In this subsection I’ll try to gather info about the venting and ducting associated with the heat pump mostly…though it may turn out to be exclusively about heat pump venting and ducting. We’ll see as we go along.
May-June 2023 – Short term cooling hack while waiting for a new basement heat pump to arrive and be installed…
Waiting for delivery of the new heat pump – and it’s hot out!
The new heat pump won’t arrive for 7 to 10 days. Then I need to inspect it for damage, and if that’s okay, install it which may take a couple days as I try to scare up some help lifting it as it’s 275 pounds, and then test it and hope that it works correctly right out of the box. It’s a big complex machine and they do sometimes fail earlier then expected.
So I wanted to have a backup plan as last week without AC was very uncomfortable in this 36 foot, Class A with two slides. Reaching the 90’s in the early afternoon. Front of the RV is facing west so it gets the full force of the afternoon sun for several hours. I’ve put reflective screen in the front windows but it only seems to keep the inside from going more than 5 F over outside temps. Awnings are extended of course.
Anyway, I do visit Facebook and noticed the FB Marketplace has quite a few ACs for sale on there, often for reasonable prices. Hmm.
Long story short, I bought two window mount ACs, an 8,000 BTU and a 5,000 BTU (8K & 5K) and once I got them home, I went to work trying to figure out where to install them. After some thought, I temporarily installed the 5K unit on the kitchen counter and blew that unit’s waste hot air out of the sink’s window right behind it. Made a kludged together vent setup so most of the hot air out of the back of the AC went outside. For sure just a temporary setup. The 5K AC worked and output nice cold air but struggled to keep the living area cool, so I removed it and set the 8K in the same place. Did an excellent job keeping the inside as much as 12 degrees cooler then outside temp.
With the 5K BTU unit, I decided that the bedroom escape window was the best place for it. And that’s really the only window I have back there I could use. I thought about how to mount it, and for the longest time I was considering building a stand outside to set it on. Like the AC stands that most of my neighbors build when without working ACs in their RVs, I could see that sort of window AC setup all around me in this RV park. But I considered that an RV’s metal surround windows are hella strong, I’ve taken them out before and they are stout. So, I thought, why not just strap a 1″ x 4″ stick across the window and lean the AC’s top rail against that, while the bumps in the bottom of the AC’s case are captured by the window frame bottom rail (as that’s what they are designed to do)? Doing that would mean I could do all the install work alone and wouldn’t need to build (or buy) wooden stands to support them. Of course during an earthquake they would likely dance right out of the windows and hit the ground but we don’t get many of those here in eastern Oregon.
So that’s what I did first for the bedroom unit, and then since that worked so well for that fairly lightweight AC, I also rigged that setup for the heavier 8K BTU unit. Turned out that I had two pieces of 1 x 4 wood that I’d cut for other projects that were just the right length.
I’ve since removed that ugly multi-colored place mat in this picture and slid the AC to the left. Then put reflective bubble insulation in the gap.
The 1″ x 4″ stick was exactly long enough to span the window frame and hold the AC in place and I put double sticky tape on the back of the stick on each side where it would contact the 1/4″ wide metal edging of the window when installed. That would hold it from slipping side to side and dropping out of the window frame if I bumped the AC during a night time bathroom trip. Then I put a single screw through the metal bracket on top of the AC (came with it as part of the installation option accessories) into the wood to hold it in place as I horsed it into place in the window. Wouldn’t want it to fall those 7 feet to the ground. No need to remove the window but I did use a cardboard box taped to the window and the AC with packing tape (shown here) to hold the window open allowing exhaust air from the AC’s condenser to disperse easily. Placed reflective bubble insulation behind the day/nite shade so that area is blocking the sun well now. Maybe I’ll change the cardboard box to a stick of wood. Nope, never did. Worked fine as it was.
Update: I removed that unsightly multi-colored table mat and slid the AC over to the left so it was right up next to the left side of the window frame. Then I used a piece of cardboard to fill that small gap, on the right side I used a piece of insulating bubble wrap (the kind with aluminum foil on both sides) to fill in the right side. Also used the bubble insulation up in the upper section of the window for more blocking.
