Head Scratching Boiler Fault - Ideal Mini C28

[WilliamTwo]

Hi, hope someone can help with this.

I have an Ideal Mini C28 boiler running on LPG that has developed a strange fault. It started off by intermitently not firing on either hot water or heating. When this happens if repeated attempts are made immediatley it still does not fire but if left for half an hour it would usually work fine. This occurred maybe one in every ten attempts but now it is much more frequent.

When it fails you can hear the pump run but no fan. The pump turns off after a few second and the single green light on the facia flashes quicker for a few seconds. I have found however that when it fails on heating if you leave the heating on and run a hot tap the boiler will always fire. It does not work the other way round.

I have had an engineer look at it. He replaced the air pressure switch but this made no difference. He now thinks it maybe one of the two PCBs but is not sure which one, the control or ignition?

It will be a big gamble to pay for him to replace one of the boards without guaranteed success.

Any ideas how to pinpoint the problem? Thanks.

 

[Tibbot]

Pump not pushing the flow switch. Needs investigating first. Beware anyone who points to the PCB as a first resort. I will never understand what some engineers think the PCB actually does.

 

[WilliamTwo]

Many thanks Tibbot.

To be fair to my engineer he has spent a lot of time, several visits and calls to Ideal's helpdesk trying to diagnose the problem. I will check he has considered a pump/flow switch issue. Would this explain the strange behaviour of always firing if the heating fails until a hot tap is turned on briefly? Incidently i cannot get the heating on now unless i do this.

 

[Agile]

A chimpanzee would probably spend many hours doing simple addition sums. A 10 year old child would do them in minutes!

Your engineer may have spent time on it but he is still a muppet.

Think about it, if he knew what he was doing then why would he need to call the manufacturers?

As stated the pump proving switch is not being reliably operated. This is a common problem on this model. Your engineer seems very lacking in knowledge!

Tony

 

[WilliamTwo]

Thanks Tony. Time to find a new engineer by the sounds!

Excuse my ignorance but i assume a flow switch and pump proving switch are one of the same? Is the solution to normally change the switch or could it be a pump problem? Is there only one switch or one each for both heating and water? (i'm having problems with both)

 

[Agile]

Same thing.

Changing the pump and/or the switch is unlikely to solve the problem.

Its a common misconception that fixing boilers is just a matter of changing parts!

So it follows that if you change enough then eventually you will have a working boiler! But that's not necessarily so!

Tony

 

[WilliamTwo]

Ok, thanks again Tony.

You mentioned earlier that this is a common fault with this boiler so i guess the million dollar question is what is the common solution if it is not changing parts?

 

[WilliamTwo]

Any more pointers to the possible solution would be greatly appreciated.

Also i dont quite understand, if it were the flow switch why does the boiler always work when demand for both heating and water is called?

 

[Agile]

The problem is caused by a lack of flow in certain operational configurations.

There can be several or a combination of causes and that's where the skill of the engineer ( not yours though ) is required to diagnose.

Tony

 

[Slugbabydotcom]

Ok, thanks again Tony.

You mentioned earlier that this is a common fault with this boiler so i guess the million dollar question is what is the common solution if it is not changing parts?

The common solution is to diagnose the correct part [in the singular] and just change that as opposed to changing pcbs and then other random things until you get the right one.

As pointed out earlier you need to have the pump flow switch operation checked out before you go any further.