A. O. Smith NW 37-670 Installation Manual

COMMERCIAL ELECTRIC BOILERS

A DIVISION OF A. O. SMITH CORPORATION

RENTON, WASHINGTON

www.hotwater.com

Instruction Manual

MODELS NW 37-670

INSTALLATION - OPERATION - SERVICE -

MAINTENANCE - LIMITED WARRANTY

ASME

Thank you for buying this energy efficient boiler
from us. We appreciate your confidence in our
products.

PLACE THESE INSTRUCTIONS ADJACENT TO BOILER AND NOTIFY OWNER TO KEEP FOR FUTURE REFERENCE.

PRINTED 0110 316392-000

SAFE INSTALLATION, USE AND SERVICE

Your safety and the safety of others is extremely important in the installation, use, and servicing of this boiler.

Many safety-related messages and instructions have been provided in this manual and on your own boiler to warn you and others of
a potential injury hazard. Read and obey all safety messages and instructions throughout this manual. It is very important that the
meaning of each safety message is understood by you and others who install, use, or service this boiler.

This is the safety alert symbol. It is used to alert
you to potential personal injury hazards. Obey all
safety messages that follow this symbol to avoid
possible injury or death.

DANGER indicates an imminently hazardous

DANGER

WARNING

CAUTION

situation which, if not avoided, will result in
death or injury.

WARNING indicates a potentially hazardous
situation which, if not avoided, could result in
death or injury.

CAUTION indicates a potentially hazardous
situation which, if not avoided, could result in
minor or moderate injury.

CAUTION used without the safety alert symbol

CAUTION

All safety messages will generally tell you about the type of hazard, what can happen if you do not follow the safety
message, and how to avoid the risk of injury.

The California Safe Drinking Water and Toxic Enforcement Act requires the Governor of California to publish a list of
substances known to the State of California to cause cancer, birth defects, or other reproductive harm, and requires
businesses to warn of potential exposure to such substances.

This product contains a chemical known to the State of California to cause cancer, birth defects, or other reproductive
harm. This appliance can cause low level exposure to some of the substances listed.

•  QualiedInstallerorServiceAgency:

Installation and service of this boiler requires ability equivalent to that of a Qualied Agency (as dened by ANSI below) in the eld

involved. Installation skills such as plumbing and electrical supply are required in addition to electrical testing skills when performing
service.

indicates a potentially hazardous situation
which, if not avoided, could result in property
damage.

IMPORTANT DEFINITIONS

•  ANSIZ223.12006Sec.3.3.83:

“Qualied Agency” - “Any individual, rm, corporation or company that either in person or through a representative is engaged in and is

responsible for (a) the installation, testing or replacement of gas piping or (b) the connection, installation, testing, repair or servicing of

appliances and equipment; that is experienced in such work; that is familiar with all precautions required; and that has complied with all

the requirements of the authority having jurisdiction.”

2

GENERAL SAFETY INFORMATION

PRECAUTIONS

DO NOT USE THIS APPLIANCE IF ANY PART HAS BEEN UNDER

WATER. Immediately call a qualied service technician to inspect

the appliance and to replace any part of the control system which
has been under water.

If the unit is exposed to the following, do not operate boiler until all

corrective steps have been made by a qualied service agency.

1. External re.

2. Damage.

3. Firing without water.

GROUNDING INSTRUCTIONS

This boiler must be grounded in accordance with the National Electrical
Code and/or local codes. These must be followed in all cases. Failure
to ground this boiler properly may also cause erratic control system
operation on ELECTRONIC CONTROL models.

This boiler must be connected to a grounded metal, permanent wiring
system, or an equipment grounding conductor must be run with
the circuit conductors and connected to the equipment grounding
terminal or lead on the boiler.

When servicing this unit, verify the power to the unit is turned off prior to opening the control cabinet door.

HYDROGEN GAS (FLAMMABLE)

Hydrogen gas can be produced in a hot water system served by this boiler

that has not been used for a long period of time (generally two weeks or
more). Hydrogen gas is extremely ammable. To reduce the risk of injury

under these conditions, it is recommended that the hot water faucet be
opened for several minutes at the kitchen sink before using any electrical
appliance connected to the hot water system. If hydrogen is present there
will probably be an unusual sound such as air escaping through the pipe

as the water begins to ow. THERE SHOULD BE NO SMOKING OR

OPEN FLAME NEAR THE FAUCET AT THE TIME IT IS OPEN.

3

TABLE OF CONTENTS

SAFE INSTALLATION, USE AND SERVICE...........................................................2

GENERAL SAFETY INFORMATION .......................................................................3

Precautions ....................................................................................................3

Hydrogen Gas (Flammable) ...........................................................................3

TABLE OF CONTENTS ...........................................................................................4

INTRODUCTION .....................................................................................................4

Preparing for the Installation ..........................................................................4

DIMENSIONS AND CAPACITIES DATA .................................................................5

FEATURES AND COMPONENTS ..........................................................................8

APPROVALS ...........................................................................................................9

MODEL AND RATING .............................................................................................9

LOCATING THE NEW BOILER ...............................................................................9

Facts to Consider About the Location ............................................................9

INSTALLATION .....................................................................................................10

Required Ability ............................................................................................10

General ........................................................................................................10

Pressure Relief Valve ...................................................................................10

