FPS-650 and FPS-1250 Legacy Overview

Applies to: N2-BLAST FPS-650 and FPS-1250 fire protection nitrogen generators. These are legacy models running the earlier controller platform, not the touchscreen used on current units. They are still supported — parts availability and upgrade paths vary by unit.

The FPS-650 and FPS-1250 put nitrogen into dry and pre-action sprinkler piping in place of compressed air, so the oxygen that drives internal corrosion is not there to drive it. Both are self-contained: an internal oil-free compressor, filtration, a pair of PSA beds, a nitrogen storage tank and a controller, in one cabinet.

The two share a platform and most of their behavior. Where they differ, they differ sharply — including which way the bypass handle points, which is the first thing to get right on either machine.

The bypass handle — the two models are opposite

Both machines have a manual 3-way ball valve that switches the sprinkler system between nitrogen from the generator and bypass air. Our documentation records the handle positions for these two models the opposite way round from each other, and the FPS-1250 is also opposite to the current FPS-500 and FPS-900.

Model	Handle upright / up	Handle horizontal / out	Source
FPS-1250	Bypass — system on air	Normal — system on nitrogen	Operating manual, Appendix B, and the FPS-1250 layout sheet
FPS-650	Normal — system on nitrogen	Bypass — system on air	FPS-650 layout sheet only

FPS-650 layout sheet. The legend at right is the primary source for this model: AIR BYPASS = HANDLE OUT, N2 = HANDLE UP (normal operation). Click to open it full size and read the legend yourself.

FPS-1250 layout sheet — note the legend is reversed from the FPS-650. N2 = HANDLE OUT (normal operation), AIR BYPASS = HANDLE UP. The same sheet records the internal nitrogen storage as 16.8 gallons.

⚠ Warning — read the placard on the machine in front of you The placard on the unit governs. If it disagrees with this article, follow the placard and tell us. The FPS-650 figure above rests on a single layout sheet, and these two models being opposite is exactly the situation that produces the mistake worth avoiding.

That mistake is specific: a technician who reads the wrong polarity leaves the generator bypassed on air while believing the system is on nitrogen. Everything that would tell them otherwise — a supervisory signal, an indicator — is what they then dismiss as a nuisance. The system keeps its pressure and quietly loses its corrosion protection.

▲ Attention — no placard, or you cannot read it? Test, do not guess With bypass air available and the generator stopped, set the handle to the position you believe is bypass and draw a little gas at the system. The bypass position is the one where the air compressor cuts in and the gauge recovers and holds. In the nitrogen position with the generator stopped, pressure decays as the storage tank draws down and never recovers.

Confirm with a purity reading at the outlet if you have a Quick-Check or a portable analyzer — bypass drifts toward air within minutes of flow, nitrogen holds its commissioned value. Then mark the handle so nobody has to work it out again. Forcing and restoring bypass deliberately is covered in N2-BLAST Bypass Mode — Automatic, Forced, and Restoring Nitrogen.

ℹ Note — the "Air Bypass Option" is an alarm, not the bypass These models offer an Air Bypass Option, and the name is misleading. It is not a way to bypass — it is a monitor that alarms when the generator is being bypassed by the air compressor. It exists specifically to catch a bypass valve left open, or the generator left switched off, so that a system running on air cannot do so unnoticed.

Where it is fitted, 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. It stays lit until the handle is returned to the normal position.

If a unit does not have this option, nothing tells you the system is on air other than the handle position itself — which is why the placard and the handle matter as much as they do.

FPS-650 and FPS-1250 side by side

	FPS-650	FPS-1250
Installation	Wall mount or floor	Floor standing only
Cabinet	12.68" W × 10" D × 29.5" H	26" W × 18" D × 59" H
Weight	About 84 lb	About 265 lb
Nitrogen storage	Separate 100 lb tank, 15.1" OD × 50" H, about 75 lb	Internal
Options	BlastOff, Air Bypass Option	BlastOff, Air Bypass Option, internal Quick Fill Compressor
Shipping	Cardboard carton	Wooden crate — unbolt from the crate, lift out, floor-jack into place
Shipping lock bolts	Fitted. Remove all four before operating.	Fitted — the 4 colored bolts at the cabinet base. Remove them before operating.

What is on the outside of the cabinet

Both models present the same seven external items, with two differences worth knowing before you plumb or wire one.

Item	FPS-650	FPS-1250
N2 out	¼" NPT ball valve, with a ¼" NPT male to ½" NPT female adapter supplied to take it out to ½" plumbing	¼" NPT ball valve
Audible alarm	Audible electric buzzer	Audible electric buzzer
Storage pressure gauge	⅛" NPT × 1½", 100 PSIG	160 psi gauge
System controller	On the panel	On the panel
Drain	¼" OD through-wall coupling	¼" OD through-wall coupling — two of them
Power	Power entry module, 20 A	Power entry module, 20 A
Nitrogen storage	External 100 lb tank, supplied with wall brackets and strap	60 lb integral tank. The FPS-1250 layout sheet gives the same tank as 16.8 gallons

FPS-650 panel layout. Note the callout at right: remove all four shipping lock bolts before operating.

