442A fire alarm, communication and building automation practice questions.

Five free practice questions on fire alarm, communication and building automation: block E of the Red Seal 442A Industrial Electrician exam, about 10 of its 100 questions. They are in the exam's format: four options, one correct answer. Answer each one before opening the explanation. No account, no email.

01The questions

1. Procedural · Maintains fire alarm systems

   A vane-type waterflow switch on a warehouse sprinkler riser sends short alarms a few times a month. Each clears within seconds, no water is flowing, and the times match municipal pressure surges. What is the correction?

   1. Rewire the switch to a supervisory zone.
   2. Increase the switch's retard (delay) setting.
   3. Fit an end-of-line resistor at the switch.
   4. Replace it with a valve-position (tamper) switch.
   Show the answer

   B. Correct. A surge moves the vane for a moment; the retard makes the switch wait before it closes its contact, so short surges are ignored while sustained flow from an open sprinkler still alarms. Keep it within the maximum delay permitted for the system.

   Why not the others

   A. A waterflow switch reports a fire: sprinkler water is flowing. It must stay on an alarm input. The surges are dealt with by giving the switch more delay, not by downgrading its signal.

   C. An end-of-line resistor lets the panel supervise the wiring for opens; it does nothing about a vane that flicks on a pressure surge. The cure is a longer retard so a brief surge is ignored.

   D. A valve-position switch supervises whether a control valve is open; it cannot detect water flowing in the riser. The waterflow switch stays and gets a longer retard.

2. Recall · Installs building automation systems

   Occupancy sensors will switch the lighting in a plant's locker room, where rows of lockers and shower partitions block the view from the ceiling. Which sensor suits the room?

   1. Ultrasonic.
   2. Passive infrared.
   3. Photoelectric light level.
   4. Passive infrared with a long time delay.
   Show the answer

   A. Correct. An ultrasonic sensor fills the space with inaudible sound and detects the Doppler shift from movement, including reflections from behind lockers and partitions, so it does not need a direct line of sight.

   Why not the others

   B. A passive infrared sensor sees only the heat of people within its direct line of sight, so anyone behind a row of lockers or a partition goes undetected and the lights switch off on them. Ultrasonic sensing fills the room.

   C. A light-level sensor measures how much light is in the room, which is useful for daylight dimming, not for detecting people. Detecting occupants behind obstructions calls for ultrasonic sensing.

   D. A longer time delay only postpones the switch-off: someone showering behind a partition for longer than the delay is still unseen and goes dark, and the lights burn longer after everyone leaves. Ultrasonic sensing does not need line of sight.

3. Recall · Installs communication systems

   When an optical time-domain reflectometer (OTDR) tests a new fibre link, why is a launch cable of a few hundred metres connected between the instrument and the link?

   1. So the link's first connector lies past the dead zone.
   2. So the OTDR can work out the fibre's refractive index.
   3. So more light is delivered to the far end of the link.
   4. So the OTDR's laser is protected from reflected light.
   Show the answer

   A. Correct. The strong reflection at the OTDR's own port blinds the receiver for a short distance (the dead zone). The launch cable puts the link's first connector beyond it, so that connector's loss and reflectance can be measured; a receive cable at the far end does the same for the last one.

   Why not the others

   B. The refractive index (group index) is entered from the cable maker's data to set the distance scale; a launch cable does not measure it. The launch cable moves the first connector of the link past the dead zone.

   C. A launch cable adds fibre, so it adds a little loss; it never raises the light at the far end. Its purpose is to move the link's first connector out of the OTDR's dead zone so that connector can be measured.

   D. An OTDR is built to receive reflections; that is how it works. The launch cable's job is to get the link's first connector out of the dead zone at the instrument's port so it shows up on the trace.

4. Procedural · Installs fire alarm systems

   A fire detector is needed under the hood of a paper machine's dryer section. The air carries steam, and the temperature climbs quickly each time the hood doors open, peaking at 50 °C (122 °F). Which detector suits the location?

   1. An ionization-chamber smoke detector.
   2. A rate-of-rise heat detector.
   3. A photoelectric smoke detector.
   4. A fixed-temperature heat detector.
   Show the answer

   D. Correct. Steam defeats both kinds of smoke detector and the quick normal temperature swings defeat a rate-of-rise element. A fixed-temperature heat detector, rated suitably above the 50 °C peak, responds only to a real fire.

   Why not the others

   A. Steam, moisture and air movement disturb an ionization chamber and cause nuisance alarms, so smoke detection of either kind is unsuitable under a dryer hood. A fixed-temperature heat detector rated above the 50 °C peak fits the conditions.

   B. A rate-of-rise element alarms on a fast temperature climb, which is what happens every time the hood doors open here, so it would false-alarm in normal operation. A fixed-temperature detector rated above the 50 °C peak ignores the swings.

   C. Steam scatters the light in a photoelectric chamber much as smoke does, so this detector would false-alarm every time the hood vents. A fixed-temperature heat detector rated above the 50 °C peak ignores steam and the normal temperature swings.

5. Procedural · Maintains building automation systems

   A duct humidity sensor in a paper warehouse reads 8 %RH higher than a calibrated reference held beside it, at both 40 %RH and 60 %RH. Site procedure allows a software offset of up to ±10 %RH before a sensor must be replaced. What correction is made?

   1. A new sensor in place of the old one.
   2. An offset of +8 %RH on the input.
   3. A span reduced by 8 % on the input.
   4. An offset of −8 %RH on the input.
   Show the answer

   D. Correct. The same 8 %RH error at two points shows a constant offset, not a span error, so subtracting 8 %RH makes the reading match the reference across the range. Record the as-found and as-left values.

   Why not the others

   A. The error is a steady 8 %RH, inside the ±10 %RH the site procedure allows for a software offset, so replacement is not called for yet. Enter −8 %RH and note the drift for the next check.

   B. Adding 8 %RH doubles the error, pushing the reading 16 %RH above the true value. The sensor reads high, so the offset subtracts: −8 %RH.

   C. A span change corrects an error that grows with the reading. Here the error is the same 8 %RH at 40 % and at 60 %, which is a constant offset, corrected by −8 %RH.

02Answer key

03What block E covers

Block E covers the low-energy systems in a plant: fire alarm detectors, signal and supervisory circuits, sprinkler flow and tamper switches, access control and security, structured cabling, fibre and industrial Ethernet networks, and building automation systems, with the DDC controllers, sensors and actuators that run HVAC and lighting.

The Red Seal Occupational Standard names this block “Installs and maintains signalling and communication systems”. It carries 10% of the exam, about 10 of the 100 questions, split across three tasks. The share column is each task's weight within the block, as the standard publishes it.

04What the questions turn on

Polarized appliances allow supervision

Fire alarm horns and strobes have blocking diodes so the panel can supervise the circuit in reverse polarity without sounding them. On alarm the polarity flips and they operate; one installed backwards conducts in standby and upsets the supervision.

A closed valve is supervisory

A sprinkler control valve's tamper switch sends a supervisory signal, not an alarm, because the fire protection is impaired rather than a fire detected. It operates well before the valve is fully shut, so a partly closed valve is reported too.

Same network, unique host number

With a 255.255.255.0 mask, the first three numbers of an IP address are the network part. A new device must share them with the PLC, take a host number nothing else uses, and be recorded in the address log.

Interpose between DDC and starter

A DDC binary output is a small dry contact, often rated for 24 V AC. It switches the coil of an interposing relay, and that relay's own contact, rated for the control voltage, operates a 120 V starter coil.

05The other blocks

The 442A exam has six blocks. Each has its own page of free questions:

The 442A Industrial Electrician practice exam page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.