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Fire Alarm -- Maintenance

A Friday-Afternoon-Repair is not a true repair, it is making the fire alarm control panel not see troubles
A Friday-Afternoon-Repair isn't a repair. It's a way of hiding troubles on a fire alarm control panel so the owner doesn't have to listen to the trouble sounder all weekend. Presumably this is done so the fire alarm service company can return the following week to fix the troubles.
Douglas Krantz -- Fire Alarm Engineering Technician, Electronic Designer, Electronic Technician, Writer






What is a Friday Afternoon Repair?

By Douglas Krantz

If the fire panel shows normal, you may never get back to fix a trouble; if the fire panel shows trouble, you'll always come back to fix it.

Sometimes, when replacing a fire alarm control panel, ground faults suddenly show up on the building wiring. The ground faults actually had been there all along, but were hidden.

The previous fire alarm company had performed a "Friday-afternoon-repair" by disconnecting the ground fault circuitry - - and had the intention of finding the ground fault the following week. They never got back to fixing the ground fault.

This kind of "fix" is common among some fire alarm service companies, and is a problem.

Whether it's moving the end-of-line resistor to the beginning of the line, paralleling a single phone line to make the panel think there are two different lines, or disabling the ground fault circuitry, be careful when making the panel normal.

If you don't return the next week, you may never return because, at least from the owner's perspective, there is no reminder on the fire alarm control panel that the system needs fixing.

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The trouble light and sounder on the fire alarm control panel is a reminder that there is a problem. This reminder isn't just for the fire alarm service company; it's also for the owners. If the panel shows its trouble light, and keeps sounding the trouble buzzer, to the owners there's a problem that needs to be fixed. The owner won't let the alarm company forget the problem, which is actually a good thing.

If you have to leave for some reason, whether it's a broken connection on a class B circuit, bad phone line, or a ground fault on the system, leave the panel in trouble.

Remember, rather than "fixing" the trouble light, you're better off leaving a panel in trouble and explaining the trouble to the owners. They'll be the ones to want you back to fix the trouble.







Douglas Krantz

Describing How It Works
writer@douglaskrantz.com
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612/986-4210

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Electrical Flow


On this website, most references to electrical flow are to the movement of electrons.

Here, electron movement is generally used because it is the electrons that are actually moving. To explain the effects of magnetic forces, the movement of electrons is best.

Conventional current flow, positive charges that appear to be moving in the circuit, will be specified when it is used. The positive electrical forces are not actually moving -- as the electrons are coming and going on an atom, the electrical forces are just loosing or gaining strength. The forces appear to be moving from one atom to the next, but the percieved movement is actually just a result of electron movement. This perceived movement is traveling at a consistent speed, usually around two-thirds the speed of light. To explain the effects of electrostatic forces, the movement of positive charges (conventional current) is best.

See the explanation on which way electricity flows at www.douglaskrantz.com/
ElecElectricalFlow.html
.