roof top air questions

[4106-123]

new to this board purchased a 4106 and  im completly redoing it the question i have is that my bus has 2 roof airs on it one is a duotherm 15000 and coleman mach unsure of btus. they are both older units. ive cleaned the evaporator coils and filters. the problem i seem to be having is that after they run for a while and the temp gets down to around 78 dgrees  i can hear the compressors cutting off for a while and them come back on after a short while, both are set to high cool and lowest temp. seems to me they are cycling on the thermosat but  i would assume they would pull the temp down a lot lower? 2nd question im think of removing them in the future and replacing with some of the low profile units, and would like to get imput on which model to go with even thinking of heatpumps? regards george

[4106-123]

one addtional question when going down the road will the roof airs keep the bus at a resonable temp around the drivers area. the bus has foamed sides fatory insulation in ceiling, pensula windows some are dual pane replaced the entry door weather stripping

[DavidInWilmNC]

I'm not sure of the performance issues of your current units.  As to heat pumps, I'd definitely get them.  They produce a lot of heat when it's above 40 out.  I have a Carrier 15K heat pump, and it works great (but it's not a low profile model).  If I were doing it again, I'd get low profile heat pumps.


David

[TomC]

I have a 40 x 102 transit that has huge single pane windows with a light tint and 2.25" blown insulation (very effective).  My front A/C is positioned so it can blow right on the drivers seat.  The second in the middle and the third over the bed.  I can drive with just two running up to 100 degrees, then I kick in the third.  I have Coleman 13,500btu with heat strip-the heat strip is just about useless (it does heat, just takes a long time and you have to put up with cold swirling air while it warms up).  If I were to do it again, I'd use the DuoTherm low profile Penquin 15,000btu heat pump.  My Colemans only have a two speed fan which is more like medium and high-too noisy for quiet night time use.  DuoTherms have 3 speed fans.

As to your not getting lower temps- remember that a healthy roof top A/C will put out about 20 degrees less than what the room temperature is.  So at the 78 degree cut off, the air coming out of the A/C should be around 58-which is not as cold as it could be.  A trick I did with my front A/C was to open up the inside part and put a piece of black electrical tape around the temperature bulb. This insulated the bulb enough to trick the A/C into running colder.  Since the unit is over 13 years old, obviously it hasn't hurt it.  On all three A/C's I have to cut back the thermostat to the 9 o'clock position so the inside temp does not dip below 70.  The coldest I've seen inside on the coldest setting is 58 degrees!  Good Luck, TomC

[Nick Badame Refrig/ACC]

Hi George,

Welcome!

From what you discribe, it sounds like your units are cycling off on the anti-freeze sensor. Reason, because they are most likely low on refrigerant.

The lower the refrigerant charge, the more the evep will freeze over.

If the units are older, then you may want to upgrade to the more efficiant ones along with the low profile models.

As far as your using them over the road, depends on how well you are insulated.

Good Luck
Nick-

[Danny]

Tom,

I did the same thing with black electrical tape last week with mine...  Great minds!  Worked great

Danny

[gus]

Make sure your AC filters are clean, this could cause the evap to freeze up.

I cut a hole in the bottom of my front Coleman unit and used a small fan to blow the air directly on the driver-you wouldn't believe the difference.

I'll send you a photo if you like.

My 4104 body is essentially the same as a 4106 and I can tell you that the front AC will not cool the driver unless you have made major modifications to the insulation and AC air flow.

[JohnEd]

My two roof tops are very old.  One is the oe from a 74 Winnebago and the other was purchased in 93.  They both work great!  I also removed the bottom plastic defuser just for grins and I think the units put out double the air.  I hear that ducting the roof air dramatically reduces the air flow and cooling.  Just what I heard.

I think the major prob with cooling while underway is with air penetration.  Can't cool the neighborhood.  Plug the leaks and it should be the same as while parked.


John