Icos He30 combi boiler resolution L9/H9 fault codes

[Ulsinus]

My boiler is an Ideal Icos HE30 boiler. This supplies the central heating and a separate heat store - in other words a big cylinder - for domestic hot water.
It is not a combi boiler.
The boiler is 10 years old and it has been serviced by the original installer each year since installation. It has been reliable since installation.
The boiler is pressurised at 2bar.
Radiators fitted TVRs. All radiators heating OK. Radiators bled.
The CH system has a magnet debris filter.
No issues when the boiler is heating the DHW cylinder.
In the heating season each year I increase the boiler temperature control to near maximum.
This heating season the boiler has locked out a few times.
Fault code display alternates between L9 and H9 which relates to temperature monitoring thermistors.
Resets display without problem and then runs for another week or so before it locks out again.
I don't believe both thermistors have gone out of whack. So maybe a problem with water temperature?
At last week's annual service the boiler passed as good to go by the plumber. He confirmed that the pump was working correctly. The pump is a CPC CP63.
That said he was reluctant to get involved with resolving cause of the fault codes.
He said it could be one of many things and suggested I contact Ideal as it has special test equipment that could diagnosis the root cause rather than willy-nilly approach of swapping out of components.
I wonder given the extensive experience and knowledge of forum members their views, what the problem might be, and how it can be resolved in a cost effective manner.

 

[Aquarius]

It can be several issues as your engineer states, and perhaps it would be best to engage with Ideal for a fixed price repair. I think you could be right with the thermistors, and could be something as simple as the pump.

 

[Ulsinus]

Thank you Aquarius for your prompt and helpful reply.

 

[townfanjon]

Codes you mention are over heat codes , ask your engineer to get his clamps out.
Also , boiler pressure from cold approx 1 bar not 2 bar and don't forget Icos’s were cheap low cost boilers , 10 years isnt bad for one ,however I have around 5 /6 on about 12 ish years old .

 

[Ulsinus]

Thank you Townfanjon for your reply and advice.
A couple of more questions if I may.
Can you explain what his 'clamps' are and why they are relevant in finding the problem?
Is it a problem if the pressure is left at 2 bar.
Is there some sort of pressure sensor in the boiler controls that would be affected and contributing to the problem?

 

[Aquarius]

Can you explain what his 'clamps' are and why they are relevant in finding the problem?Is it a problem if the pressure is left at 2 bar.

Thermostat pipe clamps - checking temperatures.

2 bar not ideal (no boiler pun intended), not really much of an issue imo.

 

[Brambles]

Your heating engineer really should be able to address this issue as part of an annual service. Diagnosing / repairing overheating boilers is all part of the job

 

[Ulsinus]

Thermostat pipe clamps - checking temperatures.

What should the temperature values be?

 

[Brambles]

Ulsinus,

The use of temperature clamps are one tool for trying to diagnose the cause.

The boiler overheat trip is one of the last lines of defence ( before the prv) to prevent steam forming in pressure envelope. If the boiler is tripping on overheat, it should be properly diagnosed and repaired. Very often it is the result of a minor issue, but it can be a sign that there is something far more serious going.

Before you ask, you don’t want steam forming in the pressure envelope, if the prv fails you could get a very nasty surprise

 

[Ulsinus]

Thanks Brambles.
Sadly that horse has bolted.
I mean to say the annual visit was last week and he didn't do it then.
So I'm reluctant to spend another £100.
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The boiler overheat trip is one of the last lines of defence ( before the prv) to prevent steam forming in pressure envelope. ...

Thank you Brambles for highlighting this particular hazard.
Much appreciated.