Siemens: How to Design a Pump Control Panel

Application Requirements:

Design a Simplex Pump panel for a 50 horsepower, 480 VAC, 3 phase 60Hz Pump Motor

Control voltage is 120 VAC
Use IEC devices
22mm pilot devices
Wallmount enclosure – outdoor rated
Main circuit breaker with door mounted operating handle
CPT with primary and secondary fusing
Hand – off – auto switch, overload reset button, run and off indication
(2) Normally open (NO) auxiliary contacts for remote indication
Terminal strip for incoming connections
Recommended wire and wireway

Selection Process and Components:

Starter

A starter is needed to turn on and off the motor, as well as provide electrical overload protection to the motor. We will need to select both a contactor and an overload relay.

Contactor

Size the contactor by matching the coil voltage (control voltage) and horsepower at the designated voltage
COIL VOLTAGE – 120VAC
HP – 50HP @ 480 VAC.

Part Number: 3RT2037-1AK60

Overload Relay

Size the overload relay using the Full Load Amps of the motor (reference motor FLA chart). Match the overload frame size to the selected contactor frame size
Motor FLA – 65A
Contactor frame size – 2

Part Number: 3RB3036-1WW1

Starter Auxiliary Contacts

Auxiliary contacts pass a signal based on the current state of a contactor, allowing indication to a remote device (such a PLC or pilot light).
The selected contactor already has 1 included Normally Open (NO) aux contact. A 2nd one needs to be added.
Select an IEC Contactor Aux Contact based on a minimum of 1 NO Contact with a frame size compatible with the selected contactor (Size 2). We will select a front mount with 4 NO Contacts, but any of the multiple Design Assurance options would have sufficed.

Part Number: 3RH29111FA40

Pilot Devices

Hand – Off – Auto (HOA) Switch

A Hand-Off-Auto (HOA) switch, is a 3 position maintained selector switch that allows for starting a motor manually (Hand), turning off manually (Off), or allowing a separate control circuit or PLC to control the motor (Auto).

Part Number: 3SU1150-2BL60-1NA0

Run Indicator Light

A Run light is typically Red and indicates that a machine is running. Select a 22mm Pilot Light based on color (Red) and match the lamp type to the application control voltage (120VAC)

Part Number: 3SU11536AA201AA0

Off Indicator Light

An Off light is typically Green and indicates that a machine is not running
Select a 22mm Pilot Lights based on color (Green) and match the lamp type to the application control voltage (120VAC)

Part Number: 3SU11536AA401AA0

Reset Button

A reset button will allow us to send a reset signal to the overload relay to reset after an overload condition trips the relay (and we have resolved the condition that caused the overload).
A reset button is typically black.
Select a 22m Pushbutton based on color (black)

Part Number: 3SU11500AB103BA0

Control Power Transformer (CPT)

A Control Power Transformer (CPT) is used to convert converts one voltage (typically incoming power) to another (typically control power). Our application has an incoming voltage of 480VAC (which will power the motor); we also need 120VAC in the panel for our control circuit. To size the transformer, determine the load in Volt-Amps (VA) of all devices that are 120 VAC powered, then follow the guidelines in the “How to Select a Control Power Transformer” blog post to calculate the Applied Inrush VA and determine the correct VA.

Total Inrush Current = 188 VA (Contactor) + 2.4 VA (Red Pilot Light – 120VAC x 0.020 A Current Consumption) + 2.4 VA (Green Pilot Light)
= 192.8 VA

Total Sealed Current = 16.5 VA (Contactor) + 2.4 VA (Red Pilot Light) = 2.4 VA (Green Pilot Light)
= 21.3 VA

Applied VA=√(192.8^2+21.3^2 )
= 193.97

Using table, minimum 50 VA transformer is required. Select 100VA

Part Number: MT0100A

CPT Primary Fuse Block

The Primary Fuse Block allows for the use of fuses to protect the transformer from over current.

Part Number: KCCFPX2R

CPT Primary Fuses

Select the Primary Fuses (Qty 2) using the sizing tables from the “Control Power Transformer (CPT Fuse Selection Guide” . Use the Motor Circuit table since our application is a motor circuit.
Select the primary fuses using the sizing tables. Find the intersection of the selected transformer VA rating (100) and the primary voltage (480 VAC). The required fuse is 1A (pick 1.5A – next available size in selection table)

Part Number: 2 x ATDR1-1/2

CPT Secondary Fuses

Secondary fuses prevent the devices connected to the transformer from receiving too much current.
Select the secondary fuse using the sizing tables. Find the intersection of the selected transformer VA rating (100) and the secondary voltage (120 VAC). The required fuse is 1.25A (pick 1.5A – next available size in selection table)

Part Number: ATDR1-1/2

Main Circuit Breaker

The main circuit breaker provides overcurrent protection to the entire panel based on the total current consumption of the entire circuit, by preventing the wires in the panel from conducting more current than they are rated for. All power to the panel can also be turned off via the main circuit breaker.

