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Questions for the experts ( or mildly skilled...)

NYCEGUY01 on Tue July 06, 2010 11:20 PM User is offline

Year: 19969
Make: Chevy
Model: K3500
Engine Size: 5.9
Refrigerant Type: 134
Ambient Temp: 95
Country of Origin: United States

OK guys I have a few q's.

I have a 96 Chevy 3500. I have installed a 5.9 Cummins Diesel engine. The A/C system is stock except I am running the stock 1993 Dodge compressor.

The system works great.

The issue I have is the engine overheats while towing heavy in the summer especially when I use the A/C. While attempting to relocate the condensor ( to allow more airflow to the radiator ) I poked a hole in it... UGH...

Anyway I went on a trip without the condensor in the truck ( I had removed it because of the hole ) and my overheating issue was solved ( at least in the motor, Inside the cab was plenty warm..lol)

Basically the stock condensor was just blocking too much air for the motor to run cool.

I obviously need a new condensor but dont want to put one back in thats going to block the airflow to my radiator again.

Ive seen the small ones for hot rods etc.. that are remote mounted with a fan or even the aftermarket ones here. How big of one do I need to maintain the A/C ???

I have enough room below the Radiator and Intercooler to mount something around a 26"x12" or so and keep it from blocking my Radiator completly. I just dont want to buy the condensor
and have new hoses made if its not going to be enough....

The truck is an extra cab and I want to cool it as good as the stock A/C system did...

How small of a condensor can I get away with ???

chris142 on Tue July 06, 2010 11:43 PM User is offline

CK out the fan and condensor on the 04ish Dodge pickups with the gas engines. They are mounted off to the side and itty bitty but they seem to work well.

iceman2555 on Tue July 06, 2010 11:45 PM User is offlineView users profile

Instead of wondering how small the condenser can be...why not diagnosis the engine cooling system to determine why there is not sufficient cooling for both the rad and condenser?
If the engine cooling system is functioning as it should, this cooling issue should not be a problem.
The use of a 'relocated or smaller condenser' is not necessary on other diesel trucks we have serviced. The Cummings engine used in this vehicle works in the Dodge frame and cools well as designed from the factory.
It seems the cooling issue is not the condenser but the lack of sufficient air flow....perhaps a fan clutch that is not functioning, a rad that needs service.....these would be the first items that should be checked. The statement that this overheating occures when towing on a hot day...but works other times with no problem....sure points to a cooling system concern to me.
Good luck!!!

-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

NYCEGUY01 on Wed July 07, 2010 12:01 AM User is offline

No more gains can be had on that front.
I am running a Griffin dual 1.25 row Aluminum radiator and a very large aftermarket Powerstroke intercooler.
The truck runs alot of fuel and the twin turbos need the intercooler to keep the EGT's in check. The truck Dynos over 650 hp and well over 1100 ft/lbs of torque.
The condensor fins are very dense compared to the i/c and rad and just not enough air gets through.
The Radiator is shrouded with large electric fans drawing air ( 5000+ CFM worth)

Similiar setups in Dodge trucks experience overheating while towing.

I have no more room for a larger radiator or intercooler.

As soon as the condenser was removed the overheating engine ran normal temps. The added airflow not blocked by the condensor did the trick.

HECAT on Wed July 07, 2010 9:18 AM User is offline

Quote
Originally posted by: NYCEGUY01
As soon as the condenser was removed the overheating engine ran normal temps. The added airflow not blocked by the condensor did the trick.

This shows that your set-up (intercooler, radiator, seals, shrouds, fans, etc) are adequate without A/C. The condenser needs cool air flow and sheds heat. It needs to be in front and will add additional heat load to the existing heat exchanger stack, which must be capable of handling the additional load. You can try and mount the condenser elsewhere(?), but it is going to need lots of fans and good air flow when moving. If it is too small or does not have enough air flow; the head pressures (high side) will be way too high, which will produce poor vent temps and shorten the life of the compressor.


-------------------------


HECAT: www.hecatinc.com You support the Forum when you consider www.ackits.com for your a/c parts.

FLUSHING TECHNICAL PAPER vs2.pdf 

94RX-7 on Wed July 07, 2010 11:26 AM User is offline

The electric fans simply don't move enough air when towing in the summertime with the A/C on. Go back to the mechanical fan....

ice-n-tropics on Wed July 07, 2010 11:55 AM User is offline

Great! 650 Hp. That took some smarts and you don't want to mess it up.
The goal should be a world class A/C but the 154.9cc Sanden compressor is borderline at best for such a task.
Look at a few ambulances and fire trucks with remote condensers with 12 volt fans from Red Dot.
This may be an application for 2 condensers in series. The first remote condenser would dissipate the majority of BTUs with incoming superheat and then to a final low condenser in the ram air flow below the radiator and Charge Air Cooler (CAC).
hotrodac

-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

bohica2xo on Wed July 07, 2010 12:37 PM User is offline

Ah, the 5,000 cfm 12v 20 amp electric unicorn....

I have a real 5k cfm rated fan working nearby. It takes 12.6 amps @ 120vac to run it, and the blast from a 24"x36" open duct will take you hat off @ 10 feet. If I could get that sort of airflow in my pickup, it would move without letting the clutch out...

