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Old 04-22-2013, 05:29 PM   #1
Redward
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Cougar Lite Furnace issue

I just bought a 2013 Cougar Lite 28RDB. I was not impressed with the heat and flow from the vents. I am upgrading to a 40,000 BTU furnace and asked the dealer to drop the belly pan. There seems to be an excessive amount of 3" vent tubing required to feed the bathroom and bedroom vents. The tech suggested removing the 40' of 3" and doing a straight run with 1 1/2" ducting. To balance the flow, adjustable floor vents will be used in the back vent and living room. Any opinions?
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Old 04-22-2013, 06:02 PM   #2
SteveC7010
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Originally Posted by Redward View Post
I just bought a 2013 Cougar Lite 28RDB. I was not impressed with the heat and flow from the vents. I am upgrading to a 40,000 BTU furnace and asked the dealer to drop the belly pan. There seems to be an excessive amount of 3" vent tubing required to feed the bathroom and bedroom vents. The tech suggested removing the 40' of 3" and doing a straight run with 1 1/2" ducting. To balance the flow, adjustable floor vents will be used in the back vent and living room. Any opinions?
(My Dad was a plumbing and heating contractor so I grew up around these systems. RV heating is almost identical to forced air heating in a residence.)

Smaller ducting will not solve the problem. If there is an excess of 3" ducting, remove the excess, but don't downsize. The size of the ducting is directly related to the amount of air that can be moved through it. The furnace's fan can only move so many cubic feet of air per hour. If you reduce the size of the duct, you restrict the air flow.

Your plan for adjustable floor vents is sound. That allows you to balance the air flow throughout the trailer.

If it were my wallet on the line, I'd invest in a duct fan or two first before spending the money on a furnace upgrade.

As I have said in several previous threads, part of the problem with RV heating systems is that they are full of leaks, mostly in sloppy connections. I accessed my furnace and plugged up all kinds of leaks on the distribution box alone. There were several loose connections where the ducting meets the box. The covers of unused duct outlets were loose and flapping. I used HVAC tape to seal things up and noticed an immediate improvement in air flow at all the vents.

The cold air return is usually a single opening in the base of a wall or cabinet by the furnace. Any obstructions there will reduce air flow back to the furnace. Also, if your furnace is in a dead space that has other areas to it, that will further reduce cold air return to the furnace because the furnace is drawing intake from dead spaces rather than from your living areas.

Some of the Keystones use solid wall ducting under the floor rather than the round dryer vent stuff. Many folks have reported here that they have found crushed ducting or large leaks of some kind. My Cougar has heat duct to the front bedroom that are just a sheet of tin pop-riveted to the aluminum floor joists. Not a bad way to do it, but there is considerable air leakage along the edges. More HVAC tape to the rescue.

By using tin ducting or the dryer vent stuff, there is a lot of heat loss out through the wall of the ducts in the basement or storage areas and in the under belly area. If the under belly is not pretty much totally enclosed to be almost air tight, that heat loss is increased. Since some of us need some of that heat loss to prevent freezing of pipes and tanks in the under belly and storage areas, insulating the ducting is an individual decision. I will probably insulate some or all of mine in the underbelly since we don't use the trailer in freezing weather. I may hold off doing the ducting in the basement because that provides some warming of the bathroom and bedroom floors.
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Old 04-23-2013, 08:02 AM   #3
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Steve basically summed it up. I wouldnt reduce the size of the duct work. The increased un-insulated duct length is there for a reason (underbelly heating as told to me by the manufacture)
Installing adjustable registers and sealing system leaks should help your problem.
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Old 04-23-2013, 09:35 AM   #4
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Though it is just my opinion, I tend to doubt if the extra flexible duct length is present for underbelly heating. The flexible ducts on my Alpine were the "insulated" type. And while the insulation of these flexible ducts is questionable, it adds little to the heating of the uninsulated underbelly. It appears that the additional duct length is actually the use of standard length ducts - 10', 15', etc. It would probably cost more in worker-hours to custom cut and fit the flexible ducts rather than just use a 10' duct to span 5' of space.

If one checks some of the modifications I did on the Alpine mentioned in previous posts under Mods, I removed some 5' of 6" flexible duct between the distribution collar through the floor and the kitchen vent. One reason to remove this extra length was that the shorepower cable was resting on one of the horseshoe bends of this duct and crushing it - thus limiting heated air distribution. I also found the two flexible ducts that distributed heated air to the rear of the Alpine were crushed under the fresh water tank. Once I corrected these problems, the standard Suburban furnace heated the Alpine quite nicely!

Honestly in my own opinion, I would check the flexible duct work in the underbelly for "crush points". I wouldn't change the size, etc., of the flexible ducts, but I would remove the extra lengths.

On a similar note, it was also apparent that sometime during the build, when the door-side hydralic piston was tested to move the slide, the pistion "blew up" - probably around a connection fitting. My Alpine had a "strange piston" that did not match the other pistons, and there were hydralic fluid drops and pools throughout the rear underbelly. There was also hydralic fluid soaking the insulation of the flexible duct that connected to the kitchen vent. Though I cut about 5' of duct off, there still was some "fluid wetting" left in the insulation. After the warranty period of a year, when one drops the coroplast and examines the underbelly, it is surprising what one finds!

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Old 04-23-2013, 12:48 PM   #5
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How are you guys getting access to all this stuff? I have been reading these posts for sometime as I have never been close to satisfied with how my Cougar 5th wheel heats the bathroom and bedroom. I assumed I would just have to live with it (cooling too sucks in the bedroom but that's another matter). I think I should at least explore the extra and unsealed duct theory to see if I can get some improvement. Oh, the adjustable floor vent solution as well.

