AC cools a bit but not like it should - Fiberglass RV


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Old 10-08-2015, 01:57 AM   #1
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Name: denny
Trailer: 2001 Scamp 16 layout 3
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AC cools a bit but not like it should

AC on a scamp trailer cools but owner said it is not what it should do on a really hot day. Trailer is 13 years old but not sure if AC was perhaps added later. Thinking it might have been since it is toward the front of the trailer a few feet from an escape and vent hatch. It also has a 3" hole in the shroud on top which I could perhaps repair. Any advise ?????
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Old 10-08-2015, 08:01 AM   #2
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Roof top RV A/C units covers are, basically, cosmetic. The cooling circuit is contained within it's internal ducting. A hole in the cover shouldn't make a huge difference in cooling capacity. Check the temp output, I would be looking for at least 18-20 degrees below ambient. Of course you could always just have a clogged air filter or a very dirty/clogged condenser on top


That said, they do occasionally leak Freon and the result is poor cooling. Unfortunately, almost all of these units were not designed to be recharged and the end result is that it is usually a better bet, $$$ wise, to just replace the unit.


I have seen posts indicating it being close to $200 just to install the charging ports and recharge the system, and you will still have a 13 y.o. unit.
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Old 10-08-2015, 09:06 AM   #3
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"Not what it should be" is a judgement call. Reducing the temp inside the trailer by 20 degrees on a 100 degree day might be OK with one person and unacceptable to another. The AC in my trailer will reduce ambient temp by 33 degrees and on a really hot day, I would still like more. To really check the function of the unit a digital thermometer will give you the answer.
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Old 10-08-2015, 09:30 AM   #4
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We have only a 5000 btu Air Conditioner and find it adequate to get the temperature to 80 F on a 90+ day. The removal of the humidity and the lowering of the temp seems to be enough to make us comfortable.

Our AC sits in the bottom of the closet. We have a portable 12 volt Endless Breeze fan to move the cooling air around. We usually set the fan on or near the couch and blow air towards the rear of the trailer.
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Old 10-08-2015, 09:40 AM   #5
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Name: Darral
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My Scamp has the roof-mounted Coleman Polar Cub. 9200 btu. Bringing the temp down has ONLY been a problem when the gas stove burners were active. Otherwise, my A/C has no problem in southern temps in the 90's keeping it apx 78 deg.

To check:
I have a digi thermometer that has an external probe attached. As mentioned in a previous post, you have to compare two different temps. I let the probe rest in the filter area and record the temp. Then I let the probe rest at the outlet vent. I've ALWAYS had 15+ (usually higher) deg. difference between the two. I do the same with small room A/Cs AND my central unit in my house.

If it's less than 15 deg difference, I would say it's low of freon. With that old of a unit, I would replace it. That way, you will get all new seals as well as a new unit with a new compressor, fan motor, coils, wiring, housing, insulation......
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Old 10-08-2015, 11:35 AM   #6
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Mobile is fairly hot and humid and the 9000 BTU mini-split I installed will keep it cooled down to 70*F inside and still not really break a sweat doing it.
Of course it is not the typical trailer A/C system by any means.
22 SEER heat pump and VFD inverter works great. Also of course I have not yet beat the thing over the road either.
It is more complicated and more plumbing involved, but it doesn't weigh much (if any) more than a roof top unit and the majority of the weight is fairly low.

In my experience if you check the current draw when it is putting out max cooling the current should be close to the max rating and if it is low the Freon may be low. Otherwise the charge should be close.
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Old 10-08-2015, 11:54 AM   #7
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JD, I've seen your installation...quite nice may I add. But, I'd love to know what it weighs. My Coleman 9200 btu weighs 96 lbs (according to specs). BUT, one thing about mine, it's centered over the axle. Have you seen any issues mounting it near the tongue?

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Originally Posted by redbarron55 View Post
Mobile is fairly hot and humid and the 9000 BTU mini-split I installed will keep it cooled down to 70*F inside and still not really break a sweat doing it.
Of course it is not the typical trailer A/C system by any means.
22 SEER heat pump and VFD inverter works great. Also of course I have not yet beat the thing over the road either.
It is more complicated and more plumbing involved, but it doesn't weigh much (if any) more than a roof top unit and the majority of the weight is fairly low.

In my experience if you check the current draw when it is putting out max cooling the current should be close to the max rating and if it is low the Freon may be low. Otherwise the charge should be close.
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Old 10-08-2015, 12:34 PM   #8
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Darral T.

The mini-split weighs about the same. the condenser goes about 63 lbs. and the inside unit abut 16 lbs and then add the weight of the lineset to that for about the same total.
The weight is distributed to some extent front to rear since the condenser is in front of the body and the inside unit in the rear. There is some bias toward the front overall.
I can't say that there is an issue with the mounting or not yet, but soon!
My 16' Scamp is mostly just the rear half of the frame and the shell. Everything else is new or modified to some extent.

I have tried to keep the heavier items during the initial part of the build near the axle and toward the front and the frame has been extended about a foot to lessen the tongue load and increase the stability.
I do have more between the shell and hitch than I want, but I couldn't find a better place to put it with my layout.
I am at 300 lbs tongue load without the battery installed (behind the axle) or the bed frames and storage bins installed and loaded.

My goal is to be at 200 lbs and 26-3000 lbs total and perhaps 8% on the tongue.
All of this will have to be figured out further into the build. All I can go on is my estimates currently, but this is easier than the airplanes I used to work on and less critical as well.

My best guess is that my "super Deluxe" 16' Scamp will weigh in on the heavy side which is why when I bought the axle I had it built for 3000 lb. and changed to 14" wheels and tires from the 13". I thought the 13" were a little marginal for the application.
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Old 10-08-2015, 01:25 PM   #9
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FWIW, you want 10-15% Tongue weight. At 8%, I'd be a little concerned about "sway" on the 16'er. Just a thought and something to beware of.