FPS-1250 dimensions and external components. Work to the dimensions on the drawing supplied with your job rather than to the rounded figures in the table below.

Specifications

Item	Both models
Nitrogen purity	98.0% or better
Nitrogen storage pressure	55–75 PSIG
Nitrogen cut-out (enters standby)	70 PSIG nominal, working band 65–75 PSIG
Nitrogen cut-in (returns to run)	About 62 PSIG — 7–10 PSIG below cut-out. Factory preset, no field adjustment.
Cabinet port connections	½" NPT female
Compressor	Integral, oil-free
Electrical	110–240 V / 50–60 Hz / 1 phase, 20 A breaker. A dedicated circuit is suggested. The 20 A breaker is built into the on/off rocker switch. Confirm against the nameplate on the unit before running the circuit — supply arrangements have varied across the production life of these models.
Listing	UL 508A ICP approved
Ambient temperature	40 °F to 90 °F, indoors, upright
Noise	Under 75 dBA
Warranty	12 months or 1000 hours from shipment, whichever comes first

ℹ Note — 55–75 PSIG is a range, not a setpoint pair The storage pressure specification and the cut-in/cut-out setpoints are different things, and reading the range as a pair is how wrong numbers get into circulation. Cut-out is 70 PSIG nominal and cut-in is about 62. See What Are My Cut In/Out Pressures?.

How it runs

Two normal states. In Run, the unit is making nitrogen and feeding the storage tank. At 70 PSIG the tank is full, the pressure switch signals the controller, and the unit enters Standby — air flow through the generator stops and the compressor stops once it reaches its cutout pressure. When the system draws nitrogen and tank pressure falls to about 62 PSIG, it returns to Run and recharges automatically.

Standing by rather than purging continuously is deliberate: it saves compressor motor hours and extends the life of the PSA media and the filters. A unit that never reaches standby is telling you something — most often a leak downstream, which shortens the life of the machine and wears the compressor. See N2-BLAST System Leak Check Procedure.

When the power switch is turned on the controller decides for itself which state to enter. The display shows the current state, run hours and alarm status.

	What to do
Starting	Turn on the power switch and make sure the gas line valves are open.
Stopping	Close the valves on the gas lines. Powering the unit down is not necessary for a normal stop.
Emergency shutoff	Turn off the power switch on the side of the control panel.
A quick sanity check	The pressure gauge on top of the cabinet should read between 50 and 80 PSIG. Below that, check power first, then leak-check the system.

The controller

The controller face. Run hours top right, system status below it. Mode Select is at the left of the button row; Alarm Simulation is button 5 and Filter Change Reset is button 0.

The buttons on the controller face do nothing while it is locked. If the display reads LOCK, press and hold the Mode Select button to unlock it — and repeat that to lock it again when you are done. Unlocked, two functions become available.

Function	How	What happens
Alarm Simulation	Hold button 5 for 3 seconds	Simulates an alarm and trips the alarm dry contact for 2 seconds, so the wiring back to the building system can be proven without creating a real fault. Useful at commissioning and worth doing before you rely on that contact.
Filter Change Reset	Hold button 0 for 7 seconds	Resets the 1000-hour filter timer and clears the filter alarm. An audible beep confirms it. No beep, no reset.

Display	Meaning
Run	Producing nitrogen and filling the storage tank.
StdbY	Tank is full. Production stopped until pressure falls to cut-in.
LOCK	Controller locked — hold Mode Select to unlock.
FILtr	Filter change overdue. Shown in red.
b ōFF	BlastOff leak detection has tripped. Shown in red with a buzzer — see below.

⚠ Warning — do not modify the controller program Modifying the program voids the warranty. If the program fails, cycle the power first; if that does not recover it, call us rather than working on it.

BlastOff leak detection — it stops the generator

BlastOff is an option on these models, factory fitted or retrofitted in the field with some rewiring. It watches for the signature of a leak downstream of the generator — pinholes, loose fittings, a poorly seated connection in the piping out to the fire protection system.

When it trips it sounds a buzzer, displays b ōFF in red, and shuts the generator off until the problem is dealt with. It can also be tied into a dry contact so the alarm reaches the building management system.

⚠ Warning — a stopped generator is a system with no make-up nitrogen The documented protocol is to power the unit off, check for a leak, and if none is found leave it off and call your service company. Resetting is a power cycle — off, then on.

