Simplex 4246-1 Wiring Diagram

Does anyone have a wiring diagram for one of these? Or a relay logic fire panel? I want to build my own for educational purposes.

I might have a 4246 diagram but I advise against trying to reproduce one. The 4246 panel operates directly on 120 volts AC. That makes it very possible to get a nasty shock working with it. Some of the relays were quite special for use in that panel.

Here is a link to a simple relay logic control someone came up with. It operates on 24 volts DC so is much safer to work on.

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Thanks for the diagram. :slight_smile:

Voltage level should not be a problem with proper PPE or better yet disconnecting the supply before service.

Any idea is the simplex had batteries?

The 4246 was and AC panel which operated directly from the 120 VAC line. No transformer or power supply of any kind. It used series AC notification devices. It did not use batteries because no part of a 4246 operates on DC.

I found the 4246 drawing.

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Huge help! :slight_smile: What is a supervisory power circuit? When did code require batteries in fire alarm panels? Would heat detectors and gongs be enough in a modern building?

Also what are the resistors for in the simplex circuit? And why would an end of line resistor be required in this scheme?

The supervisory power circuit provides to operate the trouble light and bell in case of a failure in the operating circuits.

I don’t remember the code chapter and verse from that long ago. In my location installation of pure AC systems without battery backup ended in the late 1970’s. Maybe one of the code nerds can zero in on that answer. A lot depends on what code the local AHJ is enforcing. They have the final word.

Heat detectors are not considered to be life safety devices, so no, they are not sufficient in modern buildings. There are ADA requirements for fire notification strobes so those are required in addition to audible signals. While some government installations still use bells, horns are the normal audible signals in use today. A number of occupancy classifications require a voice alarm system using speakers in place of horns. These include high rise buildings and places of assembly.

The resistor in the 4246 between terminals S2 and S3 is the end of line resistor. Notice that the coils of relays 3 and 5 are in parallel in standby mode. The resistor provides enough current to operate the box circuit supervisory relay (relay 3) which is a low voltage coil. The resistor does not allow enough current to operate alarm operating relay (relay 5) which has a higher voltage coil. When a station is pulled the EOLR is shunted and the full 120 VAC is applied to operate relay 5.

The adjustable resistor near contact 3-1 adjusts the supervisory current in the gong circuit to a level that the signals cannot operate but enough to operate the supervisory relay coil (relay 4).

The adjustable resistor going to terminal G1 is the gong circuit compensating resistor. It drops voltage from 120 to a level needed to ring the signal devices. Foe example, if 10 six volt 1.8 amp bells are in series on the circuit 60 volts is needed to ring the bells. The resistor is adjusted to allow 1.8 amps to flow in the circuit. 60 volts is available to ring the series connected bells and the other 60 volts is across the resistor.

Makes sense.

Question- in a high rise building like say the John Hancock, what happens an alarm zone calls? Does every alarm across 60 floors and 5 sub levels sound? How does it work? Does code require supervisory circuits?

I ask because I think this would make a really cool fire alarm panel:

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That does look like it would be really awesome but there would be a hell of a lot of panels for it to work I would think.

What are the minimum requirements for an alarming system?

A complete evacuation of a 60+ story building on any alarm is impractical until the alarm is investigated. That building would have a voice alarm system which typically give an evacuation message to the alarm floor, the floor above, and the floor below. If it has a two channel system an alert message can be sent to some or all other floors. The alert message would inform those occupants that an emergency exists and to wait for additional instructions. Additional evacuation can be done with manual controls in the system or by automatic means.

There is no short answer to question about a minimum system. It depends on the characteristics of the building and the uses of the building. Here is a list of the applicable codes and standards that control the requirements for a given building.

The installer should be familiar with the relevant codes listed below, as well as any other applicable local codes and standards, when installing a fire alarm system.

NFPA 72 National Fire Alarm Code

NFPA 11 Standard for Low-Expansion Foam and Combined Agent Systems

NFPA 11A Standard for Medium- and High-Expansion Foam Systems

NFPA 12 Standard for Carbon Dioxide Extinguishing Systems

NFPA 12A Standard on Halon 1301 Fire Extinguishing Systems

NFPA 13 Standard for Installation of Sprinkler Systems

NFPA 14 Standard for the Installation of Standpipe and Hose Systems

NFPA 15 Standard for Water Spray Fixed Systems for Fire Protection

NFPA 16 Standard for the Installation of Deluge Foam-Water Sprinkler and Foam-

Water Spray Systems

NFPA 16A Standard for the Installation of Closed-Head Foam-Water Sprinkler Systems

NFPA 17 Standard for Dry Chemical Extinguishing Systems

NFPA 17A Standard for Wet Chemical Extinguishing Systems

NFPA 25 Standard for Inspection, Testing, and Maintenance of Water-Based Fire

Protection Systems

NFPA 70 National Electric Code

NFPA 72 National Fire Alarm Code

NFPA 101 Life Safety Code

NFPA 750 Standard on Water Mist Fire Protection Systems

NFPA 2001 Standard on Clean Agent Fire Protection Systems

ULC S524 Standard for Installation of Fire Alarm Systems (Canadian Systems)

UL 1076 Standard for Safety for Proprietary Burglar Alarm Units and Systems


US codes are to fire centric if you ask me. More complexity than is gained. Actually many times they simply thwart safety in their zeal.

I like the idea of setting up the relay panel so that a heat detector or flow switch closes the alarming floor and one above and one below. A light in indicate which floor is calling. A signalling riser and an alarm riser.

Voice intercom for instructions by fire fighters is a good idea though.