Douglas Krantz - Technical Writer - Describing How It Works
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Why Does Closing Some Gatevalves Show Trouble?

Early fire alarm systems did not have a supervisory condition. There are still quite a few of those systems around. Only one zone pair of wires was needed for the old system, two pairs of wire is needed for the new system.

By Douglas Krantz

Grandfather Clause

Can't live with it; can't live without it. Some say that the Grandfather Clause is the evil twin of Santa Claus because the Grandfather Clause allows continuing the archaic ways of doing things long after better methods have been developed and required.

The reason the Grandfather Clause exists, though, is because the rules and regulations that govern how we build things keep changing. New and better ways of doing things are constantly found, and our governing rules and regulations change every three years. Often, in order to change the way of doing things to match the rules requires bulldozing the building and starting over.

As better ways of erecting buildings are found every three years, just try to bulldoze all the buildings in a city that were built using archaic methods. Rebuilding much of the city after bulldozing every three years is quite expensive. The Grandfather Clause combats this high expense by allowing existing archaic construction to exist long after better ways have been enacted.

Fire alarm systems are often included in the archaic designs that are protected by the Grandfather Clause.

Before Supervisory

Early fire alarm systems did not have a supervisory condition. There are still quite a few of those systems around.

These panels had three conditions: Normal, Alarm, Trouble.

Normal - you could ignore the fire alarm system because there was no fire, and the fire alarm system was working like it always does.

Alarm - the fire alarm system had detected a fire, or it had been manually activated into alarm. The building needed to be evacuated and the firefighters needed to come, but once the building was evacuated and the firefighters arrived, the fire alarm system could be ignored until the fire was out.

Trouble - the fire alarm system made a local buzz and an amber light was turned on. The fire alarm system itself needed attention because something wasn't normal about it.

Early on, the concept of a silent alarm that did not call the firefighters (that's what a supervisory alarm basically is) was considered to be on the same level as a broken wire in the fire alarm system. It was a condition that needed to be fixed without evacuating the building.

Closed Gatevalve

Closing a gatevalve on the sprinkler system is an issue to be concerned with because the sprinkler system won't suppress a fire if the water is turned off. To warn the building owners that the gatevalve was closed, an alert was sent to the fire alarm panel.

There was no need to evacuate the building or call the fire department simply because a water valve was closed, so instead, the tamper switch on the gatevalve "broke" the wire going to the end of line resistor. Although in the rules and regulations, there was also a stipulation that using the tamper switch to "break" this wire, a flow switch alarm would still get through to the fire alarm panel.

Grandfather Clause

You ask what the Grandfather Clause has to do with this? Fifty years ago, there were no addressable fire alarm systems, all systems were conventional. Each zone had a pair of copper conductors hidden in the walls going from the zone to the fire alarm panel. A waterflow switch/tamper switch combination was a zone.

Most of the fire alarm panels have been upgraded, and the upgraded versions of the panels include supervisory alarms. However, many times the upgrade did not include going from a conventional building wide fire alarm system to an addressable system. This meant that the old "zone wires" were left in place, hidden in the walls.

Separating zones, wiring the waterflow switch alarm to an alarm zone and the gatevalve tamper switch alarm to a separate supervisory zone, would have required a new pair of copper conductors to be hidden in the walls between the water room and the fire alarm panel. The wire is cheap; hiding the wire in the walls can be very expensive.

To combat the high expense, the Grandfather Clause was "unofficially enacted". The method of breaking the wire to send a trouble signal to the panel may be archaic, and may also be a little confusing to someone not familiar with what is really causing the trouble, but the trouble gets the building owner's attention that something needs fixing.

That's why closing some gatevalves shows trouble on the panel.
Get help finding those Ground Faults - Buy the book "Make It Work - Hunting Ground Faults" by Douglas Krantz - Ground Fault Hunting becomes easier when you know what causes the ground fault and what is needed to "see" the ground fault.
Get help finding those Ground Faults - Buy the book "Make It Work - Hunting Ground Faults" by Douglas Krantz - Ground Fault Hunting becomes easier when you know what causes the ground fault and what is needed to "see" the ground fault.
Douglas Krantz -- Fire Alarm Engineering Technician, Electronic Designer, Electronic Technician, Writer

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