I fly model planes and am fully aware of CG's. A bad CG? (Tail-heavy) Yep, usually a tip-stall right into the ground!

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Darral T.

My goal is to be at 200 lbs and 26-3000 lbs total and perhaps 8% on the tongue.
All of this will have to be figured out further into the build. All I can go on is my estimates currently, but this is easier than the airplanes I used to work on and less critical as well.

My best guess is that my "super Deluxe" 16' Scamp will weigh in on the heavy side which is why when I bought the axle I had it built for 3000 lb. and changed to 14" wheels and tires from the 13". I thought the 13" were a little marginal for the application.
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Old 10-08-2015, 02:45 PM   #10
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Quote:
Originally Posted by Darral T. View Post
FWIW, you want 10-15% Tongue weight. At 8%, I'd be a little concerned about "sway" on the 16'er. Just a thought and something to beware of.

I fly model planes and am fully aware of CG's. A bad CG? (Tail-heavy) Yep, usually a tip-stall right into the ground!
I've towed with 7.5% for about 8 years and never had an issue towing with our Honda CRV and Honda Odyssey.

I do try to keep heavier items centered over the axle of the trailer and light items front and aft. As well I keep heavy items over or in front of the rear axle of the tow vehicle. Lastly we raise the pressure of all tires but particularly the rear tires of the tow vehicle, trailer tires are always inflated to maximum cold pressure.

We have towed with and without an anti-sway bar for considerable distances and not seen sway. We tow at no speeds higher than 62 mph and generally in the 55 to 60 range. We also don't travel in bad weather and would not no matter the tongue weight.

Since you're a Scamp owner, we also carry a half tank of fresh water at all times and generally empty or nearly so grey and black tanks.
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Old 10-08-2015, 02:54 PM   #11
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Name: Darral
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I dont know where the "thresh hold" is Norm. But I do know I've read where people add bike racks/bikes to the rear of their 16's and start having sway problems. The issue there for us is, we dont know what their current "tongue weight" is when that happens. It would be nothing short of interesting TO know though just for future reference.

Also, for anyone interested in just how much additional weight could be behind a 13's axle: with the WH (6 gal), grey tank (max 18 gal it will hold- I've checked mine) and fresh (12 gal); you're looking at a potential 288 lbs!! With the BLACK tank thrown in but with this in the front (9 gal), you're looking at a potential 360 lbs added to the lil Scamp! I dont tow with full tanks- never have!

Quote:
Originally Posted by honda03842 View Post
I've towed with 7.5% for about 8 years and never had an issue towing with our Honda CRV and Honda Odyssey.

I do try to keep heavier items centered over the axle of the trailer and light items front and aft. As well I keep heavy items over or in front of the rear axle of the tow vehicle. Lastly we raise the pressure of all tires but particularly the rear tires of the tow vehicle, trailer tires are always inflated to maximum cold pressure.

We have towed with and without an anti-sway bar for considerable distances and not seen sway. We tow at no speeds higher than 62 mph and generally in the 55 to 60 range. We also don't travel in bad weather and would not no matter the tongue weight.

Since you're a Scamp owner, we also carry a half tank of fresh water at all times and generally empty or nearly so grey and black tanks.
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Old 10-08-2015, 03:19 PM   #12
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As is seemingly being alluded to, where the weight is located can be as critical as the total weight/tongue weight ratios.


Adding weight towards the back to offset excessive tongue weight will be entirely different than that same weight over the axle as Norm practices.


I added a very heavy BAL leveling jack set to the back of my Hunter and, although the tongue weight was still almost at about 11-12% % of total weight, it was a case of tail-wagging-the-dog from the start and I had to take them off.


In short, adding weight to the back isn't a way to balance what may be a heavier than desired tongue and can lead to the canine like condition mentioned above.
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Old 10-08-2015, 03:39 PM   #13
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There are tow issues. Of course one is the CG and percent loading on the tongue and the other is the polar moment of inertia.
Polar moment is the concentration or distribution of weight from one end to the other.
Weight concentrated at the axle has a low polar moment and distributed to the ends has a high polar moment.
The high polar moment takes more to start an oscillation, but more to stop it as well.
Since the trigger is usually from some outside source the damping must be from the towing system itself.
A longer tongue helps damp the oscillations and the lower polar moment helps as well.
Also as Norm stated the stiffer sidewalls also helps both prevent and control the oscillations.
If the polar moment were very low then the tongue weight could also be very low as well, but zero is not possible so 8% it is.
It is likely that when the rule of thumb was developed mos were towing with old pickups that were very light in the rear end and the extra weight helped the handling, but today the suspensions and weight distribution is better.
Rules of thumb had their origins somewhere, but that doesn't mean that they apply in every case, however unless the TV rear suspension is overloaded or the handling is degraded to where the handling changes from understeer to over steer below .3 G side loading there is safety in error in this direction.
Hard to question erring in the direction of probable safety.
Personally I agree with Norm on this with a modern front wheel drive car or van. If you have a nine passenger lifted van with long overhang and soft tires it won't be safe anyway so higher tongue weight might help.
Since I failed to answer the question of threshold the correct answer id included above.
The TV and trailer must not change from understeer to oversteer at less than .3 G of side loading. And the system must be damped to where oscillations decay withing two oscillations. Every TV - trailer combination has a critical speed where the damping has decreased to zero and beyond that speed the combination will be unstable.
I have noticed that with my VW JSW the combination is well damped and very stable, probably because of the IRS and negative camber with toe-in at the rear.
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Old 10-08-2015, 05:00 PM   #14
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Could we please stick to the OP's request regarding their A/C concerns. Thanks.
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