Another Carver 3600STC problem

[Frankus]

Hi,

I got useful advice on this forum https://forums.practicalcaravan.com/threads/another-carver-3600stc-ignition-problem.68245/. I managed to get a local gas safe engineer to look at the ignition issue for me. He managed to get the flame to ignite which is great.

However, this is the issue we have and the engineer is not sure how to resolve as he is not familiar with this heater.

1. We press the control knob down and turn to the igniter position
2. The red light comes on the control knob and the ticking noise starts.
3. We can see the pilot flame in the view window
4. We keep holding the control knob down (and we’ve done so for up to 5mins), the pilot flame is still on but the control knob light is still red and the ticking noise doesn’t stop
5. We release the control knob and the flame is still on and the ticking noise is still going
6. We can turn the control knob to the left and you can see in the view window the main burner is on as the flame gets smaller or bigger depending on which direction to turn the control knob…. But the ticking noise remains and the red light is still on 🙁
7. The flame only goes out once we turn the control knob to the off position

Does this mean that the pcb for the igniter needs replaced?

Any advice I can pass onto the engineer will be greatly appreciated.

Many thanks

 

[Jcloughie]

Sounds like a failed thermocouple. A standard device readily available. Surprised if the engineer did not suggest that. Thermocouple type systems have been around for ever. Though they have now been supceeded.


John

 

[Frankus]

Sounds like a failed thermocouple. A standard device readily available. Surprised if the engineer did not suggest that. Thermocouple type systems have been around for ever. Though they have now been supceeded.


John

Thanks John. The engineer did list a whole load of “it could be this, it could be that” but he did ask if I can ask around the various forums to see if anyone had come across this on this heater before. I’ll let him know a suggested cause me be a failed thermocouple thingy and see what he does next. Many thanks

 

[ProfJohnL]

The symptoms you have described are definitely not a problem with the thermocouple.

When you press the gas valve when starting the appliance, you are physically opening a spring loaded cut off device inside the gas valve. When the flame ignites, the heat from the flame impinges on the thermocouple which generates a current which flows through the valve to an electromagnetic coil inside the gas valve which holds the gas spring load cut off open. The fact the flame remains burning when you release the valve proves it is working correctly. If the flames goes out , the thermocouple cools and produces less current, and the magnetic hold effect reduces and eventually the spring in the valve overcomes the magnet force and shut the gas supply off. This is the flame failure safety device.

What seems to be happening in this case seems to be the ignition control circuit is not able to recognise the presence of the flame. This is an entirely different function to the flame failure device and operates independently of the FFD.

Gas flames on metal burners exhibit some interesting electrical properties . The flame is conductive, but it also acts like a rectifier, and the flame can naturally produce a negative potential on an immerse electrode in the burning gas air mix. Each one of these properties can be used to produce a flame detection system that can control the operation of a reigniter. I cannot recall which method is used in the Carver Heater, but all three will need an electrode that will be immersed in the flame when its burning, and the burner through mechanical connections needs to be earthed to the control circuit. The spark electrode can often double up as the electronic flame sensor probe.

It seems more likely to be either an electrode problem, (cracked insulation or damaged wire or not in the flame path, or a faulty connection) or it a control circuit fault/ but this would likely exhibit poor sparking which doesn't seem to be the case.

It could be an important wire connection has be disturbed by the fitter who looked at the appliance which has broken the electronic flame sensing circuit.

 

[Jcloughie]

Thanks John. The engineer did list a whole load of “it could be this, it could be that” but he did ask if I can ask around the various forums to see if anyone had come across this on this heater before. I’ll let him know a suggested cause me be a failed thermocouple thingy and see what he does next. Many thanks

I take back previous my advice, I did not read your post properly. Listen to the prof.

John

 

[Frankus]

The symptoms you have described are definitely not a problem with the thermocouple.

When you press the gas valve when starting the appliance, you are physically opening a spring loaded cut off device inside the gas valve. When the flame ignites, the heat from the flame impinges on the thermocouple which generates a current which flows through the valve to an electromagnetic coil inside the gas valve which holds the gas spring load cut off open. The fact the flame remains burning when you release the valve proves it is working correctly. If the flames goes out , the thermocouple cools and produces less current, and the magnetic hold effect reduces and eventually the spring in the valve overcomes the magnet force and shut the gas supply off. This is the flame failure safety device.

What seems to be happening in this case seems to be the ignition control circuit is not able to recognise the presence of the flame. This is an entirely different function to the flame failure device and operates independently of the FFD.

Gas flames on metal burners exhibit some interesting electrical properties . The flame is conductive, but it also acts like a rectifier, and the flame can naturally produce a negative potential on an immerse electrode in the burning gas air mix. Each one of these properties can be used to produce a flame detection system that can control the operation of a reigniter. I cannot recall which method is used in the Carver Heater, but all three will need an electrode that will be immersed in the flame when its burning, and the burner through mechanical connections needs to be earthed to the control circuit. The spark electrode can often double up as the electronic flame sensor probe.

It seems more likely to be either an electrode problem, (cracked insulation or damaged wire or not in the flame path, or a faulty connection) or it a control circuit fault/ but this would likely exhibit poor sparking which doesn't seem to be the case.

It could be an important wire connection has be disturbed by the fitter who looked at the appliance which has broken the electronic flame sensing circuit.

Thanks. I will not pretend I understand all of this but I will pass all this to the engineer who hopefully can make sense of it all and help him to investigate further. Many thanks for the info

 

[Buckman]

Gary is the bets person to contact regarding Carver products. He comes highly recommended and most of us know him. https://www.arcsystems.biz/