Applies to: N2-BLAST FPS-15000 and FPS-20000 fire protection nitrogen generators. These are legacy models and still supported; parts availability and upgrade paths vary by unit.
These are the largest of the legacy N2-BLAST units: a skid-mounted two-bed PSA generator with a touchscreen controller, fed by a separate air compressor, refrigerated dryer and air receiver, and storing nitrogen in an 80 gallon tank on the skid.
▲ Attention — three legacy families, three different machines If you have just read one of the other legacy overviews, put it down. These three families share a product line and almost nothing else — not the separation technology, not the filter kit, not the maintenance schedule, and not the purity specification.
Nothing in this article should be carried to another family, and nothing from another family should be carried here.
Nothing in this article should be carried to another family, and nothing from another family should be carried here.
| FPS-15000 / 20000 | FPS-1750 / 3000 / 6000 | FPS-650 / 1250 | |
|---|---|---|---|
| Separation | PSA — two CMS beds | Membrane element | PSA beds |
| Air supply | External compressor, dryer and receiver | External compressor | Integral compressor |
| Mounting | Floor standing, skid mount | Wall mounted | Wall or floor (650), floor (1250) |
| Controls | 3.5" touchscreen | Pressure switch and lights | Numbered-button controller |
| Filter kit | FRP-006 | FRP-002 | FRP-007 |
| Purity | 98.0% or better (built to order — check your project documents) | 98.0% or better | 98.0% or better |
| Setpoints | Entered on a password-protected screen, factory set per unit | About 72 / 80 PSIG | About 62 / 70 PSIG |
The bypass handle
A manual bypass ball valve switches the sprinkler system between nitrogen from the generator and bypass air. The layout sheet for this family records it as nitrogen = handle out (normal operation) and air bypass = handle up — the same way round as the FPS-1250 and the Type II models, and the opposite of the FPS-650 and the current FPS-500 and FPS-900.
⚠ Warning — the placard on the unit governs The operating manual for these models states no handle polarity at all. The drawing above is the only source we have for this family, and handle legends have not been printed the same way across every South-Tek model generation. Read the placard on the machine in front of you and follow it if it disagrees with this article.
The mistake worth avoiding is specific: a technician who reads the wrong polarity leaves the generator bypassed on air while believing the system is on nitrogen. The system keeps its pressure and quietly loses its corrosion protection.
If there is no placard, or you cannot read it, do not work it out by trial. Get the position from the installation layout drawing supplied with the system, or call us with the model and serial number. Then mark the handle.
The mistake worth avoiding is specific: a technician who reads the wrong polarity leaves the generator bypassed on air while believing the system is on nitrogen. The system keeps its pressure and quietly loses its corrosion protection.
If there is no placard, or you cannot read it, do not work it out by trial. Get the position from the installation layout drawing supplied with the system, or call us with the model and serial number. Then mark the handle.
ℹ Note — the "Air Bypass Alarm" is an alarm, not the bypass The Air Bypass Alarm option does not bypass anything. It watches the valve. Per the installation drawing, a handle left in the bypass position illuminates a red light on the generator and signals a local supervisory alarm if it has been connected to the building monitoring panel, until the handle is returned to the normal position.
Without the option, nothing tells you the system is on air other than the handle itself.
Without the option, nothing tells you the system is on air other than the handle itself.
Specifications
These are general figures. Your unit has its own detail drawing and project specification, and those govern — this family is built to order more than the smaller models are.
