Hood-Type Commercial Dishwasher — Engineering Design

🏗️

System Architecture Overview

// Full subsystem block diagram — ECO Spray Arm integrated Hood-Type Commercial Dishwasher

🔄 Automated Wash Cycle Sequence

1

PREHEAT

≤ 10 min (startup)

2

RACK IN / HOOD CLOSE

Operator action

3

PRE-RINSE

5 sec (optional)

4

WASH

60 sec @ 60°C

5

FINAL RINSE

12 sec @ 85°C

6

DRAIN

15 sec

7

HOOD OPEN / DONE

Buzzer + indicator

Total Cycle Time: ~90 sec/rack | Throughput: 60–100 racks/hr | ECO Spray Arms active during Steps 3–5

⚙️ Key Components

🌀

ECO Spray Arms

Upper + Lower Rotating
Multi-Nozzle Design

💧

Wash Pump

0.75 kW Centrifugal
3Ø 380V / 50Hz

🔥

Wash Heater

9 kW Immersion
Target: 55–65°C

☁️

Rinse Boiler

3 kW / 8L Tank
Target: 82–88°C

🏠

Hood Motor

0.18 kW Gear Motor
Linear Actuator

🧪

Dosing Pumps

Peristaltic x2
Detergent + Rinse Aid

🖥️

PLC (S7-1200)

CPU 1214C DC/DC/DC
+SM1234 AI Module

📺

HMI Panel

Siemens KTP700
7" Touchscreen

⚡

Electrical Schematic Diagram

// Power distribution, motor control, heating circuits, and 24VDC control wiring

⚡ Circuit Breaker Schedule

Ref	Circuit	Rating	Type
QF0	Main Supply	4P 63A	MCCB C-Curve
QF1	Wash Heater EH1	3P 32A	MCB C-Curve
QF2	Boiler Heater EH2	3P 16A	MCB C-Curve
QF3	Wash Pump M1	3P 6A	MCB D-Curve
QF4	Rinse Pump M2	3P 4A	MCB D-Curve
QF5	Drain Pump M3	1P 6A	MCB C-Curve
QF6	Control Transformer	1P 6A	MCB C-Curve
QF7	Hood Motor M4	1P 4A	MCB D-Curve

🔌 Contactor / SSR Schedule

Ref	Function	Type	Coil
KM0	Safety Relay	Safety Relay 2-CH	24VDC
KM1	Wash Heater SSR	SSR 40A 3Ø	24VDC (PLC Q0.3)
KM2	Boiler Heater SSR	SSR 25A 3Ø	24VDC (PLC Q0.4)
KM3	Wash Pump	Contactor 9A	24VAC
KM4	Rinse Pump	Contactor 6A	24VAC
KM5	Drain Pump	Contactor 6A	24VAC
KM6/7	Hood FWD/REV	Reversing Contactor	24VAC

📋

PLC I/O Address List

// Siemens S7-1200 CPU 1214C DC/DC/DC — Complete I/O assignment with tag names

🟢 Digital Inputs (DI) — 14 Points

Address	Tag Name	Description	Device Ref	Signal	Type
I0.0	SB_START	Start Push Button	SB1 (Green)	NO 24VDC	DI
I0.1	SB_STOP	Stop Push Button	SB2 (Red)	NC 24VDC	DI
I0.2	SB_ESTOP	Emergency Stop	SB-ES1 (Yellow)	NC 24VDC	DI
I0.3	LS_HOOD_CLOSED	Hood Closed Limit Switch	LS1	NO 24VDC	DI
I0.4	LS_HOOD_OPEN	Hood Open Limit Switch	LS2	NO 24VDC	DI
I0.5	FS_WASH_LO	Wash Tank Low Level	FS1 (Float)	NC 24VDC	DI
I0.6	FS_WASH_HI	Wash Tank High Level	FS2 (Float)	NO 24VDC	DI
I1.0	FS_BOILER_LO	Boiler Low Level	FS3 (Float)	NC 24VDC	DI
I1.1	OL_WASH_PUMP	Wash Pump Overload	F1 (NC)	NC 24VDC	DI
I1.2	OL_RINSE_PUMP	Rinse Pump Overload	F2 (NC)	NC 24VDC	DI
I1.3	TH_WASH_OT	Wash Tank Over-Temperature	TH1 (NC)	NC 24VDC	DI
I1.4	PS_SPRAY	Spray Pressure Switch (min 1.5bar)	PS1 (NO)	NO 24VDC	DI
I1.5	SB_MODE_AUTO	Auto / Manual Mode Selector	SA1 Key-Sw	NO 24VDC	DI
I1.6	SB_MANUAL_WASH	Manual Wash Override (Maint.)	SB3	NO 24VDC	DI

