Coleman A/C fan upgrade - 6 blade to 3 blade

[Jupiter]

Yeah, I think I'll just make my own support bracket rather than deal with them again. I've got sheet metal, exterior double-sided tape and the ability to design and engineer such a complex component The only missing detail is the overall height of the bracket. Anyone know of an available schematic that details the dimensions? If not, I may have to (sniff, sniff) call RVP for the info.

I'm following the several steps of your tutorial so I'll let you know how it turns out. My work begins tomorrow when I bring the coach to the house. Weather permitting, I should be finished by the end of the weekend if the cookouts and the wine don't steal too much time away.

cheers,
Joopy

[Old Crows]

Joop, if you can wait a couple-three weeks I'll measure mine. Got a new fan kit ordered but by RVP "express next month delivery" it won't be here for 10-14 days. Heck...might get lucky and if they haven't changed the support, I'll send it to you. Although it would be simple to make.... Just hang on and let's see what's in the box.

There's another MacGuyver I made on the AC. Inside the plenum. It suffers from very sharp bends, 90* corners, and dead ends in the air return. That makes noise and screws up the air flow. I created a turning vane out of some styrofoam so the air has a less torturous path to the intake. Cut to fit and cover it with foil tape. Use foil tape to hold it in place. Also, used foil tape to seal off the horrid openings from the pressure side that was allowing conditioned air to recirculate directly back to the intake.

Coleman really has some crappy engineering and miserable execution. Reminds me of my in-laws '66 Chrysler. The 440 wedge engine and torqueflyte trans were excellent. The rest of the car was a "Kit" that required constant attention. MPG sucked....but it would go like a spotted ape!

[Jupiter]

Thanks Old Crow for the additional tips. I be sure to check out the partition between the supply and return plenums. In fact, I recall an older post from Jesse (JBMSR) on the Winnie forum about that very issue.

Waiting a few more weeks isn't an issue. We've got a week long trip next week and nothing else until mid-August. Sure, if you get an additional set of brackets we can make a deal to get them here if you don't mind.

cheers,
Joopy

[Jupiter]

Well, finally had the weather cooperate long enough to get on the the roof to try to quiet the two Coleman beasts. Based on the tutorial from Old Crow and other suggestions, this is what I did to both units in about 4 hours:

- confirmed that I have the "D" series 3 blade condenser fan.
- lightly sanded the "burr" off of the leading edge of the condenser fan blades
- lined the bonnet with dense roofing tape
- added foam pipe insulation to the compressor suction line where it contacts the bonnet.
- removed evaporator fan housing to inspect the squirrel cage fan for debris.
- inspected the foam gasket between the supply and return plenum (good to go)
- inspected the compressor isolator mounts and the entire unit isolator mounts for proper function / compression.
- added 1/4" closed cell adhesive foam to the evaporator fan housing to help with contact to the bonnet.
- added adhesive foam to close various gaps on the evap fan housing.
- pulled the wiring bundle back with wire ties from the face of the evaporator coil to help with return air flow

Bottom line.... the units are definitely quieter than they were. IMHO, I still think they are above average for interior noise. The bedroom unit still has a significant vibration which I could only reduce by jamming a wooden shim between the metal junction box and the evaporator fan housing. Sorry, no picture. Once unbolting and removing the evaporator fan housing, I noticed the evap fan housing is simply a plastic two piece clam shell that lifts right off with no fastener and the squirrel cage fan is all plastic with no balance weights at all. The fan is simply hanging on the end of a long motor shaft. At this point I can't tell for sure if the vibration is caused by the high speed condenser 3 blade fan or the squirrel cage evaporator fan. Ran out of time but my next step is to remove the 3 blade condenser fan and run the unit for a moment to see if that is the cause. If not, then the evap fan becomes the culprit because I know the compressor is not the cause. If it is the evaporator fan causing the vibration I will then have to replace the entire motor and fan assembly because it could be a slightly bent shaft or imbalanced fan which in either case are beyond my in-house repair capabilities. BTW - another clue that the evap fan may be the culprit is the fact that the motor capacitor is bolted on to the motor frame and I found the capacitor mount was broken off which I suspect was caused by vibration. See first pic.

