Ultracom 30CXI has a mind of it's own!

[HansMoleman]

Hi all - I've got a Glow-worm Ultracom 30cxi combi boiler with a bit of a strange issue.

Whenever the boiler is switched on (even if the heating is switched off) the pump seems to be continuously running and the flame is on. This is heating up my radiators despite the heating being switched off! The only way to stop it is to physically turn the boiler off at the switch.

Any ideas?

 

[ianmcd]

Do you have seperate thermostats for upstairs and downstairs ?

 

[HansMoleman]

Nope only one thermostat - it even does it when the thermostat is disconnected!

 

[CBW]

How old is the boiler, and is it a new fault? Any parts replaced recently? Is there a time switch built in the front?

 

[HansMoleman]

It's around 10 years old I believe, nothing has been changed recently, it just suddenly started doing this. Interestingly I followed the manual to get the current state when the burner is on it shows S.24 which is apparently a normal state under pre-heat mode. I don't know what pre-heat mode is or how to turn it off, the manual doesn't give any info either.

What I don't understand is why the boiler is firing up with zero demand for CH or DHW at all...the only way I can get my radiators to cool down is to turn it off!

 

[Mister Banks]

Is there a frost thermostat?

 

[HansMoleman]

From the manual it says:

"The appliance has a built in frost protection device that protects the boiler from freezing. With the gas and electric supplies ON and irrespective of any room thermostat setting, the frost protection device will operate the pump when the temperature of the boiler water falls below 8C. A timer is used so that the temperature can be checked periodically. After 10 minutes the pump will be stopped if the temperature is higher than 10C or has already reached 35C. The burner will activate if the boiler temperature does not reach 10C after 30 minutes or at any time if the temperature drops to 5C.The burner will switch off when the temperature reaches 35C"

I'm wondering how does the boiler measure this temperature and could this be faulty?

 

[CBW]

If the rads are heating up when the preheat is on then it’s likely the diverter stuck in heating mode. Try the following for turning preheat off, then get a gas safe registered engineer to come and take a look for you

 

[Johntheo5]

I would have thought pre heat would be for the DHW side?.

 

[CBW]

Is there a frost thermostat?

Doubt it will show S24

 

[CBW]

I would have thought pre heat would be for the DHW side?.

It is

 

[HansMoleman]

So I think I've cracked it after reading the manual - I checked the code state and it said pre-heat mode, noticed that there was an option in the boiler settings to disable pre-heat mode...low and behold the boiler is behaving completely normal! I wonder why it decided to go into pre-heat mode continuously out of the blue?

For future reference (pages 51, 52 and 53):

https://www.glow-worm.co.uk/glow-worm/to-be-reviewed/ultracom-1/ultracom-cxi-157268.pdf

 

[Johntheo5]

The rads shouldn't be heating though, as above, maybe something up with the diverter valve.
Next time using DHW check boiler flow pipe , shoukd be cold/cool.

 

[HansMoleman]

Yep I think I've temporarily fixed the issue but not properly, what would cause the boiler to get "stuck" when pre-heat mode is enabled and the radiators to get hot? Is the diverter valve hard to swap over? And is this the same as the '3-way valve' noted in the manual?

 

[HansMoleman]

Is there anyway I can test the diverter valve?