🔴 Digital Outputs (DO) — 10 Points

Address	Tag Name	Description	Device Ref	Load	Type
Q0.0	KM3_WASH_PUMP	Wash Circulation Pump	KM3 Contactor	0.75kW M1	DO
Q0.1	KM4_RINSE_PUMP	Rinse Boost Pump	KM4 Contactor	0.37kW M2	DO
Q0.2	KM5_DRAIN_PUMP	Drain Pump	KM5 Contactor	0.37kW M3	DO
Q0.3	KM1_WASH_HTR	Wash Tank Heater (SSR)	KM1 SSR 40A	9kW EH1	DO
Q0.4	KM2_BOILER_HTR	Rinse Boiler Heater (SSR)	KM2 SSR 25A	3kW EH2	DO
Q0.5	SV1_FILL	Water Fill Solenoid Valve	SV1 (24VDC)	15W Valve	DO
Q0.6	KM6_HOOD_UP	Hood Open (Motor FWD)	KM6	0.18kW M4	DO
Q0.7	KM7_HOOD_DN	Hood Close (Motor REV)	KM7	0.18kW M4	DO
Q1.0	M_DET_DOSE	Detergent Dosing Pump	Peristaltic P1	24VDC	DO
Q1.1	M_RIN_DOSE	Rinse Aid Dosing Pump	Peristaltic P2	24VDC	DO

🔵 Analog Inputs (AI) — SM1234 Module

Address	Tag Name	Description	Sensor	Range	Type
AIW64	TT_WASH_TEMP	Wash Tank Temperature	PT100 via TX1	0–100°C → 4–20mA	AI
AIW66	TT_BOILER_TEMP	Rinse Boiler Temperature	PT100 via TX2	0–100°C → 4–20mA	AI

💾 Internal Memory / Data Block — DB1

Address	Tag Name	Type	Description
DB1.DBW0	STEP	INT	Current sequence step (0–10)
DB1.DBW2	FAULT_CODE	INT	Active fault code
DB1.DBD4	WASH_TEMP_SCALED	REAL	Actual wash temp in °C
DB1.DBD8	BOILER_TEMP_SCALED	REAL	Actual boiler temp in °C
DB1.DBD12	WASH_SETPOINT	REAL	Wash temp setpoint (default 60.0°C)
DB1.DBD16	BOILER_SETPOINT	REAL	Boiler setpoint (default 85.0°C)
DB1.DBD20	CYCLE_COUNT	DINT	Total racks washed (lifetime counter)
DB1.DBX24.0	AUTO_MODE	BOOL	Auto mode active flag
DB1.DBX24.1	PREHEAT_DONE	BOOL	Both temps at setpoint
DB1.DBX24.2	FAULT_ACTIVE	BOOL	Any fault condition active
DB1.DBX24.3	CYCLE_RUNNING	BOOL	Wash cycle in progress

💻

PLC Program — Ladder Logic (IEC 61131-3)

// Siemens S7-1200 SCL + Ladder Logic — Full wash cycle sequencer + safety interlocks

📁 Program Structure — OBs & FBs

// ═══════════════════════════════════════════════════════════ // PROJECT : Hood-Type Commercial Dishwasher — K-ONE Industries // PLC : Siemens S7-1200 CPU 1214C DC/DC/DC // SOFTWARE : TIA Portal V17 — SCL + LAD Mixed // VERSION : 1.0 DATE: 2026-03 // ═══════════════════════════════════════════════════════════ ORGANIZATION_BLOCK OB1 // Main Cyclic Execution (every 10ms) FC_Safety_Check(); // FC1 — Safety interlock evaluation (highest priority) FC_Temperature_Ctrl(); // FC2 — Preheat / PID temperature control FC_Sequencer(); // FC3 — Main wash cycle state machine FC_Alarm_Handler(); // FC4 — Fault detection and alarm output END_ORGANIZATION_BLOCK

🔴 FC1 — Safety Interlock Chain (Ladder)

RUNG 0001 — E-Stop Master Safety Chain // Any fault → de-energize KM0 Safety Relay

|----[/I0.2]----[/DB1.DBX24.2]----[ I1.1]----[ I1.2]----[ I1.3]----( M0.0 ) | SB_ESTOP_NC FAULT_ACTIVE_NC OL_WASH OL_RINSE TH_WASH_OT SAFETY_OK