Anyway, can I gain access just through the pass through storage compartment? Do you actually crawl around in there?

So sorry for hijacking your thread.
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Old 04-23-2013, 03:48 PM   #6
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Originally Posted by Poppy's 5th Wheel View Post
How are you guys getting access to all this stuff? I have been reading these posts for sometime as I have never been close to satisfied with how my Cougar 5th wheel heats the bathroom and bedroom. I assumed I would just have to live with it (cooling too sucks in the bedroom but that's another matter). I think I should at least explore the extra and unsealed duct theory to see if I can get some improvement. Oh, the adjustable floor vent solution as well.

Anyway, can I gain access just through the pass through storage compartment? Do you actually crawl around in there?

So sorry for hijacking your thread.
No hijack! Your question is a reasonable part this topic.

In the basement of my fiver, there is a panel which forms the rear wall. By removing that panel, I fully exposed my furnace and distribution box. If your furnace is just rear of the basement, it's probably the same. Regardless, there should be some kind of removable panel at the furnace.

The ducting that runs under the main floor of the fiver can only be exposed by dropping the coroplast belly. You may not have to drop it all, but probably one side the length of the trailer. Or you may want to cut access flaps here and there. That procedure is extensively discussed in many older threads. Either will work well.
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Old 05-08-2013, 02:47 PM   #7
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fixed

I got my Cougar Lite back this week, with the new 42k BTU furnace; Big difference in air flow. I had the dealer pull all of the ducting, shorten it where possible, and tape all connections. Fired it up this morning 40°f to 65° took 40 minutes. It should keep the trailer warm, in the mountians, even though it was not designed to do so. Still a little pissed at Keystone, for not engineering a better method of ducting. The furnace, labour and taxes came to $1800.00
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Old 05-08-2013, 04:40 PM   #8
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This is more of a question than anything. In this thread it was suggested not to reduce the size of the heat ducts because it would restrict flow, but in the same breath it was suggested to install adjustable heat registers. Isn't that doing the same thing, restricting flow? Larger ducks increase volume while smaller lines increase velocity.

Now don't get me wrong I do not condone reducing the diameter size. I do like the idea of reducing the length and definitely taping the joints.

I would also guess that when the ducts are located has a great effect. If they are run in an unheated area and are not insulated in any way.

Just thought I would throw this out there.
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Old 05-08-2013, 05:06 PM   #9
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I don't believe that having adjustable, louvered heat registers would restrict the flow. The volume of air moving through the duct remains the same except that instead of allowing some of it to escape through the register at one place (by closing the louvers), that same volume moves along the ductwork to the next register where it may escape into a different area.

If you have 3 registers for example, and close off 1 of them, the air escapes through the remaining 2. You are not reducing the size/diameter of the ductwork but rather reducing the number of outlets for that air to flow out. I don't see any restrictions along the length of the ductwork.
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Old 05-08-2013, 05:51 PM   #10
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Originally Posted by Fastback View Post
This is more of a question than anything. In this thread it was suggested not to reduce the size of the heat ducts because it would restrict flow, but in the same breath it was suggested to install adjustable heat registers. Isn't that doing the same thing, restricting flow? Larger ducks increase volume while smaller lines increase velocity.

Now don't get me wrong I do not condone reducing the diameter size. I do like the idea of reducing the length and definitely taping the joints.

I would also guess that when the ducts are located has a great effect. If they are run in an unheated area and are not insulated in any way.

Just thought I would throw this out there.
A very reasonable question.

If you reduce the duct size, you permanently limit the flow on that leg of the system. By sticking with a larger duct size throughout, you then can use the adjustable vents to balance the flow throughout the trailer. Or you can force more flow into one part of the trailer in the evening, and then change the flow for sleeping hours.

The velocity can only be increased in a smaller duct with an adequate air pump (fan) so just decreasing duct size with a fairly lazy motor like the one found in our RV's really doesn't give that much benefit. There are still other legs of the system with larger ducts that will take the flow and in turn the velocity away from the smaller duct.

My home has 6" ducting throughout, regardless of the length of the run. By installing adjustable registers, I can limit the amount of hot air that gets into the room closest to the furnace and that forces more flow to the registers further away. Many residential ducting systems have adjustable gates in the ducting which allows even finer tuning of the air pressure in each leg. But it's all the same size ducting for the most part. The ultimate goal is fairly even heating throughout the home.

I don't think RV heating systems are poorly designed, but I do firmly believe that the assembly methods are the root of most poor heating issues in RV's. Like I said earlier, a few minutes with some HVAC tape at the distribution box on the end of the furnace gave an immediate noticeable improvement in my trailer. We've all read the threads with crushed ducting or foreign objects in the ducting.

One final point. My Cougar has a straight run of ducting from the furnace to the rear of the trailer with 3 open registers in it. The living space is a great room with open kitchen, dining area, and living room area. The register closest to the furnace gives of the most flow and the one down at the end where our couch and rockers are located gets very little flow at all. If I partly close the one closest to the furnace, more warm air is sent to the further registers. It is then pulled back to the furnace's cold air return. With some careful adjustments, I can provide a uniform temp throughout the entire room.
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Old 05-09-2013, 07:08 PM   #11
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As a heating contractor, what Steve said.. and very well put, I might add..
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Old 05-10-2013, 08:28 PM   #12
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It's true bedroom heat sucks ! Looking at the solid ducking in a fifth wheel I have found ducting in kitchen and living area and then found ducting hose going up to a short piece of solid ducting going to bathroom and bedroom. The problem I found was the ducting hose comes straight into the bathroom not in the middle of the solid ducting (air is not evenly distributed for bedroom or bathroom. All the heat is in bathroom. I'am going to install adjustable retries .to see if this helps.
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