Dual Heater Control

[JoeRuscito]

Im wondering if it makes sense to use a potentiometer dial to control each of the two cabin heater fans individually. Any issues with doing this? It seems like it would be nice to have more finite control of the air passing over the exchanger. Ive had a heater that worked like this in an RV (not the plane) and with only low or high options you got to choose between being run out of the vehicle (too hot) or putting up with the fan noise to little or no effect.

[Dave S]

Joe,

Makes total sense to be able to control the two fans separately - Wish I had that - most of the time in the winter, both fans going at the same time generates too much heat - so it is either on or off and I end up continuously turning the single switch on and off to get that happy medium heat. If it is below zero F OAT, then both need to be on.

Frankly, I think all a person would need is separate switches for each fan - so both, one or none could be activated.

I don't think you need to be concerned about the fan noise - both of the muffin fans going full blast can't even be heard with the engine running - they are pretty quite.

[jiott]

The DPDT switch that comes with the optional heater kit allows both fans, one fan, or none. You don't need two switches. Personally I have never found the need for variable speed control of the heater fans.

[Shadowrider]

I replaced both fans with fans that move 2 times the air then the supplied ones, and ditched the switch for a rheostat. The rheostat controls both at the same time. Anywhere from nothing to 100 percent. Hoping to stay warm when I am up in the flight levels.


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[GuppyWN]

I’d be curious to know more about your setup.

[JoeRuscito]

Thanks all! I think I will opt for dual rheostats and replace the fans with upgraded ones if needed. I think the fine tuned control makes sense. Just wanted to make sure there was no obvious reason not to do it, for example the fan motors being limited to one speed/power input.

[Shadowrider]

Joe why dual rheostats? If you install one it can slow both fans down to almost nothing?

[rv9ralph]

I am still working on electrical theory, but....

Using rheostats to control the fan speed doesn't reduce the current draw (rheostats use resistors to reduce voltage). Using a two stage switch to turn on fans one at a time or both will reduce current draw when on one fan.

The cockpit of a Kitfox is not that big. Reducing the fan on the co pilot or pilot only will still affect the whole cockpit and both occupants will feel the result.

Just my thoughts to think about≥

Ralph

[JoeRuscito]

Thanks guys and thanks for the links to the reostat and upgraded fans. Why use such a substantial Pcb? Aren’t there simpler pots/reostats? Is there some advantage to this dedicated motor control? Just to dissipate resistance heat?

I know the cabins small but it helps when it’s not blowing right on top of you! I figure worst case it’s easier to put an extra hole in the panel now and not use it. Rather than not have a hole and want one.





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[Delta Whisky]

It appears to me that the amazon link is to a PWM (Pulse Width Modulator using MOSFETs in the circuit; so it should be very efficient) and not a rheostat and appears, to me, to be the way to go. Driving the small motor(s) in our planes shouldn't heat it past it's design limit at all. Appears to be a great solution but we'll need a EE to weigh in on this as well.