So what did the OEM cummins have for a fan?


Tex:
I agree the daimler-chryscrap compressor is not the best choice. A secondary condensor was common on the mini-vans with dual A/C. That condensor was more or less designed for liquid, or foam. Probably a good choice for a bit of subcooling in a system like this.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

NYCEGUY01 on Wed July 07, 2010 3:40 PM User is offline

Quote
Originally posted by: 94RX-7
The electric fans simply don't move enough air when towing in the summertime with the A/C on. Go back to the mechanical fan....


Even with the A/C turned off the truck ran hot. I believe it was just blocking too much airflow.

iceman2555 on Wed July 07, 2010 3:47 PM User is offlineView users profile

Would be interesting to know the type fans being used, mfg'er, size of fans, number of blades and true cfm ratings, amp draw etc. Some of these companies overly rate their 5000 + cfm is a tremendous amount of air flow, esp when pulled thru a fan shroud opening.
Have seen many of the aftermarket performance suppliers vastly over rating the performance level of their fans.
The condenser on this vehicle should have been a 'tube and fin'. These units are not known for a high degree of density.
It may be possible to mount a remote condenser to the side of the OE space similar to the 2000 Dodge Ram type condenser mounting. The use of a smaller PFHE unit would probably equal the heat transfer ability of the larger tube and fin unit and offer a 'path for increased air flow'.


-------------------------
The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson

NYCEGUY01 on Wed July 07, 2010 3:51 PM User is offline

Quote
Originally posted by: bohica2xo
Ah, the 5,000 cfm 12v 20 amp electric unicorn....



I have a real 5k cfm rated fan working nearby. It takes 12.6 amps @ 120vac to run it, and the blast from a 24"x36" open duct will take you hat off @ 10 feet. If I could get that sort of airflow in my pickup, it would move without letting the clutch out...



So what did the OEM cummins have for a fan?





Tex:

I agree the daimler-chryscrap compressor is not the best choice. A secondary condensor was common on the mini-vans with dual A/C. That condensor was more or less designed for liquid, or foam. Probably a good choice for a bit of subcooling in a system like this.



B.


The Dodge had a single mechanical fan. That is not an option in this chassis / motor combo. Its actually (2) 2500 cfm fans that draw 16-18 amps 12v each in an aluminum shroud. The amount of air these things draw is substantial. Unfortunatly they are also very loud.

The amount of air the condensor blocked was substantial. It covered the entire front of the Rad and I/C.

The compressor seems to cool the truck fine as long as there is a condensor installed. Right now there is not. Im ready to put something back in though.


From what I have read the PF condensors are 1/3 more efficient. Would this mean that I could use a condensor 1/3 smaller and expect the same performance from the A/C system ?

If I could get away with something half the size of the origional I could easily mount it below the Rad and I/C so it would have direct airflow while moving. A fan could be installed for slow driving and idling etc....


bohica2xo on Thu July 08, 2010 12:09 AM User is offline

Well, Tim shows two condensors for that truck. One is a Serpentine, and the second is a Piccolo. Both are roughly the same size 27" x 15.5". No T&F units. Do you know what type of condensor you actually had?

Is your truck a standard cab, extended cab, or 4 door?

To put this into perspective, a 1998 Dodge Caravan mounted a 27 x 15 condensor, and on vehicles with rear air added a second condensor that was 15 x 5. You really NEED all of that area if you want cooling.

Relocating the condensor to some other place to keep it from pumping heat into the overloaded heat exchanger stack is possible. As Tex mentioned, Red Dot makes remote mount condensors for commercial applications. Perhaps a bed mount with an electric fan, along with a secondary unit in series with some ram air...

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

ice-n-tropics on Thu July 08, 2010 9:28 AM User is offline

The normal single condenser operates like 3 heat exchangers:
1) Desuperheater (sensible) heat dissipation from the hot gas with a 20 to 50 degree temperature drop
2) Condensing (latent) heat dissipation from 100% gas to 100% liquid refrigerant without temperature change
3) Subcooling (sensible) heat dissipation from the liquid with a 3 to 25 degree temperature drop

26 X 12 is about 1/3 to 1/2 of what you need for the crew cab unless there is a double the normal air velocity, hence the recommendation for a remote de-superheater and 1/2 the condensing/latent heat dissipation condenser upstream of a 12 X 26 condenser which completes the condensing and creates subcooling.
The 1/3 more efficient condenser claim could be for cases where the air pressure drop is unrealistically high.
Ideally, the condenser heat dissipation capacity BTUs equals the evaporator heat absorption capacity (about 18,000 BTU or more after hot soak) plus the input energy to the compressor (ranges between 6000 to 12000 btu of higher).
Therefore a single 12 X 26 condenser with fan will be problematic
hotrodac

-------------------------
Isentropic Efficiency=Ratio of Theoretical Compression Energy/Actual Energy.
AMAZON.com: How To Air Condition Your Hot Rod

Edited: Thu July 08, 2010 at 9:41 AM by ice-n-tropics

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