WIRING DESIGN GUIDE 

1. SCOPE

This document is intended as a guide to determine a wiring layout for Sentry installations. It is not a substitute for good engineering practices. The installation design and wiring specification must be specified by the project engineer.  They will be knowledgeable of the power requirements and any state and local codes.

 2. BASIC RULES

A. All power wiring from terminal boards to host panels must be 18 gauge minimum.

B. Never put more than 10 host panels (less with optional features) on a run from a terminal board. This usually means a separate cable for each side of a hallway.

C. Never bring a DC or data cable back to a terminal board where it can form a loop. Loops attract noise and transients and are NOT allowed.

D. Always use 4 separate wire colors for the power pair and data pair. The panels data line components can be damaged if directly connected to the DC power leads. Sentry uses white & black for DC + & -, and red & green for data + & - .

E. The data pair MUST always be accompanied by the DC common (-) wire, all the way back to the console.

F. Data wires must be twisted pairs.

G. Use shielded cable for both data and audio when the intercom option is used.

H. If you not sure about something, call Sentry and ask.

 3. VOLTAGE REQUIREMENTS

All Sentry devices have been specifically designed to minimize current requirements. All panels and other Sentry devices 

MUST have at least 9.0 volts to perform properly.

 4. VOLTAGE DROP

When designing the wiring of a building for the installation of the Sentry system, current requirements and voltage drops are major concerns. All wire and cable has resistance, and this resistance will cause a voltage drop. Sentry devices require a minimum voltage to operate, therefore voltage drops and line loses are an important consideration. The amount of voltage drop is determined by the wire gauge, cable length, and the current.

5.WIRE GAUGE

The larger the wire conductor, the smaller the gauge number, and the greater current capacity. Larger wire conductors will exhibit less voltage drop loss than small conductors. Shorter cable lengths have less voltage drops than long cables. Refer to section 15 for wire resistance.

 6. RECOMMENDED CABLE

Sentry recommends the use of a 2 pair cable. One pair is 18 gauge wire size and the other pair is 22 gauge. The 18 gauge pair is used for the DC voltage and the 22 gauge pair is used for the serial data. Sentry recommends the West Penn Wire, 374 or equivalent. Sentry documentation, wiring diagrams, and wire colors refer to this West Penn cable.

 7.CONFIGURATION

Sentry systems are generally configured with each apartment operating independent of one another. When a specific installation uses the Sentry Fire Alarm Interface, the smoke detector horns can be activated by the console. This system feature allows the apartment smoke detectors to act as auxiliary fire alarm announcement devices. When the building or zone has a fire alarm, the interface will direct the console to activate the smoke detect or horns in the apartments located within that building or fire zone. This feature does not alter the fire alarm system operation and is an optional, auxiliary sounding system only. The use of the Sentry Fire Alarm Interface may be governed by local codes. Small apartments are usually equipped with a Host Panel and a smoke detector. Larger apartments can have up to 4 smoke detectors and up to 6 remote call stations.  

8. CURRENT REQUIREMENTS

Device current requirements are listed in Table 1. These currents are added to determine voltage drops. "Standby" current is smoke detector current when it is not alarming.

DEVICE CURRENT REQUIREMENTS
TABLE 1

APARTMENT CURRENT REQUIREMENTS
TABLE 2

9. OPTIONAL APARTMENT DEVICES

Apartments can include optional equipment powered through the panel wiring. Some of these devices include: Wireless pendant receivers, dome lights, intercom panels, and remote call switches. Some installations include program options which allow control of smoke horns, dome lights, and intercom as PA speakers. It is important to understand which interfaces are ordered with a system to properly determine total current draw.

Typical installations, (without fire interface): each apartment draws the current listed under STANDBY in Table 2 above. When smoke is detected the current draw increases to the amount shown under ALARM. For this type of installation, worst case estimate of current draw is figured with all apartments on a common power and data cable to be in STANDBY, except the furthest apartment is in ALARM. The worst case voltage drop is calculated from this current.

Fire Alarm Interface: all the smoke detectors in the apartments connected to the same cable can go into ALARM at the same time, therefore every apartment on a common power and data cable will be drawing the maximum current. The worst case voltage drop is calculated from this current total.

The number of apartments that can be connected to a common power and data cable is significantly lower when the system is connected to a fire alarm interface. This is because of the higher voltage drops associated with the higher current from all the smoke detectors alarming at one time.

Seldom will more than 1 of 2 dome lights be lit at once, but when a fire alarm interface is used to activate smoke horns, and turn on the dome light during a smoke alarm, ALL dome lights will turn on at once, along with the smoke horns, an additional load of 160mA per apartment. The P.A. All-Call feature will activate all P.A. amplifiers in the intercoms simultaneously.

10. CABLE LIMITATIONS

Table 3 lists the maximum recommended number of apartments on the same power and data cable in a typical installation. For the calculations, a power supply of 13.0 Volts and the minimum voltage requirement of 9.0 Volts at the host panel is used. This table does not calculate any of the possible option. Table 4 lists the same equipment and options but is figured using a fire alarm interface.

 Notes: Last apartment of the cable in full alarm. Other apartments in standby mode.  18 Gauge power cable pair.  Cable run to supply figured at same length as between panels.

RECOMMENDED MAXIMUM NUMBER OF APARTMENTS ON CABLE
Table 3

 Notes: All apartments on the cable in full alarm. 18 Gauge power cable pair. Cable run to supply figured at same length as between panels.

RECOMMENDED MAXIMUM NUMBER OF APARTMENTS ON CABLE
Table 4

11. GROUPING

In an effort to minimize voltage drop, wire apartments in groups of no greater than the number listed in tables 3 & 4. Figure 1 on page 6 shows wiring layout examples, the incorrect methods violate the number of apartments rule.

In high-rise buildings, it proves wise to install all power supplies on the same floor, about center to the building. 10 or 12 gauge wire supplies the terminal board locations. This configuration make servicing easier and protects the system from lightning damage. See the example on page 7.

 12. SPECIAL CABLING

Some system designs require longer distances between the apartment groupings and the power supply. In these cases, larger wire conductors are needed to reduce voltage drop. Usually a 14, 12, or 10 gauge wire pair is used for DC voltage, with a separate 22 gauge data pair.

In most cases the heavy duty wire is only required between the power supply and the first apartment, then the apartments are usually arranged in groups that can use the recommended 2 pair cable. Use this guide to determine current, then chose an appropriate wire to keep the apartment panel voltage above 9 volts.

 13. DATA WIRE PAIR

The data wire pair is specified by Sentry as 22 gauge. This gauge is adequate for data on most installations of up to a half mile. If the data cable will be run between an apartment group and console, underground, or greater than 1000 feet, it is recommended to install an 18 gauge.

 A common conductor MUST run with all data pairs. Where a cable is required for data only, the cable must include a shield or drain wire.

 14. AUDIO CABLES

Installations involving audio communications use a separate shielded audio cable that runs along side the power/data pair. See the audio wiring diagrams for the recommended cable. Long data lines running parallel to audio should also be shielded.

Always ground the shield (or drain wire) ONLY at the console end by connecting to the computers case.

 15. WIRE RESISTANCE

Table 5 shows the DC resistance of copper wire at the gauge sizes mentioned in this guide.

Wire Resistance (copper)

Table 5

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WIRING DESIGN GUIDE (PDF)
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