Baxi 100HE Plus - overrun and anti-cycle issue

[Joepfl]

Hi All

Have had the above system boiler connected to a 'megaflow' type system for 3 years now and its never really performed to its capabilities even though I've set it to use the 100btu capability. Very often it overruns and goes into this anti-cycle mode, which obviously prolongs the duration of the HW and CH demand/recovery. This has been from since its been installed by a 'Gorgi' registered engineer.
I've had other lockout issues in the past and had to swap L and N to get it to work again and this seemed to resolve the anti-cycle issue for some time. I've swaped the L and N around again and still the overrun issue persists. I've had a good look around but before I go replacing parts which could be the cause does anyone have any suggestions.

Many thanks
JP

 

[baxpoti]

How have you got the 'jumpers' set?

 

[Joepfl]

Hi Baxpoti, thanks for your help.

From memory - I believe I removed the jumper that will produce the full 100+k BTUs, but I will make sure when I get home tonight.

 

[Joepfl]

Yes the red jumper was removed to produce the extra BTUs - bottom left of pcb - as suggested by the manual

 

[baxpoti]

How many jumpers are there and what colours are they? (should be top left on green board).

Or you have a 100/2?

 

[Joepfl]

well there were two on the bottom left of the PCB, a blue one 'CN11' and a red one 'CN12'. I've removed the red one to produce the full 103K Btu/hr as suggested in the manual.

The symptoms are: when called for HW or CH the boiler goes into startup process, pump on, followed by Fan on, then ignition with gas on. The fan and gas flow increase to the point which I believe is max and stays there for about 10/15 seconds, then gas and fan speed diminishes to the point od switching off the gas, then followed by 1 minute of pump overrun, then then off for 3 mins. At this stage the boiler is still on, after the 3mins then does startup procedure again, this time the gas and fan speed do not increase to the max point, and in my opinion sits at a very resonable low level and stays on for considerebly longer period of time but then eventually goes into this anti-cycle mode.
The manual says that if the flow temperature is greater than the set point then pump overrun occurs, followed by anti-cycle. What is this 'set point' .......?

Thanks

JP

 

[baxpoti]

You have the later PCB

Try this, remove the PCB, on the now exposed 'front' of the PCB is a potentiometer, using a small screwdriver, make sure it is turned fully clockwise.

 

[Joepfl]

will do, will let you know the outcome,

Thanks

JP

 

[Joepfl]

no difference I'm afraid, I put the jumper on again and now it will work for +- 10mins and then anit-cycle for 3mins and then back on and so on.
Its beter but not working as supposed to.