FPS-500 and FPS-900 Overview – South-Tek Systems

Applies to: South-Tek Systems N2-BLAST® FPS-500 and FPS-900 fire protection nitrogen generators.

The FPS-500 and FPS-900 are compact, wall-mounted nitrogen generators built specifically for fire protection. They supply high-purity nitrogen (98.5%+) into dry-pipe and pre-action sprinkler systems to displace the oxygen and moisture that drive pipe corrosion, extending the life of the sprinkler network and reducing the risk of corrosion-related leaks and obstructions. Both are part of the South-Tek N2-BLAST® product family.

What these systems do

Oxygen and humidity trapped in sprinkler piping cause electrochemical, galvanic, and microbiologically influenced corrosion (MIC) — the leading cause of premature pipe failure in dry and pre-action systems. By replacing that air with 98.5%+ nitrogen, the N2-BLAST FPS interrupts the corrosion reaction at its source. The unit maintains a nitrogen "supervisory" atmosphere in the piping at low flow, so it works continuously in the background rather than as a high-volume gas supply.

ℹ Note The FPS-500 and FPS-900 are designed for fire protection service only. They are not intended for quick fills or as a general shop-air/nitrogen source; install a separate compressor for other air needs.

How the system works

A built-in oil-free air compressor feeds filtered air through a pressure swing adsorption (PSA) process that separates nitrogen from the compressed air by valve sequencing. The nitrogen is held in a storage tank and delivered to the sprinkler system on demand.

▲ Attention — the storage tank is a separate wall-mounted vessel The nitrogen storage tank is not inside the cabinet. It is a separate wall-mounted cylinder, 15" in diameter and 50" tall — allow 55" for manifold clearance — secured with a strap and a wall-fastened D-ring. So the installed footprint is the 12-3/4" × 12" × 27" cabinet plus the tank, and both need wall space and structure. This is the single thing most often missed when someone sizes a riser room off the cabinet dimensions. Full detail: Site and Utility Requirements.

Built-in air supply and filtration. An integral oil-free compressor supplies the air. Three filter stages protect the generator: a 2-micron pre-filter on the compressor intake, a 5-micron particulate filter for bulk particles, and a 0.1-micron coalescing filter for the finer carryover. All three are replaced together in kit FRP-007 at 12 months or 1,000 run hours, whichever comes first.
Nitrogen generation and storage. Two PSA beds produce 98.5%+ nitrogen, held in the wall-mounted storage tank and delivered at up to 70 PSI to the piping.
Automatic cut-in / cut-out. A mechanical pressure switch starts and stops nitrogen production to hold system pressure. The unit enters Standby at 70 PSIG nominal (expect 65–75 PSIG) and returns to Run once tank pressure falls 7–10 PSIG below that. These are set on the switch at the factory. On a standard unit there is no setpoint screen — check the behaviour on the storage-tank gauge instead: note the pressure as the unit enters Standby and the pressure when it restarts. Outside those bands, suspect the pressure switch. Units built with the optional pressure transducer do expose these setpoints on the controller. Either way, do not adjust them without consulting South-Tek Systems.
Patented BlastOff® leak detection. BlastOff monitors for abnormal gas usage and raises an alarm on a suspected leak. The alarm can be audible, visual, and a dry-contact signal to a Building Management System (BMS). Power-cycle the unit to reset the alarm, but do not repeatedly reset it without finding the cause.
Purity monitoring — where the sensor is fitted. With the optional oxygen sensor the controller tracks oxygen content in percent and in PPM and raises a high-oxygen alarm. Units built without it have no on-board purity readout. Confirm what the unit was built with before troubleshooting a missing reading, and contact South-Tek for the correct sampling method on that build — do not improvise a tap on a pressurised line.
Controller. Both models use the same controller, which displays status and run hours and drives the alarm outputs. Programs are password-protected from the factory and must not be altered without South-Tek's written consent.
Manual air bypass. A 3-way ball valve on the left side of the cabinet switches the riser onto compressed air. It is intended for the 30-minute fire protection piping fill test. Its position is sensed magnetically and raises the bypass alarm, which also drives the common alarm dry contact — so a connected fire panel or BMS will see it. Notify the monitoring company before you move the handle. While the unit is in bypass the riser is held on compressed air, not nitrogen, so corrosion protection is suspended: keep it as short as the work allows, then return the handle to the normal run position and confirm the bypass alarm clears before you leave. Some builds carry a second 3-way valve for the air inlet — identify the bypass handle by its placard rather than by counting valves. Automatic bypass is a feature of the larger FPS models; on these two it is manual only.
Monitoring outputs. One voltage-free common alarm dry contact on both models, pooling bypass, BlastOff® and power loss — and, on the FPS-900, the filter alarm as well. There is no separate contact per alarm on this family, so the panel sees “an alarm” without knowing which. On the FPS-900, resetting the filter alarm also pulses this contact for about one second — tell the monitoring company before you do a filter reset so it is not logged as a real event. Plus a user-configurable 4–20 mA analog output (ambient temperature as standard; oxygen percent, trace O₂ in PPM, or supply pressure where those sensors are fitted). Modbus RTU over RS-485 is available as an option, and it is the communication path on these models. If a project needs Modbus TCP/IP, BACnet, or an Ethernet connection, confirm availability with South-Tek before specifying it.

Choosing between the FPS-500 and FPS-900

The two models share the same cabinet footprint and weight, 1/2" NPT female connections, 40–100°F ambient range, and 98.5%+ purity. They differ in nitrogen output capacity — rated by the volume of the largest single sprinkler zone they can supervise — and also in rated current, high-voltage option, and filter element part numbers:

FPS-500 — rated to a largest single zone of 500 gallons.
FPS-900 — rated to a largest single zone of 900 gallons.

