So, on the interstate yesterday I passed a couple of Prevost's and both of them had roof top a/c's lining the roof. Both had 5 a/c's up there! I'm building my GM and a/c's are one of the things I'm trying to figure out and I've been reading the recent posts about mini splits and how may roof a/c's and all that. Some say 1 is enough, most say 2, and a large group say 3. But I have never read on any of these boards needing 4 let alone 5! Is there something I'm missing? ???
Thanks,
Eric
funny you ask that - was asked the same yesturday, hope you don't mind hijacking the thread..
If a high enough BTU unit and lowest am-page unit is used surely this eliminates the need for extra units?
Any recommendations?
Many/most of those units are entertainers with 20kw gens and promoters money to burn...
They are dressing rooms for as many as 8 people sweating and putting on Alice Cooper make-up :)
Moh peeps moh heats. If you have 6 or 12 people riding in those things, it's gonna get hot going down the road on a hot sunny day. Most of us don't need such cooling power.
I have seen some crew buses retro fitted with roof top A/C units run off an appropriate gen set. One had six (6) units on top. It all depends where and how the coach is used. Sitting in the sun going nowhere in 120F heat with 25 guys inside would place a very high demand upon cooling indeed. HB
FWIW, over the road air is usually around 96,000 btu.
I posted this on another site
this is my next set up ... 18k unit above drivers window with a 6 k or a 9 k cassette unit over the rear bed were the roof shaker is now . 240 volt single condenser in the same spot as the one I have now . higher seer for better use of power with 240 volt . I just got my 4024 hybrid inverter to day and already have a outback 120 volt to 240 volt transformer .as I have had no problems with the old system and I think the 2 unit 240 volt system should work fine but as Bob has said if something craps out no a/c . the problem I have is I am running out of space to put stuff . not sure when I will change it over as with my 3 k inverter gene and with the help of the new 24 volt hybrid inverter I will be able to run both a/c units I have now when driving . when parked my 9 k will cool the coach fine other then trying to get the cool air into the bed room so when I have to I turn on the roof shaker . man is it load ! why can't someone make a r/v roof shaker that is efficient and quiet . with the split units you can hardly hear them
dave
Our 35 ft MC5a has two 13500 units and it's more than adequate for us in the SoCal desert. Most times we just close the door to the back (bed and bath) and run with one unit on. Of course, we are both comfortable at 80 degrees. If changing anything though, I would go with a 15000 BTU unit up front. It also should be as far forward as possible.
I guess this depends on
1. what color your bus is
2. how well insulated
3. how air tight
4. are your windows insulated
5. what is the solar heat gain
For the last four years I lived in full sun, Florida in a 31' vintage Airstream that is very well insulated shell, non insulated windows, white roof, and I can keep it cool with a 120vac 8000BTU window unit so does a well insulated bus really take that much more cooling?
I know when I was gutting my 4106 there was almost no insulation and no thermal isolation.
Quote from: Darkspeed on June 17, 2015, 06:47:35 PM
I guess this depends on
1. what color your bus is
2. how well insulated
3. how air tight
4. are your windows insulated
5. what is the solar heat gain
6. how many kids open the door how many times :)
I have three roof units which is barely enough on a hot day. On a 107 degree day in the desert, even with a white roof, the units would start shutting down because they couldn't reject heat fast enough. I don't think more units would have helped. If I ever went to the desert in that heat again I would probably build covers over the A/C units with Reflectix with an air space kinda like the Saudi MC5 double roofs.
I've run our roof airs in 107 degree heat and they never shut down on us. I'm wondering why they shut down in certain cases and not in others. Another thing we did once in Wisconsin when it was over 100 degrees and we only had 13,500 roof air, was during the hottest part of the day, I took a garden hose and watered the roof of the coach and set the hose nozzle in such a way as to mist the roof top a/c cooling fins. Made a difference and got us through the week of over 100 degrees in a bus with just one tough little Coleman 13,500
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We have four in 45' and I am very glad I have each one of them. I usually run two but on very hot days in direct sun we will sometime run three. They are not ducted so with an AC unit in four positions I can decide which two or three to run. There are only three of us in the bus. With 12 people in there it is very easy to see why five are necessary. I have bus air while moving down the road and hate to do without it even for a day.
Davy
They also do 5 so that if one fails there is some backup.
Another reason for all those roof airs on touring band coaches is the crew all have different schedules. Between unloading the trucks, rigging and trussing, flying and line checking the PA, hanging and aiming lighting there are people coming and going out of those buses all day. It's kinda like opening your fridge a couple hundred times a day outside in the heat.
