| Author | Message | ||
| Spencer Champion (Spencer)
Registered Member Username: Spencer Post Number: 14 Registered: 4-2006 Posted From: 72.152.135.252 Rating: N/A |
Hi all. I am getting ready to start on my 4501. Need 3 roof top A/C units. Someone said a while back that the best ones to get were the ones with 3 speed fans. I am thinking of a 13.5 for the front and two 15K for the back. Any suggestions for which brands. Thanks. Spencer | ||
| Kyle Brandt (Kyle4501)
Registered Member Username: Kyle4501 Post Number: 350 Registered: 9-2004 Posted From: 65.4.185.50 Rating: N/A |
Yeah, the brand that goes in the basement! LOL | ||
| R.C.Bishop (Chuckllb)
Registered Member Username: Chuckllb Post Number: 173 Registered: 7-2006 Posted From: 4.240.213.44 Rating: N/A |
Kyle....Amen....and amen!  RCB | ||
| Jerry Liebler (Jerry_liebler)
Registered Member Username: Jerry_liebler Post Number: 257 Registered: 3-2005 Posted From: 67.141.34.62 Rating: N/A |
Ductless splits are quieter, more efficient,and deliver more actual cooling for any given rating. They also don't put ugly warts on a bus roof. Regards Jerry 4107 1120 | ||
| David (Davidinwilmnc)
Registered Member Username: Davidinwilmnc Post Number: 178 Registered: 7-2005 Posted From: 75.180.200.138 Rating: N/A |
If you do use three roof mount units, put the highest capacity ones in the front (where most of the heat is) and the smaller one in the rear. I'd also recommend heat pumps (NOT heat strips). They cost about $100 more per unit but will heat the bus nicely when it's above 40 outside. The others are right about basement air. I have an 8,200 BTU modified window unit used as a basement unit for the bedroom. It keeps the bedroom nice and cool when it's in the 90's out and is as loud as a quiet refrigerator. Also, it was cheap - about $160. David | ||
| Spencer Champion (Spencer)
Registered Member Username: Spencer Post Number: 15 Registered: 4-2006 Posted From: 72.152.135.252 Rating: N/A |
I thought about a split for the front so as not to mess up the view from the upstairs windshield. The idea for the two 15's up front is most likely the way to go with the smaller for the bedroom. Spencer | ||
| Nick Badame Refrigeration Co. (Dnick85)
Registered Member Username: Dnick85 Post Number: 144 Registered: 2-2006 Posted From: 75.197.250.188 Rating: N/A |
Hi Spencer, The units with 3 speeds are the Dometic Penguins. The folks above have given you good advice about using the higher capacity's up front. Most of the 40ft coaches that we install theese in are layed out with 15,000 btu Heat Pumps front and rear and a standard 13.5 or 15k unit in the middle with a electric heat strip. The Dometic comfort control thermostats are able to operate all three zones with a single t-stat. This gives you more then enough capacity of A/C in in extreme heat and more then enough capacity in cold down to 38 deg's. The electric heat strip will give you added heat in temps below 38 deg's. Redundency is very important in your bus. I also have diesel fired heat back-ups because I live in the north east. I have also found myself using my coach in all kinds of weather even though I never thought I would. Whoda Thought! Good Luck Nick- | ||
| Buswarrior (Buswarrior)
Registered Member Username: Buswarrior Post Number: 1041 Registered: 12-2000 Posted From: 70.53.131.153 Rating: N/A |
If it were me, I'd get all three as big as they come, if I didn't go basement system... No one ever complains of too much cooling, or too much heating, or too large of a toilet tank, for that matter... But, they sure are unhappy when there is not enough. In doing calculations, busnuts sometimes forget about the need to cool down a coach that has sat all day in a sunny parking lot. Like at an attraction, event or whatever, where you had to leave it with the generator shut off. The stock HVAC, with 80 000 btu (and up) had some work to do to get the interior to cool down... Ask any coach driver what it takes to get an empty coach cooled back down before the passengers arrive once it roasts inside! I'd go for a matched set of 15K ones, for their capacity, matching exterior appearance, and then they are all interchangeable, if you find yourself in some unexpected situation. No busnut ever ripped an AC off the roof on something low, have they? happy coaching! buswarrior | ||
