When connecting the heater of an outdoor fire alarm annunciator, is it acceptable to tie into the fire alarm system’s power supply (circuit disconnecting means)?
Most definitely NOT! CAN/ULC-S524 stipulates that the fire alarm system must be serviced by a dedicated circuit. Many technicians (including those that are factory trained on the subject equipment) feel that a tie-in to the fire alarm AC circuit is an acceptable means of ensuring the power to the annunciator heater is not inadvertently compromised. This is not the case! I have seen a number of transformer failures where the secondary windings have “opened” without affecting the primary side and thereby tripping the breaker (some transformers may even employ a fused secondary). The proper way to monitor power to the annunciator heater is through an appropriately rated low voltage relay connected to the secondary output. The fire alarm system can supervise a normally closed contact on the relay (which would trigger “open” – or show as “normal” when energised) through a latching supervisory input on the common control. You could parallel this connection to the same circuit monitoring the
Related Questions
- When connecting the heater of an outdoor fire alarm annunciator, is it acceptable to tie into the fire alarm system’s power supply (circuit disconnecting means)?
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