The main breaker also protects the panel from a short circuit (which can generate MUCH more current than a typical overcurrent situation).

Select the main circuit breaker based on 1.) Short Circuit Interrupt Rating (determined by the main electrical power from the utility company) 2.) Total Current Consumption of devices using 480 VAC multiplied by a factor of 150%

Total Current Consumption = (Motor FLA (65A) + CPT Input Current (.12 A – Calculated using the formula I=(100 VA)/(√3 × 480 VAC)) X 150%
= 97.68

Select a 110 A circuit breaker.

Part Number: 3VA51114EC310AA0

Main Circuit Breaker Lugs

Lugs are used to physically connect the wire to the line and load side of the circuit breaker terminals.

Size lugs based on the compatible frame size of the transformer.

Select Qty 2 compatible with 3VA51 circuit breaker frame

Part Number: 2 x 3VA91330JB11

Main Circuit Breaker Handle

A circuit breaker handle allows for manual control of a circuit breaker from outside the enclosure.

Select a circuit breaker handle based on type (Rotary Through the Door) and Compatible Breaker Frame (3VA51). Verify that the NEMA rating fits our outdoor application (NEMA 3R)

Part Number: 3VA91370FK31

Power Distribution Block

A power distribution block allows for the distribution of main power to multiple devices.

Select based on max current of the circuit (97.68 A). Round up to the 175 A power distribution block

Part Number: MPDB67563 + Cover – MPDBC6667

Terminal Blocks and Accessories

Terminal blocks allow for easy wiring and distribution of power and signals throughout the panel.

Select feed through terminal blocks and ground terminal blocks based on wire gauge to be used (18AWG for 120VAC circuit) – UT 2.5, and UT 2.5 PE
Part Number: 3044076; 3044092

End covers electrically isolate groups of terminal blocks. Select based on compatible blocks (UT 2.5)
Part Number: 3030271

Partition plates visually isolation groups of terminal blocks. Select based on compatible blocks (UT 2.5)
Part Number: 3047167

Plug in bridges jumper groups of blocks together for distribution of the same voltage to multiple devices. Select based on compatible blocks (UT 2.5) and number of positions (10) – Note that these can be cut to desired number of positions.
Part Number: 0800886

DIN Rail

DIN Rail is used to mount components inside an enclosure.

Select the AWC recommended DIN Rail.

Part Number: 1201730

Wire

Wire is sized based on current capacity.

We will typically use different wire colors based on the circuit.

Size the wire for the main 480 VAC circuit based on the chosen main circuit breaker (110A) using the “Wire Size and Selection Criteria” blog post – 1 AWG wire

Select colors using selection criteria:
480VAC Phase 1,2,3 – Brown + Orange + Yellow
Part Number: WITHHN01STRBRW; WITHHN01STRORN; WITHHN01STRYEL

480VAC Neutral – Grey
Part Number: WITHHN01STRGRY

480 VAC Ground – Green
Part Number: WITHHN01STRGRN

Size and select the 120 VAC circuit wiring the same way (based on the total output current of the CPT – 0.91 A):

16 AWG – MTW (based on its recommended use inside panels)
120VAC Hot – Black
Part Number: WIMTW16STRBLK

120VAC Neutral – White
Part Number: WIMTW16STRWHT

120VAC Ground – Green
Part Number: WIMTW16STRGRN

Wireway

Wireway allows for routing of wire inside the enclosure in a neat manner.

Select wireway based on dimensions that allow required wire amount to fix, and desired color.

Part Number: 3240199

Enclosure

Select an enclosure with an outdoor NEMA rating (3R minimum) that fill allow for all components to fit with ample space for airflow and wiring.

Part Number: WM303008NC

Nitin Patel is an Automation Specialist for AWC, Inc. in the Dallas, TX office. He is a Certified Siemens Technology Specialist for Factory Automation. With over 14 years of experience in industrial automation, he has a BS in Electrical Engineering from Texas A&M University.