Johnson Controls PD 180 THRU 240 Refrigerant Mains, Take Adequate Precautions, Line Sizing

430645-YIM-D-0610

Refrigerant Mains Take Adequate Precautions

This Split-System (Air Condensing / Heat Pump / Air Handling) unit is one component of an entire system. As such it requires specific application considerations with regard to the rest of the system (air handling unit, duct design, condensing unit, refrigerant piping and control scheme).

Failure to properly apply this equipment with the rest of the system may result in premature failure and/or reduced performance / increased costs. Warranty coverage specifically excludes failures due to improper application and Unitary Products specifically disclaims any liability resulting from improper application.

Please refer to the equipment Technical Guide, Installation Manual and the piping applications bulletin 247077 or call the applications department for Unitary Products @ 1-877-UPG-SERV for guidance.

Line Sizing

When sizing refrigerant pipe for a split-system air conditioner, check the following:

1.Suction line pressure drop due to friction.

2.Liquid line pressure drop due to friction.

3.Suction line velocity for oil return.

4.Liquid line pressure drop due to vertical rise. For certain piping arrangements, different sizes of suction line pipe may have to be used. The velocity of the refrigerant vapor must always be great enough to carry the oil back to the compressor.

5.Evaporator Located Below Condenser - On a split system where the evaporator blower is located below the condenser, the suction line must be sized for both pressure drop and for oil return.

6.Condenser Located Below Evaporator - When the condenser is located below the evaporator blower, the liquid line must be designed for the pressure drop due to both friction loss and vertical rise. If the pressure drop due to vertical rise and friction exceeds 60 psi, some refrigerant will flash before it reaches the thermal expansion valve.

Flash gas:

1.Increases the liquid line pressure loss due to friction that in turn causes further flashing.

2.Reduces the capacity of the refrigerant control device which starves the evaporator.

3.Erodes the seat of the refrigerant control device.

4.Causes erratic control of the refrigerant entering the evaporator.

Many service problems can be avoided by taking adequate precautions to provide an internally clean and dry system and by using procedures and materials that conform to established standards.

Use hard drawn copper tubing where no appreciable amount of bending around pipes or other obstructions is necessary. If soft copper is used, care should be taken to avoid sharp bends that may cause a restriction. Pack fiberglass insulation and a sealing material such as permagum around refrigerant lines where they penetrate a wall to reduce vibrations and to retain some flexibility.

Support all tubing at minimum intervals with suitable hangers, brackets or clamps.

Braze all copper-to-copper joints with Silfos-5 or equivalent brazing material. Do not use soft solder. Insulate all suction lines with a minimum of 1/2" ARMAFLEX or equivalent that meets local codes. Liquid lines exposed to direct sunlight and/ or high temperatures must also be insulated. Never solder suction and liquid lines together. They can be taped together for convenience and support purposes, but they must be completely insulated from each other.

The liquid and suction service ports on the condenser section permit leak testing, evacuation, and partial charging of the field piping and the evaporator without disturbing refrigerant stored in the condenser during initial installation.

Before beginning installation of the main lines, be sure that the evaporator section has not developed a leak in transit. Check pressure at the Schrader valve located on the header of each coil. If pressure still exists in the system, it can be assumed to be leak free. If pressure DOES NOT exist the section will need to be repaired before evacuation and charging is performed.

A bi-flow solid core filter-drier MUST be field-installed in the liquid line of every system to prevent dirt and moisture from damaging the system. Properly sized filter-driers are shipped with each condensing section.

NOTE: Installing a filter-drier does not eliminate the need for the proper evacuation of a system before it is charged.

A field-installed moisture indicating sight-glass should be installed in the liquid line(s) between the filter-drier and the evaporator coil. The moisture indicating sight-glass can be used to check for excess moisture in the system.

Both condenser and evaporator sections have copper sealing disks brazed over the end of liquid and suction connections. The temperature required to make or break a brazed joint is high enough to cause oxidation of the copper unless an inert atmosphere is provided.

NOTE: Dry nitrogen should flow through the system at all times when heat is being applied and until the joint has cooled. The flow of nitrogen will prevent oxidation of the copper lines during installation.

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