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vskid3 05-07-15 07:08 PM

Fifth Wheel RV Efficiency Mods
My wife and I moved into a 28' 2003 Keystone Cougar fifth wheel a couple months ago. Its been an interesting exercise in downsizing our living space and possessions. Energy usage is one area that likely didn't shrink compared to the house we were renting (at least per square foot). I would like to fix that. This trailer is kind of a stepping stone towards a different RV/tiny house/small regular house, so I'll be trying to keep the mods cheap, high ROI, and/or transferable.

So far I've put Reflectix in about half of the windows and in the roof vents. I can feel the reduced temperature on the back of the shade for one of the windows on the insulated vs uninsulated part. Reducing usage is the other main mod so far. I washed dishes with warm water in the house, now I mainly use just cold. I still need to work on getting my water usage down, though.

Now, on to some of the trailers specs and future plans. My ultimate goal is to be off the grid energy-wise, though this probably won't happen in this trailer, but in a future RV/tiny house/small regular house.

Part of this includes going propane-free, and is something I'm already doing/shooting towards. In this trailer, the furnace, 6 gallon water heater, and oven/stove all use propane. I've only used enough propane to test each of them. When it was cooler outside, a 1500w resistance space heater was used instead of the furnace (electric is included where we're staying, so I justify this by using the money saved to go towards mods to reduce the need for the space heater). The water heater has an electric mode that we've been using. The recovery rate on electric is about half of propane, which helps to reduce usage because when the shower goes cold, you either tough it out or call it good. ;) Stove is replaced by using the microwave or the toaster oven and hot plate we've purchased. I would like to find a more elegant solution than the toaster oven and hot plate, but other than a induction hot plate, we'll probably wait until we're in whatever dwelling we have in the future.

Heating and cooling are another area that I believe could be improved upon. The roof AC doesn't seem like the most efficient option, and the space heater we used for heat is definitely something that can only get better. I would like to use a heat pump for my cooling and most of my heating needs, but I'm not sure what my best option would be. A ~$1000 mini split would be nice, but I don't know how they would like travel. A portable AC seems like a good option, though from my research on here, they don't seem very reliable and its hard to find one with two vent hoses, most are just one. There are also roof mounted RV specific heat pumps, but reliability is an unknown.

The fridge can use either propane or electric. It is very inefficient, using 4-5kwh a day according to my kill-a-watt even though I only opened is maybe 6 times that day. Not only that, its also tiny inside. A dorm/apartment size fridge should be able to fit in its place, while at least doubling the space and likely using less than half the power. The fridge is right next to the water heater. I would like to use the fridge to preheat the water heater's input line. I've seen discussion on doing this, but not much on how to actually do it.

This trailer has a 30A power hookup. Normally its fine, until the AC is running, the water heater is on, and the microwave is on, tripping the main breaker. I've considered converting to 50A to make it possible to use a tankless water heater, but I think that's more than I want to do to this trailer. I would like to get a surge protector for the trailer, some even display power usage, which would help me track how much mods help.

That's all for now. I'll post more later and add pics when my post count is high enough. My biggest question right now is what kind of heat pump I should look into getting. Thanks.

Daox 05-08-15 06:47 PM

I'm glad to see a post on this.

It sounds like there is quite a bit of room for improvement, that is good.

Also, I upped your post count so you should be able to post links and pictures.

vskid3 05-25-15 12:36 PM

Thanks, Daox! I've added a picture of the truck and trailer to the first post. The big rectangle on the back half of the trailer is the slide out. Its about 12' long and slides out about 3', really opens up the living area/kitchen. Here's a quick video I made of the interior of the trailer when we bought it. Many changes have been made in the arrangement and addition/removal of furniture since then.

I've still been slacking with doing mods. Only changes I've made since my first post are putting Reflectix in the other windows of the slide and changing all the commonly used 12v lights to LEDs. The LEDs are a huge power saver/heat reducer, wish I had purchased them from the start.

doug30293 08-04-15 09:57 AM

I just looked at your embedded video. The layout is nearly identical to my 02 Four winds, which we will be living in shortly.