▲ Sizing rule Size by the total gallonage of the largest single zone, not the sum of all zones. Work from the zone volumes on the project submittal and confirm the model selection with South-Tek before ordering.

Specifications

Specification	FPS-500	FPS-900
Nitrogen purity	98.5%+	98.5%+
Coverage (largest single zone)	500 gal	900 gal
Nitrogen outlet pressure	Up to 70 PSI	Up to 70 PSI
Cut-in / cut-out (mechanical pressure switch)	Cut-out (enters Standby) 70 PSIG nominal, 65–75 PSIG; cut-in 7–10 PSIG below cut-out. Factory preset on the switch and not displayed on a standard unit — verify on the storage-tank gauge. Units with the optional pressure transducer show these setpoints on the controller. Do not adjust without consulting South-Tek
PSA sieve beds	Two on both models
Nitrogen storage tank	Separate wall-mounted vessel — 15" diameter × 50" tall, allow 55" for manifold clearance. Not inside the cabinet
Annual filter kit	FRP-007 — three elements plus O-rings, replaced at 12 months or 1,000 run hours, whichever comes first. Element part numbers differ between the two models, so confirm by serial number when ordering
Cabinet dimensions (W × D × H)	12.75" × 12" × 27"	12.75" × 12" × 27"
Cabinet weight	84 lb	84 lb
Standard power (Option 1)	110–120 VAC, 60 Hz, 1-ph, 3.3 A	110–120 VAC, 60 Hz, 1-ph, 3.5 A
Optional power (Option 2)	220 VAC, 50 Hz, 1-ph, 1.4 A	240 VAC, 50 Hz, 1-ph, 1.4 A
Over-current protection	15 A breaker	15 A breaker
Gas connections	1/2" NPT female	1/2" NPT female
Drain connections	Two × 1/4" OD push-to-connect couplings — plumb both, individually
Compressor	Integral, oil-free	Integral, oil-free
Noise level	<60 dB. Wear ear protection while the equipment is running
Ambient temperature	40–100°F (4–38°C)	40–100°F (4–38°C)
Installation	Wall-mounted (optional floor-mount kit)	Wall-mounted (optional floor-mount kit)
Controller display	Hours / BlastOff / Bypass / Operate / Standby	Hours / Power On / Operating, plus the bypass and BlastOff® alarm screens — see Operation and Alarms
Approvals / certification	UL 508A open-type industrial control panel certification. The O&M manuals make no FM Approval claim for these models. If the job is FM-insured, obtain the FM status in writing from South-Tek for the specific model and configuration being ordered, before submitting.

Typical installation profile

Both models are designed for indoor installation in a nonhazardous area, mounted upright to a weight-bearing wall or suitable rack. An optional floor-mount kit is available.

⚠ Warning — room ventilation Nitrogen is not poisonous, but it displaces oxygen and high concentrations can cause asphyxiation. Install the unit in a well-ventilated room that is not sealed off from normal living-space air changes, and vent the generator's exhaust gas outdoors or into a large, well-ventilated room. Do not install near a heat source or where steam or water is present. The 6" side clearance below is for cabinet cooling airflow — it does not satisfy this room-ventilation requirement.

Leave at least 6" on the left side of the cabinet for ventilation, and never block it — the left side is the ventilation face and also carries the 3-way bypass and outlet valve handles (lower left). The control panel, the tube and pipe connections, and the front cover are all accessed from the front.
Leave 36" minimum at the front for access to the control panel, the tube and pipe connections, and the front cover. This is a requirement, not a preference: inadequate access clearance voids the warranty.
Two 1/4" OD push-to-connect drain couplings are at the bottom right of the cabinet. Plumb both to the nearest suitable site drain. Site practice is to run them individually and open to atmosphere; do not cap them.
Secure the unit to the wall at both the top and bottom flanges. Failure to do so could cause damage or bodily injury. Both models use the same wall-mounting bracket kit, STS Part # A05-TYP1-RD (ordered separately), which fits standard 16" wall-stud spacing. If the studs are not 16" on centre, reinforce the mounting area with 1/2" or thicker plywood before hanging the unit — it vibrates continuously while the compressor runs. Otherwise use the cabinet mounting holes to fasten the unit securely and level to a wall or an existing rack. All mounting holes take 1/4" screws and anchors, which are not supplied.

Utility profile

Built-in oil-free air compressor — no external air supply required for nitrogen generation.
Standard power: 110–120 VAC, 60 Hz, 1-phase. A high-voltage option is available — 220 VAC on the FPS-500, 240 VAC on the FPS-900; on the FPS-900 wiring changes apply. Confirm the built voltage on the unit nameplate before rough-in — it is set at the factory.
Built-in 15 A over-current protection device (breaker).
Hard-wired terminal-strip connection is the factory default and no line cord is supplied. A cord-and-plug variant can be specified at order, so confirm the as-built connection method against the order before rough-in.
UL 508A open-type industrial control panel certified; electrical schematics available on request.
Required operating environment: a nonhazardous indoor location at 40°F to 100°F (4°C to 38°C). If the unit arrives before the room is ready, store it upright — preferably in its shipping box — in a dry, climate-controlled room at 60°F to 80°F, keep gas lines capped and dry, and never stack anything on top of it.

Before following a procedure

Confirm the exact model number on the unit nameplate before following a procedure or ordering service parts. While the FPS-500 and FPS-900 are very similar, always use the procedure or document that matches the model when available.

Manual downloads

Need help? South-Tek Systems Service — Phone: (910) 415-1880 · Open a support ticket at support@southteksystems911.zendesk.com or through the Help Center.