Understand what that means on a fire protection system: while the generator is off, nothing is replacing the gas the system is losing. Supervisory pressure will fall at whatever rate the leak dictates. Tell the building owner and the alarm monitoring company before you leave a unit switched off, let them decide how it is handled, and treat finding the leak as urgent rather than scheduled.

Never reset it repeatedly. A BlastOff that trips daily is reporting a real fault, and clearing it each morning is how a leak runs for months.

Finding a leak on these models

The general method is in N2-BLAST System Leak Check Procedure. These two models have their own way of splitting the problem, using the two ball valves on the storage tank.

Step	What to do	What it tells you
1	With the unit powered on, close both ball valves on the nitrogen storage tank and note the tank pressure.	The generator is now shut into its own volume.
2	Let it run. It should reach Standby within about 10 minutes.	If it cannot reach standby at all within about ten minutes, check power and whether an alarm is standing before you assume a large leak. The ten-minute figure is from the manual; the rest is our guidance.
3	Wait 5 minutes and watch whether it stays in Standby.	Stays in Standby → the leak is downstream of the generator. Tank pressure also changed → the leak is in the tank fittings. Tank pressure held → look at the building piping. Returns to Run → the leak is inside the cabinet.
4	For a cabinet leak: open the front cabinet door and find the nitrogen storage tank. Close the upper ball valve on the red manifold — the tank outlet — and watch the gauge above the cabinet for 60 seconds.	Pressure dropping → the leak is between the output ports, the gas blender if one is fitted, and that closed valve.
5	Still running, close the lower ball valve — the tank inlet. It should reach Standby within 5 minutes, then hold for 60 seconds.	Leaves Standby → the leak is between the check valve and the tank outlet valve. Holds, or never reaches standby → call us.

⚠ Warning — working in an open cabinet on a running machine This procedure has you inside the cabinet while the unit is operating. Wear safety glasses whenever the cabinet door is open with the machine running, and use ear protection.

Use a spray bottle on non-electrical parts only. Isolate the section and relieve the pressure before opening any fitting — closing a valve stops the gas, it does not depressurize the pipe.

Nitrogen is not poisonous but it displaces the oxygen you breathe and gives no warning. Vent to outdoors or a large well-ventilated space, never into a small closed room, and keep the unit in a room with normal air changes.

Push-to-connect fittings are allowed a small leak rate — up to about 5 cc/min is normal and is not the fault you are looking for.

Safety rules that apply to the whole machine

• Never disable or bypass a safety relief valve. They are ASME stamped and fitted throughout the system deliberately.
• Never let pressurized gas exhaust from an unsecured hose. A loose hose whips and can injure seriously. If a hose bursts in use, close all isolation valves if it is safe to do so, and power the unit down.
• Nitrogen is not poisonous, but it displaces the oxygen you breathe and gives no warning. Vent exhaust and any venting gas outdoors or into a large, well-ventilated space — never a small sealed room. Install the unit somewhere with normal air changes.
• Safety glasses whenever the cabinet door is open with the machine running, and ear protection while it operates.
• Isolate and depressurize before any mechanical work. Disconnect supply power before any electrical work.
• Only qualified people — competent on both electrical and pneumatic equipment — should install, maintain or repair these units, and only approved parts that meet or exceed the original specification should be used.
• The owner is responsible for keeping the unit in safe operating condition.

Maintenance

⚠ Warning — powering down is not isolating Before any mechanical work, including changing filters: completely isolate the incoming and outgoing pressures to the generator, and depressurize the section you are working on. Switching the unit off leaves gas trapped in it. A filter bowl removed with pressure still behind it comes off with force.

For electrical work, make certain the generator is disconnected from the supply power first. Only people qualified to work on electrical and pneumatic equipment should be doing this work, and replacement parts must meet or exceed the original specification.

Remove the front cover to reach the filters. The annual kit for both models is FRP-007 — the same kit listed for the FPS-500, FPS-900, FPS-900-RS and FPS-1650 in Annual Filter Replacement (FRP-007).

Filter	Rating	Interval and method
Air intake pre-filter	On the compressor intake	Yearly or 1000 run hours, whichever comes first. Remove the cap, take out the element, wipe the bowl with a clean dry cloth, fit the new element.
Particulate	5 micron	Yearly or 1000 run hours. Confirm the gauge after the bowl reads 0 PSIG, unscrew the bowl counterclockwise, rinse it in warm water, dry it, fit the new O-ring from the kit, then change the element with a Philips screwdriver.
Coalescing	0.1 micron	Same interval and the same bowl routine. The element unscrews counterclockwise by hand.

FPS-650 filter locations.

FPS-1250 filter locations. The particulate and coalescing filter sits behind the copper coil and twists off; the air intake housing twists at the top to reach the element.