If your EPDM roof is original and showing signs of age I can definitely recommend you either replace it or top it with Liquid Roof. That made an almost unbelievable difference in my ceiling temperature. Prior to the coating my trailer would get above 115F inside on a 90F day (AC off). It now stays below 100F under similar conditions.

The temperature yesterday was 97F. My knees blistered while kneeling on the slide out which has not been coated. At the same time I could rest my hand on the coated roof without discomfort. I don't have an IR gun to provide numbers but my best guess is a surface temperature difference of 30F.

The standard RV AC is 13.5K BTU. I think this is gross overkill. If time permits I am going to temporarily hack a standard 5K window shaker to see if it will keep up with August heat in Georgia. I think it will if one doesn't mind inside temperatures up to 78F.

There are a few tube videos of off-gridders running 5K units successfully from solar panels. Now that is a valid justification for PV's.

vskid3 08-04-15 09:11 PM

Liquid Roof looks awesome, I'll have to look into that more this fall when its cool enough for me to even consider standing on the roof for a couple hours. My roof is in pretty good shape, but it would be nice to know that its for sure sealed.

Are you sure about the stock AC being overkill? Mine runs for probably 6-7 hours straight during the heat of the day trying to keep the temp at 76F. Even then, it can creep into the low 80s inside if its a particularly hot day. This is with Reflectix in all the windows. I would definitely look into replacing the rooftop AC with a mini split if mine ever dies. I've read that RV AC's BTUs are overrated and mini splits are usually underrated, so a 10-12k mini split would be plenty. Would also be much better than resistance heating or the propane furnace during the winter.

I've actually done a couple mods recently. Got a dryer (I know, a step in the wrong direction efficiency-wise) and made a window vent for it so now we don't need a big drying rack up all the time to keep up with laundry. I'll try out an indoor vent during the winter to see if I can save some of the heat without turning the trailer into a rain forest. I replaced the slide style thermostat with a battery powered digital one. Temperatures are much more consistent, I would highly recommend doing this. Also replaced the shallow two basin kitchen sink with a deeper, single basin stainless steel model. Dishes are easier to wash and to let pile up between washings. :D

doug30293 08-05-15 10:11 AM

Liquid Roof is quite expensive and it is a lot of work. If I were doing it over I would replace the EPDM skin. There was damage to the OSB underneath where the trim failed at the rear. This required pulling up about six feet of the skin.

With little more effort I could have pulled the entire roof, replaced the fiberglass with spray foam, and used lighter/stronger plywood instead of the OSB. That OSB is lightly nailed to flimsy trusses and tends to lift the nails over time.

Back when our trailers were built the rooftop AC units were available in three or four sizes from 6K up to 13.5K. The only thing readily available now is 13.5K or 15K. Yours might be 8K which would explain its inability to keep up. Texas summers don't help.

The roll out awning on the passenger side cuts heat penetration through the wall if it is facing the sun. It will also self destruct in a heavy rain or wind as I found out last week. Sunchaser (Dometic) uses the same flimsy tube extrusion for anything from 8FT up to 25FT. Our 20FT literally snapped in the middle. I'm told many full-timers and snowbirds just leave theirs rolled up and use a $79 flea market pop-up to avoid the cost and possible damage to the side of the trailer. If I repair mine I will use mesh sun shade fabric instead of solid vinyl.

I am going to look into Reflectix. But I may just use pink EPS foam sheet. We blocked one window in our house with 3/4" EPS that was getting the afternoon sun. Blocking that one window noticeably reduced our cooling requirement. I'm cooling 2300 sq.ft with two 5K window shakers. It was 101F yesterday and our inside temp topped at 77F.