RUNG 0002 — Hood Interlock: Pumps only run when hood is CLOSED // LS1 = hood closed switch

|----[ M0.0]----[ I0.3]----( M0.1 ) | SAFETY_OK LS_HOOD_CLOSED PUMP_PERMIT |----[ M0.0]----[ I0.4]----( M0.2 ) | SAFETY_OK LS_HOOD_OPEN HOOD_OPEN_CONFIRM

RUNG 0003 — Water Low Level: Block heaters if water insufficient

|----[ M0.0]----[ I0.5]----( M0.3 ) // WATER_OK = safety & not low level | SAFETY_OK FS_WASH_LO_NC WATER_OK

🌡️ FC2 — Temperature Control (SCL)

FUNCTION FC_Temperature_Ctrl : VOID VAR_TEMP wash_temp_real : REAL; boiler_temp_real: REAL; END_VAR // ── Scale AI raw (0-27648) → °C (0-100°C) ── wash_temp_real := NORM_X(MIN:=0.0, VALUE:=INT_TO_REAL(AIW64), MAX:=27648.0) * 100.0; boiler_temp_real:= NORM_X(MIN:=0.0, VALUE:=INT_TO_REAL(AIW66), MAX:=27648.0) * 100.0; // ── Store scaled values to DB ── DB1.WASH_TEMP_SCALED := wash_temp_real; DB1.BOILER_TEMP_SCALED := boiler_temp_real; // ── Wash Tank Heater Control (ON/OFF Hysteresis ±1°C) ── IF M0.3 // WATER_OK THEN IF wash_temp_real < (DB1.WASH_SETPOINT - 1.0) THEN Q0.3 := TRUE; // KM1 Wash Heater ON ELSIF wash_temp_real >= (DB1.WASH_SETPOINT + 1.0) THEN Q0.3 := FALSE; // KM1 Wash Heater OFF END_IF; // ── Boiler Heater Control ── IF boiler_temp_real < (DB1.BOILER_SETPOINT - 1.0) THEN Q0.4 := TRUE; // KM2 Boiler Heater ON ELSIF boiler_temp_real >= (DB1.BOILER_SETPOINT + 1.0) THEN Q0.4 := FALSE; // KM2 Boiler Heater OFF END_IF; ELSE Q0.3 := FALSE; Q0.4 := FALSE; // Heaters OFF — no water END_IF; // ── Preheat Ready Flag ── DB1.PREHEAT_DONE := (wash_temp_real >= DB1.WASH_SETPOINT - 2.0) AND (boiler_temp_real >= DB1.BOILER_SETPOINT - 2.0); END_FUNCTION

🔄 FC3 — Main Wash Cycle Sequencer (SCL State Machine)

