EM1 and TXV and coldest air

[magnakansas]

I am removing an air conditioning system from a shuttle bus.... I will have the entire system ... wires, controllers, condensers, compressor and lines.

I think I know enough to make this all work like a factory install.

I also think some folks here, know how to "tune" a system to get maximum cooling from it too.

Can I have your words of wisdom about how to get maximum cooling.

I will have dual compressors and the firewall mount system is going to be a separate issue.

This is a MCC EM1 and I think CM3 ... I will use - probably the enhanced sanden.

william

[cadillackid]

heres what I do to make an EM1 evaporator sit right above freezing at the coil..



1. the sanden SD7 enhanced compressor is the perfect size for 1 EM1 evaporator.. dont try to run more on it.



2. calculate your compressor RPM and pulley it accordingly.. I over-drive my compressors . the diesel engine maximum RPM is likely somewhere in the 2400-2600 RPM range. the compressor maximum safe sustained RPM is 4000-4500. if you have the ability on an electronic engine to trip a relay based on RPM you can pulley the compressor even more aggressive and have a cut out when you are near its redline..



3. I use big hose. the lengths are long and usually there are multiple bends and curves.. refrigerant flow is like driving on a road.. it slows down on curves and corners.. the bigger the pipe the easier the flow.. I run #10 discharge (comp to condenser).. #8 liquid (condenser to evap inlet). #12 suction (evap to compresor inlet).


4. clean clean clean - clear the dirt off of the coils on used equipment.. run a foam coil cleaner on both coils ..


5. FLush the evap, condenser, and compressor free of all oils so you can start fresh.. the EM1 / CM3 condenser, SD7 compressor take a total of 8 inches of oil.



6. ** READ CAREFULLY **. I use ES-134a re[placement refrigerant.. it is extremely cold and has good saturation even at idle.. the downside is there is a degree of flammability to it.. R-134a works as well. I just like the better thermal qualities the ES-134a


7. Airflow.. - take into account where you put your condenser in regards to engine heat.. my front condenser thats on the left side right behind the battery box takes more heat in than my rear condenser behind the rear wheels..



8. electricals - run big enough wire.. evaporator and condenser each pull someplance in the 20-25 amp range each.. the run from your battery to your A/C relay panel may be somewhat long.. I come right off the battery to a circuit breaker and ran 6 gauge wire to a circuit breaker next to the battery and then down to the A/C relay panel.. this is hot all the time but my control panel shuts the unit off via its relays..



those are some pointers.. let me know any more info you want / need and we can go from there.. just this summer I repurposed an EM1 (I used a new CS-3 because the original was damaged from ohio winters).. and it works great as my rear system.
-Christopher

[magnakansas]

I have kept all these notes.... I made a point to keep in mind hose size and routing so has to keep bends to a minimum.

I will install air "guides" to direct air underneath. Keep as much heat from engine / transmission away from intake air for the condenser. I think I will also be able to duct "ram" air flow from outside the bus body to feed higher pressure air to condenser at the skirt. I feel very good about knowing how to direct air flow and aerodynamics.

I never thought about pulley speeds on the compressor.... I intend cruise rpm in 6th to be about 1900 rpm and if I drop to 5th at 65 mph engine speed would be 2500 rpm.... so I will work on some sort of circuit that can count crank rpm and shut out relays over 2600-2700 rpm. I do have the dodge crank speed sensor and can use that for ac circuit speed sensor.... now I have to go to some ciphering.

I found a place in Iowa.... from what you said, and looking at the SDS, I assume this is the supplier you are talking about...

I have the hoses that came with the EM1 system, IF these hoses are not the same as size as you used, how to did you alter the size at the evaporator? I have not yet check sizes of fittings screwed into the TXV..... Did you change the fittings?

thanks again for sharing your work and knowledge.

william