Here's a few pics of the process. Thanks folks for all the help

[Jupiter]

One more pic. Oh, and the evaporator housing had foil face 1/2" fiberglass insulation on the inside but I still added 1/4" dense foam on the outside to help with noise and to help insulate.

Cheers,
Joopy

[Old Crows]

Jup, good job! The more I see of Coleman... I'll say no more.....


It's never going to be perfect... But much better... Still we're making a silk purse out of a sow's ear....

[Jupiter]

Yeah, I never suspected the A/C's would be such a big deal. But, when spending as much time as we do in the coach every year, it has become a significant annoyance. This latest effort has helped take away the rub. Thanks for posting your effort Old Crow.

Actually, I'm on the road right now for 5 days field testing the mods and boy is it ever hot and humid. Should get plenty of run time on the A/C's.

cheers,
Joopy

[Old Crows]

Is it possible to relocate the capacitor from the motor to the housing to remove the small amont of mass on the motor?

Very difficult to balance that squirrel cage on a stick.... The trick would be to look at the motor mounts. Too soft? Too hard? Probably not worth a lot of effort.

I also found another source of noise/vibration not related to the A/C. Inspect the generator's installation. I found a screw head on the side of the generator hard against a frame member. Loosening and shifting the generator with a big lever achieved several mm clearance. Every little bit helps.

[zman-az]

I was thinking of using spray on bed liner for the AC Cover vs the foam foil tap. The foil covering to me is a flat hard surface that would reflect sound vs the inconsistent soft texture of the bedliner. Probably some better stuff out there but bedliner in a spray can is easy to find.

[Old Crows]

Originally Posted by zman-az

I was thinking of using spray on bed liner for the AC Cover vs the foam foil tap. The foil covering to me is a flat hard surface that would reflect sound vs the inconsistent soft texture of the bedliner. Probably some better stuff out there but bedliner in a spray can is easy to find.

The foil faced butyl tape was suggested by a local hot rod/stereo shop. Does the same thing as the expensive sound deadening material (Dynamat) but oodles & oodles cheaper. It's also easy to work with.
Aside from the heat reflecting property of the aluminum foil... it reflects energy away from the inside of the "box" when its in the sun ... and should, in cold weather, reflect heat back into the "box." The soft butyl material absorbs vibration and adds damping mass to light weight bonnet despite the slight offset of the foil. And, it resists heat transfer.


If the spray on was soft and thick enough it would also act as a mass dampener and maybe insulate a bit. Any bed liner I've see is quite hard. If you can get it to permanently stick to the smooth plastic a spray on foam insulation would work but may not provide enough "mass" in a thin coating. Any flexing of the bonnet may cause it to work loose.





Interesting idea.... Worthy of some thought.

[Jupiter]

latest update:

Just returned from a 4-day field test after doing the A/C modifications. Yes, the rooftop units are a bit quieter but it appears that my efforts have simply buffered the symptom (noise/vibration) and have not addressed the root cause. I still have the annoying harmonic vibration (think RUM...RUM...RUM...), and its pronounced enough that I can actually feel the harmonic vibration on the sink countertop, shower door rattle, towel rack, etc. Vibration like that takes its toll on everything sooner or later.

So, today as a test I removed the 3-blade (D series) condensor fan and briefly ran the A/C unit. The vibration was virtually completely gone. It appears as though the high speed condensor fan is the culprit. The small hp, high RPM fan motor (perhaps 3,450) is solidly mounted on three thick rubber isolators that have no adjustment especially given that there is less than a quarter inch clearance between the fan blades and the metal J-box. Frankly, IMHO I think the solution is a lower speed condenser fan motor with a larger, slower fan that moves the same CFM is the solution but that's not going to happen on this model. This high speed condenser fan design simply creates too much jet-like air noise and the high RPM motor tends to amplify the smallest of imbalances in the shaft or fan which creates the vibration.

The cooling performance is fine. So, at this point I'll have to sort through the remaining options and continue to search for more solutions.

1) Work with Coleman engineering to resolve the issue.

2) Work with Winnebago for a replacement solution. Recently checked out a 2016 Adventurer with a slightly different looking rooftop unit (probably Coleman) that was slightly noisy outside (but acceptable noise level) and the inside was softly quiet in terms of air noise and had no noticeable vibration at all. I was so envious

3) Go back to the 6-blade condenser fan which creates obnoxious noise outside but is much quieter inside in terms of vibration.

