Chaffoteaux Brittony Boiler problem

[bela57]

This is my first post, so I am hoping that someone can help us.
We have a 7-yr old boiler that provides the heating & hot water and a Grohe 1000 thermostatic shower unit.
Over the last year, we have a periodic problem with the shower running cold for a couple of minutes before returning to the set temperature and then worsens over a couple of months to where the ignition system switches off during use and has to be manually reset.
We have had 3 separate engineers attempt to fix the problem. They each replaced different parts (1 replaced the thermistor, 1 changed the main circuit board and the other the water quantity control valve). Each of these interventions has totally resolved the problem for 2/3 months before it gradually deteriorates again to where the ignition system switches off again.
The shower unit has been checked as fully functioning.
We are planning to replace the boiler with a Vaillaint ecotec pro 28 but are unsure if this would solve the problem.
Please can you advise what may be cause of this problem and how it may be resolved.
Thank you so much.
Best regards

[Rydell]

Good Morning May I ask if the boiler goes out when running other hot supplies for the same length of time within the property? If not then I would think its some thing to do with the flow rate of hot water within the boilers domestic heat exchanger. The shower would reduce the flow through the valve of the hot water shower valve to mix on the thermostat. Therefore causing the hot water thermostat to over heat and return into ignition mode. With respect to French manufacturious of boilers, Chaffoteaux Brittony combi's are not the most reliable of appliances. I would recommend the installation of a Vaillant Ecotec but use the 'E' not the pro? The installation would be neater using the E as it has built in filling loop and sound proofing also other useful mechanical requirements. Good luck with the installation I'm sure this will fix your problem. Costing should be about £1850 using a 831E and power flush rads. Maybe update bedroom TRV's and room thermostat extra price down to installer to give price.

[flat pack]

sound to me the gas safe men have tuck you up

[bela57]

Thanks for response, it is really helpful, and helps us understand the problem.
No problems when running other taps.
with very best wishes

[david williams]

chaffoteaux boilers carefully un pack and tip streight into a convenient skip

[THOMASA]

Are non return valves fitted to shower feeds? If so are they functioning - debris under seating etc. Has PRV been fitted to incomming main? High cold pressure exceeding hot reduced pressure through heat exchanger may cause back flow through hot feed if NRV's faulty, can cause symptoms decribed.

[Jonwells]

It looks (with boiler tripping over heat), like it's a boiler problem of sorts, ( thats not hard to work out, i know), it can be a number of things, but as your getting rid, why worry, but with the chaff boiler, as you said, get it gone.
Valiant boilers are good, just make sure that your engineer has checked flow rates from the cold main etc, etc and that the new boiler can feed the mixer shower. Make sure system is power flushed correctly, I advise a filter on heating circuit, and make sure inhibitor is added and boiler is commissioned properly using a flue gas analyser and make sure bench Mark is filled in and you get your part L gas safe cert. Jon

[shorticus]

Any particular reason why we're digging up two year old threads!?