ACtion Magazine - January/February 2015 - (Page 26)

Routing A/C and heater hoses Blake Gordon D uring installation of the air conditioning/heater system in truck, agricultural or off highway equipment, the air conditioning hose and line location is often determined by convenience of installation. Manufacturers generally build a very good air conditioning/heater assembly, but many times the installation is what causes technicians to scratch their head and wonder why the system will not cool the cab on a hot day. In many cases, when the equipment manufacturer installs the air conditioning/heater units, it seems that there is very little understanding of the potential impact of where the hoses are located. In the refrigeration cycle, the role of the condenser is to remove the heat from the refrigerant so that it will condense into a liquid. When there is sufﬁcient refrigerant charge in the condenser, it will gain some added beneﬁt of being sub-cooled. Using a pressure/temperature chart as an example, at 151 psi (10.41 Bar or 1041.1 kPa) the refrigerant condenses at 112°F (44.4°C). If this refrigerant is heated by any outside source like the air conditioning liquid line being attached to a heater hose, a high pressure compressor discharge Part No. 795-01 Cadmium-Free Braze Al Aluminum Brazing Kit Featuring DAYCOAT Advanced Flux Coating Technology TM hose, a hydraulic line, or is in close proximity to an engine, exhaust system, or some other heat source on the vehicle, the liquid refrigerant will begin to vaporize (change state) in the hose or tubing before it reaches the expansion valve. This results in the air conditioning evaporator no longer meeting the expectations of the vehicle operator. Simply by separating the hoses and insulating them against the heat, the refrigerant will stay below the vaporization point and deliver maximum cooling to the cab of the unit. If the suction hose or line is attached to a heat source, the suction vapor will expand to the point where the compressor has little or no dense vapor to pump. At this point the compressor discharge pressure will be lower than normal, in a possible vacuum, and the discharge vapor will be very hot to the point where paint will burn off the compressor body. From the picture of the combined air conditioning/heater hoses, below, you can see that the air conditioning hoses are tied to the heater hoses. The engine cooling system, with a pressure radiator cap and antifreeze, operates well above 180°F (82.22°C). With the refrigerant changing state at 112°F (44.4° C), at 151 psi it will be vaporized before it reaches the dryer and the expansion valve. Once the refrigerant vaporizes, the air exiting from the air conditioning ducts will be warm to hot. The dryer location is also extremely important with respect to a heat source. The best place to mount the dryer is where there is plenty of cooler airﬂow across it. Good locations include the vehicle frame rail, in front of or alongside the radiator. Some manufacturers of micro tube condensers have turned to using a condenser with a dryer built into the manifold on the end of the condenser. Unfortunately, these dryers are not always serviceable and as a result, if the air conditioning system has been left open due to a failed compressor, broken hose or a loss of refrigerant, it is necessary to replace the condenser/dryer unit. Managing your air conditioning/heater hoses results in a better overall performance of the air conditioning unit. ❆ Blake Gordon Air Conditioning Trainer for Polar Mobility Research Ltd, Calgary, AB. You can reach Blake at abgordon@telusplanet.net Reader Reply BrazeAl BrazeAl BrazeAl: The Solution To All Your Aluminum Brazing Needs! TM Call Johnson Mfg. @ 800-747-0030 or S.A. Day @ 888-735-2805 www.johnsonmfg.com johnsonmfg@aol.com www.saday.com info@saday.com 26 ACTION * January/February 2015 Note the hoses are tied together (which should never happen). http://www.johnsonmfg.com http://www.macsw.org/imis15/MACS/Publications/ACtion_Reader_Reply/MACS/Publications/ACTION/ACtion_Reader_Reply.aspx?hkey=ac24bddb-c045-442a-813c-cbf05f88ac4d http://www.johnsonmfg.com http://www.saday.com

Table of Contents for the Digital Edition of ACtion Magazine - January/February 2015

Outlook
Service Port
Leonard's Law
Member Profile
Compressor clutches
Recognizing career achievement
Virtual View
Heavy duty and off road
Industry News
Association News
New Products
Last Watch

ACtion Magazine - January/February 2015