Cabin Heat Conversion

How to keep the Cessna 170 flying and airworthy.

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aquanaut
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Joined: Wed Dec 01, 2004 6:20 pm

Cabin Heat Conversion

Post by aquanaut »

OK guys, this will take a minute to get up to speed, but I need advise. I have a 48 170 with a O-300-B that just past TBO. I've been looking for a mid-time replacement and last week I found one off (I helped take it off) a 170 B which is about to get an upgrade to a 180 hp. I bought the engine Firewall forward, including prop and spinner. I'm currently running the pancake mufflers and the new engine has Hanlon Wilson's on it. I'd like to use the Hanlon's but in addition to that I'd like to convert the heater system in my 170 to that of the 170B. As we all know the heater in the 170 may just as well have been left off, but I've heard the system in the B Model is very effective. I realize in order to do it I'd have to get the Control Valve, and the Cabin Duct work and I'd also have to move the battery box toward the center of the firewall to make room for the Control Valve. I know it would be a fair amount of work but the cabin heat is the only thing I dislike about the airplane. Has anyone out there done this sort of thing or have any idea what it would take.
Thanks in advance for any help or insight you can lend.
Dave
Dave Esslinger
hilltop170
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Re: Cabin Heat Conversion

Post by hilltop170 »

Dave-
I had a C-180 heater system installed on my 1951 170A with the Hanlon-Wilson mufflers. It is pretty much the same as the -B model heater I think. The heater valve was put on the left side where the old one was. New side panels with heat ducts had to be fabricated. It came out very nice and works great but was unable to fit in a defroster outlet due to lack of space.
IMG_2729_1_1.JPG
C-180 heat valve modified to 2" scat tube
C-180 heat valve modified to 2" scat tube
C-180 firewall heat duct
C-180 firewall heat duct
New aluminum side panel with integral heat duct
New aluminum side panel with integral heat duct
New aluminum side panel with integral heat duct
New aluminum side panel with integral heat duct
Last edited by hilltop170 on Tue Dec 26, 2017 5:23 pm, edited 4 times in total.
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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aquanaut
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Joined: Wed Dec 01, 2004 6:20 pm

Re: Cabin Heat Conversion

Post by aquanaut »

Richard, thanks for the pics. and the reply. What kind of paperwork did you have to do for this?
Dave Esslinger
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misterde
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Re: Cabin Heat Conversion

Post by misterde »

Dave...

I just happen to have all the parts for this conversion as depicted in previous posts. I have in my shed two wrecked 1958 C172's which I have been using as my parts sources over the years. One of the firewalls has been removed with the valve and the plenum and the other is "almost" removed but not as accessible. Separately, I have a Cessna Artic heater, it looks like a Hanlon Wilson except the air flows through it from end to end and uses 3" scat. Pictures can be available. If interested send me an email.

Dick DeCramer
'49 C170A N9007A
Northfield, MN 55057
rv8tr@deskmedia.com
507-650-1162
hilltop170
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Re: Cabin Heat Conversion

Post by hilltop170 »

aquanaut wrote:Richard, thanks for the pics. and the reply. What kind of paperwork did you have to do for this?
Dave-
I'll have to look in the logs and see if a 337 was approved or if only a logbook entry was used. I asked the shop that did the work and they can't remember. The logs are in Texas and I'm in Alaska until Sept. 30.
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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aquanaut
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Re: Cabin Heat Conversion

Post by aquanaut »

Richard, I can wait, thanks for the reply. I've gotten great insight from Gahorn. But I'm always open for more.
Thanks
Dave
Dave Esslinger
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n2582d
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Re: Cabin Heat Conversion

Post by n2582d »

I too am in the process of upgrading the heater on my '52 170B. Could someone give me a measurement of the vertical distance between the top couple of rivets which fasten the tunnel to the firewall (circled in picture below) and the bottom row of rivets on the heater duct?
Firewall.png
Gary
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mongo2
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Re: Cabin Heat Conversion

Post by mongo2 »

Hello All

Looking to verify the correct placement of the spacers involved in the heater valve assy. As shown I have the "larger' spacers against the firewall patch plate, and the smaller on top, thus the plate slides on the spacer and not the patch or firewall.
It does seem a bit loose, and when closed, there is a gap at the bottom of the slide plate (thickness of the lower spacer) where engine or firewall air can get by and into the interior duct. Of course I set the spacers in reverse, and that puts the slide plate against the firewall, and flush to it, with no gap, but that means more metal to metal contact. I've looked at the 100 series Maint manual at all the various versions of this setup, and cannot seem to see it clearly.

Comments Please..

Rick

Image
Rick Champagne
C-170A N5475C
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gfeher
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Re: Cabin Heat Conversion

Post by gfeher »

I've been studying this and the zillion other threads on the forum about improving the '52 and earlier cabin heat. I'm reviving this one to ask a question that I haven't seen addressed. Seems like the most effective improvement is to change the '52 and earlier cabin heat system to the '53 and later system by swapping out the heater valve on the firewall to the '53 and later one and then adding the interior/cabin ducting of the '53 and later system. (An over-simplification, but bear with me). (That's what Richard did in his conversion in this thread. The C-180 parts he used are the same as the ones used in the '53 and later system.) However, the '53 and later cabin heater valve is also a separate cabin air valve, and the '53 and later models have a separate cabin air control knob on the panel that the '52 and earlier models don't have. (I hope you're still with me.)