And here’s the 8K BTU unit in the living room window. Don’t have as much trim work to do with this setup. And it just hangs there nicely balanced. Hardly any strain on the wooden cross piece or the window frame. Placed reflective bubble wrap in the rest of the window as the sun does hit it late afternoon. This AC does weigh a bit (more than the 5K naturally) so I wore my two knee braces, my back brace, and two elbow braces as I horsed it into place. And as with the other AC I had screwed the board to the bracket so it wouldn’t fall out of the window while moving the AC into place. Worked well as a safety feature while slipping the AC into the window opening. And as a permanent brace to keep the AC in place so no outside stand was needed. Naturally, I tilted both ACs the required 1/4″ per foot down in the back so any condensate would drain outside.
Over on the left side, I just stuffed a kitchen towel into the gap. This 8K unit had the accordion window fillers but I didn’t see a need for them with this installation and removed them. Worked better that way I think. 
I still have to petty up the trim on both installs, but I’m satisfied that the two ACs amounting to 13,000 BTUs will be enough to keep me cool for the 1-2 weeks I’ll need to get the new heat pump AC up and running. It’s supposed to be in the 90’s for the rest of the week, and likely the week following as well so this was the only way to be cool temporarily that made sense to me.
The gap over the top of the AC was pretty much filled with the retracted Day/Nite shade and I rarely felt any hot air sneaking in from that gap.
Here’s how it looked after finishing the trim…of course if this was going to be a long term installation, I’d have gotten a stick that spanned the entire window, then stained it a wood color to match the cabinets above. But since it is only a 2-3 week temporary installation I didn’t bother. BTW, it was nice and solid in position. No odd vibrations or anything.
FYI: The window width is 58″ and the 1″X4″ stick I used is 52″.
Update: I can tell why this RV needs a 26,000 BTU heat pump after a few days in 90 degree weather. The 2 window ACs amounting to 13,000 BTU are just barely keeping it 12 degrees below outside temps. And it takes some work to get it that much different too. So it’s 78 F inside and 90 F outside. I’ll be happy to install the new heat pump soon. They did do a fair job though. After all, most ACs are set to never provide cooling below 20 F from ambient. This is to prevent something that AC inventors and pioneers discovered early on. They’d have a 100 F day, would advertise ‘It’s cool inside’ and generally fill a theater. The systems in those days got the temp down to 68 F. When the show opened, as the audience would enter or leave the theater many would promptly pass out from the sudden change in temp. So, it’s been a rule since the 1920’s to design cooling systems so it can’t get an inside space any cooler then 20 degrees lower then ambient. Refrigerators can of course, but not ACs. Back to my point, even 12 F lower then ambient is pretty good. The Coleman heat pump never got my RV any lower than 20 degrees lower, so those two small ACs did pretty good. But, haven’t had a 100 degree day either.
So that’s my short term hack while waiting on the heat pump. Once the heat pump is installed, is cooling and keeps cooling well for a week or two, we’ll be in the heat of the summer and I should be able to make a profit selling these two ACs. They cost me $130 for the two and it turned out when I asked for an address from the seller, it was someone that last year lived right behind me here in this same RV park in an RV and they’d since moved into a manufactured home just up the street. The ACs they were selling were from their now sold RV. So we knew each other and they are less then a block away.
As it happens, both of these purchased ACs are relatively new so they have modern multi-speed compressors and due to that they run quieter, also have multi-speed fans, so I can leave them on all day and they’ll shut off when reaching the digital set temperature or most of the day they’ll be running at slower speeds maintaining the temp then automatically increase speeds as it gets hotter. In other words, they’re less annoying then older ACs that were just full on/full off with a crude thermostat operation. I’m pleased I found them listed for sale and the two working separately in the front and rear of the RV make it much more comfortable as opposed to one large 12,000 BTU unit that I considered buying prior. So they are installed the easy way and will help keep me cool for what I hope is just a short period until I change over to the heat pump AC. What I learned is that it’s unnecessary to buy and build a wooden stand for these light weight ACs. I am pretty confident that even a 12,000 BTU could be mounted only using a 1″X4″ wooden brace instead of a stand. Just realizing that saved me a considerable amount of time and some money.
