Applies to: South-Tek Systems N2-BLAST® FPS-500, FPS-900, FPS-900-RS, and FPS-1650 — the models that take annual filter kit FRP-007.
Does NOT apply to: FPS-3250 and FPS-5000, which take kit FRP-013 and have a different filter layout — see their preventive maintenance article. Also does not apply to FPS-10000, FPS-16500, or FPS-22500.
These four models share the same filter hardware: a two-bowl filter body inside the cabinet holding the particulate and coalescing elements, plus a pre-filter on the compressor intake. Kit FRP-007 replaces all three elements and the two bowl O-rings. Replace them annually or at 1,000 run hours, whichever comes first, and reset the service timer afterwards.
⚠ Warning — read before you start Stop the unit at the controller first, then open the disconnect and lock it out — never the other way round. Removing power does not depressurize the machine; the pressure check in step 4 is separate and still required. Only qualified personnel should perform this work. Nitrogen displaces oxygen and gives no warning — it is colorless and odorless. Work in a well-ventilated space, never in a closet, pit, or sealed room, and never enter a confined space downstream of a vent without a calibrated meter reading 19.5% O₂ or higher. Use only approved replacement elements — non-factory filters are not qualified for this machine and can put moisture into the separation beds.
▲ Attention — this takes a fire protection system out of service While the generator is down it is not replenishing nitrogen in the riser. Notify the building owner or facility representative and the alarm monitoring company before you start — opening the disconnect de-energizes the common alarm contact, which on the FPS-500, FPS-900 and FPS-900-RS is the power loss alarm, and without warning that reads as a fault at the panel. Follow the site impairment procedure, keep the window to the length of the job, and confirm the system is back at supervisory pressure and out of bypass before you close out.
What is in the kit
| Item | Where it goes | Qty |
|---|---|---|
|
Pre-compressor filter element 2 micron on the FPS-500 and FPS-900; on the FPS-900-RS and FPS-1650 order by kit and serial number |
On the compressor intake, not on the filter body. It is the element most often forgotten. | 1 |
|
Particulate element 5 micron |
First bowl on the filter body — bulk particles. | 1 |
|
Coalescing element 0.1 micron |
Second bowl — aerosols and fine carryover, the stage that protects the separation beds from moisture. | 1 |
| Bowl O-rings | One per bowl. Replaced every time, not reused. | 2 |
ℹ Note — order by kit number The element part numbers inside FRP-007 differ between models. Order the kit by number — FRP-007 — and give South-Tek the serial number of the unit so the right elements ship. Do not order individual element numbers from another unit's paperwork. To request pricing, see Requesting a Quote for Replacement Filter Kits.
What to have with you
- The FRP-007 kit for the unit's serial number, unopened until you are at the machine.
- Warm water, and a clean dry cloth.
- Soapy water in a spray bottle for the leak check.
- Safety glasses and hearing protection. The cabinet is open and the machine runs at the end of the job.
- A lock and lockout tag for the branch-circuit disconnect, and the site's impairment tag.
- O-ring lubricant, for FPS-900-RS units.
- Something to record the date, the run hours, and the kit used.
Procedure
| # | What you do | What you should see |
|---|---|---|
| 1 | Notify the building owner or facility representative and the alarm monitoring company, declare the impairment under the site's impairment program, and hang the impairment tag before you begin. Then stop the unit at the controller and let it come to a stop — on the FPS-1650 that is what vents the filter section, so it must happen before power is removed. Only then open the disconnect and lock it out. The compressor is inside the cabinet and can start on a pressure call at any moment, and stopping the unit from the controller does not isolate it — the branch-circuit disconnect is the isolation point. | Impairment declared and tagged, building owner and monitoring company both notified, unit stopped at the controller, supply locked out. |
| 2 | Isolate the generator from the riser and from any external air supply. On the FPS-500, FPS-900 and FPS-900-RS the generator outlet is a 3-way valve that selects Nitrogen Out or Bypass — it is not an isolation valve. Isolate at the manual ball valve between the nitrogen storage tank and the riser, and leave the 3-way valve in the Nitrogen Out position. On the FPS-1650, valve off the outlet. If the unit is fed by an external air compressor, close that inlet valve too. Isolating incoming and outgoing pressure is required before any mechanical work on this machine, filter changes included. | Outlet valve closed and the riser holding its own pressure. The riser is now on stored nitrogen and is not being replenished. The impairment window opened at step 1 — keep it short. |
| 3 | Remove the front cover — four screws on the FPS-900-RS — and locate the two-bowl filter body on the bracket in the middle of the cabinet, and the compressor intake pre-filter. | Both bowls and the pre-filter cap accessible. |
