Amerex builds two 5 lb ABC dry chemical extinguishers on its aluminum-valve platform that look, at arm's length, like the same product. The B402 and the B500 read identically down most of Amerex's catalog chart: 15.25 in tall, 7.25 in wide, 4.25 in deep, a 12–18 ft initial discharge range, a 14-second discharge time, a 195 PSIG nominal operating pressure, even the same shipping weight. They share the same aluminum valve assembly, the same 195 PSI gauge, the same valve stem, spring, collar O-ring, and ring pin — and the same downtube inside the cylinder. On Amerex's own parts list, exactly one piece of hardware separates them.
Then you read the nameplate. The B402 is rated 3A:40B:C; the B500 is rated 2A:10B:C — a step down in Class A coverage and one quarter of the Class B rating from the same size and shape of cylinder. Amerex's catalog prints the two ratings one column apart and moves on, but its literature does document two concrete differences between the units if you know where to look. And once you've picked one, a single page of the Amerex Parts Book lists every part either unit will ever need — along with five other models you might not guess are the same machine underneath. Both halves of that story are below.
The two spec sheets, side by side
| B402 | B500 | |
|---|---|---|
| UL rating | 3A:40B:C | 2A:10B:C |
| Capacity | 5 lb ABC dry chemical | 5 lb ABC dry chemical |
| Amerex item number | 15280 | 15312 |
| Valve assembly | 11823 aluminum | 11823 aluminum — same part |
| Gauge | 03103-P, 195 PSI | 03103-P — same part |
| Downtube | 06212 | 06212 — same part |
| Hose & horn assembly | 14849-P (.157) | 06215-P (.147) |
| Recharge chemical | Charge 555 (dedicated to the B402) | Standard ABC — Charge 552 / 550 / 509 |
| Discharge time | 14 seconds | 14 seconds — same |
| Initial discharge range | 12–18 ft | 12–18 ft — same |
| Operating pressure | 195 PSIG | 195 PSIG — same |
| Height × width × depth | 15.25 × 7.25 × 4.25 in | 15.25 × 7.25 × 4.25 in — same |
| Shipping weight | 9.25 lb (9.5 lb as B402T) | 9.25 lb (9.5 lb as B500T) — same |
If the rating shorthand is new, our guide to what fire extinguisher UL ratings actually mean unpacks it. The short version here: the B402 carries four times the Class B rating of the B500 and one step more Class A coverage, in a package with identical published dimensions, weight, range, and discharge time.
What actually differs between the B402 and the B500
Two differences are documented, and both are easy to miss.
The fill. The Amerex Parts Book lists ABC recharge chemical in three generic sizes — "Charge 552, 25 lb. pail," "Charge 550, 50 lb. pail," and "Charge 509, 400 lb. drum" — with no model restriction. Then it adds one dedicated line: "Charge 555, 50 lb. pail – Model B402." The B402 is the only hand portable in the Parts Book's ABC charge list called out by model name. Amerex's current price list identifies Charge 555 as its ABC F-13 chemical, and we stock it as the 555 ABC F-13 recharge. Both fills are ammonium phosphate base ABC dry chemical, but they are not the same charge — the service manual's recharge procedure requires "the correct amount and type of dry chemical specified on the label (nameplate)," and the nameplate on each unit names which one it takes.
The discharge hardware. The one line on the shared parts list where the two models take different parts is the hose and horn assembly: 14849-P for the B402 and 06215-P for the B500. The Parts Book prints an orifice size beside each — .157 for the B402's assembly against .147 for the B500's. Everything upstream of the hose, from the downtube to the gauge, is the same part number.
What doesn't differ goes further than you'd expect. Amerex's dry chemical service manual gives one operational temperature range for both: "-65°F to +120°F (-54°C to +49°C) or -40°F to +120°F (-40°C to +49°C) [please see the nameplate on your extinguisher]." And in the catalog's extinguishers-at-a-glance chart, the two models' rows are identical — the same 4.25 in cylinder diameter, the same included 888 wall bracket (818 vehicle bracket on the T versions), and the same USCG-approved bracket options (818, 821, 861H).
One parts list covers them both — and five more models
The Amerex Parts Book doesn't give each model its own page. It groups the whole line into a couple dozen parts lists, and the list that serves these two is titled "5 - 20 lb. Dry Chemical (Hose & Horn) Aluminum Valve Models." Seven current models share it, exactly as Amerex prints them: "B402 - 5 lb. ABC," "B500 - 5 lb. ABC," "B443 - 6 lb. ABC," "B456 - 10 lb. ABC," "B479 - 5 lb. PK," "A411 - 20 lb. ABC," and "A413 - 20 lb. PK." Two agents, four capacities, one platform.
