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/threads/12374-Cabin-Heater-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:

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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

[Birdseyeview]

Jim -
All your comments make sense. Thanks. Where did you get your Thermo Bob thermostat? Do you have a part number or model number?

[avidflyer]

Here you go. TB1 Thermo-Bob, Universal Remote Thermostat Rotax (watt-man.com) (https://watt-man.com/new-shop/thermo-bob-1-kit-1-inch-fittings/)

[AvDES LLC]

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:

31553

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.

this is EXACTLY why I pulled the fans and went with ducted air. Yes those fans move air, but not much. And with the cabin as poorly sealed as it is, they were pushing enough air to keep anything but the tips of my big toes warm. That issue solved itself with the ducted air, however it took the development of a shroud and mounting etc etc.

I also just have standard y fittings on the main coolant lines. No thermo bob so no ability to comment there.

[Birdseyeview]

[QUOTE=AvDES LLC;107021]this is EXACTLY why I pulled the fans and went with ducted air. Yes those fans move air, but not much. And with the cabin as poorly sealed as it is, they were pushing enough air to keep anything but the tips of my big toes warm. That issue solved itself with the ducted air, however it took the development of a shroud and mounting etc etc.


I may have missed some of the discussion history here so please excuse me if you've already explained this in another post. Have you been flying with this set up to prove that it provides plenty of heat into the cabin? Does it ever provide too much heat? If so, how do you plan to regulate the flow to shut it off during the summer?

[AvDES LLC]

i have just crossed the 100hr threshold with this setup in my plane and it provides plenty of heat to keep myself and my lady warm in the Reno winters. It does get a bit toasty in the spring / summer months and to solve that I simply put a ball valve on the inlet line. When it’s hot out, close the ball valve and zero coolant flow takes place through the exchanger.

[bbs428]

I weighed a new 8" rad. fan I was thinking of using. It blows a lot of air but it's 1lb 13oz. Plus the amp draw. Ouch!

I think I'm warming up to your shroud. Weight would be miniscule compared to the bigger, stronger fan plus the savings in amps.
I might be able to bend up some aluminum sheet but not sure if it would look as good. I don't have much in the way of sheet metal tools/benders/brakes.
My heater core is 8"x 8" so I'd have to make my own variation. Now would be the time to do it!

Is that 3" hose from the firewall to the shroud?

Thanks for posting - really got me thinking in a different tangent.

[AvDES LLC]

Glad it got you thinking outside the normal box. These engines don’t have much for electrical output and sucking some up with a big fan isn’t always the best idea in my
mind. If you want to aim more for the “certified” approach, you can run a small 2 inch duct to a muffler shroud and have the outlet to that shroud go into a through bulkhead ducting port and into the shroud on your cabin heat heater.

drop me a pm if you want to discuss shrouds and whatnot. I can steer you in the direction of a possible solution to your dilemma.

[jiott]

I can understand some of you wanting to go the "certified" approach with muffler shrouds, etc, especially those who live in very cold climates. But I do want to say that the automotive style hot water heater is one of the great features that drew me to the Rotax engine. Not having to worry about CO leaks from exhaust cracks, and not having to annually do the fairly laborious inspections inside the shroud area is a big deal to me personally. I don't have to worry about what if an exhaust crack occurs 6 months from annual time-better have a very good CO detector in the cockpit. Exhaust cracks are far from uncommon or rare on our Kitfoxes as we all know. Sure, I know the certified world lives with this potential problem very successfully, but it takes eternal vigilance and extra labor. I live in the Pacific Northwest and have never wished for better cabin heat for 10 years now, using the standard Kitfox supplied cabin heat option with two computer fans. Just wanted to throw this other side out there FWIW.

[AvDES LLC]

100% agree with the above in the sense that there are many many ways to skin this cat - sadly my cabin is so poorly sealed at the cowl to windshield interface (about a 1 inch wide open gap) that outside air POURS into my cabin and it gets cold as **** pretty quick - that’s the main reason my fan setup was pulled - the power draw was secondary.

now a word of caution on pulling air from under the cowl -

yesterday I spent the day installing an oil cooler conversion kit on a Rans S7. Owner has the 912uls with the ball and socket style exhaust. This is a VERY well taken care of plane; the owner meticulous about literally everything. While flying with an instructor the instructor asked why it smelled like exhaust in his cabin and he mentioned this to me while we were working. Upon inspection of the ball and socket fittings it is extremely evident that there are no less than 10 spots in the joints of that exhaust system that are displaying the signs of blow-by.

this was a first for me. I have the older slip together exhaust and had yet to deal with this ball and socket style before. If you’re planning on ducting air from under the cowling and you have the ball and socket style rotax muffler, I STRONGLY suggest first inspecting that system and ensuring it is very well sealed.

[sonex293]

Larry, in reference to your diagram in Post #9. Is this the way Kitfox recommends you plumb the coolant lines? (i.e. in parallel to the main coolant radiator).

Anyone have any thoughts on getting maximum flow through the cabin heat radiator (which uses 5/8" hose) without sacrificing main engine cooling (which uses 1" hose).

==
Michael

[Birdseyeview]

Larry, in reference to your diagram in Post #9. Is this the way Kitfox recommends you plumb the coolant lines? (i.e. in parallel to the main coolant radiator).


==
Michael
The Rotax diagram that I modified (in post #9) reflects the way my build manual instruction say to plumb the cabin heater. I've never seen a diagram published by Kitfox that shows the cabin heat exchanger included.

[avidflyer]

I have the heater installed on my new Kitfox 4 build, and here is what I did. As the heater core has 1" fittings, I ran through the firewall, through the heater core, back out through the firewall and then to the radiator. I am using a thermobob, but rigged up something that doesn't allow the thermostat to close completely, so I'm not using the bypass line. JImChuk

[avidflyer]

A bit further along. JImChuk

[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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Just an update on the effectiveness of my heater setup.
I flew in 35 deg. cool morning autumn air and was pleasantly surprised that it really did a nice job. I have a valve on the engine side of the firewall connected to a choke-style on-off knob. The 4 high-speed computer fans do a nice job without too much noise or amp. draw. The electrical switch is just on-off with all four at full power when on. You can vary the amount of coolant flow to vary the heat output. I thought about some kind of air diverter, but the center console does a nice job dispersing the heat in the cabin.

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[patrick.hvac]

+1 for the thermobob.
I'm in Canada and use of an oil T-stat as well as coolant t-stat is pretty much mandatory.
Priority one is making sure oil and coolant temps are above minimums.
The thermobob bypass line goes to my heater core. Kitfox uses a Setrab 50-616-7612. PWM controller on the fans adjusts the temp (no isolation).
I have seen situations where using the heater cools down the bypass enough that I can run out of heat from the engine so that needs attention in flight.
Seal up the tail which sucks the heat out like a vacuum. I am aware of some that use an insulated divider behind the seat to keep the heat in too.