Piping Connections And Valve Operations; Connecting Pipes - Mitsubishi Electric City Multi PURY-P72TNU-A-BS Manuel D'installation

9-5. Piping connections and valve operations

Before heating the brazed sections, remove the gas and oil that are trapped in the pipes.
- Failure to do so may generate fire, resulting in serious injury.
Ventilate the room while servicing the unit.
- If the refrigerant leaks, oxygen deficiency may result. If the leaked refrigerant comes in contact with a heat source,
toxic gas will be generated.
Store pipes indoors, and keep both ends of the pipes sealed until just before making a flare connection or
brazing. (Store elbows and other joints in plastic bags.)
- If dust, dirt, or water enters the refrigerant lines, the refrigerant oil will deteriorate and the compressor will malfunction.
Keep the service valves closed until refrigerant charging is completed.
- Failure to do so will damage the unit.
Place a wet towel on the service valves before brazing the pipes to keep the temperature of the valves from
rising above 120ºC (248ºF).
- Failure to do so may result in equipment damage.
Keep the flame out of contact with the cables and metal sheet when brazing the pipes.
- Failure to do so may result in burnout or malfunction.
Braze the pipes with a nitrogen purge to avoid oxidation.
- Oxidized flux inside the refrigerant pipes will cause the refrigerant oil to deteriorate and cause the compressor to
malfunction.
9-5-1. Removing the pinched connecting pipes
The unit is shipped with the pinched connecting pipes attached to the high- and low-pressure side service valves to prevent gas leakage.
Take the following steps ① through ③ to remove the pinched connecting pipes before connecting refrigerant pipes to the outdoor unit.
① Check that the service valves are fully closed (turned clockwise all the way).
② Remove the gas in the pinched connecting pipes, and drain out all the refrigerant oil. (See Ⓔ below.)
③ Remove the pinched connecting pipes. (See Ⓕ below.)
<A> <B>
Ⓓ
Ⓔ

9-5-2. Connecting pipes

・The refrigerant pipe from the outdoor unit is branched at the pipe end, and each branch is then connected to an indoor unit.
Indoor unit
High-pressure pipe
Outdoor unit
Low-pressure pipe
Branched section
・When connecting pipes, make sure the service valves are completely closed.
・Commercially available pipes often contain dust or debris. Always blow them clean with a dry inert gas.
・Take care to prevent dust, water or other contaminants from entering the pipes during installation.
・Reduce the number of bending portions as much as possible, and make the bending radius as big as possible.
・Do not use any commercially available anti-oxidizing agents since they may cause pipe corrosion and degrading of the refrigerant oil. Please
contact Mitsubishi Electric for more details.
・Make sure that the pipes are not in contact with each other, unit panels, or base plates.
・Refer to the twinning kit Installation Manual for how to install the twinning kit.
WT09106X03
<A> Refrigerant service valve (high-pressure/brazed)
<B> Refrigerant service valve (low-pressure/brazed)
Ⓐ
Valve shaft
Ⓐ
The unit is shipped with the valve closed. Keep the valve closed while connecting pipes or
evacuating the system. Open the valve upon completion of this work.
Ⓑ
Turn the shaft counterclockwise as far as it will go (90˚) to open the valve, and clockwise to
close it.
Ⓒ
Ⓑ Stopper pin
Prevents the shaft from turning 90˚ or more.
Ⓕ
Ⓒ Service port
Through the service ports, you can charge refrigerant, remove the gas in the pinched
connecting pipes, or evacuate the system.
Cap
Ⓓ
Remove the cap before turning the shaft. Put the cap back on upon completion of all work.
Severed section of the pinched connecting pipe
Ⓔ
Brazed section of the pinched connecting pipe
Ⓕ
Connecting method
Brazed or flared
Brazed
Brazed
Brazed
GB-22