Baxi has me scratching my head

[Aarony1990]

HI, I'm looking for some advice from someone who may have encountered my problem before. I'm a gas engineer and i have been trying to solve an issue with a baxi duo-tec 28 HE. The boiler randomly calls for CH when the thermostat is not, the green LED lights up for around 5 minutes before deciding to fire up. I have exchanged the old thermostat (Salus) and replaced the primary ntc sensor and still have the same problem. Baxi technical are adamant that it's the new thermostat but like i had said it is brand new. Can anyone help me at all? Thanks.

 

[ShaunCorbs]

Are you getting any calling for ch ?

 

[Aarony1990]

Are you getting any calling for ch ?

The thermostat fires the CH when it's turned up straight away. But once you turn the thermostat to off the CH will stop then shortly after the boiler seems to think the thermostat is calling for heat agaim. Everyone I've spoken to is just as baffled mate

 

[Chuck]

The thermostat fires the CH when it's turned up straight away. But once you turn the thermostat to off the CH will stop then shortly after the boiler seems to think the thermostat is calling for heat agaim. Everyone I've spoken to is just as baffled mate

I'm not familiar with the specific model and am too lazy to check right now, but for this sort of issue:

Make sure you aren't using a 24V thermostat on a 240V system.

If it's an on/off control type use a light switch in a plastic box as a 'dummy' thermostat. Try it connected instead of the Salus and if 'symptoms persist' directly into the boiler using relatively short leads.

Faulty wiring (borrowed neutrals, leakage across terminals in junction boxes, etc.) can cause strange symptoms. Find a sparks who likes CH doing controls (many don't IME) to help with these.

It's quite possible that this is a boiler issue but one normally wants to rule out exterior (and cheaper to fix) causes first, of course.

 

[ShaunCorbs]

Wireless thermostat?

 

[Aarony1990]

I'm not familiar with the specific model and am too lazy to check right now, but for this sort of issue:

Make sure you aren't using a 24V thermostat on a 240V system.

If it's an on/off control type use a light switch in a plastic box as a 'dummy' thermostat. Try it connected instead of the Salus and if 'symptoms persist' directly into the boiler using relatively short leads.

Faulty wiring (borrowed neutrals, leakage across terminals in junction boxes, etc.) can cause strange symptoms. Find a sparks who likes CH doing controls (many don't IME) to help with these.

I have a mechanical clock i was thinking of putting in to see if this eliminates the fault. I have checked all terminals and all readings were fine. The receiver for in question for the thermostat is plugged into the baxi mechanical clock they are made for these boilers so I'm confident the voltage is ok for that. Do you know if these boilers have some kind of frost stat built in at all?

 

[Aarony1990]

Wireless thermostat?

Yes mate. Salus (can't remember model from memory) it's the one where the receiver is designed to replace the standard mechanical clock on the right hand side. Has 4 prongs L/N and your 2 switch

 

[Aarony1990]

That is the thermostat there

 

[ShaunCorbs]

Best to fit a wired one as there know to have problems with devices on a similar frequency

Eg wifi, door fobs etc

 

[king of pipes]

Fit the genuine baxi mechanical timer or put the link back in to rule out a external faults bud then go from there, cheers kop

 

[oz-plumber]

Wire the thermostat through the outdoor sensor stat - 24 volts ( from memory ). Change the parameter on the baxi controller.
Loop the 240 Volt thermostat and see if the problem persists.

If the problem persists then it would be the thermostat.

 

[jonnyswamp]

If it's a wireless Salus, alter the dip switches on both receiver and sender
Other wireless signals will affect it when left on default settings

 

[masons]

probably find its next doors wireless signal 🙂 , agree with ShaunCorbs