# Relay Output Module - Quick Reference SSO **Device Type:** Binary Output - Relay **Signal:** Binary ON/OFF command from controller **Power:** 24VAC (coil) / Contacts rated for load voltage **Version:** 1.0 | **Date:** Dec 2025 --- ## DEVICE OVERVIEW **Common Models:** - Johnson Controls VMA-1600 series, Honeywell RP/RD series, Functional Devices RIB relays, Siemens S-Series, ICM Controls **Used For:** Switching pumps, fans, heat/cool stages, unit heaters, exhaust fans, boilers, chillers, electric heat **Specifications:** - **Coil Voltage:** 24VAC typical (sometimes 120VAC or 24VDC) - **Contact Types:** * SPST (Single Pole Single Throw) - Common * SPDT (Single Pole Double Throw) - NO/NC/COM * DPDT (Double Pole Double Throw) - Two circuits - **Contact Ratings:** * Resistive loads: 20-30A typical * Inductive loads (motors): 1/2 to 2 HP typical * Pilot duty (FLA): Check amp rating on relay - **Enclosure:** Panel mount, DIN rail, or NEMA enclosure - **Wire Type:** 18AWG for coil, 14-12AWG for contacts (load dependent) **Environment:** 32-140°F, 0-95% RH non-condensing (panel mount) --- ## SAFETY - PPE REQUIRED - ☑ Safety glasses (ANSI Z87.1) - ☑ Insulated gloves (if working on powered circuits) - ☑ Hard hat (mechanical rooms) - ☑ Voltage-rated tools (if working energized) ### HAZARDS - ⚠ **HIGH VOLTAGE** - Contact side may be 120VAC, 208/240VAC, or 277VAC - ⚠ **ARC FLASH** - Potential when switching high current loads - ⚠ **ROTATING EQUIPMENT** - Relay may control fans, pumps (LOCKOUT if servicing) - ⚠ **STORED ENERGY** - Capacitors in some motor circuits ### LOCKOUT/TAGOUT - [ ] **REQUIRED for contact wiring:** Lock out power to load circuit before wiring contacts - [ ] **NOT required for coil wiring** (if 24V control only) - [ ] Verify zero voltage with meter before touching contacts - [ ] For motor loads: Wait for complete stop before approaching ### ELECTRICAL CODE COMPLIANCE - [ ] Follow NEC Article 430 for motor circuits - [ ] Overload protection required for motor loads - [ ] Proper wire gauge for load current - [ ] Relay must be rated for load voltage and amperage --- ## INSTALLATION CHECKLIST ### TOOLS NEEDED - Wire strippers (multi-gauge: 18AWG coil, 14-12AWG contacts) - Screwdrivers (appropriate sizes) - Multimeter (DMM) - **REQUIRED** - Voltage tester (non-contact preferred) - Wire nuts or terminal blocks - Label maker - Torque screwdriver (for high-current terminals) ### MATERIALS - Relay (rated for application) - Wire (appropriate gauge for load) - Wire nuts or terminal blocks - DIN rail or mounting hardware - Enclosure (if not panel mount) - Fuse or breaker (if required for protection) ### PRE-INSTALL - [ ] **CRITICAL:** Verify relay coil voltage matches controller output (24VAC typical) - [ ] **CRITICAL:** Verify relay contact rating ≥ load current and voltage - [ ] For motors: Check relay rated for motor HP and voltage - [ ] Confirm contact configuration (SPST, SPDT, DPDT) matches application - [ ] Review wiring diagram and load specifications - [ ] **LOCKOUT power to load circuit** ### INSTALL STEPS 1. **Mount relay:** - Panel mount: Secure to DIN rail or mounting holes - Field mount: Install in appropriate NEMA enclosure - Verify adequate clearance for wire bending radius - Leave access for service 2. **Wire relay COIL (Control Side - 24VAC):** - **FROM CONTROLLER:** * Wire 1 (hot): Controller binary output terminal (usually labeled C1, C2, etc.) * Wire 2 (common): Controller 24VAC common - **18AWG wire typical** - Tighten coil terminals: 7-9 in-lbs - Label: "AHU-1-SF" (example: AHU-1 Supply Fan) 3. **Wire relay CONTACTS (Load Side - Line Voltage):** - **VERIFY POWER OFF with multimeter before touching!** - **Wire sizing:** Per NEC for load amperage: * 15A load: 14AWG minimum * 20A load: 12AWG minimum * >20A load: Consult NEC Table 310.16 - **Typical SPST wiring:** * Line (hot) from breaker → Relay contact (L or line side) * Load (motor, heater, etc.) → Relay contact (T or load side) * **Do NOT switch neutral** - code violation for most applications - **SPDT wiring (if used):** * COM: Common terminal (line voltage in) * NO: Normally Open (energized to close) * NC: Normally Closed (energized to open) - Tighten contact terminals: 12-15 in-lbs (higher current = tighter) - **Double-check polarity and connections before restoring power** 4. **Install overload protection** (if motor load): - Separate overload relay or motor starter typically required - Follow motor