102DL3 AC

[Jcparmley]

I am building out my MCI 102dl3.  The PO had cut the AC lines that went up to the overhead bin AC units so all the freon has leaked out.  I am debating on wether I should keep the OTR AC or get rid of it.  I sure would like to have the extra bay space.  I am not sure if the system even works.  I would need to cap the cut lines, evacuate the system and charge the system just to find out if it works. 

My other thought is to purchase a Carrier rooftop condenser unit that is used on a school bus.  Here is a pic of the unit.  It has a cooling capacity of 83K BTU.  It requires the same compressor that my coach has.  If I were to use this system I could eliminate the original AC Condenser Bay as well as the Main Heater Core Bay.  Thus having all the advantages of OTR Heat/AC but also have all the advantages (bay space) of ripping it out.  I would mount the overhead bin AC Evaporators above the seating area in the living room and also connect the driver AC evaporator into the system.  I would eliminate the main cabin AC evap that is under the floor.  Each over head unit is 1.5 ton and the drivers AC unit is 1.5 ton.  If I am correct that is 54,000 BTU. 

I would of course still have to keep the OTR AC working, which is hard to do and expensive, but the roof condenser seems much more efficient and perhaps will cost less in the long run.  What are your thoughts?

[buswarrior]

What are you going to do for heat going down the road?

The roof units fail miserably at driving the heat below your knees...

The dreams some transit makers had when the low floors started... passengers froze their asses while their heads were sweating...

Happy coaching!
Buswarrior

[Jcparmley]

I was planing on doing what TomC did.  He took the main heater core and installed it in the cabin with two 12inch radiator fans.  He said it worked well.  It wouldn't' be to hard to route the heater core inside the cab.

What are you going to do for heat going down the road?

The roof units fail miserably at driving the heat below your knees...

The dreams some transit makers had when the low floors started... passengers froze their asses while their heads were sweating...

Happy coaching!
Buswarrior

[Jim Blackwood]

The two bin units are 1.5 ton but the dash air has a 1 ton TXV. I've seen it referred to as having a 1.5 ton capacity but I suspect that is just the evaporator coil, it would be limited by the expansion valve. So 4 tons instead of 4.5 and that could make a difference. The main evaporator is a 10 ton unit and does a good job, the others are supplemental.

A 30lb can of r134 will cost you about $100. Because the compressor has 3 way service valves you should be able to use the compressor to draw down the system by discharging out the high side service valve. So not that large of a cost to check it all out.

Jim

[chessie4905]

I thought the rooftop unit was a condenser only, so the rest of system could be placed in the best !ocation.

[Jcparmley]

Yes, the rooftop unit I am considering (the one the the pic) is just the condenser.  I would use that and take out the OTR condenser and free up that bay.  I would also relocate the heater coil to inside the cab under a closet with some radiator fans.  I would use the two overhead bin Evaporators and the one dash Evaporator for OTR AC. I would not use the main cabin evaporator. 

I thought the rooftop unit was a condenser only, so the rest of system could be placed in the best !ocation.

[Jcparmley]

HI Jim

What do you mean bu using the compressor to draw down the system?  So if the compressor has a three way service valve I am assuming that there is a way to close off the over head bin lines?  Those are the lines that were just cut with a sawzall.  Are you suggesting I wouldn't have to cap those lines? 

The two bin units are 1.5 ton but the dash air has a 1 ton TXV. I've seen it referred to as having a 1.5 ton capacity but I suspect that is just the evaporator coil, it would be limited by the expansion valve. So 4 tons instead of 4.5 and that could make a difference. The main evaporator is a 10 ton unit and does a good job, the others are supplemental.

A 30lb can of r134 will cost you about $100. Because the compressor has 3 way service valves you should be able to use the compressor to draw down the system by discharging out the high side service valve. So not that large of a cost to check it all out.

Jim

[buswarrior]

You need to cap the carved off pipes.

You'll need a vacuum pump to evacuate, and it takes a few hours.

System can't evacuate itself from this open to air condition.

