Air conditioner mod?

finally got into it yesterday. Found a couple of things that needed sealing, nothing huge but cumulatively it was quite a bit. A little duct tape and pressing down the existing stuff and much better. Seemed to have better temp. drop after I was done but it was late in the day. For sure worth the 30 minutes it took.

DutchmenSport wrote:

nayther wrote:
...Took some foil tape and sealed between the two plenums and it helped A LOT!

I did the same thing, not knowing what I was doing, just made obvious sense to do it since air cold air was being sucked right back into the AC and not forced out into the living space. I used aluminum stove pipe tape (extremely sticky and meant to be used on gas water heater or gas furnace flue pipes). So the tape will never be a problem. Once all the holes were plugged, BIG, BIG change in air output!

Good tip here! Easy fix and costs nothing but some tape.

We changed the older 15k Coleman AC in my in laws camper to a new 15k Coleman and had to tape the insulated divider in. My original plan was to seal off all the holes but after I got the units switched out I wanted to make sure it ran before I did anything else and it blew the divider out. I had to tape it in just to run the unit. Luckily I had a full roll of foil tape.

sjturbo wrote:
I recently saw a ytube vid on cutting out the plastic "grill" on the fan output side of the condenser and replacing it with metal lath to improve air flow and thus improving the efficiency of the air conditioner. Has anyone tried this? And did you notice any difference?

One of the real reasons for the mod is to make the Coleman Mach 8 quieter. They sound like an old turbojet taking off, and are real annoying. the rounded "BBQ" grill grid smooths the airflow and helps with the sound level.

The kit is marketed strictly as a noise reduction kit.

http://www.perfectcasita.com/ma8norefukit.html

Individual parts of the kit, link below.

http://www.perfectcasita.com/fred.html

Charles

nayther wrote:
AC is my business

Yes, increasing air flow across the coil will reduce head pressure, thus reduce suction pressure making the air colder, to a point. I'd like to see accurate before/after air flow readings, not "modeled" with a little 12 volt fan. CFM and static pressure (that's the pressure loss across the louvers he's reducing) are not a linear relationship. The proof really is in the reduction of head pressure and there is no before/after reading.

I found a big installation error on my last rig and this reminds me to check this one. When they installed the ducted conversion on my last one they did not seal the supply and return plenums properly, meaning a lot of air was just short cycling between supply and return, not getting to the space. Took some foil tape and sealed between the two plenums and it helped A LOT!

Not an A/C "spurt" by any means, but your first point makes sense and one needs the actual facts and not just "seat of the pants" WAGS. As to the second one, that IMO is probably much more common and I have heard of issues concerning the poor sealing of the supply plenum both to the ducts and between it and the return plenum.

Larry

This is a mod that I found on another forum: http://www.irv2.com/forums/f121/coleman-mach-ac-mods-350816.html
It made a great difference in initial cooling down and also on very hot days. The vent used was too thick for my dometic so I used an marine inspection port. It has a screw in cover,not the louvers. I was very please with the results.

Nice to see so many have thoughts on the matter. I have had a few different makes and models of trailers and one 5er. They all have lacked quality in construction. That said I do enjoy the diy aspect of finishing what was started,(to a point). Good thing the auto makers are regulated or we would all be broke down on the side of the road!
BTW the duct tape is a must on all ducting, vents and returns.

I agree with nayther. It is doubtful that there would be enough airflow increase (if any) to make a difference. Also over the long run the fine mesh can load up with dirt and actually reduce the airflow. Addressing the interior duct sealing and design will yield bigger rewards.

DutchmenSport wrote:

nayther wrote:
...Took some foil tape and sealed between the two plenums and it helped A LOT!

I did the same thing, not knowing what I was doing, just made obvious sense to do it since air cold air was being sucked right back into the AC and not forced out into the living space. I used aluminum stove pipe tape (extremely sticky and meant to be used on gas water heater or gas furnace flue pipes). So the tape will never be a problem. Once all the holes were plugged, BIG, BIG change in air output!

Good tip here! Easy fix and costs nothing but some tape.

Yep, sealing the "ducting" inside the A.C. unit made a HUGE difference on mine as well. For those who might be doubting it, consider how poorly RV's are built and adapt those same poor techniques to sealing the A.C. ducting. I actually removed all of the A.C. vents and sealed the "ducts" there as well.

Mid July in Moab where outside high temps were 105f - 108f and inside my TT was 75f. I do need to mention the TT was mostly shaded by large trees.

Not to say the mod this thread is about won't have an impact too, but don't think that this airflow mod is the only thing that needs to be done to correct poorly constructed RVs... which is all of them.

nayther wrote:
...Took some foil tape and sealed between the two plenums and it helped A LOT!

I did the same thing, not knowing what I was doing, just made obvious sense to do it since air cold air was being sucked right back into the AC and not forced out into the living space. I used aluminum stove pipe tape (extremely sticky and meant to be used on gas water heater or gas furnace flue pipes). So the tape will never be a problem. Once all the holes were plugged, BIG, BIG change in air output!

Good tip here! Easy fix and costs nothing but some tape.

My 92 Coleman came with shroud designed so that the compressor coils were open with nothing covering them. Not sure why they eventually changed the design.