| David (Davidinwilmnc)
Registered Member Username: Davidinwilmnc Post Number: 179 Registered: 7-2005 Posted From: 75.180.200.138 Rating: N/A |
The problem with oversizing an A/C (without being able to re-heat the air and having to cycle the compressor) is humidity. A bigger A/C will cool quicker, sure. At night (or on a coolish day) after showers, cooking, washing dishes, etc, the units often don't need to remove much heat so the compressors won't run much. The humidity will be too high for comfort. That's why I'd recommend one smaller unit in the smallest area - the bedroom. Another option is to use a dehumidifier. I have one in the house and it'll kick on during a shower. I have a spare one that's destined for the bus. I HATE humidity! My 15K and 8.2K BTU units will cool the interior from around 105 to the upper 70's in a couple of hours max. If I leave them both on continuously, they'll keep the interior in the mid to lower 70's while in the mid 90's outside. I'll still install another big unit, either a basement or roof mount, as I'd like to cool things even quicker and for redundancy. David (Message edited by DavidInWilmNC on July 11, 2007) | ||
| ChuckMC9 (Chucks)
Registered Member Username: Chucks Post Number: 1126 Registered: 10-2003 Posted From: 70.2.4.210 Rating: N/A |
"The problem with oversizing an A/C (without being able to re-heat the air and having to cycle the compressor) is humidity. A bigger A/C will cool quicker, sure. At night (or on a coolish day) after showers, cooking, washing dishes, etc, the units often don't need to remove much heat so the compressors won't run much. The humidity will be too high for comfort." I'll definitely add support to this point of view. I have only two rooftops, both 15K. In this, my first summer fulltiming on a trial basis, I chose a monthly with extensive shade coverage. Before I knew we were going to have serious rain. all. summer. long. With the lack of direct sun combined with mostly overcast for weeks on end, it's not that hot inside, but 90% humidity. In order to remove the humidity I have to FREEZE inside! With only one unit on!!! I've begun to look at dehumidifiers, and actually wondered if I should downsize to three 13.5's. | ||
| James Robinson (Jjrbus)
Registered Member Username: Jjrbus Post Number: 87 Registered: 12-2000 Posted From: 76.1.180.218 Rating: N/A |
Bingo, Dave and Chuck!! I've got a 35 ft bus with saudi roof,painted ultra white, spray foamed, insulated floor and thermo windows. 2 13.5 roof airs. Here in FL in order to keep humidity down I have to keep bus way too cold. If I have to replace an AC unit I will put an 8K in the rear. If doing bus again I would put in 3 mini splits, one large two small. I would not use basement air, becuse I do not want to give up any bay space. | ||
| ChuckMC9 (Chucks)
Registered Member Username: Chucks Post Number: 1128 Registered: 10-2003 Posted From: 70.2.4.210 Rating: N/A |
The downside could be that your kWh goes up quite a bit. I don't know how much, but it's gotta be significant if the compressors are on a lot more, wouldn't you think? This will become increasingly important in times to come. | ||
| Greg Roberts (Eagle 20) (Gregeagle20)
Registered Member Username: Gregeagle20 Post Number: 218 Registered: 4-2002 Posted From: 66.68.239.237 Rating: N/A |
In my Eagle I have three ducted roof units that are Carrier 13500 BTU units with the digital remote controls. I ducted the center and front units together so I would have the option to send more cooling to the front. I also ran the rear ac ducting down to the rear lounge and to the front side of all six of my bunks so that each bunk has it's own vent. This makes for the best sleeping! | ||
| david anderson (Davidanderson)
Registered Member Username: Davidanderson Post Number: 210 Registered: 2-2004 Posted From: 75.53.31.102 Rating: N/A |
Ah, as Fastfred used to call them, "carbunkles". I have 3 low profile Colemans and common ducting for the front and center like Greg's bus. I used carbunkles because they were cheaper, didn't use bay space, and someday, they will fail, so it will be easy to unbolt and replace. I've had mine since 2001 and only have had to replace a fan motor capacitor on one of the 3 units. Otherwise, no problems. I also ducted the front unit to the driver with overhead registers that blow on my face and registers that blow on the windshield for defrosting. Works great. The only thing I wish it had was a 3rd fan speed that was very low. This would help with dehumidification in rainy climates like written above and lessen the freeze the coach dilema. David Anderson | ||
