Unit installation

July 2009 Application Note 1022

P a g e | 2

August 21, 2006

MEMO: Refrigerant Accessories

Please be advised that we do not recommend the following accessories on our ductless

air conditioners or heat pump units.

Filter Driers: Our units are made in the factory under clean conditions and are brazed

using dry nitrogen. They are charged with clean oil and new refrigerant. When the line

sets are attached using flare connections the copper is clean. Under clean conditions

filter driers are not necessary and will only cause pressure drops in the system.

Sight Glasses: The outdoor unit contains the metering device. The purpose of a sight

glass is to check the condition of the liquid refrigerant prior to metering device. Since

sight glasses are placed prior to the metering device at the indoor the sight glass would

be useless and only create a pressure drop in the lines.

Traps: Traps create pressure drops in our systems. They are commonly used to help in

oil return to the compressor. Since the velocity of the refrigerant is greater when the

metering device is placed in the outdoor unit oil return is not a problem. If a trap is not

preventable, it must be a minimum of twelve inches in length.

Albert R. Blyler

Senior Application Specialist

Mitsubishi HVAC

Due to continuing improvement, above specification may be subject to change without notice.

2013 P-Series and M-Series - Application Notes (June 2013)

APP-72