RB
I have 5 roof tops on a 45ft bus I never ran all 5 yet but 3 sure did a good job setting Wed in the 120 degree heat plus 3 is all you can run off 50 amps lol but it was nice to know I had the 2 extras if needed
Well some buses have many small sections so that way each room can be controlled separately. Either way it's really a "cool" bus.
Quote from: Scott Bennett on June 17, 2015, 08:05:24 PM
I've run our roof airs in 107 degree heat and they never shut down on us. I'm wondering why they shut down in certain cases and not in others. Another thing we did once in Wisconsin when it was over 100 degrees and we only had 13,500 roof air, was during the hottest part of the day, I took a garden hose and watered the roof of the coach and set the hose nozzle in such a way as to mist the roof top a/c cooling fins. Made a difference and got us through the week of over 100 degrees in a bus with just one tough little Coleman 13,500
Almost without fail the A/C units would start to shut down around 4 pm every day as the heat peaked. It was 107 degrees in the shade and warmer in the sun. The 20 amp breakers would trip or the A/C units would just shut themselves down. I do have 12 gauge wire to the A/C units. We were boondocking in the desert so no water to spray on the A/C units.
Swamp coolers would have been better if we had the water to supply them.
The only time we had a problem with an AC refusing to work was one summer on a trip that got to about 130 degrees! Not even the dash AC would work. What is the make of yours that shut down at 107?
Makes me wonder if they're better off getting a reefer unit off a 53' trailer. After all, those thing can chill an entire trailer load of ice cream down to 10 degrees in the desert...
I have Atwood, Carrier, and one other brand of of rooftop A/C unit. They all had issues, but the Carrier less so because it cools a smaller area.
A trailer refrigeration unit would be heavy, noisy, consume a lot of diesel, and not be designed to keep a space at 72 degrees. Such a unit would probably be so over sized that it would not properly dehumidify.
Weak breakers,all ac units the amp draw goes up in 100+ degree temps plus the generator output drops
Yes. You need five, depending on your build. We put five, on Clifford's bus, because it heats up. Sitting in 120d weather needs three. However, now try driving in 120d. You will be using four, if not five. We built that bus so we would always be comfy, no matter what. -30 to +120. Been there done that.
And you did a good job John we are amazed how easy it is to cool ;D.I do not understand the concern about the seer and amp draw on a AC unit in a bus which is a RV not your house or home unless you full time.
We just buy fuel for the generator or plug in at a RV park and let the park pickup cost of the electricity to me the seer and amp draw is not that important unless I am missing something lol which can happen
I am concerned because my bus (when complete) will be my full time home and I always strive to be as efficient as possible anyway.
This is one reason im putting so much effort into insulation and thermal isolation on the rebuild.
I know there is a growing trend, especially in my generation, toward the Bus Home & Tiny Home full timers.
We need a new designation, HV? RV = Recreational Vehicle , HV = Home Vehicle?
Quote from: Darkspeed on June 19, 2015, 08:16:52 AM
I am concerned because my bus (when complete) will be my full time home and I always strive to be as efficient as possible anyway.
This is one reason im putting so much effort into insulation and thermal isolation on the rebuild.
I know there is a growing trend, especially in my generation, toward the Bus Home & Tiny Home full timers.
We need a new designation, HV? RV = Recreational Vehicle , HV = Home Vehicle?
Residential Vehicle? (That's actually the idea of someone on another forum.) Or how about COW - Condo On Wheels?
John
The breakers in my case were practically new. I was using some of those two breakers in one slot for the A/C units, but I rearranged things to run the A/C units off full sized breakers. I really need to replace the breakers as they have tripped too many times now. I will be doing a minor rewire that will include getting rid of the double breakers and new breakers for some of the circuits.
Hi Guy's,
We install 5 roof airs on entertainer coaches for 2 reasons:
1- Most entertainer units only have dash air so, going down the road gen-sets are usually humming
to run as many roof airs as possible to keep the cabin areas cool.
2- Redundancy... A leasing company would not want to have a coach out of commission because of
an A/C unit failing while bands are at a concert.
There is no such thing as too much A/C
Nick-
There is also a big difference in having ducted A/C or the old style hang down direct discharge type. I have three direct discharge old style Coleman 13,500btu. Usually only need 2 going down the road. Was in 108 degree weather once and kicked on the third-only to have my wife wearing a sweater. Nothing better than having old style mechanical thermostats that rarely go out-mine haven't in 21years.
The big difference is insulation. I have 2.25" of sprayed foam insulation. Also, the windows. When I had the original bus windows that rattled and leaked air, it was hard to keep the bus cool. Then had custom Pen glass windows made. Even though they are only single pane and lightly tinted (like to see out even at night), they are very tight and quiet. So much so, I have to keep the roof vent open in the bathroom at all times otherwise with all windows and vents closed, when you close the entrance door, it pops your ears. Good Luck, TomC