FUNCTION FC_Sequencer : VOID // ═══════════════════════════════════════════════════════════ // STEP DEFINITIONS: // 0 = IDLE / STANDBY // 1 = FILL WATER (if tank low) // 2 = PREHEAT WAIT // 3 = READY (awaiting hood close + START) // 4 = PRE-RINSE (5 sec) // 5 = WASH (60 sec — ECO spray arms active) // 6 = DRAIN WASH WATER (15 sec) // 7 = FINAL RINSE (12 sec — boiler water) // 8 = DRAIN RINSE (10 sec) // 9 = HOOD OPEN + CYCLE COMPLETE // 10 = FAULT HOLD // ═══════════════════════════════════════════════════════════ CASE DB1.STEP OF // ──────────────────────────────── 0: // IDLE — System standby // ──────────────────────────────── Q0.0 := FALSE; Q0.1 := FALSE; Q0.2 := FALSE; IF NOT I0.5 // FS_WASH_LO triggered — tank low THEN DB1.STEP := 1; // → Fill water ELSIF DB1.PREHEAT_DONE THEN DB1.STEP := 3; // → Ready for cycle ELSE DB1.STEP := 2; // → Preheat END_IF; // ──────────────────────────────── 1: // FILL WATER // ──────────────────────────────── Q0.5 := TRUE; // SV1 Fill Valve OPEN IF I0.6 // FS_WASH_HI — tank full THEN Q0.5 := FALSE; DB1.STEP := 2; END_IF; // Fault: Fill timeout > 3 min → Step 10 IF T_FILL_TIMEOUT.Q THEN DB1.STEP := 10; DB1.FAULT_CODE := 1; END_IF; // ──────────────────────────────── 2: // PREHEAT — Wait for temperature // ──────────────────────────────── // Heaters controlled by FC2 — just wait IF DB1.PREHEAT_DONE THEN DB1.STEP := 3; END_IF; // ──────────────────────────────── 3: // READY — Await hood close + START // ──────────────────────────────── // Close hood if operator pressed START in open state IF I0.0 AND M0.0 // START pressed AND safety OK THEN Q0.7 := TRUE; // KM7 Hood Motor — Close END_IF; IF I0.3 // Hood CLOSED confirmed THEN Q0.7 := FALSE; Q1.0 := TRUE; // Detergent dose pulse START DB1.STEP := 4; END_IF; // ──────────────────────────────── 4: // PRE-RINSE (5 seconds) // ──────────────────────────────── Q0.0 := M0.1; // Wash pump ON (if hood closed) Q1.0 := FALSE; // Detergent pulse ends T_PRE_RINSE(IN:=TRUE, PT:=T#5S); IF T_PRE_RINSE.Q THEN DB1.STEP := 5; END_IF; // ──────────────────────────────── 5: // WASH CYCLE (60 seconds — ECO Spray Arms) // ──────────────────────────────── Q0.0 := M0.1; // Wash pump ON → drives ECO spray arm rotation // Spray arm rotates by water jet reaction — no separate motor needed // PS1 pressure switch confirms arm is spinning (≥1.5 bar) IF NOT I1.4 // Spray pressure lost THEN DB1.FAULT_CODE := 3; DB1.STEP := 10; // Fault: Low Pressure END_IF; T_WASH(IN:=TRUE, PT:=T#60S); IF T_WASH.Q THEN Q0.0 := FALSE; DB1.STEP := 6; END_IF; // ──────────────────────────────── 6: // DRAIN WASH WATER (15 seconds) // ──────────────────────────────── Q0.2 := TRUE; // KM5 Drain Pump ON T_DRAIN1(IN:=TRUE, PT:=T#15S); IF T_DRAIN1.Q THEN Q0.2 := FALSE; Q1.1 := TRUE; // Rinse Aid dose pulse DB1.STEP := 7; END_IF; // ──────────────────────────────── 7: // FINAL HOT RINSE (12 seconds @ 85°C) // ──────────────────────────────── Q0.1 := M0.1; // Rinse pump ON → boiler water through rinse nozzles Q1.1 := FALSE; // Rinse aid pulse ends // Verify boiler temp before rinse (NSF-3: min 82°C) IF DB1.BOILER_TEMP_SCALED < 80.0 THEN DB1.FAULT_CODE := 4; DB1.STEP := 10; // Fault: Boiler Temp Low END_IF; T_RINSE(IN:=TRUE, PT:=T#12S); IF T_RINSE.Q THEN Q0.1 := FALSE; DB1.STEP := 8; END_IF; // ──────────────────────────────── 8: // DRAIN RINSE WATER (10 seconds) // ──────────────────────────────── Q0.2 := TRUE; T_DRAIN2(IN:=TRUE, PT:=T#10S); IF T_DRAIN2.Q THEN Q0.2 := FALSE; DB1.CYCLE_COUNT := DB1.CYCLE_COUNT + 1; DB1.STEP := 9; END_IF; // ──────────────────────────────── 9: // CYCLE COMPLETE — Open Hood // ──────────────────────────────── Q0.6 := TRUE; // KM6 Hood Motor — Open IF I0.4 // LS2 Hood OPEN confirmed THEN Q0.6 := FALSE; DB1.CYCLE_RUNNING := FALSE; DB1.STEP := 0; // → Back to IDLE END_IF; // ──────────────────────────────── 10: // FAULT HOLD — All outputs OFF // ──────────────────────────────── Q0.0 := FALSE; Q0.1 := FALSE; Q0.2 := FALSE; Q0.3 := FALSE; Q0.4 := FALSE; Q0.5 := FALSE; DB1.FAULT_ACTIVE := TRUE; // Reset via operator STOP button (I0.1) IF I0.1 AND NOT I0.2 // STOP pressed, no E-stop THEN DB1.FAULT_ACTIVE := FALSE; DB1.FAULT_CODE := 0; DB1.STEP := 0; END_IF; END_CASE; END_FUNCTION

🚨 FC4 — Alarm Handler (Ladder)