| Kyle Brandt (Kyle4501)
Registered Member Username: Kyle4501 Post Number: 351 Registered: 9-2004 Posted From: 65.23.106.193 Rating: N/A |
Aren't the newer & more efficient a/c's running a higher evaporator core temp & higher air speed to minimize condensation? Cooling air is cheap, it is removing the water that's expensive as the phase change from vapor to liquid takes the most energy. So humidity is already an issue with the super efficient home units. Also, since start-up of a motor draws the most amps, having a smaller a/c unit would alow the unit to run longer & reduce starts. The smaller unit would pull fewer amps while running, hence the possibility for saving. | ||
| James Robinson (Jjrbus)
Registered Member Username: Jjrbus Post Number: 88 Registered: 12-2000 Posted From: 76.1.180.218 Rating: N/A |
Sometimes I can get carried away with savings. I've been known to spend a $100 to save $1. With the AC's is it really that important that I spend $1 a day on electric or $1.10? I'd rather spend $1.10 and be comfortable. | ||
| Nick Badame Refrigeration Co. (Dnick85)
Registered Member Username: Dnick85 Post Number: 146 Registered: 2-2006 Posted From: 75.198.64.21 Rating: N/A |
Hi Kyle, In RV A/C systems, some roof top units have trouble evacuating the condenced water from the coil. I have found that the blower it's self is the problem. Theese high speed fans are creating a negitive preassure at the evaporator coil and preventing the condensate water from properly draining from the pan. When your coach feels humid inside, try turning off the A/C and run to the outside and you will see a tremendous amount of water rushing out of the drain ports. On theese units, it's helpfull to have a automatic fan setting so when the compressor cycles off, so will the fan, releasing the build up out from the pan. On units without this auto feature, the fan runs continually forcing the unit to circulate humid air forever... Hope this helps Nick- | ||
| ChuckMC9 (Chucks)
Registered Member Username: Chucks Post Number: 1132 Registered: 10-2003 Posted From: 70.2.51.208 Rating: N/A |
NICK - you been holding out on us, Keemosabe!!! How come in ALL the research I did I never found this mentioned???!!! I searched Escapees, RV.net, iRV2 and a boatload of others and never saw this issue. Well I did exactly as you described, with results exactly as you described! So until I can rig up one of them fancy house thermostats and relays to power-down the entire units, looks like I can turn off the AC manually once an hour or so and it would help? This is an amazing discovery. I had just assumed that it was recirculating the already humid air inside, but your description gives the impression that the unit is actually adding to the humidity inside when the compressor is not on. Well thanks for the tip. That's why you get the big bux, huh? Guess I'll have to rearrange the project list once again! LOL "When your coach feels humid inside, try turning off the A/C and run to the outside and you will see a tremendous amount of water rushing out of the drain ports. On theese units, it's helpfull to have a automatic fan setting so when the compressor cycles off, so will the fan, releasing the build up out from the pan. On units without this auto feature, the fan runs continually forcing the unit to circulate humid air forever... " | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 629 Registered: 10-2003 Posted From: 71.58.117.21 Rating: N/A |
Spend $100 to save a $1 ????? Where did you get a good deal like that? Man, I never seem to find those deals. | ||
| Nick Badame Refrigeration Co. (Dnick85)
Registered Member Username: Dnick85 Post Number: 149 Registered: 2-2006 Posted From: 75.198.196.7 Rating: N/A |
Hi Chuck, I discovered this problem 4 years ago with Ductless Split systems. Seemed that all my customers were complaining about the humidity. After extencive research, I figured out the "holding water problem". Then on to RV's.... Nick- |