P40 Suburban install saga 1971

[Living31]

The "before". Last year, I removed the upper shelf and replaced it with dollar store dish racks for a place to dry my gloves and felt packs.





Old out.(the insulation boards were just there because I was using them for knee rests)

[Living31]

The plenum box I had made by a local sheet metal shop, inspired directly from Minno's fine work. The pipes are metal 4 inch round ducting.



Starting to run the ducting, under the bed. The red and blue are water lines; I switched over to pex last year and ran the water lines and drain line along the ducting to help prevent freezing. (I have a rear bathroom Sovereign)



The massive (but quiet) inline fan, I obtained for a great price. Since I had one fan for two 4 inch ducts, I used ammo boxes(airtight) for switch points, employed a hole saw to cut the holes and duct collars with foil tape to attach and seal. The holes are offset, so the duct to the rear bathroom is a straight shot for more volume and the duct, which terminates in the bedroom, is offset for less volume.



Looking back toward the rear bathroom. I should have noted for last picture, the fan is rubber mounted to the bedframe and vibration free.



The tub/shower had to be removed to keep running the ducts and water lines together. Two questions arose here: The first, I am assuming the P trap is aftermarket because I can't imagine Airstream would have designed it to be dropping through the floor. The second, why are there two vent pipes?



After the same area has been insulated and wrapped with reflective foil. The tub/shower covers this area. Also, the rear bathroom duct terminates under the rear bathroom sink; it is at floor level, pointing towards the front of the trailer.




Back to the front, holesaw, duct collars, for the plenum box (metal tape to seal coming later) Mounted plenum box on top of a piece of fire resistant/heat resistant fireplace hearth. Note: Minno's plenum height measurement, plus the hearth, came out a perfect fit.
Insulating the rear of the Suburban is a piece of Spaceloft, that fancy, overpriced, insulation with minimal thermal conductivity. I picked up a couple of pieces a while back, just to check out the stuff, and finally found a good home for some.
In this picture you can see the layout of all the vents.

[Living31]

The P40 mounted to the plenum box. A couple of L brackets were added to make it more solid. You can see the original 4 vent holes. They were covered with vent hole covers and foil taped.



Installed and operational. There is more room to the left of the furnace, but the location of the unit was dictated by the inlet and exhaust holes in the shell.
A note on the black vent covers for anyone going round duct. I purchased those black vent covers (they snap on) off ebay for $2 each and that included shipping.

[Living31]

In no particular order:

The inline duct fan--It's overkill and even though the motor and running parts move quietly, as advertised, the sound of the air it moves, is similar to speeding down a quiet highway with the driver's window down.

I purchased a fan speed control switch, which should arrive this week, and will run it at reduced power.

Why the fan is needed. The short runs of the ducts to the front and kitchen create easier outlets for warm air. I want more air to the rear/rear bathroom, as I have a supplemental heater for the front.

Why the fan is not needed. I did not realize the extent of impairment of my 1971 Suburban. When it was operating at "full" power, the air from the rear bathroom vent trickled out. I wrongly assumed this was standard Suburban operation. The unassisted fan on the P40 blows powerfully out of every vent. (albeit more from the front vents than the rear)

The metal duct work. It should provide less air resistance and greater air movement than the flexible "dryer hose type of ducting. It is sharp, really sharp, really really sharp and a hassle--go with dryer hose.

The plenum box. It came out slick and was only $40

The P40. So far, so good, I am anxious to see how the newer furnace impacts propane use over the winter. The only downside is the P40 is loud. I can sleep through anything, so that is not a problem, but it is loud to where you have to turn up the TV or talk loud, when it kicks on. The current plan, subject to change, is to box in the area around the furnace (keeping with Suburbans spacing guidelines) and line it with Dyanmat Extreme or some flame resistant like product. Suggestions are welcome.

Thanks for reading and thank you to everyone who has graciously given their time to answer my tedious questions.

I will add more if I think of something I missed

[Living31]

Quick edit: I didn't take a picture showing the hole in the top of the plenum box and the furnace with the vent kit installed. Trust me, it's there.

[Living31]

Talking to fellow at work about this project and he thought by "dryer hose" I meant actual home clothes dryer hose. Truthfully, I do not see why actual home clothes dryer hose wouldn't work, but I meant flexible HVAC ducting Flexible Duct from Master Flow | The Home Depot - Model#: F6IFD4X300

[Living31]

All ducting and the water/drain lines tucked in. I keep the hitch in the trailer because it was darn spendy.

After a week, the heater is still loud and I am still planning on a dynamat (or like product) future, but the noise is easy to live with.

My insanely overpowered duct fan maybe not so insane. I have monitored it and when operating at full power (the speed control switch has arrived and installed) the reduction of air exiting the front two vents is not significant. However, the airflow increase out of the rear two vents is very noticeable. If I can get the inline fan wired with the furnace blower fan the two noises will mix together nicely. I will likely call an electrician for that project, I would feel terrible messing up my shiny new furnace.