| Item | FPS-15000 and FPS-20000 |
|---|---|
| Nitrogen purity | 98.0% or better per the model specification for the FPS-15000 and FPS-20000. The general PSA table earlier in the same manual gives a range of 95–99.999%, set at the factory, because that table covers the whole PSA product line rather than these two models. The project documents for your unit govern. |
| Nitrogen operating pressure | 60–100 PSIG. Options outside that range exist — ask us. |
| Nitrogen cut-in / cut-out | Factory set per unit and not published. See below. |
| Installation | Floor standing, skid mounted |
| Display | 3.5" HMI touchscreen |
| Nitrogen storage | 80 gallon tank on the skid. Storage pressure up to 80 psig. |
| Cabinet port connections | ½" NPT female, and the installation drawing confirms all connections are ½" NPT female unless otherwise specified. |
| Electrical | 110–240 V / 50–60 Hz / 1 phase, protected by a 7 amp fuse. Supply it from a circuit rated for 20 amp service, and ground it. Read the label on the unit — see the open item at the end of this article. |
| Size and weight | 24" × 20" × 64". 600 lb (FPS-15000) / 730 lb (FPS-20000). |
| Ambient temperature | 40 °F to 90 °F per the model specification. The manual also carries a general PSA figure of 40–104 °F and a feed-air limit of 33–100 °F — work to the tightest of them. |
| Noise | Under 80 dBA without the compressor — the compressor is separate equipment and adds to it. |
| Sieve bed design pressure | 150 PSIG |
| Storage tank design pressure | 140 PSIG |
Cut-in and cut-out — where to read them
Unlike the smaller legacy models, this family has no published cut-in and cut-out figures. A pressure transducer on the storage tank feeds the controller a 4–20 mA signal, and the setpoints are entered on the touchscreen. They are set at the factory for your unit.
To read them: Menu → Pressure Transducer Setup. A password prompt appears — touch the blue box for the keypad and enter the password South-Tek supplied with your system. The screen shows the cut-in pressure, the cut-out pressure and the debounce time.
⚠ Warning — do not adjust the setpoints They are factory set, and adjusting them can alter both the nitrogen purity and the flow the system was designed to deliver. On a fire protection system the purity is the corrosion protection you are paying for.
The control program is proprietary and locked at the factory. Any change requires our assistance and must be done by us. Unauthorized changes to the program can void all warranties and may damage the system or cause it to malfunction. Read the setpoints if you need to know them; call us before changing anything.
The control program is proprietary and locked at the factory. Any change requires our assistance and must be done by us. Unauthorized changes to the program can void all warranties and may damage the system or cause it to malfunction. Read the setpoints if you need to know them; call us before changing anything.
The touchscreen
| Where | What it shows or does |
|---|---|
| Upper left — power | The main power switch is built into the touchscreen. Green means on, red means off. Touch and hold the indicator for 2 seconds to change state. A manual stop halts the PSA cycling and nitrogen production; you do not need to stop airflow from an air receiver, because the generator stops the delivery of airflow internally. |
| Lower left — system status | Green Run is operating, Red Stop is a manual stop, and Amber Standby means the unit has reached its nitrogen storage pressure and paused PSA cycling until it needs to run again. |
| Main screen | Nitrogen tank pressure and oxygen concentration. |
| Graph | Total run hours at the bottom left, plus graphs of running O₂ % and nitrogen tank pressure — press the green PSI button to switch between them. Data is sampled every 5 seconds and the graph holds 5000 points before the oldest scroll off. Useful for seeing a trend rather than a snapshot. |
| Menu | Routes to calibrations, pressure setup, timing, alarms and maintenance. |
| Valve indicators | Green means the valve is open, black means closed. |
Each of the two sieve bed towers also has its own pressure gauge on top. Watching those through a full cycle is how you see whether both beds are getting the air they should.
Feed air — this is a warranty condition, not a preference
This family depends on the air supplied to it far more than the smaller models do, because the compressor, dryer and receiver are all separate equipment somebody else specified and maintains.
| Requirement | Why it matters |
|---|---|
| Air temperature between 33 °F and 100 °F (0.5 °C to 38 °C) | Air hotter or colder than this may cause damage not covered by warranty. |
| Water dew point 40 °F (5 °C) or below | Higher moisture damages the adsorbent material and voids the warranty. A correctly sized refrigerant dryer is what keeps you inside this. |
| Minimum 100 psig operating pressure | Performance is rated at 100 psig. Higher or lower gives nitrogen production above or below design. |
| Do not exceed 150 PSIG | Operating above 150 PSIG may damage the media inside the pressure beds. If the air supply can deliver more than 150 PSIG, make sure the delivered flow is less than the safety relief capacity — ask us what that is for your unit. |
| Pipe one size up beyond 50 feet | If the run from the air receiver is longer than 50 ft, use air supply pipe one size larger than the generator inlet nozzle, or you will not get the rated flow at the inlet. |
The inlet air pressure regulator comes factory set between 100 and 150 psi for the design, with a 2" back-mount 0–160 psi gauge. Site conditions sometimes make an adjustment necessary. Set it as close to the top of each bed swing as possible: adjust slowly, watch the air-in gauge, and take the reading just before the bed swings. At the swing the pressure overshoots by up to 15% — ignore that peak, it is not your setting. Depending on the regulator you will need to loosen a turn knob or a nut slightly first to be able to adjust it; clockwise increases, counter-clockwise decreases. It leaves the factory set with 150 psi on the front side — the pressure coming into the regulator. The compressor's own output pressure caps what is available to the generator.
