Douglas Krantz - Technical Writer - Describing How It Works
Go to the Fire Alarm Home Page of Douglas Krantz -- Describing How It Works
Go to the Fire Alarm Operation Map Page of Douglas Krantz - Technical Writer
Go to the General Electrical Map Page of Douglas Krantz - Technical Writer
Go to the Fire Alarm Description Map Page of Douglas Krantz - Technical Writer
Go to the Fire Alarm Installing Map Page of Douglas Krantz - Technical Writer
Go to the Fire Alarm Maintaining Map Page of Douglas Krantz - Technical Writer
Go to the Fire Alarm Testing Map Page of Douglas Krantz - Technical Writer
Go to the Fire Suppression Map Page of Douglas Krantz - Technical Writer
Go to the Science Article Map Page of Douglas Krantz - Technical Writer
Go to the Writer Home Page of Douglas Krantz -- Describing How It Works

Fire Alarm -- Installation

Often, the HVAC people install their air diffuser at a convienent place for them, and don't know the consequences for the fire alarm smoke detector.
Photo Courtesy Integrated Fire & Security
When the HVAC Air Diffuser is placed next to a smoke detector, the air coming out of the diffuser keeps any smoke in the room from reaching the detector.
Douglas Krantz -- Fire Alarm Engineering Technician, Electronic Designer, Electronic Technician, Writer






When a New Air Diffuser is Installed, Why is the Fire Alarm Company at Fault?

By Douglas Krantz

I was at a lunch meeting where the State Fire Marshal (AHJ) was speaking. One of the things that he talked about was the spacing between an air diffuser and a ceiling smoke detector.

He said that after placing a ceiling smoke detector well away from any air diffuser, if the HVAC people install an air diffuser next to the smoke detector, it's going to be the fire alarm installer that gets "dinged" and has to move their smoke detector.

It seems unfair, fire alarm people being told to move their smoke detector because of someone else's action, but there is a reason for this unfairness.
Was this
helpful?
Yes   No



Keep in mind, that the HVAC people don't really know the spacing requirements for smoke detectors. If they're told to move the air diffuser, they aren't going to know where to move it.

On the other hand, to keep the proper spacing, the fire alarm installer knows where to move the smoke detector.

Not caring who does the work, all the AHJ is looking for is proper spacing. It's the fire alarm installer that knows the spacing requirements, so it's the fire alarm installer that moves the detector.







Douglas Krantz

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

View Douglas Krantz's profile on LinkedIn



Ask
The
Technician

Readers Questions



Short Circuit
Free Subscription
I'll Send You the
Twice-Monthly
Fire Alarm
Newsletter

Get Short Circuit


Articles

How Does Class A Fire Alarm Wiring Work?-- Fire alarm systems save lives and protect property. Fire alarm systems also break down because... Read More

Just What Is a Signaling Line Circuit (SLC)? -- The SLC (Signaling Line Circuit) is another way of saying Data and Power Circuit. Along with added power to run the sub-computers and their input and output circuits, it's a computer data-buss ... Read More

How is a Buffer Relay Wired Into a Door Holder Circuit? -- Like a door stop, a door holder keeps a fire door open. When smoke is detected, the door holder releases, allowing the door to shut. The door holder looks simple and innocuous enough... Read More

How Does One Find a Soft Ground Fault? -- Normally, we think of resistance like that of a resistor. The amount of resistance is built-in; no matter what voltage is used to drive the electrical... Read More

Can a Magnet Really be Used to Test a Smoke Detector? -- Smoke detectors usually have two ways of being tested. Smoke (smoke particles in the air, or some sort of canned smoke), and magnets (the activation of an internal magnetic... Read More



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
.