So here's my question: as a practical matter, completely apart from cabin heat, how much of an advantage (or disadvantage) is the separate cabin air control? Does it add anything to your comfort or enjoyment when you are not using cabin heat? For example, does it really add anything during the summer? How well does it work when the cabin heat is off? The air comes from the engine compartment and enters the cabin at your feet, so I wonder.

I'm aware that the separate '53 and later cabin air valve can cut off air from the engine compartment in the event of an engine fire. That's not the issue.

The reason I ask is that I understand that the interior/cabin ducting of the '53 and later system may provide most and maybe close to all of the heating improvement over the earlier system. If the separate cabin air control of the layer system doesn't provide much of a separate advantage, eliminating the valve change would significantly simplify this upgrade.

Thanks for any info you may have.
Gene Feher
Argyle (1C3), NY
'52 170B N2315D s/n 20467 C-145-2
Experimental J3 Cub Copy N7GW O-200
hilltop170
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Re: Cabin Heat Conversion

Post by hilltop170 »

Gene-
The air shut-off valve is only there for fire/smoke safety as you acknowledged. The valve is normally left in the open position and provides cabin fresh air circulation with or without heat as desired. It should never be closed with the heat on but can be closed with the heat off but I don't know why you ever would. I like lots of air circulation and it does help in the summer. The shut-off valve control cable knob could be placed in the parking brake control knob location.

Installing a two-piece heat header with the early style rotary heat valve like David did would provide better heat distribution to the front seats than with the rotary valve only, but the rear seats would still be lacking. As you alluded, the rotary valve does not need an additional control cable, all air flow stops when the heat is off, with the rotary valve.

One tip if you fab your own heat header, vent holes directed down at an angle toward your feet and/or horizontal probably would work best. I think horizontal would be best because they would not overheat your feet. Holes directed up under the panel are not needed and take away from getting heat where it is needed. I taped over the holes on mine that point up and it works much better.

That's my opinion, anyway.
Last edited by hilltop170 on Fri Dec 29, 2017 2:45 am, edited 1 time in total.
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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gfeher
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Re: Cabin Heat Conversion

Post by gfeher »

Thanks for your input Richard. I was thinking about installing the header that I showed in my email to you, along with side panel ducts, as you recommend. But I was wondering about the need to change out the firewall heater valve. I would do it if it provided a real advantage when the heat was off. What's driving this is a comment or two I read in a thread or two that given that you need to change the input of the '53 and later heater valve to accept 2" scat tubing, the heat output of that modified valve is about the same as the original '52 and earlier valve, and provides more than enough heat. So if that's the case and the separate cabin air control doesn't really add any separate value, why go to the trouble of switching the valves if I can make the system work as well with the current valve? I now rely on the wing root vents and windows for cabin air in the summer, so I don't know if I'm missing anything by not having cabin air available from a header and side vents below. What's throwing me is that the "fresh" cabin air that would come out of the header and side vents would come from the engine compartment. I dont have any experience with it so I don't know if that's good or bad.
Gene Feher
Argyle (1C3), NY
'52 170B N2315D s/n 20467 C-145-2
Experimental J3 Cub Copy N7GW O-200
hilltop170
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Re: Cabin Heat Conversion

Post by hilltop170 »

The "fresh" air does come from the engine compartment but it's pressurized cool air from above/upstream of the engine, not after it has gone thru the cylinders to cool them. There is a strong flow even thru 2"

If you are satisfied with your cabin ventilation in the summer as it is, a header by itself with your existing heat valve should be good. No need to change out the heat valve or add side panel ducts.
Last edited by hilltop170 on Fri Dec 29, 2017 2:52 am, edited 1 time in total.
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
User avatar
gfeher
Posts: 571
Joined: Fri Sep 26, 2014 9:19 pm

Re: Cabin Heat Conversion

Post by gfeher »

Thanks Richard. That gives me an idea of its effectiveness. Sounds like it adds value.
Gene Feher
Argyle (1C3), NY
'52 170B N2315D s/n 20467 C-145-2
Experimental J3 Cub Copy N7GW O-200
hilltop170
Posts: 3481
Joined: Sat May 06, 2006 6:05 pm

Re: Cabin Heat Conversion

Post by hilltop170 »

Yes, in Texas in the summer it helps. In New York in the summer, maybe not so much.
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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n2582d
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Re: Cabin Heat Conversion

Post by n2582d »

I wonder about how much engine cooling air is lost when that vent is open in the summer. There has been a lot of discussion here about making sure your baffling is "tight" to keep the cylinder temps down. Then we open a 3" dia. hole in the baffling. :? Here's what Cessna added on the right boot cowl on their 180/185's. It feeds into the manifold on the firewall.
Vent.jpg
Gary
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