| 4 | Confirm the filter section is at zero on the gauge. On the FPS-1650 the filter section vents itself as the unit stops at the controller — read the gauge after the copper coil. On the FPS-500, FPS-900 and FPS-900-RS, do not assume it self-vents. On the FPS-500 and FPS-900, read the 0–160 PSIG gauge on the filter assembly itself, on the bracket in the middle of the cabinet. On the FPS-900-RS, read the gauge on the filter assembly on that same mid-cabinet bracket. Either way it is not the nitrogen storage gauge — prove zero on the filter gauge before you touch a bowl. Any gas released here is compressed air from ahead of the separation beds, but nitrogen elsewhere in the cabinet displaces oxygen and gives no warning — ventilate the room, and never do this work in a closet, pit, or sealed space. | 0 PSIG on the gauge, and no sound of venting. If it does not fall to zero, stop and contact South-Tek — never loosen a bowl, fitting, or drain to find out. The system stays impaired until this is resolved — keep the impairment open, and tell the building owner and the monitoring company that the window is extending. |
| 5 | Free the bowl drain tubing before lowering a bowl, and do not pull on the tubing. The drain fittings are push-to-connect — see How Do I Remove a Push-to-Connect Fitting? | Tubing free, fittings undamaged. Do not yank on the tubing. |
| 6 | Remove both bowls by turning each one counter-clockwise and lowering it off the body. | Both bowls off, elements still in place. |
| 7 | Remove the old elements. Particulate: pull the plastic element housing out of the bowl, twist off the black plastic cover, and pull the element off. Coalescing: twist it counter-clockwise to remove. | Both old elements out. Keep them separate from the new ones. |
| 8 | Clean the bowls — before any new element goes in. Rinse the debris out with warm water, then dry each bowl with a clean dry cloth. | Bowls clean and completely dry. Water left in a bowl goes straight toward the separation beds. |
| 9 | Check the auto-drains while the bowls are off — each should be clear. Do not disassemble a drain; if one is fouled or will not clear, contact South-Tek. The system stays impaired until this is resolved — keep the impairment open, and tell the building owner and the monitoring company that the window is extending. | Both drains clear. A plugged auto-drain is what puts water into the media. |
| 10 | Fit the new O-rings — one per bowl, both from the kit. Discard the old ones. | A new O-ring seated in each bowl. If the kit does not contain an O-ring for each bowl, stop and call before reassembling. |
| 11 | Fit the new elements — both of them. Particulate: fit the element, refit the black plastic cover, and put the housing back in the bowl — the reverse of step 7. Coalescing: twist the new element clockwise to seat it. On the FPS-900-RS, lightly lubricate the element O-rings and seals if they are dry. | Two new elements in, each in the bowl it came from. Do not close up with an empty coalescing stage — it is the one that gets missed. |
| 12 | Refit both bowls to their own housings, turning clockwise until each seats — the opposite of removal — then reconnect the drain lines — push each tube in until it seats and give it a light pull to confirm it is locked. | Bowls seated squarely, drain lines locked. Reconnecting before the bowl is turned home twists the tubing back out. |
| 13 | Replace the pre-compressor filter. Twist the cap clockwise to remove it, pull the old element, wipe the housing with a clean dry cloth — do not rinse it — and fit the new element. | Third element in. All three are now replaced. |
| 14 | Refit the front cover, remove your lock and tag, then restore power at the disconnect and start the unit. | Cover on before power on. The only time the cabinet is open with the unit running is the leak look in step 15, with PPE on. |
| 15 | Leak check. With the cover on and the unit running, listen at the cabinet and confirm it builds pressure normally. If you need eyes on the bowls, this is the one cover-open-while-running check in this procedure: wear safety glasses and hearing protection, keep hands and the spray bottle clear of the compressor, fan and control panel, spray soapy water on the bowl seams and drain fittings only — never on electrical components — and close the cover as soon as you have looked. Keep the room ventilated while the cabinet is open. | No leaks, and the unit builds pressure normally. Push-to-connect fittings may show slight bubbling; up to about 5 ccm is acceptable. If you find a leak, do not touch it while it is under pressure: refit the cover, open the disconnect and lock it out again, and prove zero on the filter gauge exactly as in the pressure-check step before opening anything. |
| 16 | Reset the filter service timer — see the table below, which differs by controller. | Reset confirmed on the display. Reset it even if the alarm had not appeared yet, or the next reminder arrives at the wrong interval. |
| 17 | Close out. Reopen the tank-to-riser ball valve, and the external air inlet valve if you closed one. Confirm the riser is back at supervisory pressure and that the outlet valve is in the normal Nitrogen Out position — on the FPS-500, FPS-900 and FPS-900-RS that is the handle on the cabinet; on the FPS-1650 confirm the controller is not showing a bypass alarm. Clear the impairment tag, and tell the building owner and the monitoring company that the system is back in service. Record the date, run hours, and kit used. | System supervised on nitrogen, no active alarms, service recorded. |
Resetting the timer — by controller, not by model
Go by the controller in front of you rather than the model number on the order, because the same model shipped with different controllers over the years.