Hmmm, six replies to my post and they're all mine, hopefully self posting won't impact my vision.

[Living31]

Now is where I take something simple and make it overly complicated. I will forgo the technical specifications because this is based on “in the field” observation.


If I run the inline fan, from the moment the furnace blower fan cycles on, until it cycles off, then the air for the first few minutes is cool and it remains warm after the furnace blower fan stops.


While the simplest, easiest and most straightforward approach, to wiring the inline fan, would be to have it operate in time with the furnace blower fan, how could be installed to engage a set number of minutes after the furnace cycles on and disengage a set number of minutes after the furnace cycles off?


I have attempted this a few times manually and found it effective, but am lost on what type of delay device would create this automatically.

[idroba]

For what it is worth, the P trap cutout in the floor was original factory way of doing things. On the ones of that era I had there was a molded plastic piece on the bottom for access and so the mieces could not get in (Ha, they are much smarter than Airstream engineering)

Good furnace instal, BTW.

[Living31]

Greeting fellow Idahoan, and from the cold end of the State. Truthfully, I have only driven through Kooskia, but have been to Grangeville many times.

The lack of plastic on that P-trap could explain my mouse invasion this summer. It was a commendable but short lived assault. By the end of the first week it was Me=3 mice=0. Haven't had a mouse problem since.

I only overlapped bubble foil insulation over that hole; images of me messing up the tub/shower reinstall or cutting a rear water line precluded sealing it.

The furnace is strong, but drafts are still an issue. I wish Airstream was made Airtight.

If I had my way the only windows would be a row of a half dozen double paned sealed view windows(the little oval ones) each side about 5foot up from the floor. They would let light in and give a view of trees or the sky and both me and the Ms. could walk around in our undies without worry.
As I see it, if I am staying in a park, I don't want to look at you and you don't want to look at me and if I am camping, when I want to look around at natures beauty I will be outside.
It would make it much easier to keep it warm in the winter and cold in the summer.
Sitting around and peaking out of windows is for cats.

[idroba]

Originally Posted by Living31

Greeting fellow Idahoan, and from the cold end of the State. Truthfully, I have only driven through Kooskia, but have been to Grangeville many times.

(well, you will have to remedy that this next summer)

The lack of plastic on that P-trap could explain my mouse invasion this summer. It was a commendable but short lived assault. By the end of the first week it was Me=3 mice=0. Haven't had a mouse problem since.

(sorry, but you may have more in the future. I bet that is not the only hole in the floor that is not sealed)

I only overlapped bubble foil insulation over that hole; images of me messing up the tub/shower reinstall or cutting a rear water line precluded sealing it.

The furnace is strong, but drafts are still an issue. I wish Airstream was made Airtight.

(I wonder if your drafts are not more of hot air rising, cold air sinking due to the relatively poor thermal qualities of the AS, not the air leaks. Other than those mouse entry points in the floor where the pipes go through, I have not found a lot of air leakage in my Airstreams over the years)

If I had my way the only windows would be a row of a half dozen double paned sealed view windows(the little oval ones) each side about 5foot up from the floor. They would let light in and give a view of trees or the sky and both me and the Ms. could walk around in our undies without worry.
As I see it, if I am staying in a park, I don't want to look at you and you don't want to look at me and if I am camping, when I want to look around at natures beauty I will be outside.

(I always liked the vista view windows for that reason, you could keep the curtains or blinds closed and still look out and let light in)


It would make it much easier to keep it warm in the winter and cold in the summer.
Sitting around and peaking out of windows is for cats.

(what, no cat in your family? LOL)

Hmm, could not post because the message was too short.. I guess the is more to answering in the original message than I thought.

[perryg114]

Ok let me ask some questions. You put in a bigger furnance because you wanted more heat and you also put in a booster fan to get more heat to the rear of the trailer? I have noticed that in my rear bedroom 31 that not much heat gets back there compared to the front of the trailer. I have not tried it yet but running the fan in the AC, potentially with the heater strip might tend to even out the temperatures.

Perry

[Living31]

Originally Posted by perryg114

Ok let me ask some questions. You put in a bigger furnance because you wanted more heat and you also put in a booster fan to get more heat to the rear of the trailer?

Yes, and yes


My AC fan is an energy sucker and is on the ceiling. Unless your 31 is different, some low power small fans (even CPU fans) could move around the cabin air.
I attached a fan to the heat source. When the fan is on, warm air shots out the bathroom vent like a hair dryer. Even though the fan is loud, it is nice to have warm toes when you're shaving.

[Living31]

idroba,I just put the final details on a week long elk hunt north of Salmon. So, next month, I will be nearer the cold end.

[Living31]

Here is shot in the dark on one of my draft problems. A nasty cold air draft comes right at foot level across the very front of the Airstream. It seems come from the door side of the trailer, but it is forward of the door. I have sealed the front windows, front side window and the door and it is still here. I even taped foil insulation from the bottom of the front windows to the floor and it didn't slow down the foot breeze at all. Is there some hole up in the front that I am missing?