manufacturer recommendations - Size per motor FLA (Full Load Amperage) 5. **Label all wiring:** - Coil wires: Controller designation - Contact wires: Load identification - Include voltage level on contact wiring (e.g., "120VAC - AHU-1-FAN") 6. **Restore power** (after verification) ### POST-INSTALL - [ ] Relay mounted securely - [ ] Coil wired to controller (24VAC typical) - [ ] Contacts wired to load (proper gauge wire) - [ ] All terminals tight (verified with pull-test) - [ ] Labels applied to all wiring - [ ] Overload protection installed (motor loads) - [ ] Power restored - [ ] Work area cleaned - [ ] Photos taken --- ## EXPECTED READINGS ### PRE-POWER (Power OFF to BOTH Coil and Contacts) - **Coil Resistance:** 50-500 ohms typical (24VAC coil) - **Contact Continuity (relay de-energized):** * NO contacts: Open (infinite resistance) * NC contacts: Closed (<1 ohm) * COM to NO: Open * COM to NC: Closed ### COIL POWER-UP (24VAC applied to coil) - **Coil Voltage:** 24VAC ±10% (21.6-26.4V acceptable) - **Coil Current:** 50-200mA typical (depends on relay) - **Audible Click:** Should hear relay "click" when energized - **Visual Indicator:** Some relays have LED when energized ### CONTACT VERIFICATION (Relay Energized) - **Contact Continuity (relay energized):** * NO contacts: Closed (<1 ohm) - **THIS IS WHAT SWITCHES LOAD** * NC contacts: Open (infinite resistance) * COM to NO: Closed * COM to NC: Open ### LOAD SIDE VOLTAGE (Relay Energized, Power to Contacts ON) - **Across Load:** Should measure line voltage (120V, 208V, 240V, 277V, etc.) - **Voltage Drop Across Contacts:** <0.5V typical when closed --- ## PROOF OUT TESTS ### TEST 1: Coil Function Test (Safe - Low Voltage) - **Do:** Command relay ON from controller - **Expect:** * Hear relay click * LED illuminates (if equipped) * Measure 24VAC at coil terminals - **Pass If:** Relay energizes with audible click ### TEST 2: Contact Switching Test (POWER OFF TO LOAD SIDE) - **Do:** With load power OFF, measure contact continuity - **Command relay:** OFF → ON → OFF - **Expect:** * OFF: NO contacts open, NC contacts closed * ON: NO contacts closed, NC contacts open * Hear click each time - **Pass If:** Contacts switch properly with each command ### TEST 3: Load Operation Test (FULL SYSTEM TEST) - **WARNING:** Load power now ON - high voltage present - **Do:** Command relay ON from controller - **Expect:** * Relay clicks * Load energizes (motor runs, heater energizes, etc.) * Measure voltage across load terminals - **Pass If:** Load operates when relay commanded ON ### TEST 4: Load Verification (Motor Loads) - **Do:** Observe motor startup - **Expect:** * Motor starts smoothly (no excessive inrush) * Motor runs without overheating * No tripped overload relay * Normal operating current (measure with clamp meter) - **Pass If:** Motor operates normally, current within FLA rating ### TEST 5: Cycling Test - **Do:** Cycle relay ON/OFF 10 times rapidly - **Expect:** * Relay responds each time * No sticking or hesitation * Load starts/stops reliably - **Pass If:** Reliable operation through multiple cycles ### TEST 6: Controller Integration - [ ] Relay appears in controller binary output list - [ ] Controller can command relay ON/OFF - [ ] Status feedback correct (if wired) - [ ] Graphics show relay state - [ ] Sequence operates correctly (staging, interlocks, etc.) - [ ] No faults or errors --- ## TROUBLESHOOTING ### RELAY DOESN'T CLICK / NO COIL VOLTAGE 1. Measure voltage at controller output: Should be 24VAC when commanded ON - **If no voltage at controller:** Controller output failed or not programmed 2. Check coil wiring connections tight 3. Test continuity of coil wiring end-to-end: <5 ohms 4. Measure coil resistance: Should be 50-500 ohms - **If infinity:** Coil burned out - replace relay 5. **If voltage present but no click:** Replace relay (coil failed) ### RELAY CLICKS BUT LOAD DOESN'T RUN 1. **Measure voltage across load terminals:** - **If no voltage:** Contact wiring problem or power not on 2. **Check contact side power:** - Measure at breaker/disconnect: Should have line voltage - **If no voltage:** Breaker tripped or power source issue 3. **Check load wiring:** - Verify load connected to correct relay terminals - Check for loose connections - Test continuity through contacts when energized: <1 ohm 4. **Check overload relay** (motor loads): - May be tripped - reset and retest - May need adjustment or replacement 5. **Test load