Problem with Fanmaster Carver 1800SC

[Johnny]

I have a problem with Fanmaster Carver 1800SC. The stove heats up, but there is no good heat transfer due to the slow operation of the fan.
When I set it to AUTO FAN GAS, the fan does not work at full speed, the voltage at the connector is 8.7V, when it is set to SLOW FAN GAS, the voltage at the connector is 5.67V. The BD679 transistor gets very hot after a few minutes, probably because the C-E voltage = 2.7V.
Voltage Base to ground in AUTO FAN operation = 9.86V and in SLOW FAN mode = 5.96V.
The transistor has been replaced, it also heats up.
The motor connected directly to the battery works normally and has a higher speed than from the electronics board (it is ok, maintained).
Please help, why is this happening?
Thank you very much and sorry for my poor English

 

[ProfJohnL]

Hello Johnny,

It is obviously difficult for us to know exactly what the problem is becasue we can't see or touch the appliance. But you have supplied some good details which might give us some clues.

Based on the Vbe voltages of the you have measured, the low fan speed (5.96 -5.67V) 0.3V seems very good for a darlington device, and the high speed voltage drop BE 9.86 to 8.7V) 1.16V, is actually quite typical for a darlington with its double be junctions. If its getting excessively hot then it points to the load (motor) drawing too much current.

The first idea I have is with the age of the product (at least 23 years) the fan motor bearings and or brushes may well be wearing out, preventing the motor spinning at the correct speed. This could lead to it having a higher current draw than it should. This could explain if the BD679 is getting too hot. As far as I'm aware there are no OEM motor spares available, but you might find a motor (12Vdc 1.2A) of the same size might substitute.

The second issue could be the fan impeller might be blocked with dust and debris. The fan can be carefully cleaned, but do not bend or distort any blades.

 

[Johnny]

Thanks @ProfJohnL
The fan connected to the battery runs at a higher speed and draws 1.5A.
Everything inside the Fanmaster is clean, it looks like it was used very rarely or not at all.
Is it normal to have 2.7V on the Collector-Emitter connector of the BD679?

 

[Johnny]

I think that the reason for the lower fan speed may be too low voltage on the transistor base.
There is an operational amplifier that I bought and am waiting for delivery (approx. 14 days)

 

[ProfJohnL]

Thanks @ProfJohnL
The fan connected to the battery runs at a higher speed and draws 1.5A.
Everything inside the Fanmaster is clean, it looks like it was used very rarely or not at all.
Is it normal to have 2.7V on the Collector-Emitter connector of the BD679?

I dont have the circuit schematic of the fanmaster, so I cannot categorically say whether the Vce can or should rise to 2.7V.

But based on your figures and description the BD679 seems to be configured as a voltage follower, with the motor load on the emitter in which case depending on action of the preceding circuitry feeding the base of the Darlington transistor the Vce will vary and could easily reach 2.7V depending on the motor speed the controller demands.

But, if the controller is demanding maximum speed and the motor is drawing too much current its possible the the transistor is not turned on hard enough to saturate the be junctions. and the transistor could be dissipating too much power and its getting hot.

 

[Jcloughie]

Is it possible that the fan itself is not running freely? Perhaps it just needs a mechanical service. Strip, clean, and lubricate.

John

 

[Johnny]

I dismantled the engine and performed maintenance, first with compressed air, then washing, degreasing and moisturizing the bearings.
The brushes are like new.
After that, the motor itself - without the turbine - consumes a current of 0.7A.
After installing the turbine - as before - approx. 1.6A

 

[Johnny]

After mounting the motor and connecting to the Fanmaster electronics:
in FAN mode: 1.05A; 7.65V,
in SLOW mode: 0.47A; 4.23V.
The radiator is warm but not hot.
Are these correct measurements?

 

[ProfJohnL]

After mounting the motor and connecting to the Fanmaster electronics:
in FAN mode: 1.05A; 7.65V,
in SLOW mode: 0.47A; 4.23V.
The radiator is warm but not hot.
Are these correct measurements?

The current consumptions seem about right.

I'm not sure I understand your reference to the "Radiator" can you provide a picture?

For general information, the Carver 1800SC, is only rated to produce 1.6kW of heat into the caravan, The fanmaster will take some of that heat and blow it through the ducts. That means the convected heat from the heat exchanger will be reduced when the fan runs.

 

[Johnny]

I wrote heat sink in the sense of transistor heat sink. Previously, after a few minutes of operation, it was hot, but now after motor maintenance it is only warm.
After mounting the whole thing to the Fanmaster and running on gas for an hour, the fan does not slow down and the trailer is finally warm.
I am very sorry @ProfJohnL that you are so far away personally wanted to thank you , your help was spot on.
You are a very good person 👍

 

[ProfJohnL]

Its been a pleasure to be able to help, and especially to be be able to delve into the electronics in this detail.

