Potterton Promax 15/2 HE Plus - PCB configuration

[ohohseven]

Hi,

Our new build house was fitted with a Potterton Promax 15/2 HE Plus boiler heating a thermal store for mains fed hot water and radiators with TRVs (except 4 of them) in a 'Y' plan configuration. I've never been overly happy with this setup and we've been having an ignition lockout issue with the boiler recently.

I've recently had it serviced with a new spark electrode being fitted and I've just swapped out the PCB assembly to rule out any faults in that which may be affecting the boiler failing to strike up in the allotted time before going into lockout.

The thing that I noticed is that the PCB has two jumpers on the board, labelled CN11 (Blue) & CN12 (Red). Now my question is, what do these actually do?

In the generic installation manual it suggests that they are fitted as default, but on a Promax 30 HE Plus the CN12 (Red) jumper could be removed to increase the the output from 22kW to 30.18kW. It then goes on to say that "if the boiler is used in conjunction with a Thermal Store, the boiler can be adjusted" by removing both the CN11 & CN12 jumpers.

Now for the last 7 years they have been fitted! What effect will it have by removing them? Is it going to increase the output of my smaller 15/2 boiler? The manual makes no attempt to describe what these jumpers do and note that it does say "can be adjusted", not "has to be adjusted".

I guess in my long-winded way I'm hoping a Potterton expert can tell me the theory behind the operation of this boiler with regards to the jumpers and a Thermal Store.

Many thanks for your time & help.

Regards

Sean

 

[bolshy]

If you aren't a RGI, you shouldn't be messing with jumpers that affect the rated output of a boiler. Many recent Baxi group boilers have jumpers to alter the heat output, as is clearly explained in the manual. This is to match the boiler output to the heating load on larger boilers in larger properties. I see you have also changed the pcb, but if you haven't got the required knowledge and equipment, how can you determine whether the boiler is operating correctly at it's intended rate? Is there sufficient working gas pressure for any higher rate settings? A pcb change requires a repeat of commissioning checks as it's the brain of a modern boiler. If you're not a RGI, please have the combustion checked by one.

 

[ohohseven]

Bolshy,

Thanks for your reply.

I've changed the PCB with a direct replacement and I've left the jumpers exactly where they are.

What I wanted to know was if anyone knew what the actual effect of jumper configuration is as I have the commissioning manual and it doesn't not explain it at all. I'm pretty sure the RGI that installed it also had no idea and unless they had been specifically trained on this Potterton boiler then they are very unlikely to know what the effect of the second jumper is otherwise both jumpers would have been removed as suggested in the manual.

At the moment the boiler appears to be igniting better with the replacement board which is why I replaced it.

I will have to locate a Potterton trained RGI to get an answer to this one.

Cheers

 

[bolshy]

What you want to know is if you remove the jumpers yourself, how will this affect the operation of the boiler? You've already changed the pcb of this boiler without having the knowledge or equipment to test the operation of the boiler afterwards. How has this affected the operation of the boiler? It may be lighting better in your opinion, but is it's combustion correct? You don't know because you can't test it. The manual states a combustion check should be carried out after component replacement and without a flue gas analyser, you can't do this. After pcb replacement, the commissioning procedure checks the boiler is operating as it should. The circuit board is hooked up to just about everything.
Lastly, your boiler isn't an HE 30 model, which the jumpers apply to. It's a 15/2 and appears to be self regulating in response to load. If you value your safety, get the boiler checked by a RGI, a Potterton trained one if you like.