My comment in another thread a few years back about windows not making much difference in our cooling bill was short sighted at best.

vskid3 08-09-15 12:57 AM

Any idea where I should look to find the BTUs of my AC? Behind the intake cover inside and looking through the side vents on top are wiring diagrams, but no mention of BTUs or a model number. I found a brochure online for the year after my trailer and the only AC mentioned is 13.5k BTU. I've read in a few places that most RVs can only stay about 20F below outside temps, which is about what I manage in my trailer. I do have all the windows Reflectix'd, though, so I should be doing a little better...

I have no shade where I'm parked, but the awning is on the south side of the trailer. It makes a noticeable difference in how well the AC keeps up in the heat of the day. Unfortunately, its enemy, wind, is pretty common here and it can pick up quick. I only have it out when I'm home and the wind is a breeze or slower.

jeff5may 08-09-15 06:45 AM

Some quick tips:

For the windows you don't look out of, fab up a filler panel of polyiso rboard and/or EPs as thick as you can. For windows you do, fab up storm windows out of lexan as thick as you feel like affordable.

In all those outboard storage compartments, line the back walls with eps or rboard. The contents of the compartments will act as thermal mass and help keep the interior regulated better. Spray paint or contact paper may keep the significant other happy.

For the btu rating of your rooftop unit, the model number should tell you. If not, the compressor label and model number will. These units can be morphed into a heat pump and performance is not too shabby for the size, the units themselves use the same major components whether they are built as a heat pump or not.

For the lights and fridge and water heater, a small solar array will power them all no problem. For the heating and cooling, not cost effective for your demands. A small dehumidifier hacked into a water to water unit could leverage your solar power source to move more heat between the fridge and water heater. The water loop could be rigged to provide minimal heating and cooling as a byproduct of the high or low temperatures demanded by the fire and ice boxes.

I hope that I have spurred your imagination sufficiently, if not, I'm sure there are many more ideas to ponder.

doug30293 08-09-15 09:54 AM

I just remembered another issue with the AC. If yours is ducted through the ceiling you can improve its efficiency by blocking those ducts at the AC and purchase or fabricate a new return grille. The ductless grille is still available from Dometic but the filter is too restrictive.

Both cold air and return are squeezed through that 14 inch square hole under the AC unit. To make matters worse there is a six inch square metal junction box in the middle of that hole, further restricting air flow. Finally, the return air filter is an 8 X 12 piece of washable foam.

The ceiling ducts are highly pressurized to compensate for being grossly undersized. Each duct is about ten feet long with an internal cross section of about 12 square inches. Mine leak cold air into the ceiling cavity.

I am fabricating a new intake duct that will pull upward through a 14 X 14 pleated household filter and direct the cold air front and back in two streams along the ceiling. More filter area and the lack of ducts will improve air flow. The fan motor is quite large to compensate for the large pressure drop. With a better intake and no ducts you should get by with lower fan speed. The Dometic slide t-stat has two fan speed settings. The motor, however, has three.

I temporarily bypassed my ducts to see if there was a difference in AC on-time and it was substantial. The airborne and mechanical noise levels were also reduced.

The only disadvantage of ductless is that you will have to leave the bedroom door open to get cool air.

doug30293 08-09-15 10:36 AM

Off-grid campers all tell me the biggest single drain on the battery is the heater fan. The awful noise it makes should be a clue. From my experience it is also the most wasteful consumer of propane.

About twenty years ago a friend of mine came to the same conclusion and installed hot water radiant heating in his brand new motorhome. The wife was not happy about 3/4" copper pipe screwed down on top of the carpet around the perimeter of the living space. It was, however, a significant improvement in comfort and efficiency. This fellow was from Sweden, where he said this was how all RV's are heated. He had the heating unit shipped from Sweden, though I suppose they might now be available here. It wasn't cheap.

Copper pipe on the carpet isn't an option for me either. I haven't figured out where to put the PEX without it being an eyesore. One possibility is to put several loops in the floor duct and force air through it with a few computer fans. I could also hide about 30 feet under and behind the couch, no problem until the wife has a hot flash while watching TV.

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