Happy coaching!
Buswarrior

[TomC]

Since my transit bus was from Portland, Or, it did not have A/C, just heat. I installed 3-13,500btu Coleman A/C's with heat strips in 1994 powered by a 10kw Powertech Diesel Genset. Except for cleaning the filters and the A/C's condensers, I have done nothing to the A/C's. I just got back from Mammoth a month ago and driving through Mojave it was 104. Running just 2 of the roof tops, it was a comfortable 75 inside. I have the front A/C mounted close enough to the driver's seat so I can aim the air towards me and then also have a dash mounted fan blowing on me. Works well, and I'll say it again-have done nothing but cleaning maintenance on the A/C's. Granted my fuel mileage takes about a 1mpg hit, but sometimes fuel mileage isn't the only expense. Just mount 3 or 4 roof tops and run your Diesel genset running down the road. Good Luck, TomC

[chessie4905]

I've always wondered if running a big alternator and inverter to run ac units instead of running a generator actually saves any money since the engine will be burning more fuel or just trading dollars .

[Jcparmley]

I don't have a disesel generator yet.  I have a 12.5 kW gas air cooled but I don't think running that while driving would work well.  Some people caution running gas gen while on the road. 

Since my transit bus was from Portland, Or, it did not have A/C, just heat. I installed 3-13,500btu Coleman A/C's with heat strips in 1994 powered by a 10kw Powertech Diesel Genset. Except for cleaning the filters and the A/C's condensers, I have done nothing to the A/C's. I just got back from Mammoth a month ago and driving through Mojave it was 104. Running just 2 of the roof tops, it was a comfortable 75 inside. I have the front A/C mounted close enough to the driver's seat so I can aim the air towards me and then also have a dash mounted fan blowing on me. Works well, and I'll say it again-have done nothing but cleaning maintenance on the A/C's. Granted my fuel mileage takes about a 1mpg hit, but sometimes fuel mileage isn't the only expense. Just mount 3 or 4 roof tops and run your Diesel genset running down the road. Good Luck, TomC

[Jim Blackwood]

JC, if you look at the service manual, there is a cutaway of the service valves on the compressor heads. The valve has two seats, one fully open and one fully closed. I'll need to look at it again but depending on whether that second seat closes off the compressor or the line determines if you can draw down the system with the compressor. Basically it is a chamber with three inlets: line, compressor, and service port. One seat closes the service port, the other closes either the line or the compressor. Useful when doing an R&R on the compressor so I would think it closes off the line, leaving the compressor open to the service port. If that is the case you can run it in to that position on the discharge line, open the service port to the free air, and run the compressor to suck the air out of the system. Depending on the condition of the compressor you should be able to draw down to better than 27" and although 29" is sort of standard, in terms of air left there isn't that much difference. If you want to get picky about it you could stop there and hook up a 2 stage vacuum pump to finish the job though. At the very least it'll let you know the condition of your compressor and  whether you have any leaks. Of course there will be a certain amount of air still in the compressor when you finish if you don't suck that out.

Yes, you have to either reconnect your lines or cap them off. Take a look at your A/C system plumbing diagrams. You'll see thermal expansion valves and electric solenoid valves. Now is the time to plan out any changes, while the system is open. Bear in mind that if you eliminate the major primary evaporator without making any substitution, the system will have to store the majority of the refrigerant as a liquid in the accumulator and condenser since it won't be going anywhere. You could probably reduce the charge quantity accordingly.

Another thing worth considering, is that it is quite possible to install a second compressor in parallel with the engine driven one. Because the ports use one way poppet valves there is a built in pair of check valves to prevent backflow. So installing a 110 or 220v compressor into the system is very feasible, allowing the system to run off either the engine or shore power.

Take note of where your cold air discharge is going. Getting even cool air distribution may be a challenge.

Jim

[thomasinnv]

Jared there are many many rv's running all over this continent with gas generators running. It's been done for years and theres no reason not to as long as it's installed properly and has adequate airflow while under way to keep it from overheating.

[Jcparmley]

Are there any suggestions on how to keep a gas gen quiet and keep good airflow?

Jared there are many many rv's running all over this continent with gas generators running. It's been done for years and theres no reason not to as long as it's installed properly and has adequate airflow while under way to keep it from overheating.