Worcester Greeenstar 24i - very low system temperature

[81ll]

Pls help

I'm working on a greenstar 24i boiler and the CH system temperature is very low which means the rads & DHW are warm at best.

I'm the 2nd engineer to look at the boiler, other guy changed fan, electrodes & pcb.

I have set system temperature to max on the boiler control panel still no change.

I'm going back to the boiler and will be checking the thermistors, working pressure & combustion figures are OK, but was wondering if anyone has seen this before and what else I can check

Any suggestions would be appreciated

 

[ShaunCorbs]

flow pipes inside the boiler hot?

 

[Dotty]

Moved off open forum.

 

[81ll]

Check below boiler which were cool, so I thought would also be cool inside. Will check those.

I'm thinking I might even vent heat exchanger

 

[81ll]

Moved off open forum.

Is this post still visible to other engineers

 

[ShaunCorbs]

Is this post still visible to other engineers

visible to public

 

[AllyBongo]

Thermistors and inlet pressure would be my 1st check. Is the pump noisy? Could be a blockage or worn pump.
I had a system recently which wasn't that great, after a bit of investigating I found an old bypass (gate valve) that was fully open, closed it and the system was perfect afterwards. So it could also be something outside the boiler

 

[mikeyc]

Poor circulation perhaps, such as blocked return ect. Boiler will be looking for a difference between Flow and return. Isn't it something like 20 degrees?

 

[harrygashull]

Try Primary thermistor
unlikely diverter valve as problem consistent between CH and HW
check pump and system water quality.
check Auto air vent and bleed main heat ex

is it a 24i system?

 

[81ll]

Poor circulation perhaps, such as blocked return ect. Boiler will be looking for a difference between Flow and return. Isn't it something like 20 degrees?

If it was poor circulation would the boiler at least heat up then the burner would go out. On this boiler burner stays on.

 

[81ll]

Try Primary thermistor
unlikely diverter valve as problem consistent between CH and HW
check pump and system water quality.
check Auto air vent and bleed main heat ex

is it a 24i system?

What's the best way to test the pump, is it open the vent and stick a screwdriver in it .

If the water quality was bad would it not heat up then the burner go out. With this boiler the burner stays on and water is Luke warm.

 

[Gas74]

Check fan pressure. If heat ex is dirty you get poor heat and dhw

 

[kb76]

Had one yesterday where boiler stat knob was not alighned correctly on pcb potentiometer and set too low after a new board was fitted. Thermistor or under gassed possibly. Low pressure and faulty pressure gauge reading maybe?

 

[81ll]

Thanks for responses all.

Turns out it was an issue with the thermistor

 

[gileros]

Just one to look out for on these boilers is the bottom of the heat exchanger, even if fga is as it should be then doesn't mean the heat exchanger is ok, need to get your gauge on the fan pressure test point, if it's less than -3.1 when it fires up the it's going to be full off crap at the bottom. I've even seen all the crap solidify so new heat exchanger was required.