Filter maintenance is the primary routine service task for the N2-GEN™ CPi & CPx Series. Clean filters protect the carbon molecular sieve (CMS) from moisture and particulate contamination, which directly affects nitrogen purity and generator longevity. The filter kit and replacement schedule differ between CPi and CPx models — and for CPx models, they also differ depending on when the unit was built.
CPi Models — Filter Kit FRP-001
CPi models (2CPi, 4CPi) include three filters: an air intake pre-filter on the compressor, a 5-micron particulate filter, and a 0.1-micron coalescing filter. All three must be replaced annually or every 1,000 run hours, whichever comes first.
Air Intake Pre-Filter
- Power down the system and remove the front cover.
- Locate the pre-filter on the air intake of the compressor.
- Twist the pre-compressor filter cap clockwise to remove it.
- Pull out the old filter element and wipe the filter bowl clean with a dry cloth.
- Install the new element and replace the cap.
Particulate Filter
- Confirm zero pressure on the filter bowl (the gauge after the filter housing reads 0 PSIG).
- Unscrew the filter bowl counterclockwise and remove it.
- Rinse the bowl with warm water to remove debris; dry with a clean cloth.
- Replace the old O-rings with those provided in the FRP-001 kit.
- Remove the old particulate element using a Phillips-head screwdriver and install the new element.
- Reinstall the bowl into the filter housing.
Coalescing Filter
- With bowl removed (same procedure as particulate filter above), twist the coalescing element counterclockwise to remove it.
- Install the new element in the reverse order.
- Reinstall the cleaned bowl with fresh O-rings.
After Replacing CPi Filters
- Replace the front cabinet cover.
- Power on the unit. The compressor will start and begin producing nitrogen.
- Check filter bowl connections for leaks.
- Reset the filter timer using one of the two methods below.
Filter timer reset — Method 1 (filter reset button on electrical panel): Press and hold the dedicated filter reset button until an audible beep confirms the reset.
Filter timer reset — Method 2 (controller face buttons): Unlock the controller by pressing and holding the Mode button. Then press and hold the Filter Change Reset button for 7 seconds. An audible beep confirms the timer has been reset and the filter alarm cleared.
CPx Models — Identifying Your Filter Generation
CPx models (2CPx, 4CPx) were produced with two different filter assemblies depending on manufacture date. Before ordering a replacement kit, identify which generation is installed by checking the color of the filter housings inside the cabinet.
| Housing Color | Manufacturer | Replacement Kit | Unit Age |
|---|---|---|---|
| Black | Wilkerson | FRP-1-1 | Older units |
| Off-white | ASCO | FRP-019 | Newer units |
CPx Models — Wilkerson Filters (Black) — Kit FRP-1-1
Units with black Wilkerson filter housings use kit FRP-1-1. The three filters are replaced on a staggered schedule based on contamination loading.
| Filter | Rating | Replacement Interval |
|---|---|---|
| Particulate | 5 micron | Every 3 months (4× per year) |
| Coalescing | 0.01 micron | Every 6 months (2× per year) |
| Absorber | 0.003 micron / activated carbon | Every 12 months (1× per year) |
CPx Models — ASCO Filters (Off-White) — Kit FRP-019
Units with off-white ASCO filter housings use kit FRP-019. All three filter elements are replaced on the same 6-month schedule. The kit includes 2 of each element, covering a full year of service in a single order.
| Filter | Rating | Replacement Interval |
|---|---|---|
| Particulate | 5 micron | Every 6 months (2× per year) |
| Coalescing | 0.01 micron | Every 6 months (2× per year) |
| Absorber | 0.003 micron / activated carbon | Every 6 months (2× per year) |
CPx Filter Replacement Procedure
The replacement procedure is the same for both filter generations. The only difference is the bowl removal method in step 4 — note which applies to your unit.
- Valve off the incoming air supply to the generator.
- Open the service valve after the filters to relieve pressure. Confirm 0 PSIG on the air supply gauge.
- Disconnect any condensate drain tubes from the bottom of the filter bowls.
- Remove each filter bowl:
- Wilkerson (black housings — FRP-1-1): Push the bowl latch down and rotate counterclockwise while pulling down. If the bowl is difficult to turn, push the clip up while rotating.
- ASCO (off-white housings — FRP-019): Twist counterclockwise and pull down.
- Inspect each bowl. If a bowl is full of water, investigate the auto-drain for blockage before proceeding.
- Remove the filter element by unscrewing it counterclockwise. Note the condition of the element — if excessively dirty before the scheduled interval, shorten the replacement frequency for that filter.
- Wash the bowls in soapy water, rinse thoroughly, and dry with a clean cloth. An air gun may be used to clear debris.
- Install the new filter elements and replace O-rings as needed.
- Reinstall the bowls in the correct housing in reverse order of removal, ensuring each bowl is fully seated.
- Reconnect the condensate drain tubes.
- Slowly open the air inlet valve to repressurize the filter housings. Inspect all connections for leaks.
Contact South-Tek Systems
Phone: (910) 415-1880
Email / Ticket: support@southteksystems911.zendesk.com