During the past few months, we have discussed a variety of issues related to special extinguishing systems. In all of these columns, we’ve talked about the what and the why, but very little about the how. This month, we will look at the more practical side of installation.
If you’ll recall, in August we covered the use of relays for fan control. In September, we investigated looking for and selling special extinguishing systems. Finally, in October, we talked about special hazard systems, specifically for use in kitchens. To bring us full circle, we’ll now uncover how to make the fire connection with each one.
Interfacing With a Kitchen System
Almost every commercial kitchen is equipped with a kitchen fire suppression system designed to 1) knock down a fire on a cook top, oven or fryer; 2) shut down the electricity that feeds the equipment; 3) disconnect natural gas or propane; 4) shut down the make-up air and activate the exhaust fans to remove smoke from the area; and 5) notify fire authorities of the situation using a fire alarm control panel equipped either with a city-tie or DACT.
In most special extinguishing systems, a set of contacts are provided, either mechanical or via an electrically controlled relay. It is to these contacts that a variety of auxiliary equipment must interface.
Essentially, there are two ways to connect to either one. They are: 1) a direct connection between the two, or 2) through a fan control system.
The direct method is the most common and entails running the appropriate wiring from a fire alarm panel to the fire suppression head; in this case, a kitchen restaurant system (see photo on page 26 of the December issue). There are a variety of interface methods employed for this purpose, but the one illustrated is probably the most common.
Please note the leaf switch within the head can be disconnected from the alarm system by simply pulling out a plug assembly. The end-of-line (EOL) resistor must be installed in such a manner that when this occurs, the alarm panel signals a supervisory problem.
Here, the EOL is not simply installed in parallel with the incoming initiating circuit, but it must first travel through the NC contacts of the leaf switch and then back to the alarm panel (see fire suppression box on page 27 of the December issue).
Interface Via a Fan Control System
In many cases, you will be required to interface your fire alarm panel with a kitchen suppression system through a fan control system (see box on page 28 of the December issue).
In this case, the contacts from the suppression head connect to the fan control system, as shown. Another set of contacts inside the fan control provides the dry contact triggers you will need for your fire alarm panel.
When using this method, be sure to ask the installer whether he will provide you with dry contacts or a voltage level. This is very important to know because not every electrician or fire suppression technician will use the same method.
This type of fan control system is designed to shut down the supply fans when the fire suppression system signals a fire has been detected. Some models also have the ability to automatically activate the exhaust fans to remove air from the location. At the same time, the alarm panel interface contacts change their electrical state, signaling the fire alarm panel that the fire suppression system has detected a fire.
