Working safely on controllers and the equipment they switch. A low-voltage controller does not make the installation low voltage: the supply that feeds it and most of what it switches run on mains power.
Isolate and lock out before working. Disconnect every source of power before opening an enclosure or touching a terminal, and verify with a meter. See Isolating Equipment.
The InteliHive runs on 24 V DC, and that part of the system is low risk. The equipment around it is not:
- The 24 V supply is mains-powered. Its input terminals are at line voltage.
- Relay contacts switch line voltage. A relay board’s contacts may carry a pump or solenoid circuit fed from elsewhere in the panel, so they can be live when the controller and the board are both unpowered.
- Wireless outputs have their own mains supply. WiFi switches and power strips are plugged in or wired to line voltage. Their output terminals and outlets are live whatever the controller is doing.
- Pumps, solenoids, and drives are usually 115–240 VAC, and some are three-phase.
- Packaged equipment is often line voltage throughout. The Repressurizer, for example, plugs into a 115 VAC outlet and drives a ½ HP motor.
Treat every terminal in a panel as live until you have measured it, including the low-voltage side. A fault or a miswired conductor can put mains voltage where you expect 24 V.
- Assume more than one source. Panels are often fed by several circuits. Identify all of them before starting.
- Verify dead with a tested meter. Test the meter on a known live source before and after you measure.
- Wait for stored charge to drain. Variable-frequency drives and large power supplies hold charge in capacitors after power is removed. Wait the time the manufacturer specifies, then measure.
- Use insulated tools and the PPE your site’s electrical safety program requires.
- Never work live unless your employer’s electrical safety program specifically permits it for that task and you are qualified and equipped for it.
- Respect ratings. Observe each output device’s contact ratings for voltage, current, and load type. Motors and solenoids are inductive, and their inrush can far exceed running current.
- Protect each circuit. Fuse or breaker each switched circuit to suit its load and your local code. Use GFCI protection where the code requires it, which includes most wet locations.
- Ground properly. Bond enclosures and equipment, and follow the grounding requirements of your local code.
- Separate signal from power. Route sensor and communication wiring away from line-voltage conductors, and cross them at right angles where crossing is unavoidable. This prevents induced noise and keeps an insulation fault on one side from reaching the other.
- Keep water out of enclosures. Use appropriate cable glands, keep the enclosure’s ingress rating intact, and do not mount electrical equipment under fittings that could leak.
- Do not modify factory wiring on packaged equipment. It usually voids the warranty and can defeat protective devices.
Electrical installation must comply with the code in force at your location: for example the National Electrical Code (NFPA 70) in the United States, the Canadian Electrical Code (CSA C22.1) in Canada, or IEC 60364 and local derivatives elsewhere. Safe work practice is covered by standards such as NFPA 70E and CSA Z462. Permits and inspection may be required.