So, now I’ll wait until it’s really hot here and sell these two ACs. Should be able to make a profit too.
Additional Heating/Cooling Information that applies to this RV.
I have a PDF file available from Winnebago, 2wkp36gd.pdf, that has almost everything in the RV shown in exploded views. Very nice. But searching didn’t turn up anything showing what’s inside the ceiling/roof interface. So I don’t have any documents that I know of that show routing of the vent channels or give part numbers for that important area of the heat pump system. It would be nice to have in the event one of the exposed vents is damaged, the roof is damaged, or if I want to pull wire through the venting system (which is actually the main reason I’d like to know). The vents aren’t in a straight line so knowing things like whether or not an offset vent is on a branch, or if it’s attached to the main vent tube via a gentle curved bend is important to know. For instance, I’d like to route a HDMI cable back to the back bedroom but without the proper information about the vent routing, it becomes more of a challenge.
Here’s a picture of the living room venting…those vents are 4″ in diameter and the louvered part rotates. There are two rows of vents on either side of the living room. They run in a straight line 33″ from the walls back to the bathroom and bedroom where the fixture inside the water closet is 27″ from the wall and one in the bedroom is 27″ as well. Both of the vents that are closer to the outer wall are on the drivers side. All the vents on the passenger side of the RV are at 33″ from the wall. I think both main channels are at 33″.
Here’s a shot of the granular foam or styrofoam bead board material that’s formed into a ‘vent’ that routes conditioned air around the RV. There’s the ceiling material, a 1/8″ thick piece of plywood it’s glued too, and then the 4″ thick granular foam. Up on the roof, that’s covered with the one piece Filon fiberglass roof. I suspect the foam is perhaps one or two pre-formed sheets that already has the vent channels formed in the foam. That’s because I can see that it’s been formed, not cut. Vents are suppose to be smooth but these aren’t. Still works pretty good.
Taking a look down the vent…this is from the middle of the LR vent looking towards the front vent around 4 feet away that’s nearly in line with the driver. It ends up being slightly behind and to the right of the drivers shoulder. It’s handy placement means cool air when driving if the generator is running. I have been doing that quite a lot lately as the engine A/C compressor isn’t running right now and using the heat pump for cooling works well. The vent’s very sharp corners and edges suggest that the ceiling comes in several pieces rather then one gigantic piece.
And the water closet vent looking towards the middle of the RV. You can see that it ‘T’s up with the vent channel that’s at 33″.
There’s another vent in the bedroom that’s only 27″ from the outside wall and I suspect it’s made this way too, where it ‘T’s into the main duct just like this one.
What happens when this foamed venting reaches the rear of the RV is that there’s a plastic 90 degree elbow that’s pushed into the two vent races. You can see in the below that each race is approximately at 33″ from the sides of the RV. And those elbows are sealed I imagine but I’ve not seen how they do that. Probably Venture tape and/or with butyl tape. Then the venting travels down outside the rear wall of the RV, joins that ‘Y’ piece and then further down another elbow which attaches to the Output Air vent of the heat pump. Then all that is covered by the fiberglass endcap. These pictures are likely just like my RV since Winnebago makes both the Journey and Itasca. I haven’t had the end cap off so I can’t really tell for sure but I assume it’s like this. Pretty slick system. I’m happy mine came with it and with the floor A/C. My old Bounder with the ceiling mount A/Cs was really noisy in the living room. I compensated by getting up early and getting the RV cooled enough that I could switch to the bedroom A/C and maintain the temp in the rest of the house with that. When that started to fail due to ambient increases, I’d wire up the bedroom A/C to an extension cord and plug into a 20 amp outlet so I’d have 2 A/Cs running. The heat pump system I have now is far superior.
So that’s all I’ve got on the venting so far. Probably don’t need much more really.