Ideal mini C28 boiler cuts out when heating is on

Slaine1674 · 25 Nov 2008

Hi, I have the following boiler which is three years old now. Never been serviced so I'm probably paying the price!

Recently, the boiler cuts out when the central heating has been running for about 10 mins or so. I've noticed that it seems to happen when the tank temperature reaches 60 degrees. Then it will go through self-ignition clicking and firing up etc, only to then cut out again. Once temperature drops to lower than 60 again the boiler will heat faultlessly until 60 on the dial and then will cut out again and repeat the cycle.

Hot water is not affected at all by this and the pressure is at 1.5 bar. Is it faulty thermistor, thermostat, faulty PCB, diverter etc ?

I've spent hours trying to get clues online and scoured these forums so I thought I'd raise my own post. Basically is it cheap fix or one for the engineers?

Hope you can help. Many thanks.

Agile · 25 Nov 2008

It sounds as if you have broken the knob shaft! Are you heavy handed?

Is there any difference between the min and max CH setting?

How does the green light flash when it gets to 60°

Tony

Slaine1674 · 25 Nov 2008

The dials for central heating temp and the hot water are at about halfway for their temperature, and are never really used since I first set them. Room thermostat on wall is set at about 25. The tank gauge seems to rest at about 30c and then go upto 60c as I mentioned before cutting out.

When heating for CH the green light flashes normally slowly every other second or so. Normal running. When it hits 60 the green light flashes quickly, signifying some error state. Then when temperature falls reverts to normal operation slow green light, until 60 and fast green then etc

Russell

Agile · 25 Nov 2008

In that case it sounds as if the CH sensor is going open circuit when it gets to 60C.

If you expose the LH side of the circuit board and move the RH dip switch down and back while heating up, then it will give a diagnostic code when the fault is activated.

You can decode that from the book or tell me what each light is doing!

Tony

Slaine1674 · 25 Nov 2008

Thanks Tony

I'll check when I get home. If I match the diagnostic light code which I'm expecting too and it is the sensor, is the replacement of this part called the thermistor and is it an expensive part? Can it be done by us budding D-I-Yers.

Thanks again.

Russell

Slaine1674 · 25 Nov 2008

Ok.

Tonight I checked PCB optical diagnostics and the lights confirmed error:

"faulty CH temperature probe NTC"

1st light off, 2nd and third lights blinking simultaneously.

This happened when the boiler cut out when it hit 60c degrees. So what next for me?

Do I need to replace the thermistor? Or the Overheat thermostat?

And where's the best place to order the parts from? Many thanks.

Russell

Agile · 26 Nov 2008

You just replace the NTC sensor, about £15 from boiler spares merchants.

Better to look for the part for a Biasi 24S, M90 or M96 as they made the boiler for Ideal.

Simple to change as long as you depressurise the boiler after closing isolation valves.

In return for my help I would appreciate it if you could post me to old one when you have replaced it as its the ideal faulty part that I can use for training purposes. Email me in my profile for the address or just search on the internet under Agile and NW10.

Tony

Slaine1674 · 26 Nov 2008

Thanks for the help, I will certainly post you the part once, I fit the new one. I have a couple of questions before i begin the job.

Can i close all valves under the boiler to be sure of isolating the correct taps?

Is it easy enough to reach the drainage valve to release the pressure?
How much pressure/ water needs to come out before it is depressurised?

Found your address online, so will post. Total cost for part £10.08+VAT

That is what you call a saving on a callout and engineer etc!

Many thanks,

Russell

Agile · 26 Nov 2008

Just close valves on laft and right pipes.

Official drain point is a white one on the right of boiler behind pump!

Pressure needs to be zero on pressure gauge or you will get wet.

Aftewr refilling alternate between hot and cold every few seconds to help to expell air from the AAV which must be loose!

Tony

Slaine1674 · 28 Nov 2008

Fixed!

Many thanks again Tony.

Faulty part is in the post to you today.

Russell

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Ideal mini C28 boiler cuts out when heating is on

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