Maintenance — kit FRP-006, and a heavier schedule than you may expect
▲ Attention — this family has a daily maintenance list The other legacy families are essentially an annual filter change. This one carries daily checks, quarterly valve exercising, annual sensor and filter work, and valve rebuilds at three and five years. Several of these are written as factory recommendations rather than hard requirements, but they are what the manual asks for. That is an industrial maintenance regime on a fire protection asset, and it is worth agreeing who actually owns it before the unit needs it.
Where a component manufacturer's schedule differs from ours, follow the more demanding one.
Where a component manufacturer's schedule differs from ours, follow the more demanding one.
| Interval | What to do |
|---|---|
| Every day | Check for air and product leaks. Check instrument air pressure. Look at the control panel. Record nitrogen concentration and flow rate, operating and ambient temperature, feed air pressure, product tank pressure, and the sieve bed pressures through one full cycle. Verify the automatic filter drain is working. Manually operate the air receiver drains. |
| Every three months | Operate the safety valves. Operate the manual valves. Both are exercise, so they still move when they are needed. |
| Annually | Test all air pilot valves. Check for air and product leaks. Change all three filter elements. Check the O₂ analyzer sensor per the manufacturer's instructions and order a replacement. |
| Every five years or 15,000 hours | Replace all the process valves. Ask us for a quote and instructions. |
| Filter | Removes | Life |
|---|---|---|
| Particulate (pre-filter) | Particles down to 5 microns | 12 months |
| Coalescing | Particles down to 0.01 microns | 12 months when the pre-filter is regularly maintained — its life depends on how well the pre-filter is doing its job |
| Activated carbon tower or element | Oil vapor down to about 0.003 ppm | Typically 12 months when the upstream filters are maintained — but its life depends on the oil content of the feed air |
The annual kit is FRP-006. The activated carbon tower is replaced as part of the change, not just the bowl elements — remove the tower and fit new activated carbon.
⚠ Warning — prove the pressure is gone, and never ignore a blocked drain Do not remove a filter bowl until BOTH the air supply gauge AND the process pressure gauge clearly read zero psig. One gauge at zero is not proof — a bowl still holding process pressure comes off under load.
Turn off the power and the supply air, then relieve system pressure by opening the wedge valve after the regulator. (One section of the manual says the wedge valve after the filters; both refer to the vent downstream of the filter and regulator set — open it and confirm zero on both gauges before you touch a bowl.)
A plugged drain system carries water and oil into the adsorber and causes permanent damage to the media. That damage is not covered by warranty, and neither is damage from using filters other than the ones we specify. When you have the bowls off, look at them — if they are full of water, the drain is not working, and that is the fault to fix.
Turn off the power and the supply air, then relieve system pressure by opening the wedge valve after the regulator. (One section of the manual says the wedge valve after the filters; both refer to the vent downstream of the filter and regulator set — open it and confirm zero on both gauges before you touch a bowl.)
A plugged drain system carries water and oil into the adsorber and causes permanent damage to the media. That damage is not covered by warranty, and neither is damage from using filters other than the ones we specify. When you have the bowls off, look at them — if they are full of water, the drain is not working, and that is the fault to fix.
- Disconnect the drain tubes from the bottom of the bowls if they are tied into a condensate drain system.
- To remove a bowl: push the bowl latch down and rotate the bowl while pulling down. On some models the bowl is held to the cover by screws instead — remove those and pull the bowl off.
- Unscrew the element off and look at it. An excessively dirty element means the interval is too long for this site.
- Wash the bowls in soapy water and rinse thoroughly. A light air gun is fine for debris. Always finish with a clean dry cloth.
- Fit the new element and replace O-rings as needed, then refit the bowl the opposite way it came off and make sure it is seated correctly.
