Our Vaillant ecoMAX pro is probably getting a bit long in the tooth now (18
years) but has been pretty reliable over the years. I did fit a replacement
gas valve recently but it was working fine afterwards.

Now, it seems to only run until the return flow gets up to temperature and
then it shuts down stopping the circulating pump (which is wired into the
boiler’s PCB). Powering the boiler down and back up seems to get it fired
up again and the water circulating again, but only until the boiler gets
warmed up again and then it’s back to sulking.

There’s no fault code displayed and the boiler just displays its normal
“power on” green LED rather than the red LED which it flashes if it’s
registered a fault.

I spent sometime checking that it wasn’t a micro switch problem in the two
motorised valves but they seem okay and I’m beginning to think it’s a
boiler PCB issue.

Does this sound plausible? Any other likely causes for this behaviour?

Tim

--
Please don't feed the trolls

Tim+ <tim.downie@gmail.com> wrote:
> Our Vaillant ecoMAX pro is probably getting a bit long in the tooth now (18
> years) but has been pretty reliable over the years. I did fit a replacement
> gas valve recently but it was working fine afterwards.
>
> Now, it seems to only run until the return flow gets up to temperature and
> then it shuts down stopping the circulating pump (which is wired into the
> boiler’s PCB). Powering the boiler down and back up seems to get it fired
> up again and the water circulating again, but only until the boiler gets
> warmed up again and then it’s back to sulking.
>
> There’s no fault code displayed and the boiler just displays its normal
> “power on” green LED rather than the red LED which it flashes if it’s
> registered a fault.
>
> I spent sometime checking that it wasn’t a micro switch problem in the two
> motorised valves but they seem okay and I’m beginning to think it’s a
> boiler PCB issue.
>
> Does this sound plausible? Any other likely causes for this behaviour?
>
> Tim
>

An update. Having turned the power on and off to the boiler several times
it seems to working now. Something’s not right, but I don’t know what…

Tim

--
Please don't feed the trolls

On 20/10/2023 19:31, Tim+ wrote:
> Tim+ <tim.downie@gmail.com> wrote:
>> Our Vaillant ecoMAX pro is probably getting a bit long in the tooth now (18
>> years) but has been pretty reliable over the years. I did fit a replacement
>> gas valve recently but it was working fine afterwards.
>>
>> Now, it seems to only run until the return flow gets up to temperature and
>> then it shuts down stopping the circulating pump (which is wired into the
>> boiler’s PCB). Powering the boiler down and back up seems to get it fired
>> up again and the water circulating again, but only until the boiler gets
>> warmed up again and then it’s back to sulking.
>>
>> There’s no fault code displayed and the boiler just displays its normal
>> “power on” green LED rather than the red LED which it flashes if it’s
>> registered a fault.
>>
>> I spent sometime checking that it wasn’t a micro switch problem in the two
>> motorised valves but they seem okay and I’m beginning to think it’s a
>> boiler PCB issue.
>>
>> Does this sound plausible? Any other likely causes for this behaviour?
>>
>> Tim
>>
>
> An update. Having turned the power on and off to the boiler several times
> it seems to working now. Something’s not right, but I don’t know what…

I did find a fault on a boiler once where the gas valve closed itself
when it got warm... However that seems far less likely on what I presume
is a premix modulating valve with stepper motor control rather than the
old fixed rate solenoid controlled valves.

Strange stuff can happen when the PSU section of the PSU starts to give
up. The main PSU reservoir cap turned out to be the culprit on my EcoTec.

