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Which Heat Box?

claycookiemonster

Well Known Member
Trying to be prudent, I got the (non angled) stainless box from ACS, but it's only now that I see how awkward that 90 degree scat tube placement is. Now I'm looking at those 45 degree orientation boxes, but there are "engine side" and "cockpit side" controls and I'm not sure what that refers to.
 
Cabin heat box

Here’s the one that you want . Make sure you get the stainless steel version
 

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Heat box

Mine is sort of like that except the control is in top and cable operates FWF. I also got the Turbo Heat Muff. Highly recommended. The builder will custom fabricate the muff to your need. I had a problem routing scat and needed the custom inlet and outlet directions.
 
I used this one https://www.aircraftspruce.com/catalog/eppages/heaterbypass.php?clickkey=13173

The angle on firewall side points toward right side of engine, which is where my SCAT hose is installed. Also the flapper door arm allows cable penetration from left side of firewall. In addition, you can add a SCAT tube and mount a 1 5/8 Stein vent on gear tower. This gets heat directed closer to pilot vs spilling out. Takes a little more work to install.
 
Trying to read between the lines on the ACS catalog, there seem to be two angled heat boxes. One specifically mentions RV 8's, but also seems to assume a plenum on the aft side of the firewall to receive the air. That heat box doesn't seem to have a 2" mounting tube that will penetrate the firewall and allow scat tubing to be attached. So, that heat box mounts flush to the firewall, and I'd have to have a plenum mounted flush to the aft side of the firewall to receive the heated air coming through the hole in the firewall?

My military mind was just going to mount scat tubing on that 2" extension and bring it to an eyeball vent. Adding a receiving plenum seems unnecessary, or am I wrong?
 
Hi Clay-

The box I used, referenced above (https://www.aircraftspruce.com/catal...clickkey=13173) has two 2" flanges, one on each side of firewall. It comes in two parts. One on engine side, other on interior, joined together with firewall between them. If you want to extend using SCAT tube and eyeball vent, this box worked very well for me.

Stein eyeball vents come in two sizes. If you choose the larger Stein vent, make sure you get the one that INCLUDEs the plenum extension to receive the SCAT. The extended plenum reduces circumference, necessary for SCAT. This plenum does have a larger lip on the end that I simply ground down so a standard 2" SCAT could be attached. Also, consider including the vent bracket from Classic aero. Feel free to private message if you have more questions and want to go this route.
 
The one I referenced from Aircraft Spruce is exactly what I have ( I actually made mine as a copy of the aluminum that came in kit . For 3 reasons , the possibility of a fire and the aluminum meltdown leaving a 2” hole in the firewall , I’m a tinker and like to challenge myself and had lots of leftover stainless steel from my dry sump inverted oil tank, and as we all know the CHEAPEST thing in the airplane is the pilot so I wasn’t about to buy on when I look at my huge “prototype pile “

Anyways back to your question this particular box does not have the ability to accept a SCAT tube to the cockpit side as the actuator arm pass through the 2” air hole

Edit: I’ve only had mine flying for a little while can’t speak to the volume of actual heat that my system provides, since I’m purity far out in the weeds from standard . However it seems to provide ample volume of air flow to warm the front seater and it shuts off all flow completely. I used the “A-740 Ractchet control #05-14072 and fabricated steel version of P/N 05-15705
GIB will probably have to shiver or wear motorcycle/snowmobile chaps and vest as I have 12v plugs for such both front and rear.
 
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A big 'ole by-the-way...

I've noticed some of the stainless steel heat box installations (a good idea) are sometimes attached with aluminum rivets (a bad idea). Worse, the cable anchor may be aluminum, fastened with aluminum rivets.

Folks, a SS box isn't going to do much good if it falls off the firewall, or the cable sheath anchor melts away and the door won't stay shut.
.
 

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A big 'ole by-the-way...

I've noticed some of the stainless steel heat box installations (a good idea) are sometimes attached with aluminum rivets (a bad idea). Worse, the cable anchor may be aluminum, fastened with aluminum rivets.

Folks, a SS box isn't going to do much good if it falls off the firewall, or the cable sheath anchor melts away and the door won't stay shut.
.

Can you provide which SS rivets you used for your entire firewall, heat box?
Thank you in advance.
 
Can you provide which SS rivets you used for your entire firewall, heat box?

Any stainless steel blind rivet or monel driven rivet will attach a heat box.

My own firewall has an insulation overlay on the engine side and no heat box. No melted rivets, no hole.
.
 

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I haven’t unpacked my firewall forward kit yet.
So I ask does a heat box come with it and if so, aluminum or stainless?

I read the overview on ACS and it has Dan’s fingerprints all over it.
 

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Any stainless steel blind rivet or monel driven rivet will attach a heat box.

My own firewall has an insulation overlay on the engine side and no heat box. No melted rivets, no hole.
.

Insulation is a great idea, any pics of your firewall? I’m planning to keep fwf clear of as many items as possible but I didn’t think there was enough room for a true fireproof insulation install.
Thanks for creating the conversation.

Disregard, I just searched past threads in this conversations. Great info!!
 
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Here’s the one that you want . Make sure you get the stainless steel version

Same SS one I used. Installed with SS screws and platenuts. I also used 3M Firestop 2000 to seal it on the firewall. Cable is on the cabin side so no worry about keeping the door closed. Used this on my 7 and same on the 8. Dual heat muffs in series in order to get enough heat for our Canadian winters.
 
I used 2 stainless AN3 bolts and hardware as per instructions.
With 3M FireBarrier of course.
 

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Okay, now what?

I got one of the smaller 45 degree heat boxes as recommended.

https://www.aircraftspruce.com/catalog/eppages/heaterbypass.php

Looks great! Curiously, while the holes on the box match the holes already in the firewall, the box can't be installed using those holes because the box would interfere with structure on the aft side of the firewall. Did anyone else find that? I can only find one way to install the box, and it's vertically with the heated air entering from below, and so the unused air will be exhausted upwards, against the general flow of air exiting the cowl at the bottom. That seems a bit odd, but maybe not fatal.

My next question, is how have you guys set up the scat tubing to combine cool outside air with heated air? Have you added another valve to decrease outside air when you really want warmth, because even when the heat box is fully HOT, it will still mix with fully COLD air from the outside, right? I've learned metal working and fiberglassing and wiring. I guess it's time for HVAC training.
 
Directing Heated air once it passes the firewall?

I don't know why this heat issue has confused me so much, but I think I'm getting it now. One final jeopardy question, are you guys installing scat tubing to route and direct the hot air aft of the firewall, or simply letting it loose there? The outlet on the -8 firewall is outboard of the left rudder pedal, so it seems like that foot will get toasty while the right foot will freeze.
 
2 choices from ACS (SS) for a RV-8. One has the lever cabin side, the other engine side. Which one?
 
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