- Reconnect the drain tubes, then open the air inlet valve slowly to pressurize the bowls and check for leaks.
The oxygen sensor
- The oxygen sensor has an expected life of more than 900,000 oxygen % hours, and its accuracy should be verified at least once a year.
- Calibration is a two-point procedure from Menu → sensor calibration. Three devices can be calibrated: O₂ PPM, Max O₂, and the PSI sensor.
- Moving a unit to a significantly different elevation is one reason calibration may be needed.
- Where a known calibration gas is used, regulate it to at least 5 psi and no more than 60 psi. The O₂ analyzer port is on the outside of most units on the right hand side — check your unit drawing for the exact location.
- If calibration is needed frequently, that is the sensor telling you it is worn out. Replace it rather than recalibrating it repeatedly.
Safety
⚠ Warning — power off before air off The manual states this on its own page, in capitals: do not disconnect or turn off air to the generator unless the generator power switch is turned off. Taking the air away from a running generator is not a neutral act.
The generator stays pressurized after shutdown. Before any maintenance, or opening any piping, always depressurize the system — failure to do so may result in injuries.
The generator stays pressurized after shutdown. Before any maintenance, or opening any piping, always depressurize the system — failure to do so may result in injuries.
- Isolate and depressurize before any mechanical work, including changing filters. Nitrogen must be vented to the outside or to a large, well-ventilated space.
- Nitrogen displaces the oxygen you breathe and gives no warning. The generator also exhausts oxygen-enriched waste gas through a silencer — keep ignition sources away from it.
- Never disable or bypass a safety relief valve on the air receiver or the product tanks.
- Pressurized gas is contained in the generator, the receiver and the product tanks even when the unit is switched off.
- Only qualified people may install, maintain or repair these units, and only approved parts that meet or exceed the original specification.
- Do not alter any controls or instrumentation. Changes without our consent void the performance specification your system was built to.
Installation essentials
The installation layout drawing supplied with your system governs. The general notes on it are worth reading before anyone orders pipe:
- All plumbing, fittings, valves and hardware between components are supplied by others. The drawing shows the arrangement, not the scope of supply.
- All connections are ½" NPT female unless otherwise specified.
- All equipment must be installed on a hard flat surface.
- Anchoring the nitrogen generator is not required by us — but follow any local or site code that says otherwise. The compressor and dryer have their own anchoring requirements in their manufacturers' manuals.
- Leave room for the air receiver and product receiver skid next to the unit, and enough space around the generator for access and routine maintenance.
- Fit flexible tubing between the compressor and the hard piping — the drawing calls for at least 24" of ½" ID flex rated for 200 PSIG and 135 °F, optional part number 002-310 — to keep compressor vibration out of the pipework.
- Fit relief valves on the air receiver and the nitrogen receiver if they were not supplied by us.
Where the documentation is unclear
| Question | What to do meanwhile |
|---|---|
| The current rating. The specification table says under 2 operating amps; the site requirements section says 7 A "as labeled on the unit". | Go by the label on the unit, which is what the manual itself says to do. The 7 A figure is supported by the fuse, which is a ¼" × 1¼" 7 amp glass time delay rated to 250 VAC. Size the circuit from the label, not from this article. |
| The daily maintenance list. It is written for an industrial nitrogen installation, and reads heavily for a fire protection asset that may be in an unattended riser room. | It is what the manual specifies. If nobody is realistically doing a daily walk, talk to us about what a workable schedule looks like for your site rather than quietly dropping it — several of those daily items are the early warning for the failures that are not covered by warranty. |
Related articles
- FPS-650 and FPS-1250 Legacy Overview
- FPS-1750, FPS-3000, and FPS-6000 Legacy Overview
- Legacy N2-BLAST Fire Protection Systems Overview
- N2-BLAST System Leak Check Procedure
- What Are My Cut In/Out Pressures?
- AutoPurge and Quick-Check Overview for N2-BLAST Systems
- N2-BLAST Fire Protection Systems Overview
Need help? Have the model and serial number and your unit detail drawing ready — this family is built to order, so the project documents answer more than a general specification can. South-Tek Systems Service — Phone: (910) 415-1880 · Open a support ticket at support@southteksystems911.zendesk.com or through the Help Center.