Douglas Krantz - Technical Writer - Describing How It Works
Go to the Writer 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
Offers from Technician's Corner


I have a question about something

I have a Question

Hello. I am working a a Siemens panel and I have "mechanical room PIV" error. I am under the impression that PIV's are located outside. Could this be another device that is missed programmed?

Signed R R

Reply

An addressable panel, like the Siemens panel you're working on, uses a Signaling Line Circuit (SLC) for communication. This is really a computer data and power buss. This circuit isn't connected to any device like the pull stations, waterflow switches, gatevalve tamper switches, it's connected to intermediary modules (usually just called modules), and then these modules are connected to the switches using Class B circuitry.

The module is basically monitoring the PIV. It looks like the programmer of the panel didn't "miss program" the panel. Rather, the programmer is trying to help you, the servicer of the system, find the module to fix the system.

"PIV" is the device that is being monitored. Yes, it's the correct "Post Indicator Valve" with a knob to turn off the sprinkler water outside the building. "Mechanical Room", on the other hand, is where you can find the module. That is placed in the message showing on the panel so you don't have to hunt all over the building looking for the module.

"Error" is some sort of trouble signal. It is saying that this module is having trouble, is completely broken, or that the Class B wiring to the PIV is having trouble. Your job is to find that module, which is where you have to start to troubleshoot. This is the device that the panel is really connected to, and not the PIV.

Keep in mind that the module has two different sides, the SLC side and the Class B side.

Using your voltmeter, the SLC side should measure an unsteady (constantly changing) voltage between 10 volts and 24 volts.

The Class B side should show a normal Class B voltage (you'll have to figure that out because each manufacturer uses a different voltage to be "normal").

The module might be having a problem, the wiring out to the PIV might be having a problem, or the end-of-line resistor at the PIV might be having a problem. Replace the module if that is what is having a problem, fix the wiring to the PIV if that is what is having a problem, or replace the end-of-line resistor if that is what is having a problem.

Douglas Krantz



Thank you much!!!

Signed R R


More Articles

Can an SLC loop (Signaling Line Circuit), whether Class B or A, also carry the power to activate (turn on) a horn strobe? -- The Signaling Line Circuit (SLC) is meant to carry signals between addressable devices (Modules and Detectors) and the panel. In some ways, the addressable devices can be thought of as extensions of the panel itself. The SLC can be thought of... Read More

The Signaling Line Circuit (SLC) is a Data-Power Bus -- The SLC isn't an RS232 communication circuit. The SLC isn't an RS485 communication circuit. Proprietary to each manufacturer, the SLC is its own type of communication-line/power-supply circuit.... Read More

NFPA's 7 Classes of Fire Alarm Paths -- The NFPA has divided the signal paths in a fire alarm system into 7 classifications: Class A, Class B, Class C, Class D, Class E, Class N, Class X. These classifications don't show how to wire up anything, these classifications show what happens when things go wrong... Read More

What is a 4 Wire Smoke Detector? -- Even though it uses an internal protection resistor and internal alarm relay contacts, a 4 wire smoke detector is basically a 2 wire smoke detector; it detects smoke and sends an alarm ... Read More

 Get your free diagram showing supervision for Class B wiring


Get help finding ground faults

Get the book Make It Work - Conventional Fire Alarm Systems


Advertisement

Want New Articles
Twice a Month?
Join Short Circuit