--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/

John Rumm <see.my.signature@nowhere.null> wrote:
> On 20/10/2023 19:31, Tim+ wrote:
>> Tim+ <tim.downie@gmail.com> wrote:
>>> Our Vaillant ecoMAX pro is probably getting a bit long in the tooth now (18
>>> years) but has been pretty reliable over the years. I did fit a replacement
>>> gas valve recently but it was working fine afterwards.
>>>
>>> Now, it seems to only run until the return flow gets up to temperature and
>>> then it shuts down stopping the circulating pump (which is wired into the
>>> boiler’s PCB). Powering the boiler down and back up seems to get it fired
>>> up again and the water circulating again, but only until the boiler gets
>>> warmed up again and then it’s back to sulking.
>>>
>>> There’s no fault code displayed and the boiler just displays its normal
>>> “power on” green LED rather than the red LED which it flashes if it’s
>>> registered a fault.
>>>
>>> I spent sometime checking that it wasn’t a micro switch problem in the two
>>> motorised valves but they seem okay and I’m beginning to think it’s a
>>> boiler PCB issue.
>>>
>>> Does this sound plausible? Any other likely causes for this behaviour?
>>>
>>> Tim
>>>
>>
>> An update. Having turned the power on and off to the boiler several times
>> it seems to working now. Something’s not right, but I don’t know what…
>
> I did find a fault on a boiler once where the gas valve closed itself
> when it got warm... However that seems far less likely on what I presume
> is a premix modulating valve with stepper motor control rather than the
> old fixed rate solenoid controlled valves.

Pretty sure this boiler pre-dates any form of gas modulation. The valve
has two solenoids in series, each controlled by two wires. I’m guessing a
modulating valve is a bit fancier.

>
> Strange stuff can happen when the PSU section of the PSU starts to give
> up. The main PSU reservoir cap turned out to be the culprit on my EcoTec.

I’ll have a closer look next time I’m in the loft.

Tim

--
Please don't feed the trolls

On 20 Oct 2023 at 19:01:55 BST, Tim+ wrote:

> Our Vaillant ecoMAX pro is probably getting a bit long in the tooth now (18
> years) but has been pretty reliable over the years. I did fit a replacement
> gas valve recently but it was working fine afterwards.
>
> Now, it seems to only run until the return flow gets up to temperature and
> then it shuts down stopping the circulating pump (which is wired into the
> boiler’s PCB). Powering the boiler down and back up seems to get it fired
> up again and the water circulating again, but only until the boiler gets
> warmed up again and then it’s back to sulking.
>
> There’s no fault code displayed and the boiler just displays its normal
> “power on” green LED rather than the red LED which it flashes if it’s
> registered a fault.
>

Isn't the green LED to show that the water preheat is active? On my ecomax no
LEDs are lit when it's off, and an amber when it's firing. I think.

> I spent sometime checking that it wasn’t a micro switch problem in the two
> motorised valves but they seem okay and I’m beginning to think it’s a
> boiler PCB issue.
>
> Does this sound plausible? Any other likely causes for this behaviour?
>
> Tim

--
Cheers, Rob, Sheffield UK

On 20/10/2023 21:39, Tim+ wrote:
> John Rumm <see.my.signature@nowhere.null> wrote:
>> On 20/10/2023 19:31, Tim+ wrote:
>>> Tim+ <tim.downie@gmail.com> wrote:
>>>> Our Vaillant ecoMAX pro is probably getting a bit long in the tooth now (18
>>>> years) but has been pretty reliable over the years. I did fit a replacement
>>>> gas valve recently but it was working fine afterwards.
>>>>
>>>> Now, it seems to only run until the return flow gets up to temperature and
>>>> then it shuts down stopping the circulating pump (which is wired into the
>>>> boiler’s PCB). Powering the boiler down and back up seems to get it fired
>>>> up again and the water circulating again, but only until the boiler gets
>>>> warmed up again and then it’s back to sulking.
>>>>
>>>> There’s no fault code displayed and the boiler just displays its normal
>>>> “power on” green LED rather than the red LED which it flashes if it’s
>>>> registered a fault.
>>>>
>>>> I spent sometime checking that it wasn’t a micro switch problem in the two
>>>> motorised valves but they seem okay and I’m beginning to think it’s a
>>>> boiler PCB issue.
>>>>
>>>> Does this sound plausible? Any other likely causes for this behaviour?
>>>>
>>>> Tim
>>>>
>>>
>>> An update. Having turned the power on and off to the boiler several times
>>> it seems to working now. Something’s not right, but I don’t know what…
>>
>> I did find a fault on a boiler once where the gas valve closed itself
>> when it got warm... However that seems far less likely on what I presume
>> is a premix modulating valve with stepper motor control rather than the
>> old fixed rate solenoid controlled valves.
>
> Pretty sure this boiler pre-dates any form of gas modulation. The valve
> has two solenoids in series, each controlled by two wires. I’m guessing a
> modulating valve is a bit fancier.

