Maintenance
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131
IM 1125-13 • REBEL ROOFTOPS
Refrigerant Charge
The Rebel unit has many configurable options that can affect
the refrigerant charge. Actual unit charge is given on the unit’s
data plate found on the inside of the control panel. The Rebel
unit uses electronic expansion valves that maintain peak
efficiency. Liquid sub-cooling and suction super heat float and
should not be used as an indication that charge needs to be
added or removed from the system. If a leak is suspected, the
full charge should be removed and weighed. Weight should be
compared against the unit nameplate data. Unit should be re-
charged with the amount given on the unit nameplate.
POE and PVE oil is hygroscopic and does absorb moisture
when exposed to atmosphere. Steps should be taken
to minimize exposure time to atmosphere during any
maintenance where the sealed system is to be opened.
Rebel 003–015 refrigerant systems use
only
Polyvinylether
(PVE) oil. Rebel 016–028 refrigerant systems use
only
Polyester (POE) oil.
IMPORTANT
Do not use POE oil in DPS 003–015 refrigerant systems and do not use
PVE oil in DPS 016–028 refrigerant systems.
Re-charging the unit
The entire system must be evacuated using a suitable vacuum
pump. The quality of vacuum is measured using a suitable
micron gauge that has been calibrated. The vacuum level
reading should be taken directly from the sealed system, not at
the vacuum pump. The minimum vacuum level is 300 microns
Hg. The vacuum pump should be isolated from the system and
the observed. Decay should not be greater than 500 microns
after 15 minutes .
The crankcase heaters should be on during the evacuation
procedure. This will help boil any dissolved refrigerant in the oil.
R410A is a zeotropic refrigerant that is made up of more
than one compound. It must be charged as a liquid from the
canister. Charging is to be done by weight and must match the
unit nameplate found on the inside of the control panel door.
When re-charging the unit there might be alarms in the MT III
controller and the Building Automation System that need to be
cleared.
MicroTech III keypad instructions for charging and/
or evacuation
Evacuating the charge:
• Navigate to the Exp Valve Set-Up Menu
• Set ManCtrl EV Op=Man
• Navigate to the Manual Control Menu
• Set Manual Ctrl=ManCtrl
• Set RcvSol Valve=Open (Heat Pump only)
• Set BP Sol Valve=Open
• Set EVO Cmd=100% (Heat Pump only)
• Set EVI Cmd=100%
• Reclaim refrigerant
Charging the system:
Static Charge (Step 1)
• Navigate to the Manual Control Menu
• Set RcvSol Valve=Close (Heat Pump only)
• Set Reheat Valve=50% (if present)
• Set EVO Cmd=30% (Heat Pump only)
• Set EVI Cmd=30%
• → When PTS>20psi: Navigate to Exp Valve Set-Up
• Set ManCtrl EV Op=Auto
Dynamic Charge (Step 2)
• Clear any active alarms (ex: Charge Loss: Problem
generated while removing charge)
• Navigate to Manual Control
• Set BP Sol Valve=Close
• Set Supply Fan=On
• Set SAF Spd Cmd=50%
• Set INV/OF Ena=On
• Set INV=On
• → When Clg State=Normal:
• Navigate to Manual Control
• Set INV Cmp Cmd=50%
• Set BP Sol Valve=Open
• Set OA Fan=On
• Set OA Fan Cmd=50%
Vary INV Cmp Cmd to maintain Te (temperature evaporator)
below 59°F. Keep an eye on Discharge Superheat to shoot for
minimum of 18°F, adjust the refrigerant being entered into the
system if Discharge Superheat begins to drop below 18°F.