RUNG 0010 — Fault Code to Tower Light / Buzzer

// FAULT CODE TABLE: // 0 = No Fault | 1 = Fill Timeout | 2 = Temp Sensor Error // 3 = Low Spray Press | 4 = Boiler Temp Low | 5 = Overload Trip // 6 = Hood Timeout | 9 = E-Stop Active // Fault active → Red tower light flashing (500ms) |----[ DB1.DBX24.2 ]----[ T_FLASH.Q]----( HL1_RED ) | FAULT_ACTIVE 500ms clock RED LIGHT // Running (no fault) → Green light ON |----[ DB1.DBX24.3 ]----[/DB1.DBX24.2]----( HL2_GRN ) | CYCLE_RUNNING NOT_FAULT GREEN LIGHT // Preheat → Yellow light ON |----[ DB1.STEP=2 ]----( HL3_YEL ) | STEP==PREHEAT YELLOW LIGHT // Cycle complete → Buzzer 3 pulses |----[ DB1.STEP=9 ]----[ T_BUZZ_PULSE.Q]----( BZ1 ) | STEP==COMPLETE 3x 500ms pulses BUZZER // E-Stop → Continuous buzzer |----[/I0.2]----( BZ1 ) | ESTOP_NC BUZZER CONTINUOUS

📊

Technical Specifications

// Machine parameters, compliance standards, and performance benchmarks

🏭 Machine Specifications

Machine Type	Hood-Type Pass-Through
Rack Size	600 × 500 mm (DIN standard)
Throughput	60–100 racks/hr
Wash Tank Volume	50 litres
Boiler Volume	8 litres
Wash Temperature	55–65°C (default 60°C)
Rinse Temperature	82–88°C (default 85°C)
Wash Cycle Time	60 seconds
Final Rinse Time	12 seconds
Total Cycle Time	~90 seconds
Water Consumption	2.5–3.5 L/rack
Spray Pressure	Upper: 2.5 bar \| Lower: 3.0 bar
Machine Dimensions	650W × 750D × 1450H mm
Machine Weight	~120 kg (dry)

⚡ Electrical Specifications

Supply Voltage	3Ø 380VAC / 50Hz
Wash Heater	9 kW (3Ø immersion)
Boiler Heater	3 kW (1Ø immersion)
Wash Pump Motor	0.75 kW / 3Ø / IP55
Rinse Pump Motor	0.37 kW / 3Ø / IP55
Drain Pump Motor	0.37 kW / 1Ø / IP55
Hood Motor	0.18 kW gear motor
Total Connected Load	~13.7 kW
Running Load (typical)	~10.5 kW
Control Voltage	24 VDC (SMPS)
Protection Class	IP54 (control cabinet)
Main Fuse	63A 3Ø MCCB
PLC	Siemens S7-1200 CPU 1214C
HMI	Siemens KTP700 7" Touch

🌀 ECO Spray Arm Specifications

Arm Design	Reaction-driven rotation (no motor)
Upper Arm	6-jet radial, 450mm diameter
Lower Arm	4-jet radial, 480mm diameter
Side Jets	Fixed, 4-point rinse boosters
Nozzle Type	Fan + pencil jet (dual mode)
Rotation Speed	~30–45 RPM (pressure-driven)
Material	SS316L stainless + PTFE bearings
Self-Cleaning	Flush-back on drain cycle
Min. Pressure	1.5 bar (PS1 switch monitored)
Coverage	360° full-basket sweep

📋 Standards & Compliance

Safety	IEC 60335-2-58 (Dishwashers)
Sanitation	NSF/ANSI-3 (Commercial Warewash)
Electrical	IEC 60947 (Switchgear)
PLC Programming	IEC 61131-3 (LAD + SCL)
Motor Protection	IEC 60947-4 (Overload Relays)
Cabinet Protection	IP54 (IEC 60529)
Pump Rating	IP55 submersible grade
Water Connection	DN15 (1/2") BSP cold water inlet
Drain Connection	DN50 gravity drain to floor
CE Marking	EU Machinery Directive 2006/42/EC

🚨 Fault Code Reference

Code	Description	Cause	Action
0	No Fault	Normal operation	—
1	Fill Timeout	Water inlet blocked / float fault	Check SV1, FS1/FS2, water pressure
2	Temp Sensor Error	PT100 open/short circuit	Check TX1/TX2 transmitters, AIW wiring
3	Low Spray Pressure	Pump fault or spray arm blocked	Check M1 motor, clean spray arms
4	Boiler Temp Low	Boiler heater failure, low water	Check EH2, FS3, boiler thermostat
5	Overload Trip	Motor overloaded or seized	Reset F1/F2, check motor current
6	Hood Timeout	Hood motor fault, LS1/LS2 failure	Check KM6/KM7, LS1, LS2 switches
9	E-Stop Active	Emergency stop pressed	Clear cause, release E-stop, press STOP to reset

Hood-Type Commercial Dishwasher System