Ah ok older than I was expecting. Has it got an always on pilot light?

Having said that, thinking back the boiler I was diagnosing did not shut
off the pump - just the flame - and I was able to measure the mains
"call for heat" to the valve remained on all the time even though the
flame went out.

Yup modulating valves normally have a stepper motor to allow it to be
driven to varying degrees of "open" (on modern boilers, you can often
hear the slight click as it steps while hunting around for the required
output level)

>> Strange stuff can happen when the PSU section of the PSU starts to give
>> up. The main PSU reservoir cap turned out to be the culprit on my EcoTec.
>
> I’ll have a closer look next time I’m in the loft.

It might be a far simpler PC on that class of boiler.

This is what the one in my ecotec looks like:

https://wiki.diyfaq.org.uk/index.php/File:Ecotec%2B_NewPCB.jpg

--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/

On 20/10/2023 21:39, Tim+ wrote:
> John Rumm <see.my.signature@nowhere.null> wrote:
>> On 20/10/2023 19:31, Tim+ wrote:
>>> Tim+ <tim.downie@gmail.com> wrote:
>>>> Our Vaillant ecoMAX pro is probably getting a bit long in the tooth now (18
>>>> years) but has been pretty reliable over the years. I did fit a replacement
>>>> gas valve recently but it was working fine afterwards.
>>>>
>>>> Now, it seems to only run until the return flow gets up to temperature and
>>>> then it shuts down stopping the circulating pump (which is wired into the
>>>> boiler’s PCB). Powering the boiler down and back up seems to get it fired
>>>> up again and the water circulating again, but only until the boiler gets
>>>> warmed up again and then it’s back to sulking.
>>>>
>>>> There’s no fault code displayed and the boiler just displays its normal
>>>> “power on” green LED rather than the red LED which it flashes if it’s
>>>> registered a fault.
>>>>
>>>> I spent sometime checking that it wasn’t a micro switch problem in the two
>>>> motorised valves but they seem okay and I’m beginning to think it’s a
>>>> boiler PCB issue.
>>>>
>>>> Does this sound plausible? Any other likely causes for this behaviour?
>>>>
>>>> Tim
>>>>
>>>
>>> An update. Having turned the power on and off to the boiler several times
>>> it seems to working now. Something’s not right, but I don’t know what…
>>
>> I did find a fault on a boiler once where the gas valve closed itself
>> when it got warm... However that seems far less likely on what I presume
>> is a premix modulating valve with stepper motor control rather than the
>> old fixed rate solenoid controlled valves.
>
> Pretty sure this boiler pre-dates any form of gas modulation. The valve
> has two solenoids in series, each controlled by two wires. I’m guessing a
> modulating valve is a bit fancier.

The Baxi I have modulates with an analogue voltage, presumably a
solenoid valve working against a spring that opens in a gradual and
controlled way.

It has a separate on/off solenoid valve so could be similar to function
as yours.

>> Strange stuff can happen when the PSU section of the PSU starts to give
>> up. The main PSU reservoir cap turned out to be the culprit on my EcoTec.
>
> I’ll have a closer look next time I’m in the loft.
>
> Tim
>

On Friday, 20 October 2023 at 19:02:00 UTC+1, Tim+ wrote:
> Our Vaillant ecoMAX pro is probably getting a bit long in the tooth now (18
> years) but has been pretty reliable over the years. I did fit a replacement
> gas valve recently but it was working fine afterwards.
>
> Now, it seems to only run until the return flow gets up to temperature and
> then it shuts down stopping the circulating pump (which is wired into the
> boiler’s PCB). Powering the boiler down and back up seems to get it fired
> up again and the water circulating again, but only until the boiler gets
> warmed up again and then it’s back to sulking.
>
> There’s no fault code displayed and the boiler just displays its normal
> “power on” green LED rather than the red LED which it flashes if it’s
> registered a fault.
>
> I spent sometime checking that it wasn’t a micro switch problem in the two
> motorised valves but they seem okay and I’m beginning to think it’s a
> boiler PCB issue.
>
> Does this sound plausible? Any other likely causes for this behaviour?
>
> Tim
>
> --
> Please don't feed the trolls
Sounds like you might need to look into the anti-cycling function of the PCB. A job for Geoff Drage (raden) if he's not managed to retire yet. Google CET or CET Ltd in Watford

