Automatic Fire Extinguisher System

Project date: 2005



One of the best things you can do for your boat is to install an Automatic Fire Extinguisher. These devices have several advantages, including:

The USCG requires a visual indication that the fire extinguisher is armed and ready for use. This is accomplished by a LED indicator, is powered through a switch on the extinguisher. As long as the extinguisher is not discharged, the switch remains closed, and current flows from ground to the LED.

The extinguisher I intend to use is known as a "clean gas agent" and uses FE-241 extinguishant, which is an evironmentally-friendly replacement for Halon. It works by dissipating oxygen, so it is not appropriate for any occupied compartment. The clean extinguishers are much superior to the portable dry chemical extinguishers, in the sense that the dry chemical extinguishers leave a corrosive residue. This residue can damage and corrode engine components, wiring, and other items. When used to fight an engine fire, there is a risk damaging the engine - and at minimum, the engine cannot be used until it is cleaned. In contrast, there is no residue after extingushing a fire with FE-241, and the possibility exists (after removing the source of the fire), you might be able to restart the engine.

 

 


 
As shown on the schematic, if the extinguisher discharges, the switch will open. This not only turns the LED off, it also removes power from the engine compartment blower. This is important, because the last thing that should be running during a fire is the blower. Not only will it remove the extingushant from the engine compartment, it will fan the fire with fresh air.

The first thing you need to do when installing an automatic fire extinguisher is to determine the area of the engine compartment - in cubic feet. Then, you select a fire extinguisher that is rated for at least that much volume - and preferrably more.

Now that I have determined I need at least 104 Cubic Feet of protection, I decided to over specify things a bit and chose a 175 CuFt fire system. I did this for two reasons. First, it was the largest extinguisher within my project budget, and I was able to determine from other V268 owners, that in the various years the V268 has been in production, the factory installed either a Kidde 150 or Fireboy 200 CuFt extinguisher. I decided to split-the-difference and go with the middle system.

The great thing about the Vista 268 is that it uses a standard wiring harness. This allows you to add accessories to the boat and use factory wiring to simplify the installation. Note that in the schematic, if your Vista 268 did not originally come with an automatic extinguisher, there will be a shorting plug installed in J018. This allows the use of a standard wiring harness regardless of whether or not the boat came with an automatic system.

The schematic is a "simplified" drawing in the sense that only those portions of the circuits that are associated with the engine ignition control system is shown. In the Four Winns documentation, this drawing encompasses several sheets, and you must trace the wiring from one page to another. This makes reading the schematic difficult, so I redrew it here. Although your boat will be different, this makes for good practice - to have useable electrical drawings of the things you change.

The shorting plug is located just above the gas tank at the front bulkhead, near the centerline of the boat. Since I intend on taking advantage of the existing wiring, I must locate the fire extinguisher within the reach of this connector. The shorting plug will be removed, and the fire extinguisher switch mounted atop the unit will be connected in its place.

When I did the tank monitor project, I ordered several sizes of molex connectors. Since I had to make a minimum order, I simply ordered spares. I installed P018 to the switch atop the fire extinguisher. This connector will plug into the wiring harness.

To keep from having to drill thru holes into the rear berth vinyl headliner, I decided to surface-mount the extinguisher using a piece of 1/2in Starboard construction panel. This piece of material will be screwed to the rear of the firewall with 11 #10x1 1/2in screws. The mounting straps were included as part of the kit. I found out later that if you get the factory installed fire extinguisher from Four Winns, they mount it on a piece of starboard like I did. Doubt they used as many screws though!

The final location of the indicator required drililng into the dash. I really do not like the mounting location, but it is the stock Four Winns location - if the fire system were ordered as a factory option - and it had the existing wiring harness in this area. I did replace the original LED supplied with the FireBoy system with one that had a threaded barrel mounting - rather than the cheap mounting method used by FireBoy. Whenever possible I like to upgrade components like this. I find that in a marine environment, using better components and fastening methods results in a more reliable system.

Next, I wired in the LED into the existing wiring harness on the dash. Unfortunately, I did not have the correct molex connector to fit the existing one. No problem, I simply went to my local Radio Shack store and picked up a molex connector set. As long as you use the 0.092 spacing molex connectors, you can remove the pins from the original connector and put them on the new one. This can be done by carefully depressing the barbs on the connector pins and removing them from he nylon shell. Here you see the back-side of the dash with the improved LED mounting and connector assembly.

I mounted the Starboard mounting panel in the desired location, near the centerline of the boat. The screws just penetrated the full thickness of the plywood bulkhead, and should provide ample support for the panel. I did have some difficulty in starting the screws, since that silver material was about 1/2in thick, and actually is nothing more than foam rubber with an aluminum film attached to the outside. I had to really push in to get the screws started - not too easy in the confines of the engine room. The silver-over-foam material is actually a soundproofing barrier.

The final task of the project is to mount the fire extinguisher to the board, plug it into the wire harness, then test to make sure the blower still worked, and verify that the LED dash light is on whenever the ignition is on. Yep, all is working fine. Make an entry into the inspection tag, and this project is done.

A couple hunderd bucks is not a real huge price to pay for an upgraded fire extinguisher, especially on a boat worth over $40K. Also, the insurance company gives around a 6% discount on the rates for this system. While that only amounts to around $25 or so per year, every bit helps. Along with the fact that we tend to boat sometimes 30 miles from the nearest port, we likely were not carrying sufficient fire extinguishers with just the two required by the USCG.

 

Bill of Materials
Automatic Fire Extinguisher FireBoy Xintex CG2-175
Electrical Components LED, connectors and wire.
Starboard and stainless hardware West Marine.

 

Reader Comments


Home    Return