going to use the boiler to only use it for 10mins every couple of hours. was i right?

as an aside can someone explain to me the controls inside a working boiler? is it

overheat stat (shuts down boiler before the water in it reaches an unsafe level of say 95 degrees) requires a manual reset because its the last safety check point in the boiler and overheating is a sign of some problem in the system, so it draws human attension to the system.

thermostat (turns the boiler on and off, to maintain the temperature of the water in the boiler within say 10 degrees of a user chosen setting, but the max temp is always lower than the overheat level of 95, say a max of 85) this is on/off level is adjusted by the dial on the front.

and that while a boiler is in a fireing cycle it is burning the same amount of gas wheither you turn up or down the thermostat. or is there a regulater adjusting the size of the flame like a cooker?

plumber came today to check around and will return monday to fit new parts.

he's going to start with a new overheat stat, a larger expansion vessel, a new prv, a room thermostat and a new aav.

the last 2 were my call.

ill report back how it works.

bster, tony, chrisr, thanks for your time and effort so far, i hope you know your good will reaches way beyond the forum posters you help. ive personaly troubleshooted many different things from simply reading the archives of this and similar sites.
funny how there is no tv series on the guys in the trade who help people on line.

According to a recent poster on this site I was " totally unhelpful as usual"

Tony

New overheat stat - well OK, though I'd rtest it, the temp's usually printed on them - it might be OK but they're only £20

New Pressure vessel - why - if water didn't come out of the "tyre valve" then it sin't leaking - did he pump it up?

New prv and aav - fine, thermostat - cheap enough, if hers is knackered.

Yes you've got it about how the boiler works. It doesn't "modulate" the burner up and down.

The system is safe to use, water-wise, as long as there's 1 bar or so on the gauge , and it's vented of air.

ChrisR said:

New overheat stat - well OK, though I'd rtest it, the temp's usually printed on them - it might be OK but they're only £20

Click to expand...

he had the boiler on for 10 mins and said the stat was knackered, he said you could probably make tea out of the hot tap. to be honest hes old school, doesnt like electrics, but it suits me as most of the young bucks are afraid of the old plumbing in our area, think m.c. esher

ChrisR said:

New Pressure vessel - why - if water didn't come out of the "tyre valve" then it sin't leaking - did he pump it up?

Click to expand...

he said the old on was to small for the size of house, could this have contributed to the prv looking like it blew? just out of pure curiosity, can you fill the expansion vessel with inhibitor when you change it, or is that just dumb?

Agile said:

According to a recent poster on this site I was " totally unhelpful as usual"
Tony

Click to expand...

i found that quote, comming from a guy with 18 posts,all in one topic, all either looking for help or trying to demonstrate that hes so smart that hed never need it.
just to put the help in this forum in context, the thing that was genuinely worrying my neighbour was that no one ever explained anything to her, they came they charged they went home ....it broke. twice.
today i explained to her how each of the parts that are being replaced worked, and i learned all that here. so today in ireland you made an 80 year old lady whos never been online feel safe again.

update : plumber came problem fixed now
he replaced the
overheat stat and the thermostat dial
the leaking AAV and PRV
and put in a larger expansion vessel (old one was 8 new 12 )
and a new room thermostat
charged about £200

bster agile chrisr .....muchos gracias