directly** (bypass relay): - **CAUTION:** Only if qualified for electrical work - Temporarily wire load directly to power - **If load works:** Relay contacts bad - replace relay - **If load doesn't work:** Load failed (motor, heater, etc.) ### RELAY STUCK ON / WON'T TURN OFF 1. **Command relay OFF** from controller 2. **Measure coil voltage:** Should be 0VAC when OFF - **If still has voltage:** Controller output stuck ON 3. **Listen for click:** Should click when commanded OFF - **If no click:** Contacts welded shut - replace relay immediately 4. **Measure across load:** Should be 0V when relay OFF - **If still has voltage:** Contacts stuck closed - **SAFETY HAZARD** 5. **REPLACE RELAY** if contacts won't open (fire hazard) ### RELAY CHATTERS / RAPID CLICKING 1. **Low coil voltage:** - Measure at relay coil: Should be 24VAC ±10% - **If <21V:** Voltage drop in wiring or controller issue - Check wire gauge adequate (18AWG minimum) 2. **Loose coil connections:** - Check terminals tight 3. **High contact load:** - Relay undersized for load - Measure load current with clamp meter - **If exceeds relay rating:** Replace with higher-rated relay 4. **Defective relay:** - Replace with known good relay to test ### CONTACTS BURNED / PITTED 1. **Caused by:** Switching high inrush current (motors, transformers) 2. **Indicators:** - Black/brown deposits on contacts - High resistance when closed (>1 ohm) - Arcing visible when switching 3. **Solutions:** - Replace relay - Add inrush current limiting (soft starter for motors) - Use relay with higher contact rating - Consider solid-state relay for frequent switching ### OVERLOAD RELAY TRIPPING (Motor Loads) 1. **NOT a relay problem** - motor or overload issue 2. Check motor current with clamp meter: - Compare to motor nameplate FLA - **If >FLA:** Motor overloaded, mechanical problem, or failing 3. Check overload relay setting: - Should be set to motor FLA - **If too low:** Nuisance tripping - adjust 4. Check for motor problems: - Bearing failure, seized load, phase loss 5. **If motor current normal:** Overload relay may be defective --- ## ESCALATION - COMPLETE BEFORE CALLING ### PRE-ESCALATION CHECKLIST - [ ] Verified coil voltage at relay (24VAC when commanded ON) - [ ] Verified line voltage at contact terminals (120V, 208V, etc.) - [ ] Listened for relay click (audible when switching) - [ ] Measured load current (if motor - compare to FLA) - [ ] Checked all wiring connections tight - [ ] Verified relay rated for load (voltage and amperage) - [ ] Tested load directly if possible (bypass relay) - [ ] Checked overload relay setting (motor loads) - [ ] Taken photos of wiring and installation ### PROVIDE THIS INFO - **Relay:** [Mfg / Model / Contact Rating / Location] - **Load:** [Type: Motor/Heater/Fan / HP or Amperage / Voltage] - **Coil Voltage Measured:** _____ VAC (when commanded ON) - **Line Voltage Measured:** _____ VAC (at contact terminals) - **Load Current Measured:** _____ A (with clamp meter) - **Load Nameplate FLA:** _____ A (for motors) - **Symptoms:** [No click, clicks but no load, stuck on, chatters, etc.] - **Relay Clicks:** Yes / No - **Overload Status:** Set / Tripped / Not applicable - **Steps Taken:** [Troubleshooting completed] ### CONTACTS - **Field Specialist:** [Phone] - **Electrician:** [Phone] (if high-voltage issue) - **Programmer:** [Phone] (if sequence/logic issue) - **Dispatch:** [Phone] --- ## COMMON ISSUES & TIPS ✓ **Relay sizing:** Always size contacts for 125% of load current (safety margin) ✓ **Motor loads:** Relay must be rated for "Pilot Duty" or motor HP ✓ **Inrush current:** Motors draw 5-8× FLA on startup - relay must handle this ✓ **Contact life:** Typical 100,000 operations, less with high current ✓ **Coil voltage:** 24VAC most common, verify matches controller output ✓ **Contact configuration:** SPST most common (single switch), SPDT for changeover ✓ **Overload protection:** Separate overload relay required for motor loads (NEC) ✓ **Wire neutral:** Never switch neutral (code violation) - only switch hot leg ✓ **Stuck contacts:** Fire hazard - replace immediately if contacts won't open ✓ **Contact cleaning:** Don't file contacts - replace relay if pitted/burned ✓ **Solid-state relays:** Consider for high-cycle applications (>10,000 ops/day) ✓ **Status feedback:** Use auxiliary contacts or current sensor for proof of operation --- **Document ID:** SSO-RELAY-001 **Revision:** 1.0 **Next Review:** Dec 2026