Hi All,
Hope you're well.
Quick recap of my shop boiler woes. (18 year old non-condensor)
2 years ago it broke so I took out the 6 months "guarantee fix"
insurance for £300. After about 10 visits and half a dozen different
engineers who changed primary and DHW Heat exchangers, diverter valve,
pump head, insulation etc it was back working but making a hell of a
noise but back to working again.

So this year We've had the random F.22 (dry fire) error sometimes
continually, sometimes the boiler would run for most of the day so we're
back on the process of elimination. Replaced NTC sensors which
temporarily appear to fix things but they were e-bay cheapies so I
replaced them again with proper Valliant ones which still didn't make a
difference.

First thing I noticed was significant pressure swing so ordered up a new
pressure vessel, filling loop valve (which has been leaking for years),
Pressure relief valve, new Flu kit, FLow/Return service valves.

oh and a vortex 300 filter.

Expansion vessel was shot, flue also mutilated by original install or by
"engineer" levering it off to remove primary HEX. The other symptoms
have been the boiler working but then going into burner anti-cycle so
the water gets hot and then the burner shuts off and the pump pumps
water around for 10 or 20 minutes even though the system temp has
dropped to 30 degrees or so.

So having put on the new expansion vessel, and valves etc it was running
virtually silently but still giving F.22 intermittently or every few
seconds. So... I've been running the system with a chemical flush and it
appears to be improving having run continuously all day yesterday.

Now, what I'm thinking is the automatic bypass valve might be blocked
open giving rise to the premature burner shut-down and excessive cooling
of circulating water as the bypass pike gets hot very quickly when the
burner starts up.

So... when I drain and flush out cleaner I'll inspect auto bypass valve
but there are 3 versions listed Presumably it's to do with the pressure
at which the valve opens and I'm guessing is relative to the head the
pump needs to pump to highest radiators?
150240 - AUTOMATIC BYPASS VALVE 2.5M
150242 - AUTOMATIC BYPASS VALVE 1.7M
150243 - AUTOMATIC BYPASS VALVE 3.5M

Both shop and flat circuits are opened/closed by 2 port valves but the
shop circuit is permanently "open" and can't be shut down with
call-to-heat, likewise the flat circuit has several radiators that can't
be closed down by TRV's so I'm thinking the auto-bypass valve could
actually be blanked off completely without any problems?

Obviously there's the questionable diverter valve which if the actuator
is connected and someone turns on the hot tap the boiler instantly drops
beck to F.22 but we don't need hot water and as the valve is
ridiculously unreliable I'd rather just leave it disconnected.

Sorry for the long lost but if anyone has any other suggestions to try
before venturing into the realms of changing the main PCB I'm all ears.

Cheers
Pete

On Tue, 24 Dec 2019 12:53:34 +0000, "www.GymRatZ.co.uk"
wrote:

snip

Sorry for the long lost but if anyone has any other suggestions to try
before venturing into the realms of changing the main PCB I'm all ears.

Can't answer your question Pete but was chatting to a heating engineer
the other day (just by chance) and he suggested that Vaillant weren't
actually as good as they are hyped up to be?

I'm not sure how reliable yours has been over the entire 16 years but
a mate has a fairly new (3 years) 'system boiler' (no IHW?) but has
just had to have a new main PCB and gas control valve.

Or maybe because of all the eco restrictions, they have just become
more complicated of late and so less reliable?

I wonder just how much more 'eco' a 3 year old boiler is, with the
environmental cost of making then replacing a gas control valve, PCB,
heating engineer diesel van visits etc over my Mums 40 year old (and
bought second hand at that) boiler that may not burn as 'green' but
has hardly had any attention (and certainly no complex parts, maybe a
couple of thermocouples) over all those years?

The HE comments re Vaillant were that they just have good advertising
[1]?

Cheers, T i m

[1] And the warranty is quite restrictive?

On 25/12/2019 08:40, T i m wrote:
On Tue, 24 Dec 2019 12:53:34 +0000, "www.GymRatZ.co.uk"
wrote:

snip

Sorry for the long lost but if anyone has any other suggestions to try
before venturing into the realms of changing the main PCB I'm all ears.

Can't answer your question Pete but was chatting to a heating engineer
the other day (just by chance) and he suggested that Vaillant weren't
actually as good as they are hyped up to be?

I'm not sure how reliable yours has been over the entire 16 years but
a mate has a fairly new (3 years) 'system boiler' (no IHW?) but has
just had to have a new main PCB and gas control valve.

Or maybe because of all the eco restrictions, they have just become
more complicated of late and so less reliable?

I wonder just how much more 'eco' a 3 year old boiler is, with the
environmental cost of making then replacing a gas control valve, PCB,
heating engineer diesel van visits etc over my Mums 40 year old (and
bought second hand at that) boiler that may not burn as 'green' but
has hardly had any attention (and certainly no complex parts, maybe a
couple of thermocouples) over all those years?

The HE comments re Vaillant were that they just have good advertising
[1]?

Cheers, T i m

[1] And the warranty is quite restrictive?

Hi T i m,
Pretty sure it's a 2002/3 model.
Apart from the hot water side which would be fine were it not for the
diverter valve it's been fault-free right up until 2 years ago and being
in the shop it's typically run between 12 and 18 hours a day 5 days a
week through heating season.

Never had it "serviced" in all that time and being a non-condensor it's
pretty simple all-be it parts are quite expensive but all parts are
still readilly available.

I'd be unlikely to buy another Valliant though, can't compare a modern
boiler with a pre-condensor and if you believe the on-line "experts"
they'd have boilers being replaced every 10 years!
Hopefully now most of the main components were replaced on the insurance
call and ones that weren't I've just replaced (apart from the fan, gas
modulater/valve and PCB it should have another 20 years life if I can
remedy the current hiccups.

Cheers - Pete