Cabin heater coolant diagram

[markwalker]

I am wanting to install a coolant cabin heater in my Kitfox 4 and I am looking for a diagram on the best way to run and connect the coolant lines.

[bbs428]

Do you already have a heat exchanger? What engine? Hard to give you a diagram without knowing your system.

Kitfox has the whole setup for sale, or you can go really experimental and get an auto heater core, a shut-off valve, hoses and a fan for a lot cheaper and fabricate away! My setup was under $150.00. A bit more if you go with a more powerful fan. Pc fans don't move a lot of air tbh.
All the hose connections are on the other side of the firewall. No wet feet! lol.

I'll see if I have a pic of it all complete. Do a search and you might find something better to go with!

Good luck.

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[AvDES LLC]

I am wanting to install a coolant cabin heater in my Kitfox 4 and I am looking for a diagram on the best way to run and connect the coolant lines.

https://teamkitfox.com/Forums/thread...r-Instructions

[markwalker]

Thanks for the pics. I am heading to Napa Auto in the morning for the heater core and this will help. Have been looking on amazon for the fan but am undecided which will work the best/Max CFM.

[AvDES LLC]

Why use fans? Do what every Cessna and piper does and port air from under the cowl and remove the additional electronics and power draw as well as additional wiring and one more switch / breaker to add to the mix

[jrevens]

Just a thought... I think that if you fly in very cold weather at all, recirculating air in the cabin is going to keep you a lot warmer than running fresh cold air through that coil. You're already getting a lot of fresh air infiltration into the cabin of the average Kitfox. "Fresh" air from the engine compartment is usually not a good idea because of possible CO, although I've seen it done on homebuilts, you wouldn't get away with that on a certified airplane.

[AvDES LLC]

You do make a good point in terms of recirculating air as a means to keep warm, but you are 100% incorrect on the means by which you “get away” with heated air coming into the cabin of a certified airplane. Look up the ducting map for a late 50’s to mid 60s Cessna 172/175 - I use this model continuously as an example as I own one and it is 100% stock and remains certified. The hot air is pulled from under the cowl from a port located in a plate that runs horizontal under the cowling half way along the cylinder heads, passed through a shroud that wraps around a muffler, and then is direct injected into the cabin. The cold air is pulled in from a small port directly on the firewall behind the engine. This idea that you’re going to get CO poisoning from ducting air from under the cowl is nonsense - in actuality there would be a higher likelihood with the certified method as it intentionally surrounds a muffler to heat the air - resulting in the requirement during annual to open the mufflers and inspect for cracks. Certified aircraft have been doing it for decades and pilots arnt falling out of the sky.

[jrevens]

Of course… I didn’t state what I meant clearly enough. I assumed you were talking about drawing warm air directly from the engine compartment, which I have seen done several times. Using a heat muff around the exhaust system is pretty much SOP. I’m very well aware of aircraft cabin heat systems. Some do it like your Cessna, and some do it a little differently, with the inlet air ducted from a flange on the cooling baffeling to the muff & from the muff to a “heat box” on the firewall for temperature control and bypass. I actually designed, built & sold a heat box that’s on many hundreds of RVs and other designs, which I sold through Aircraft Spruce, Larry Vetterman exhausts, and others. Got tired of that & eventually gave the design & tooling to a friend (Rick Robbins) who made hundreds more. If you’re suggesting ducting the inlet air from a NACA scoop or some other place on the engine baffel or cowl, strategically located away from the exhaust system, that’s good advice. When you have a water cooled engine, it’s definitely safer to completely avoid air heated by the exhaust system. In spite of yearly inspections, leaks in exhaust systems still cause periodic death in aircraft. Just a fact.

[Birdseyeview]

Lots of interesting debate in this thread on air flow through the cabin heat exchanger but has anyone every determined by temp measurements if the cabin heat exchanger itself is actually getting enough coolant flow through it to get it good and hot?

My cabin heater kit is the one sold by Kitfox with the coolant flow tee'd off the main radiator hoses and with the two computer fans. However, it just doesn't seem to send out much heat into the cabin when it's 30-40 F ambient or colder (in Northern Illinois). In contrast my Toyota's heater will drive me out if I let it go.

Although the two computer fans do seem to push some air through it that I can feel, its not exactly a hurricane and its just not very warm. I've sealed up air leaks around the firewall and elsewhere to minimize cool ambient air ingress into the cabin but I'm wondering - Is there a way to modify the coolant plumbing somehow to potentially push more coolant flow through this cabin heater to get it hot without negatively impacting the coolant flow to the cylinder heads? The following diagram crudely depicts my current plumbing:

Scan 5.jpg

My CHT seems to always hover around 180 F so it seems that my cylinder heads are getting plenty of coolant flow. Or do I need a coolant thermostat or something else to raise the overall coolant operating temp?

Does anyone have the standard Kitfox set up that proves its output is more than adequate? If so what do you attribute it to? Any thoughts are appreciated.

[avidflyer]

I have a therm-bob thermostat on my 912 Kitfox 4 to keep coolant temps up in the winter. The bypass line goes through the heater core, and I get real good heat from it, till the thermostat opens and the coolant doesn't flow as well through the heater core. On my next Kitfox, I'm going to use a small radiator with 1" lines going through it for the heater core, so all the coolant goes through the heater core hot. The bypass line will attach after the heater core. The radiator I'm using is off a Yamaha snowmobile that had a phaser engine in it. Has a nice fan on it already. Another solution for my current Kitfox would be to put a valve in the 1" line after the heater core hose, so I could force more coolant through the heater core. That would require me to monitor the CHT temp a bit more of course. I do fly in northern Mn, so I deal with much colder temps than a lot of guys though. JImChuk