| Controller | How to reset |
|---|---|
|
Black rectangular controller with a small display and five keys — Set, Next, Up, Down, ENT FPS-500, FPS-900, FPS-900-RS |
Press and hold the Down (−) key until you hear the beep and the display shows FILTER RESET. That is roughly 7 seconds; keep holding if it does not take, then release and repeat. On some builds the reset also pulses the common alarm contact for about one second, so tell the monitoring company before you do it, and confirm the panel is back to normal afterwards. |
|
Touchscreen controller FPS-1650 |
Open the filter status screen — reachable from an active filter alarm, or from the Maintenance menu when no alarm is showing. It lists the kit number, the individual elements, and the last change date. Press Change Filters, then hold Reset. Menu and button labels vary a little by program version, so go by the screen in front of you. Confirm the last-changed date updates to today. |
|
Legacy controller with a different keypad layout earlier FPS-900 builds |
Different keystroke on some earlier builds. Full procedure: Resetting the Filter Alarm on Legacy Units. If the controller in front of you has Set, Next, Up, Down and ENT keys, use the row above instead. |
▲ Attention — why the drains and the drying matter Every step in this procedure about a clear auto-drain and a dry bowl exists for one reason: water reaching the separation media damages the beds and ends their life. A bowl reassembled damp, or a drain left plugged, costs far more than the kit. If you suspect water has carried past the filters, contact South-Tek before returning the unit to service.
If something does not go to plan
| What you see | What to do |
|---|---|
| The filter gauge will not read 0 PSIG | Check the order of work first: on the FPS-1650 the filter section vents as the unit stops at the controller, so if the disconnect was opened first it may still be holding pressure. Refit the front cover, remove your lock and tag, and restore power. Stop the unit properly at the controller, watch the gauge fall to zero, then open the disconnect and lock it out again. If it still will not reach zero, stop — do not loosen a bowl, a fitting, or a drain to vent it — and contact South-Tek. The system stays impaired until this is resolved — keep the impairment open, and tell the building owner and the monitoring company that the window is extending. |
| A bowl will not turn by hand | Re-check the gauge first — a bowl that will not move is often a bowl still under pressure. If it is confirmed at zero and still will not turn, call rather than forcing it. The system stays impaired until this is resolved — keep the impairment open, and tell the building owner and the monitoring company that the window is extending. |
| The reset will not take | Confirm you are on the right key and the unit is powered up, then release and hold again. If the display still does not confirm, note the controller type and contact support. |
| A bowl leaks after restart | Refit the cover, open the disconnect and lock it out again, and prove zero on the filter gauge exactly as in the pressure-check step. Then check the O-ring is seated and the bowl is turned fully home. Never tighten a leaking bowl under pressure, and never vent it yourself — if the gauge will not reach zero, contact South-Tek. The system stays impaired until this is resolved — keep the impairment open, and tell the building owner and the monitoring company that the window is extending. |
| An element in the kit looks different from the one you removed | Stop and confirm the kit against the unit's serial number before fitting it. Do not adapt an element to fit. The system stays impaired until this is resolved — keep the impairment open, and tell the building owner and the monitoring company that the window is extending. |
What to record
- Date of the change and the run hours shown on the controller.
- Kit used (FRP-007) and the unit's serial number.
- Condition of the elements removed — heavy loading early is worth investigating.
- Whether both auto-drains were clear.
- That the timer was reset, and that the system was returned to supervision on nitrogen.
Related articles
- FPS-500 and FPS-900 Preventive Maintenance — the full schedule this filter change sits in.
- FPS-1650, FPS-3250, and FPS-5000 Preventive Maintenance — the schedule for FPS-1650 readers.
- N2-BLAST® FPS-500 & FPS-900 — Safety Guidelines
- How Do I Remove a Push-to-Connect Fitting?
- Resetting the Filter Alarm on Legacy Units
- Requesting a Quote for Replacement Filter Kits
Need help? South-Tek Systems Service — Phone: (910) 415-1880 · Open a support ticket at support@southteksystems911.zendesk.com or through the Help Center.