Powerex Medical Scroll Controller
Regulated equipment (NFPA 99, CSA Z7396.1 in Canada). Any wiring or logic change must be documented and re-verified by a qualified medical gas installer.
Manufacturer
Powerex
Display
2-line 20-char LCD or color touchscreen (newer builds).
Years produced
~2005 – present, multiple hardware generations.
Power supply
24 VDC control, 120 VAC input.
Ambient range
5 – 40 °C (indoor equipment room).
Protection rating
IP54 front.
Relay outputs
One contactor coil per scroll head + dryer + alarm + BMS common trouble.
Used on
- Powerex SES/SGP medical air skids
- Powerex laboratory air packages
- OEM-supplied to hospital projects
Features
- Head lead-lag with hour equalization
- NFPA 99 compliance logging
- Automatic changeover if a head fails
- Dewpoint & CO alarm outputs to Master Alarm Panel
Interfaces
- RS-485 Modbus RTU
- Dry contacts for BMS
- NFPA 99 remote alarm panel outputs
Sensor inputs
- Per-scroll head discharge temp
- System pressure (4–20 mA)
- Dewpoint (NFPA 99 medical air)
- CO / CO2 monitors (integrated on medical air skids)
Fault code lookup
First checks
- Head cooling fan operation
- Inlet filter
- Verify thermistor
First checks
- Dryer capacity vs demand
- Purge on desiccant units
- Verify dewpoint sensor calibration
First checks
- Contactor + overload for that head
- Motor winding continuity
- Auto-changeover to next head confirmed?
First checks
- Increased demand event
- Check all heads running
- Leaks downstream of dryers
Fault list is non-exhaustive and firmware-dependent. Always confirm against the controller’s on-screen help or OEM manual.
Sensor pin resistance & signal values
Pin-level resistance and signal values for the sensor types this controller uses. Works offline. De-energise the panel and lift one lead before ohming any element.
Wiring notes
- Two independent power feeds required by NFPA 99 — one per side of duplex/simplex skid
- Alarm outputs must be wired to Master Alarm Panel per NFPA 99 §5.1.9
- Never bypass the dewpoint or CO alarm outputs — code violation
Known issues & field notes
- Hour equalization drifts if a head is manually disabled — reset lead pointer after service
- Firmware differences between medical & lab builds — do not cross-flash
Service menu password on modern touchscreen builds defaults to 1234 but MUST be changed at commissioning per hospital policy. Older LCD units used a hidden key combo (Set + Up + Down held 5s).
Manuals & literature
Powerex — support portal
Manuals hosted per-product — search model below
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