Quote:
Originally Posted by Long & Winding road
GM Tech - I like what you did with your cover inside. How did you mod the inside part for the return side? I guess you will have to make sure that one is open all the time to maximize air flow inbound.
I basically stopped the outlet duct by cutting off the end and blocking it. That keeps the outlet air in the area where the two round added vents are. The area in front where the original outlet that slides open and closed, I covered that opening with black speaker material and glued the slide so it stays open all the time. When the AC is running, I put a piece of paper up to that front opening and it sucked the paper tight to the opening. That means it's definitely sucking in extra air there. I can also see restrictions in the inlet or outlet sides simply by watching the amperage draw change. Just closing a vent or two will change the amperage draw of the AC fan motor. What you're shooting for is actually higher amperage, low amperage means the fan is "cavitating" and not pulling air. Blocking the extra inlet vent I made makes the amperage draw change from 3.2 to 3.0 amps. Coleman's ceiling assembly MOST DEFINITELY is not optimized for good inlet or outlet airflow. Amperage draw changes drastically when you run the AC without the ceiling panel in place. Amperage even raises when you take the inlet filters out, meaning better airflow. 320 cfm is a LOT of airflow and needs big openings to keep it moving freely.
Do you think insulating around the condenser fan shroud (like your picture shows) makes a difference?
Lol. It makes no difference at all. The dynamat around the fan shroud is for strength and stability of the shroud, nothing more. It's fairly thin sheet metal riveted together. I made that shroud myself, Coleman isn't smart enough to realize a fan with huge pitched blades like that will not be very efficient when it's inlet and outlet sides are only separated by a 1/4 inch bend of sheet metal. Making it ducted like I did by adding that shroud greatly increases the efficiency of the fan.
Im looking for some more easy mods that I can do myself. Like you said they all add up after a while. So 2% here 3% there sound good to me as long as its an improvement.
I might hook up another fan or two on the shroud - so let us know more details when you can on that mod alone.
This is unfortunately another "don't try this at home" mod. haha. It obviously can be done, but it's not super easy. I originally wanted to use 110volt AC fans, but couldn't find any with a high enough static pressure so I ended up using 12 volt fans. You have to think about the physics of fluid dynamics when you're doing silly stuff like this or you can make things WAY worse really quickly. If the fans you add into a shroud like this aren't strong enough to pull against the negative pressure of the main fan, you'll end up actually pulling air in through them backwards. And also, if they aren't running, they'll pull air in through them backwards instead of pulling that air through the condenser. Obviously it can be done and if done right does absolutely make a difference, but spec'ing the fans and engineering the 12 volt power to them might be more than some of you guys want to take on. I put a relay near the thermostat that pulls higher amperage 12 volt power to feed the fans when the thermostat triggers the compressor to run. It's all automatic so I don't have to worry about turning extra fans on or off. There's a TON of airflow coming out of that shrouding around the roof AC unit now! And quite a bit blowing directly on the compressor also, which needs it since it's trying to compress 400+ psi refrigerant.
Any other easy mods/insulating that you would suggest that we have not talked about already?
Of all the super easy mods, the ceiling panel I think might be the biggest bang for the buck item to concentrate on. Like many on here have already figured out, simply adding a down vent directly below the outlet fan makes a huge difference. If I wanted a project to make some extra cash, I might consider selling modded ceiling panels. lol. Doing the intake side mods are a little harder for the do-it-yourselfer, but also makes a really big difference in the AC performance.
Your inside ceil register vent mod was awesome..... cant wait to try it out when it warms up some.
Thanks.
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Thanks to all that have kept contributing and reading this thread, we've ALL learned some good stuff! I can't wait to get my new Mach 8 Plus so I can see how the totally different design compares to the decades old models like my 15k. And I can't wait to get into some horrible hot weather so I can turn both units on full blast and have a blizzard/tornado in my Vegas! lol. I just told my wife after seeing how the mods worked out on the 15k, "We will NEVER AGAIN have a problem trying to stay cool in this coach". She liked that.
More pics for above info...
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