Bil4381
Well-Known Member
- Joined
- Oct 17, 2007
- Messages
- 884
This is part of the engine conversion and Hoerner wing tip mod for my S IILS.
Today I worked on the switch panel to set up the electric carb heat. Because I have cowl flaps I wanted to reduce the number of mechanical controls in the cockpit and through the firewall.
The Carb is a Bing 40mm ordinarily standard for the Jab 3300 engine. I believe the carb heat kit come from the UK. It's a single cylinder about 2" L X maybe 1"D. bolted to the side of the carb. It has 2 electrical studs.
It may be overkill because the Bing Carbs are constant depression carbs, i.e they don't really have a venturi in the throat. Hence icing conditions must be heavy before ice will collect in the carb. In 7 years I've never actually had carb ice. I fly spring, summer and fall.
So the carb heater module described above is bolted in place. I was at a loss to remember the carb heat wiring. But a VOM tester showed each heater coil to have a resistance of 7 ohms. That simplifies it. The switch is a DPDT (Double Pole-Double Throw) switch wired to bring 12VDC to the aft terminal on the heater, which means say 2 amps. Since I=E/R, then the current is 2 amps and that is say 28 watts.
So the switch:ON-OFF-ON is switched down and one coil is heated. They call this carb anti-ice.
Two wires are connected to the Up connections on that DPDT switch, they are brought forward to the carb heat module on the carb. One wire is connected to the Fwd Terminal and the other is spliced to the aft terminal. With UP selected and A VOM tester used the +12V contact is tested to ground and 14 ohms is indicated. That's exactly what's wanted.
Thus is you had carb ice you'd select the switch up and both coils would heat. That's say 56 watts. Presumably that's enough to melt ice in the carb with the engine running say on approach. Thus with the switch up you have carb de-ice.
Fuse- I'll try it with a 5 amp fuse but if it doesn't last i could go to either 7.5 or 10 amps.
I'll get a photo and try to get it uploaded to this site.
Bill 438
Today I worked on the switch panel to set up the electric carb heat. Because I have cowl flaps I wanted to reduce the number of mechanical controls in the cockpit and through the firewall.
The Carb is a Bing 40mm ordinarily standard for the Jab 3300 engine. I believe the carb heat kit come from the UK. It's a single cylinder about 2" L X maybe 1"D. bolted to the side of the carb. It has 2 electrical studs.
It may be overkill because the Bing Carbs are constant depression carbs, i.e they don't really have a venturi in the throat. Hence icing conditions must be heavy before ice will collect in the carb. In 7 years I've never actually had carb ice. I fly spring, summer and fall.
So the carb heater module described above is bolted in place. I was at a loss to remember the carb heat wiring. But a VOM tester showed each heater coil to have a resistance of 7 ohms. That simplifies it. The switch is a DPDT (Double Pole-Double Throw) switch wired to bring 12VDC to the aft terminal on the heater, which means say 2 amps. Since I=E/R, then the current is 2 amps and that is say 28 watts.
So the switch:ON-OFF-ON is switched down and one coil is heated. They call this carb anti-ice.
Two wires are connected to the Up connections on that DPDT switch, they are brought forward to the carb heat module on the carb. One wire is connected to the Fwd Terminal and the other is spliced to the aft terminal. With UP selected and A VOM tester used the +12V contact is tested to ground and 14 ohms is indicated. That's exactly what's wanted.
Thus is you had carb ice you'd select the switch up and both coils would heat. That's say 56 watts. Presumably that's enough to melt ice in the carb with the engine running say on approach. Thus with the switch up you have carb de-ice.
Fuse- I'll try it with a 5 amp fuse but if it doesn't last i could go to either 7.5 or 10 amps.
I'll get a photo and try to get it uploaded to this site.
Bill 438