Design

The Series 500 Special Assembly is an "open circuit" device, designed to close an electrical circuit upon activation. The compact, simply designed unit is rugged and unaffected by vibration. All metal parts are brass or aluminum, mounted on a durable, mineral-filled, phenolic base.

No exposed metal parts carry current. The electrical contacts are all silver clad and of ample size.

Large line terminals and wire ways are provided in the base for easy installation in either open wiring or concealed wiring systems.

operation

The Rate-of-Rise element consists of an air chamber, flexible metal diaphragm and restricted orifice vent that can be closely calibrated to control air flow rate in and out of the chamber.

The Air Chamber expands and contracts as ambient room temperature changes. Under normal temperature fluctuations, the unit "breathes" through the Calibrated Vent. Under rapid temperature rise conditions, air expands faster than it can be
vented, building up enough pressure to move the thin Metal Diaphragm until the flexible Silver Contact closes the electrical circuit against the Stationary Contact. When the heat is removed, the pressure is relieved through the vent and the contacts are restored to normal.

The Fixed-Temperature element is entirely independent of the Rate-of Rise. It consists of a phosphor-bronze spring held under tension by standard fusible solder. The Spring is held under tension by a spot of fusible Eutectic Alloy. When heated to its rated temperature, the alloy melts which releases the Spring and closes the contacts.

Weather/Moisture Proof Models

The Weather /Moisture Proof Models (WPB/MPB) consist of a cast metal box, gasket and special steel cover plate integrated with the Series 500 detector. A crossed wire guard is added for extra protection. The emerging wire points are sealed with epoxy, increasing the resistance to moisture, The cast metal box has 4 wire entrances for 1/2 inch rigid conduit. The unit offers combined protection against weather and condensation in the conduit.

Explosion/Moisture Proof Models

Ratings

The Explosion Proof models (EPB/MPB) are UL and FM listed for the following classifications: Class I, Group D: Atmospheres containing gasoline, hexane, naphtha, benzene, butane, propane, alcohol, acetone, benzyl, lacquer solvent vapors, natural gas.

• Class II, Group E:
  Atmospheres containing metal dust of aluminum, magnesium or their commercial alloys
• Class II, Group F:
  Atmospheres containing carbon black, coal or coke dust
• Class II, Group G:
  Atmospheres containing flour, starch or grain dust