A Vaillant 828 Ecomax

Hi I wonder if anyone can help with this little problem.

We have a Vaillant Ecomax 828 and we've had it for 8 years. About 9 months ago it intermittently kept shutting itself off. After pressing the reset it would then work again for a period between a week and 2 months.

This was until a week ago when I woke up one morning to a cold house and the boiler having the f.23 code. After reseting it worked for about three hours and then shut down showing the same code. This was the pattern for another day.

Having consulted the user manual I have checked the pump that is working fine as well as the divertor valve. I then replaced all three NTC's on Friday this appeared to cure it and the boiler operates exactly how it should do. This morning the boiler kicked in and heated the house up to desired temp and the boiler switched off but wouldn't come back on when the temp dropped. Pressed the reset button the boiler fired up for two minutes then shut down showing the F.23 code again.

I then proceeded to switch of the power (at the mains) for 5 mins and switched back on. Again the boiler worked brilliantly, heated the CHS up to the desired temp and switched off. However the system won't come back on again when the temp drops.

Just before the boiler gives the F.23 code it fires up for 30 seconds then stops, it then fires up for another 30 seconds and stops this goes on four or five times before shutting down completely.

Does this sound like a problem with the PCB? I feel the PCB is not communicating with the temp sensor and the NTC's properly.

Can anyone help or give e any ideas what to look for next?

take a look at a previous thread...

//www.diynot.com/forums/viewtopic.php?t=201872

Have you got a room stat?

Are there TRVs fitted to every radiator?

Sounds to me like there is insufficient flow rate once the house warms up. I can't recall whether the ecoMAX 8 series has an internal bypass, but if does, open it a bit more. Don't turn all the rads down, always leave one open - if you have a room stat the radiator in this area should not be equipped with a TRV.......

My best guess without being there, is the rubber hose and the copper tubes either side ar blocked. Drain, remove and replace the rubber hose (not dear) and clean the tubes with a bottle brush.

as above partial blockage. hoses, tubes, depending on model plate filter, plate heat exchanger. Maybe you should get someone in, by the sounds of your guessing technique it might work out cheaper

Yes we've got a room stat and that appears to work fine. It will tell the boiler to fire up when the temp drops. And it will fire up the boiler in the morning.

We have 11 rads on the system all fitted with a TRV. However four of the rads in the house remain fully open all the time. However having read the old post linked above we do have 5 rads upstairs (in a converted bungalow) and they heat up quickly and then close. They are also first on the CH run. I will make sure the smallest one is open on for the next few days and I will see what happens.

As for rubber hoses; had a look in the boiler and there doesn't appear to be any. Which ones do you mean?

Also there is no internal bypass.

Many thanks for the responses so far.

PS Does anyone have any idea what the going rate for a system flush will set me back?

All ecomax 800 have hoses so look again forget fiddling around with everything an listen to beer lover an Micky that's the usual problem an u will need help with this one and also they all have auto bypasses fitted

Hey thanks you lot I'm more than convinced now you are all right! Opened all the rads onto full and switched on the system. The boiler worked as it's meant to.

The CH outlet pipe under the rad was scorching hot however the return pipe was luke warm (at best) and this stayed like this for a very, very long time.

In conclusion there must be a blockage somewhere. Going to do a search of the pipes mentioned above replace and clean as necessary. I am also going to get a someone in to flush the system.

Many thanks for all the responses you have been a god send and it is much appreciated.

I will let you know the outcome.

Simon