Well, that's about it for now. And the the quest goes on...

cheers,
Joopy

[Old Crows]

Well Dang! We noticed a real reduction in that "thrum-thrum-thrum" on the inside. Almost gone! Since you've isolated the vibration to the condenser fan....that is progress. It is solidly -more or less- attached to the AC's base with rubber feet as you said. Since the motor and fan are mounted vertically, it's going to be hard to fix any vibration or oscillation in that set up. Much like the fan on a stick evaporator motor...really hard to balance.

Maybe we are getting some wonky vibration due to "wobble" in the motor/fan set? Early prop jet Electra engine whirl mode failure comes to mind. That could also explain unusual motor mount failures and blade strikes.

Might have something to do with the unit's location on the roof and any reinforcement (or lack of) and sound deadening in the roof.

Still, ours seems more noticible when the compressor is running just after starting the unit. Seems less obtrusive once it has run for awhile.

Waiting for my "D" fan to arrive and will investigate further. First thought would be to fab a 'strut/stabilizer' from the motor to the base to give it more stability.

Nevertheless, ALL these issues should have been resolved before the product was fielded....

[Old Crows]

joop, do you recall how close the fan motor is to the electric box? Could it be occasionally touching? Simple fix might be some foam pipe insulation wedged between the motor and the box....

[Jupiter]

Old Crow, the fan blade doesn't appear to be ticking the box. Wish it was that simple. I'm afraid that adding a solid stabilizer may just transfer the vibration to the anchor point but may be worth a try. Right now I've added a wedge of wood between the J-box and the indoor fan housing which helped quiet the vibration a good bit, but again not treating the root cause.

I think my next step is to reinstall the 6 blade to see how that reacts. Got the rig back in storage for a few weeks so it'll be awhile for the next update. At this point I welcome the break between trips.

cheers,
Joopy

[Old Crows]

You would be correct about vibration transfer.... I'd MacGuyver some thing with rubber buttons under the strut/frame attachment point as an insulator.

Wedgies?! That woody wedge may be part of the problem. Wood will transfer fan & motor vibes to the J-box and then to the base. Try none. Or, try something softer like a piece of thick grey tube pipe insulation jammed between the motor and the j-box. Make sure it's secured well! so you don't FOD the fan!


And check the A/C install to see that the main gasket is not over compressed.


Again, ours has a slight vibration and thrumming (no worse than the two other RV AC units I've had) when the compressor is on. More so when first starting the unit. Almost none when it's been running forms short time. And, the hard starting & shut down "thump" is now quite reduced.

((I could spin you a "vibration" yarn about an 8 hour flight across the north Atlantic as a military BRAT back in 1961 in a war weary DC-7B. Hour after hour of unsynched props. The guys in the office were doing the best they could I'm sure. But, you could see a vibration develop in the bulkhead at the front of the cabin. It would get worse and worse and then begin a slow stroll through the main cabin jiggling and vibrating everything...including you. It would mosey out the tail some place and disappear. Several minutes of calm.. then... a very slight wiggle in the bulkhead.... 8 hours, Bud! So, that's my standard....))

[ernieh]

Old Crows has finally mentioned what I think is the real problem. It's not a "vibration" as such, but it is the result of two fans rotating at close to the same speed. I suspect that the 3 blade fans changed the condenser motor speed just enough to cause the "rum rum" slightly out of sync harmonic.


Has anyone tried changing the speed on their inside fan (hi to low or low to high) to determine if it makes any difference. I don't have Mach8's on my MH, but I never have found it necessary to use the hi speed. It just seems to make more noise without changing the actual cooling.

[Old Crows]

Originally Posted by ernieh

Old Crows has finally mentioned what I think is the real problem. It's not a "vibration" as such, but it is the result of two fans rotating at close to the same speed. I suspect that the 3 blade fans changed the condenser motor speed just enough to cause the "rum rum" slightly out of sync harmonic.

Has anyone tried changing the speed on their inside fan (hi to low or low to high) to determine if it makes any difference. I don't have Mach8's on my MH, but I never have found it necessary to use the hi speed. It just seems to make more noise without changing the actual cooling.

