State Industries SW 37-670 Electrical Data, Branch Circuit, Boiler Circuits, Control Circuit

Page 12

ELECTRICAL DATA

General

Check the boiler model and rating plate information against the characteristics of the branch circuit electrical supply. Do not connect the boiler to an improper source of electricity.

Voltage applied to the boiler should not vary more than + 5% to -10% of the model and rating plate marking for satisfactory operation.

Do not energize the branch circuit for any reason before the boiler is filled with water. Doing so may cause the heating elements to burn out. Such damage is not covered under the terms of the warranty.

The branch circuit is connected to the block through an opening provided on top of the boiler.

The boiler should be connected to a separate, grounded, branch circuit with overcurrent protection and disconnect switch. These are part of the electrical supply system not components of the boiler, as such they are obtained locally. The boiler should be grounded in accordance with national and local codes.

Branch Circuit

The branch circuit wire size should be established through reference to the National Electrical Code or other locally approved source in conjunction with boiler amperage rating. Branch circuit wiring which connects to the boiler terminal block should be temperature rated at 75°C. For convenience, portions of the wire size tables from the Code are reproduced here. It is suggested the electrician size the branch circuit at 125 percent of the boiler rating and further increase wire size as necessary to compensate for voltage drop in long runs. Branch circuit voltage drop should not exceed 3% at the boiler.

Calculating Amperage/

Overcurrent Protection

The boiler is factory wired for connection to three wire single-phase or three and four wire three-phase branch circuits. In addition, a ground conductor may be required.

A diagram of the wiring “as built” is furnished with the boiler for the electrician’s use. An amperage table is on pages 7 & 12 of this manual. The boiler model and rating plate provides full load amperage data. Typical or Standard wiring diagrams are provided on pages 13 & 14 of this manual.

The rating of the overcurrent protection should be computed on the basis of 125 percent of the total connected load amperage. Where the standard ratings and settings do not correspond with this computation, the next higher standard rating or setting should be selected.

Boiler Circuits

The boiler’s electrical components are pictured and identified on page 8. The model and rating plate illustration on page 9 identifies the electrical characteristics. Basically, there are two electrical circuits:

The control circuit, where the temperature control directly or indirectly operates the contactor coils.

The power circuit, which is operated by the control circuit, carries the electrical load of the heating elements.

The following describes the circuits and includes typical wiring diagrams. All circuits are designed for 60 or 50 Hertz alternating current.

Refer to ELECTRICAL CONFIGURATION TABLE, below, and wiring diagram provided with your boiler before completing connections to electrical supply.

NOTE: Wiring diagrams in this manual are typical examples. The specific wiring diagram “as built” for your boiler is typically attached to the “inner side” of the control panel.

Control Circuit

All control circuits are operated on single-phase 120V. A transformer is used in the control circuit.

Control circuit wiring is 14 Awg, THHN or THWN type, rated 600 volts, 105°C.

Seperate instructional literature is provided with the boiler for step control.

Portion of Table 310-16

Portion of Table 310-16

Allowable Ampacities of Insulated

Allowable Ampacities of Insulated

Copper Conductors

Aluminum and Copper-Clad

Not more than three conductors in

Aluminum Conductors

 

 

 

raceway or cable or direct burial

Not more than three conductors in

(based on ambient temperature of

raceway or cable or direct burial

 

30°C, 86°F.)

(based on ambient temperature of

 

 

 

 

30°C, 86°F.)

 

 

Temperature

 

 

Temperature

 

 

Rating of

 

 

Rating of

 

 

Conductor. See

 

 

Conductor. See

 

 

Table 310-13 in

 

 

Table 310-13 in

Size

 

Code

Size

 

Code

 

 

75°C (167°F)

 

 

75°C (167°F)

AWG

 

Types RH,

AWG

 

Types RH,

 

RHW, RUH (14-

 

RHW, RUH (12-

MCM

 

MCM

 

 

2), THW, THWN,

 

2), THW, THWN,

 

 

 

 

 

 

XHHW, USE

 

 

XHHW, USE

18

 

- - - - -

12

 

15

16

 

- - - - -

10

 

25

14

 

15

8

 

40

12

 

20

6

 

50

10

 

30

4

 

65

8

 

45

3

 

75

6

 

65

2

 

90

4

 

85

1

 

100

3

 

100

1/0

 

120

2

 

115

2/0

 

135

1

 

130

3/0

 

155

1/0

 

150

4/0

 

180

2/0

 

175

250

 

205

3/0

 

200

300

 

230

4/0

 

230

350

 

250

250

 

255

400

 

270

300

 

285

500

 

310

350

 

310

600

 

340

400

 

335

700

 

375

500

 

380

750

 

385

600

 

420

800

 

395

700

 

460

900

 

425

750

 

475

1000

 

445

800

 

490

1250

 

485

900

 

520

1500

 

520

1000

 

545

1750

 

545

 

2000

 

560

1250

 

590

 

1500

 

625

These capacites relate

only to conductors

1750

 

650

described in Table 310-13 in Code.

 

 

 

 

2000

 

665

For ambient temperatures over 30°C, see

 

 

 

Correction Factors, Note 13 in Code

12

Image 12
Contents Installation Operation Service Maintenance Limited Warranty Commercial Electric BoilersSafe INSTALLATION, USE and Service General Safety Information Precautions Hydrogen GAS FlammableGrounding Instructions Table of Contents IntroductionDimension Data Sizes and Data NW37 Thru NW150Sizes and Data NW220 Thru Dimension Data cont’d Boiler Specifications StandardFeatures and Components Actual Configuration MAY VaryApprovals Model and Rating Locating the BoilerFacts to Consider About the Location Installation Required AbilityGeneral Pressure Relief ValveClosed Water Systems Thermal ExpansionElectrical Data Branch CircuitCalculating Amperage Overcurrent Protection Boiler CircuitsWiring Diagrams Diagram Three Phase Delta with Step Control Diagram Three Phase WYE with Step ControlHigh Temperature Limits Temperature RegulationOperation Filling the BoilerTemperature Controls DrainingMaintenance FlushingSediment Removal Water and Lime Scale RemovalTroubleshooting Checklist System Water TestSW-37 Thru SW-670 Electric HOT Water Boiler Limited Warranty Division of A. O. Smith Corporation RENTON, Washington