 

[Johnny]

Hello, I'm back after a weekend with the caravan...
The outside temperature forced the heating to be turned on. I turned on the Fanmaster heating and the fan in ELEC FAN AUTO mode. Adjustment using the potentiometer on the panel was correct for approximately 3 hours. Then it got cold - the fan stopped and the heating turned off.
Before leaving, I bought a PWM constant current regulator and connected it appropriately to prepare for such a situation. I turned on the gas heating and turned on the regulator, the speed was fully adjusted, it quickly became hot in the caravan.
Interesting case, right?

 

[ProfJohnL]

Can we clarify some facts please.
Are you using an 230ac power to provide heating?
Or are you using LPG for the heating?
If you are using LPG, is it Butane or Propane?
What was the outside temperature when the heater stopped working?

 

[Johnny]

Can we clarify some facts please.
Are you using an 230ac power to provide heating?
Or are you using LPG for the heating?
If you are using LPG, is it Butane or Propane?
What was the outside temperature when the heater stopped working?

Hello Mr @ProfJohnL...

Since it was my first trip with a caravan, I purchased a stay with 230V power supply.
At first, I used 230V for heating, but after about 3 hours it became cold in the caravan and I realized that the heating was not working, most likely because of the fan. I turned on the LPG heating and switched the fan to power from an external PWM controller.
Outside temperature +8*C.
The LPG cylinder contains propane + butane.
Edit:
It's possible that BD679 is dead again (?)

 

[ProfJohnL]

Nothing in your posts so far have indicated the BD679 was actually damaged. A transistor will normally fail open or short circuit. The fan motor would either receive 0 volts or full collector voltage. If the emitter voltage is anywhere between 0V and supply voltage the transistor is probably working correctly.

If you are powering the fan control from an unsmoothed "Pulse Width Modulation" (PWM) supply the nature of the power supplies output might confuse the Fanmasters control circuit. It expects to see a constant 12V supply not an intermittent one.

When you say the heater stopped, do you mean the gas heater stopped working?

 

[Johnny]

When you say the heater stopped, do you mean the gas heater stopped working?

When I say that the heater stopped, I mean heating from the 230V power supply, then I turned on the LPG heater and turned on the fan from the external power supply via the PWM controller.
LPG heating has no control over the fan's operation - the burner may be on all the time even though the fan is not working (and it is switched on on the panel).

 

[ProfJohnL]

...
LPG heating has no control over the fan's operation - the burner may be on all the time even though the fan is not working (and it is switched on on the panel).

Not quite true.

The Fanmaster has an automatic setting where the temperature of the air leaving the fanmaster is monitored, so when the air temperature is low, the fan turns slowly, and ramps up an down depending on the temperature of the air passing through the fanmaster. This prevent it from blowing hard when the air is cold.

 

[Johnny]

Not quite true.

The Fanmaster has an automatic setting where the temperature of the air leaving the fanmaster is monitored, so when the air temperature is low, the fan turns slowly, and ramps up an down depending on the temperature of the air passing through the fanmaster. This prevent it from blowing hard when the air is cold.

ProfJohnL... I'm going to have to disagree with what you're saying...
I had a disassembled Fanmaster heating part in my hand. There is only one temperature sensor in the chamber where the radiator for the electric heaters is located, and on the side of the body there is also a thermostat that disconnects if the body is overheated. This all applies only to electric heating.
As I wrote - when the electric heating turned off, I turned on the LPG heating and turned on the fan from an external controller (PWM).
If the automation was common and the system did not detect the fan operation, the burner should go out. The LPG heating worked properly.

 

[ProfJohnL]

I was involved with the industry for over 20 years and worked with many caravan based appliances including Carver Fanmaster systems

There is no direct communication between the Fanmaster and the gas heater to which it is fitted, but the sensor(ntc thermistor) is in the out flow of the Fanmaster, and when set to automatic it monitors the temperature of the airflow and if the air is cool, the fan speed is reduced (not stopped). As the air flow warms up either from the fanmasters elements, or the heat coming from the gas heater, it will ramp the speed of the fan up.

Thus the gas fire can indirectly control the fan speed. The Fanmaster does not control the gas heater in any way, it is not designed to turn the gas heater up down or off, and cannot do so. This safe because the gas heater to which the Fanmaster is fitted is firstly a convector heater and is designed to be able to discharge all the gas burners heat through the grille on the front of the heater. So if the Fanmaster is compromised it does not need to turn the gas fire down or off.

I think you need to read the instructions for the product to understand how to use it.

You can find copies of the instructions here