What about the controller that sits on yer wall. Brian

--

--:
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
briang1@blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!
"Tim+" <tim.downie@gmail.com> wrote in message
news:871382336.719516895.547774.tim.downie-gmail.com@news.individual.net...
> Our Vaillant ecoMAX pro is probably getting a bit long in the tooth now
> (18
> years) but has been pretty reliable over the years. I did fit a
> replacement
> gas valve recently but it was working fine afterwards.
>
> Now, it seems to only run until the return flow gets up to temperature and
> then it shuts down stopping the circulating pump (which is wired into the
> boiler's PCB). Powering the boiler down and back up seems to get it fired
> up again and the water circulating again, but only until the boiler gets
> warmed up again and then it's back to sulking.
>
> There's no fault code displayed and the boiler just displays its normal
> "power on" green LED rather than the red LED which it flashes if it's
> registered a fault.
>
> I spent sometime checking that it wasn't a micro switch problem in the two
> motorised valves but they seem okay and I'm beginning to think it's a
> boiler PCB issue.
>
> Does this sound plausible? Any other likely causes for this behaviour?
>
> Tim
>
> --
> Please don't feed the trolls

Tim+ <tim.downie@gmail.com> wrote:
> Our Vaillant ecoMAX pro is probably getting a bit long in the tooth now (18
> years) but has been pretty reliable over the years. I did fit a replacement
> gas valve recently but it was working fine afterwards.
>
> Now, it seems to only run until the return flow gets up to temperature and
> then it shuts down stopping the circulating pump (which is wired into the
> boiler’s PCB). Powering the boiler down and back up seems to get it fired
> up again and the water circulating again, but only until the boiler gets
> warmed up again and then it’s back to sulking.
>
> There’s no fault code displayed and the boiler just displays its normal
> “power on” green LED rather than the red LED which it flashes if it’s
> registered a fault.
>
> I spent sometime checking that it wasn’t a micro switch problem in the two
> motorised valves but they seem okay and I’m beginning to think it’s a
> boiler PCB issue.
>
> Does this sound plausible? Any other likely causes for this behaviour?
>
> Tim
>

Have you checked there isn’t air trapped in the heat exchanger?

If the pipe work around the boiler is such that the boiler is a ‘high
point’ air ( actually gas produced by water attacking the pipes etc) can
collect in the boiler. There should be a bleed point to let it escape. The
same can happen if you’ve drained the system. When you refill, the heat
exchanger partially fills and the system gets confused. On ours, it does
flag a fault.

It can also happen when you first turn the CH on in the autumn, just as the
rads need bleeding, even if you have inhibitor in the system, you still get
a bit of air / gas collecting, even if the HW system has been running.

On 21/10/2023 08:56, John J wrote:
> On Friday, 20 October 2023 at 19:02:00 UTC+1, Tim+ wrote:
>> Our Vaillant ecoMAX pro is probably getting a bit long in the tooth
>> now (18 years) but has been pretty reliable over the years. I did
>> fit a replacement gas valve recently but it was working fine
>> afterwards.
>>
>> Now, it seems to only run until the return flow gets up to
>> temperature and then it shuts down stopping the circulating pump
>> (which is wired into the boiler’s PCB). Powering the boiler down
>> and back up seems to get it fired up again and the water
>> circulating again, but only until the boiler gets warmed up again
>> and then it’s back to sulking.
>>
>> There’s no fault code displayed and the boiler just displays its
>> normal “power on” green LED rather than the red LED which it
>> flashes if it’s registered a fault.
>>
>> I spent sometime checking that it wasn’t a micro switch problem in
>> the two motorised valves but they seem okay and I’m beginning to
>> think it’s a boiler PCB issue.
>>
>> Does this sound plausible? Any other likely causes for this
>> behaviour?
>>
>> Tim
>>

> Sounds like you might need to look into the anti-cycling function of
> the PCB. A job for Geoff Drage (raden) if he's not managed to retire
> yet. Google CET or CET Ltd in Watford

Last time I spoke to him (end of last year) he was talking about
retirement, but had not yet quite got around to it :-)

--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/