My 2004 Itasca "Horizon" 40AD has a Coleman-Mach (2-Ton) Basement AC, and I prefer this type of AC over those noisy rooftop ACs.
This basement AC unit has 2 heat pumps. Stage 1 draws ~14A (compressor #1) and ~25A
when Stage1+2 is running.
So that puts a good 25-28A load on my Onan 7500 Generator with my residential refrigerator and TV and computer powered up, but this generator can handle it. I.e., my basement AC starts and restarts just fine in hot weather. And it burns about .9 gal/hr of diesel fuel at this load. What I do not know is how my generator will handle running 33A and if load balancing is a concern?
Note: My Onan 7500 is a pure sine wave generator, but it uses “inverter technology” and I think load balancing is important when you get above 15A. I’m not real clear about this, but I know Winnebago wired my L1 and L2 (50A) lines to achieve the best load balancing as they can... and I will be conducting some current measurements with both my basement AC running and my portable AC running at the same time… just as soon as I find some hotter weather (80+F), because right now it’s 72F outside, and I can’t really conduct power management calculations when the weather is this cold. So I will need to post a follow-up thread.
FIRST LET ME SAY A FEW WORDS ABOUT HOW YOU CAN IMPROVE THE COOLING OF YOUR BASEMENT AC
When Winnebago ran venting ducts up the rear cap they did NOT insulate them and consequently many owners complain their Coleman-Mach (2-Ton) Basement AC does not cool down their coach every well. However, it’s not the AC that is the problem. Rather, it’s more likely you have cracks in the tape that seals off the venting duct work on top of cooling losses due to poor or no duct insulation... and 30 feet of ducting in the roof, which all de-rates the cooling inside the RV.
So step one would be to inspect your ducts where the cold air exits the AC' and then I covered that 90-degree elbow duct with butyl-metal Water Proof Tape made by “Duck” ...which BTW I have only found this stuff at Walmart. And then for added measure I sprayed 2 cans of Flex-Seal over that entire area for added insulation. And this helped alot!
NOW LETS GET TO SUBJECT OF WHY I DECIDED TO ADD A PORTABLE AC
* On 100F days I’m mostly comfortable in my RV with both the Coleman compressors in my basement AC running, but it could be colder. Ideally, I would like to see 72F-76F inside the RV vs. 78-80F I now get.
The problem is on 95F+ days it gets to about 82 inside my RV; and when humidity is high it would also be nice to have more BTU’s of cooling at my disposal. So I came up with the idea of adding a supplemental 8,000 of BTU’s (rated at 6,000 BTU DOE).
* I selected the 8,000 BTU unit, because I think this is all I need as a supplement unit to my existing basement ACs; and I like that it runs at 6A-8A
, and is 50-52dB, which is pretty quiet and on the low side for an AC.
Here is a link to the Lowe’s website for more information about this GE-8,000 BTU AC ($320):
* I am fortunate to have 2 choices on where I install this portable AC unit and both were based on having access to a wind so I can exhaust the hot air out of the AC.
was to put it next to my couch. And all I needed to do was insert a piece of wood (see last picture below) as a shim so the sliding window can butt up against the AC’s window mounting kit (exhaust port).
was to mount the AC in the bedroom where I have a tip-out window.
I decided to go with Option 2, because a) I did not want to listen to the AC in the living room; and b) I can store the AC unit between my bed and my closet when I’m driving; and c) I think putting the AC close to the basement AC air vent may be the most efficient. (TBD)
...Besides, I will be using the basement AC fan to distribute the cooled air to the front of the RV anyway -- and maybe on somedays, I will not need to run both stages of the basement AC when I have the portable AC on. TBD. If this is the case then maybe NOT running the basement AC or just running Stage 1 will help to prolong the life of my Coleman-Mach unit. (In theory anyway.)
SO DOES IT WORK?
Answer: I don’t know yet, because we just had a cold spell in south Texas and it’s not humid outside now, but next week I will be heading towards El Paso and Yuma and then Las Vegas and Montana, so there are plenty of hot days ahead. So I will be sure to add follow-up posts at some point.
For now, I am very pleased with how easy this project was to do. And if adding a supplement 8K-BTU-AC proves to be a good upgrade, then I will run a dedicated 120V extension cord (or romex) to power this GE-Portable AC off the 20A service plug at shore power, so I don’t put an additional 8A load on my 50A service.
Note: I will also be inspecting my Automatic Transfer Switch neutral return wires too. Why? ...When I have my basement AC running in conjunction with this portable AC since I will be pushing 33A – 35A, so I want to make sure my Onan 7500 can handle this and that goes for my ATS too.
Note: I'm not sure if newer ATS relays can handle 33A for years of service, but that's another discussion. This is why I want to stick with the old style 50A, 8-pin relays in my Parallax AST-5070 and not use the more modern designs.
Can anyone explain the concept of “load balancing” and what concerns there may or may not exist when using an Onan 7500 Generator with “inverter technology.”
Note: This Onan calls for a 70A-Neutral, but what they mean by that is that each leg off the generator stator is 35A for a total of 70A... but the ATS is marketed as a 70A neutral.
Is load balancing a real factor?
ANOTHER OPTION TO USING THE PORTABLE AC
I was thinking I might be able to just run my Basement AC on Stage 1 (aka L1) together with this portable 8K-BTU-AC on L2 for load balancing, and not run the Coleman Stage 2 (aka compressor #2). This will keep the current loads down to under 25A total, and I bet this portable AC will provide better cooling than one stage of the basement AC.
…So I will need to check if my bedroom AC wall plug on the end of my dresser is connected to L2 or L1 in my circuit panel. (TBD)
* Make A template first, and then use it to cut your finished piece of wood or better still get a ridged 1/4" vinyl plank. (Start with a rectangle 6-1/8" x 24-3/4")
* Use the template to trim mark the corners on the good plank and add a notches to clear the window hardware.
* Then insulate it with a black, round rubber strip of weather proofing. (Note: You buy this weather proofing material as a double strip and then you split it down the center.)
* The last picture of wood is for the window over the couch, if you decide to go that route. (29-1/8" long x 3-1/2")
That’s all for now. The total cost was ~$360 and the pictures below will show you how I cut out the wood (or ¼” vinyl planks) to shim up against the AC window kit.