• Both filters have auto-drains plumbed outside the cabinet — connect ¼" tubing and run it to a safe drain point.
• When both elements are in and the bowls are back on, reset the filter timer and listen for the beep, refit the cover, power up, and check the bowls for leaks before you leave.
• A dirty environment shortens the interval. If the unit is somewhere dusty, ask us for a schedule that suits it rather than defaulting to a year.

Installation essentials

Full detail is on the installation layout drawings supplied with the system — the drawing governs, and there is more than one arrangement. Ask us if the drawing is not in the job file.

	FPS-650	FPS-1250
Mounting	Wall or floor. On a wall, use a weight-bearing wall. On the floor, still fasten it so vibration cannot move it or tip it over. Optional bracket kit A05-TYP1-RD fits standard 16" stud spacing; all holes take ¼" fixings.	Flat, level, hard surface. No wall mount option. Floor anchoring is not required unless local code says otherwise.
Clearance	6" minimum on the left for ventilation, 36" preferred for access to the panel, connections and front cover. Wall-mounted, allow 4" either side for cooling.	Clearance on top for the nitrogen connection, left for the panel, front for maintenance.
Drain	¼" OD tube drain port on the bottom right — plumb it to the nearest site drain.	Same principle; see the layout drawing.

⚠ Warning — secure a wall-mounted FPS-650 at both flanges Fix it at the top and bottom flanges. Fixing only one risks the cabinet coming away — it weighs about 84 lb and the compressor vibrates the whole time it runs. Where studs are not 16" on center, back the area with ½" or thicker plywood first. Keep it away from heat, steam and standing water.

• Before installation — store dry and climate controlled, 60–80 °F, upright or as boxed. Do not stack anything on it, keep the gas lines dry, and leave the power cable disconnected until the connections are made.
• Use thread sealant on every fitting. All ports are ½" NPT female.
• Leak check every line before putting the system into service. A line leak makes the unit run excessively and wears the compressor.
• Shipping damage — document it, notify the carrier first, then call us.

Internal Quick Fill Compressor — FPS-1250 only

An option on the FPS-1250 for filling a system faster than the generator alone can. It is a 1.9 HP, 120/240 VAC single-phase compressor requiring 110–240 VAC at 60 Hz. A different supply voltage needs rewiring — ask before changing it.

⚠ Warning — two separate devices, and only one of them is optional Required: over-current and short-circuit protection rated for the motor. The compressor has an internal thermal overload, resettable by hand at the back of the motor, but that overload is not this device and does not satisfy the requirement.

Recommended, and separate: an operating disconnect rated for a 20 A or more motor load, suggested to be within sight of the generator, so the compressor can be switched on and off. Without one the compressor runs continuously.

Fitting a single 20 A switch does not meet the protection requirement. Follow local and site electrical regulations throughout.

Order of operations matters, and the bypass valve is part of it:

• Switch the generator to bypass at the 3-way ball valve on top of the unit — on the FPS-1250, handle fully upright.
• Then turn the compressor on at its disconnect.
• When filling is finished, return the generator to normal first — handle horizontal.
• Then shut the compressor down at the disconnect.
• Confirm the system is back on nitrogen before you leave. A quick fill that ends with the handle left upright is a system running on air.

Where the documentation is unclear

Published openly rather than guessed at. If you have a unit in front of you that settles any of these, we would like to hear about it.

Question	What to do meanwhile
The FPS-650 bypass handle polarity rests on a single layout sheet, and it is the opposite of the FPS-1250.	Follow the placard on the unit, or run the identification test above. Do not carry a handle rule from one of these models to the other.
Start-up instructions mention a supply line from an air compressor, on a machine specified with an integral compressor.	These units have their own compressor inside the cabinet. There is no external air supply line to connect. Work from the installation layout drawing for your system.
The air intake pre-filter cap is documented as removing in the opposite direction to the filter bowls.	The bowls unscrew counterclockwise. Try the cap gently in both directions rather than forcing it.
Whether the 3-way bypass valve is fitted to every FPS-1250 or only those with the Quick Fill Compressor option.	Look on top of the cabinet. If there is no 3-way valve, there is no manual bypass on that unit — call us before assuming one exists.

Related articles

• Resetting the Filter Alarm — Legacy Panasonic Controller
• Annual Filter Replacement (FRP-007)
• N2-BLAST System Leak Check Procedure
• N2-BLAST Bypass Mode — Automatic, Forced, and Restoring Nitrogen
• What Are My Cut In/Out Pressures?
• Legacy N2-BLAST Fire Protection Systems Overview
• N2-BLAST Fire Protection Systems Overview

Need help? Have the model and serial number ready, and tell us whether the unit has BlastOff and the Air Bypass Option fitted — both are options and both change the answer. South-Tek Systems Service — Phone: [phone] · Open a support ticket at [e-mail] or through the Help Center.