Makes little to no difference on mine. "Hi" speed tends to muffle the 'back beat' but it is still there. Much less so with my mods. It's something to do with either the condenser fan, the evap fan, the compressor, or wonky mountings of all the above. I'm open minded about it but would like to definitively put an end to it.... or at least understand the cause.

IMHO, I've pretty much killed the noise from the fans and vibration from the bonnet. I'm happy with that inside and out. The only time I notice the 'thrumming' it is when the compressor is running. Thus, a more careful look at compressor mountings and pipes to/from the condenser and evaporator when I get up on the roof to replace my "C" fan with the "D" version in another couple weeks.

Yes, "Hi" does help speed cooling if the RV is heat soaked by getting the air moving. It does need to be turned to 'Lo' after awhile as it's moving too much air too quickly over the evap to move the temps and humidity down to a more comfortable level. Sort of like your 'automagic' air conditioner in the car.... it goes to high blower until the temperature begins to drop and then the fan starts to roll back once the AC has a handle on the temperature.

Got to say that I have a Mitsubishi "Mr. Slim" unit installed in my workshop. You can go out there and punch it on and in a short time you can hang meat in the shop. Once it gets to cooling the fan rolls back and you can hardly hear it. If it can't keep up it rolls up the fan and compressor to meet the need. Of course the very small compressor/condenser unit is out side the shop wall. But even that is so quiet you really have to check to see if it's running as it is nearly silent. It starts silently and throttles the power consumption based on cooling/heating needs.

Coleman needs to take a few tips.... NAH!! Just jokin'! Mitsu should get into the RV aircon biz.... I'd buy one in a heartbeat.... not even looking at the price tag.

[Jupiter]

Thanks guys for the continued thoughts. Yup, I agree. The wood wedge certainly isn't a material that should absorb vibration but I jammed it in there while on the road just as an experiment and for one reason or the other it made a significant difference.

I did check the compression of the unit mounts to the gaskets and roof and it appears to be typical. The gaskets are compressed but not squashed and there is room to further crank the isolator bolts. I even tried to squeeze some foam pipe insulation between the unit and the roof under the compressor and condenser fan area but it didn't make a difference.

Switching from hi fan to low fan helps quiet the indoor fan noise but does nothing for the vibration since the condenser fan (and compressor) still run at full RPM.
Besides, our 36M with two rooftops need all the cooling it can get in full sun to maintain indoor temps in the 70's. I just ordered a Magna Shade to help reduce solar load.

Old Crow, I'll be interested to hear how your unit reacts when you install the D series 3-blade. I'm really skeptical that this fan is the prime culprit. FWIW - the exterior fan noise is no longer a problem which is something good to cheer about. I'm sure our camping neighbors will appreciate it

cheers,
Joopy

[Old Crows]

Exterior fan noise way down!!! YEAAAAAAA! Which was the start of this big fat mess.....

[Old Crows]

Gud Newz, I identified the source of the noise & vibration.

Baaad Newz, ain't going to be a easy fix........

Had reason to visit Calypso to check the fit of a shelf I'm making. Hot. Muggy. Fired the genny and the AC. After it was fully warmed up ( or cooled down) I decided to do some testing. With the compressor and fans running... circulation fan to "ON".... I put my fingers very lightly on the return grill. I could feel a cyclic vibration and hear a rumble that coincided with the vibration.

I turned the thermostat up to turn the compressor & outside fan off. I could feel/hear the vibration/rumble with the circulation fan running!!! It's in the circulation fan! Yeaaaaa!

Needing confirmation, I turn the fan from "ON" to "AUTO"..... Keeping meh pinkies on the return grill!!!!!! I could feel the vibration start to slowdown and get a bit stronger as the fan's RPM bled off. It eventually stopped completely shortly before the fan stopped turning. It's very similar to the feel/sound of a bad bearing or out of balance spinning thingie.

If you switch the fan back ON, you can feel and hear the vibration/rumble as it spools up and the periodic vibration returns at high RPM.

So, it's the circulating fan, Guyz!!!!!!

A fix is going to take some thought ... If it is at all possible. Basically, it's a squirrel cage on a stick cantilevered off a single motor mount. Could be poorly balanced; impossible to balance; or poorly engineered mountings/ material.

It's going to take a major grey cell effort to MacGuyver a solution.