Ideal Mini HE C24 stuck in frost protect mode

[AndyBruce]

Hi, I'm hoping someone will be able to give me some advice.

I have an Ideal Mini HE C24, which was controlled by a Drayton Digistat wireless Programmer/Thermostat that was only working intermittently (the receiver would send the signal to the boiler to switch on, but nothing would happen)

I called a plumber to come and look at it and he said the programmer was at fault and so "by-passed it for now", so that the heating would come on when switched on, and run continuously until switched off. While on, the first green light and the second red light is on, which the Installation and Servicing guide says is Frost Protect Operation.

I've since found it impossible to get him to come back and properly fix it.

I've investigated the "by-pass" and found he connected the RED control wire to which the programmer connects, to the 240V live supply.
Disconnecting it and leaving out a bridge wire across the external controls connector doesn't stop the boiler firing up when switched on.
The Installation and Servicing guide only refers to an external frost protect thermostat, but the smaller user guide says it has a built in one... so I'm a bit confused there...

I have the horrible feeling putting live 240V onto the red control wire has blown the PCB, but I would appreciate any replies to either confirm this, or point me in a better direction, such as the "built in frost protect thermostat", before I buy a new PCB.

All help will be greatly appreciated, I've had this problem since last November! Thanks.

 

[McCombi]

Think you may be correct, these boilers should have volt free connections for any external controls.

 

[McCombi]

Forgot to add, the temperature sensors (thermistors) act as the internal frost thermostat on these and can be very flakey. For the sake of about £10 for both (online prices) I would try to change these first if you're competent to do so.

 

[picasso]

Its more likely he has put a link across the external control or frost protection block in the boiler, if there was 240vac sent to the pcb it would have blown and your boiler would not work at all.

 

[AndyBruce]

Thanks for the replies gents.

Brassedoff - I thought it could have something to do with that but the two manuals seemed to contradict each other, I'll replace the thermisters and go from there. I assume you mean both the DHW and CHW thermisters?

Picasso - I agree that is what he should have done, even I have been able to work that out by just reading the manual properly!
But he definately put 240v on the control wire. Instead of bridging the external control block, he disconnected the red control wire from the external control block and connected it to the live wire on the electric supply block...

The manual doesnt refer to a frost protection terminal block...
Where would this be? or is it only something you would have if you had an external frost protect system in place? (which i don't)

Thanks again

Andrew

 

[Agile]

Normally putting 240v on the connections for external controls only blows the components associated with that.

If you can measure the two sensor resistances then that will check them and should read about 10k. Only when they are at about 16k does it instigate the frost protection.

Sometimes its just dirty connections and removing and replacing the plugs a couple of times on the sensors will cure it.

If its a two PCB boiler then look at the back left of the left PCB and lift a rubber protective foam and see if there is any obvious burning of anything under it. Even if there is not it may still have been damaged, probably the bridge rectifier.

Tony

 

[McCombi]

Its more likely he has put a link across the external control or frost protection block in the boiler, if there was 240vac sent to the pcb it would have blown and your boiler would not work at all.

Seen quite a few of these and Vokera compacts with mains into volt free, without blowing the board, however I'm usually there for breakdowns as boiler doing strange things.

 

[McCombi]

Thanks for the replies gents.

Brassedoff - I thought it could have something to do with that but the two manuals seemed to contradict each other, I'll replace the thermisters and go from there. I assume you mean both the DHW and CHW thermisters?

Picasso - I agree that is what he should have done, even I have been able to work that out by just reading the manual properly!
But he definately put 240v on the control wire. Instead of bridging the external control block, he disconnected the red control wire from the external control block and connected it to the live wire on the electric supply block...

The manual doesnt refer to a frost protection terminal block...
Where would this be? or is it only something you would have if you had an external frost protect system in place? (which i don't)

Thanks again

Andrew

Yes I would just replace both, get them pretty cheap.

 

[Agile]

Although not officially recommended you can actually operate them with a 230v feed. However it has to be on the correct wire!

But doing that is unsafe as it means the boiler can be live inside after being isolated from the mains which is dangerous. It also means the fuse in the boiler can blow and still leave parts live.

The boiler has a built in frost protection based on the sensors.

You can also connect a separate external frost stat to the connection block. But thats irrelevant in your case.

Tony