Across all seven, the wear parts are common:
| Part no. | Amerex description | Fits |
|---|---|---|
| 11823 | "Standard Valve Assembly - 5, 5½, 6 & 10 lb. with Loop" | B402, B500, B443, B456, B479 |
| 11824 | "Standard Valve Assembly - 20 lb. with Loop" | A411, A413 |
| 03103-P | "Gauge - 195 PSI" | All seven |
| 06092-P | "Valve Stem Assembly" | All seven |
| 01074-P | "Spring" | All seven |
| 05241-P | "Collar O-Ring" | All seven |
| 00160-P | "Ring Pin" | All seven |
| 01387-P | "Lock Wire Seal (Yellow)" | All seven |
| 11825 | "Lever & Rivet" | All seven |
| 11826 / 12405 | "Handle & Rivet" | 5–10 lb models / 20 lb models |
Only two lines on the list pick a part by model rather than by size class — the hose and horn assembly, and the downtube:
| Model | Hose & horn assembly (orifice) | Downtube |
|---|---|---|
| B402 — 5 lb ABC | 14849-P (.157) | 06212 |
| B500 — 5 lb ABC | 06215-P (.147) | 06212 |
| B443 — 6 lb ABC | 05248 (.152) | 03397 |
| B456 — 10 lb ABC | 05564-P (.191) | 01519 |
| B479 — 5 lb Purple K | 05248 (.152) | 06212 |
| A411 — 20 lb ABC | 11221-P (.209) | 11674 |
| A413 — 20 lb Purple K | 11223 (.177) | 11674 |
Read that closely and the platform sharing crosses agent lines: the Purple K B479 takes the same hose and horn as the 6 lb ABC B443, and the same downtube as both 5 lb ABC models. If you keep a mixed rack of these extinguishers — a B500 by the office door, a B402 in the shop, a B456 at the loading dock — the bin of service parts behind them is remarkably small.
What this means when you own one
Amerex is emphatic that this platform is not mix-and-match with the aftermarket. The Parts Book states: "To protect the UL listing and to keep the warranty in effect Amerex replacement parts must be used," and warns that "The Amerex warranty is voided by the use of generic, off-the-shelf or substitute parts. DO NOT SUBSTITUTE." The service manual for these models says the same about chemical and hardware alike, and adds the operating rule that matters most in practice: "RECHARGE FIRE EXTINGUISHERS IMMEDIATELY AFTER ANY USE."
The maintenance work itself — annual maintenance, six-year teardown, hydrostatic testing of the cylinder every 12 years — belongs to trained fire equipment service professionals with the proper equipment. We don't perform service; we supply the factory parts those professionals install, by the part numbers above.
So which one do you buy?
Choose the B500 when the requirement is a standard ABC unit and 2A:10B:C meets your specification — offices, retail, light commercial occupancies. For most light-hazard placements it is exactly enough extinguisher.
Choose the B402 when the hazard justifies more Class B capability — fuels, solvents, shop and garage environments — or when you simply want the highest-rated 5 lb ABC in Amerex's aluminum-valve line. It occupies the same footprint, hangs in the same 5 lb class brackets, and costs nothing extra in space or weight to mount.
Both models also come in vehicle-bracket and chrome variants — B402T, B500T, B402C, and so on, all in Amerex's current price list. Those suffixes are Amerex's configuration code, not different extinguishers; our guide to decoding Amerex model numbers covers what each letter changes.
What we stock
The extinguishers — the B402 and B500 themselves, their platform siblings the B456 10 lb and A411 20 lb, and the full ABC dry chemical collection.
Shared platform parts — the 11823 and 11824 valve assemblies, the 03103-P 195 PSI gauge, the 06092-P valve stem assembly, and the 05241-P collar O-ring, with the rest in valves, gauges & downtubes and O-rings, seals & pull pins.
Model-specific parts — every hose and horn assembly and downtube in the tables above, in hoses, nozzles & horns and the full service parts catalog.
Recharge chemical — the B402's dedicated Charge 555 F-13 and the standard ABC charges, in the recharges collection.
Outfitting a building or a fleet and not sure which of the two fits the specification — or matching parts to a rack of mixed models? Send us the model list and we'll come back with options, pricing and lead time — request a quote.
Sources
Model roster, part numbers, fitment, recharge charge assignments and Amerex's part descriptions above are taken verbatim from the Amerex Parts Book (P/N 27277), principally its parts list for 5–20 lb dry chemical hose-and-horn aluminum valve models. UL ratings, item numbers, capacities, dimensions, shipping weights, discharge times, ranges, operating pressures and bracket fitments are from the Amerex Portable Fire Extinguisher Catalog. Maintenance and recharge requirements are quoted from Amerex Owner's Service Manual 05602 for stored pressure hand portable dry chemical extinguishers (ABC, Regular and Purple K); the Charge 555 F-13 designation is from Amerex's current price list. Where a rating or part is critical to your application, confirm it against the extinguisher's own nameplate and Amerex's current documentation, and confirm hazard classification and maintenance requirements with a qualified fire protection professional and your authority having jurisdiction.
ShopAmerex.com is owned and operated by Centurion Holdings Group LLC, an independent authorized distributor of Amerex Corporation products. We sell equipment and factory OEM service parts — we do not perform inspection, service, hydrostatic testing or recharging.