Water Line Connections ...............................................................................10

Closed Water Systems ................................................................................. 11

Thermal Expansion ......................................................................................11

ELECTRICAL DATA ...............................................................................................12

General ........................................................................................................12

Branch Circuit ...............................................................................................12

Calculating Amperage/Overcurrent Protection .............................................12

Boiler Circuits ...............................................................................................12

Control Circuits .............................................................................................12

WIRING DIAGRAMS .............................................................................................13

OPERATION ..........................................................................................................15

Important ......................................................................................................15

General ........................................................................................................15

High Temperature Limit ................................................................................15

Filling the Boiler ............................................................................................15

Initial Start Up ...............................................................................................15

Temperature Regulation ...............................................................................15

Temperature Controls ...................................................................................16

Draining ........................................................................................................16

MAINTENANCE ....................................................................................................17

Schedule ......................................................................................................17

System Cleaning ..........................................................................................17

Flushing ........................................................................................................17

Sediment Removal .......................................................................................17

Lime Scale Removal ....................................................................................17

TROUBLESHOOTING CHECKLIST .....................................................................18

Not Enough or No Hot Water .......................................................................18

Water is Too Hot ...........................................................................................18

Boiler Makes Strange Sounds ......................................................................18

Leakage Checkpoints ...................................................................................18

WARRANTY ..........................................................................................................19

INTRODUCTION

Thank You for purchasing this boiler. Properly installed and
maintained, it should give you years of trouble free service.

Abbreviations Found In This Instruction Manual:

• ANSI - American National Standards Institute

• ASME - American Society of Mechanical Engineers

• GAMA - Gas Appliance Manufacturer’s Association

• NEC - National Electrical Code

• NFPA - National Fire Protection Association

• UL - Underwriters Laboratory

PREPARING FOR THE INSTALLATION

1. Read the “General Safety” section of this manual rst and
then the entire manual carefully. If you don’t follow the safety

rules, the boiler may not operate safely. It could cause DEATH,
SERIOUS BODILY INJURY AND/OR PROPERTY DAMAGE.

This manual contains instructions for the installation, operation,

and maintenance of the electric boiler. It also contains warnings
throughout the manual that you must read and be aware of.
All warnings and all instructions are essential to the proper
operation of the boiler and your safety. READ THE ENTIRE
MANUAL BEFORE ATTEMPTING TO INSTALL OR OPERATE
THE BOILER.

Detailed installation diagrams are in this manual. These

diagrams will serve to provide the installer with a reference
for the materials and method of piping suggested. IT
IS NECESSARY THAT ALL WATER PIPING AND THE
ELECTRICAL WIRING BE INSTALLED AND CONNECTED
AS SHOWN IN THE DIAGRAMS.

Particular attention should be given to the installation of

thermometers at the locations indicated in the diagrams as
these are necessary for checking the operation of the heater.

fuses always use the correct size for the circuit. See page 12
through 14.

The principal components of the heater are identied on page 8.

The model and rating plate on page 9 interprets certain markings
into useful information. Both of these references should be used
to identify the heater, its components and optional equipment.

2. The installation must conform with these instructions and the
local code authority having jurisdiction and the requirements
of the power company. In the absence of code requirements,

follow NFPA-70 (current edition). The National Electrical Code

may be ordered from: National Fire Protection Association, 1
Batterymarch Park, Quincy, MA 02269.

3. If after reading this manual you have any questions or do not
understand any portion of the instructions, call the toll free
number on the back cover for further assistance.

A sample rating plate and barcode tag are shown on page 9 of

this manual. In order to expedite your request, please have the
serial number and item ID from the barcode tag available for the
technician.

4. Carefully plan your intended placement of the boiler. Examine
the location to ensure the boiler complies with the “Locating the

New Boiler” section in this manual.

Installation and service of this boiler requires ability equivalent

to that of a licensed tradesman or qualied agency (page 2) in
the eld involved. Plumbing and electrical work are required.

5. For installation in California this boiler must be braced or
anchored to avoid falling or moving during an earthquake. See
instructions for correct installation procedures. Instructions may

be obtained from California Ofce of the State Architect, 1102 Q

Street, Suite 5100, Sacramento, CA 95811.

Be sure to turn off power when working on or near the electrical

system of the heater. Never touch electrical components
with wet hands or when standing in water. When replacing

6. Massachusetts Code requires this boiler to be installed in
accordance with Massachusetts 248-CMR 2.00: State Plumbing
Code and 248-CMR 5.00.

4

DIMENSION DATA

SIZES AND DATA NW37 THRU NW150

Model Number

Prex Gal. Cap. Std. KW Input

NW
NW
NW
NW
NW
NW
NW
NW

NW
NW
NW
NW

NW
NW
NW
NW
NW

NW
NW
NW
NW

* All ttings under 4” will be threaded type. All ttings 4” and larger will be anged. 3” ttings extend 4” beyond jacket.

** Where overall height is a problem a larger diameter vessel with a reduced height may be furnished.

Lifting lugs and channel skid base on 96 gallon and larger units.

37
37
37
37
37
37
37
37

60
60
60
60

96
96
96
96
96

150
150
150
150

45K
60K
75K

90K
105K
120K
150K
180K

210K
240K
270K
300K

330K
390K
420K
450K
480K

540K
600K
660K
720K

D E F G** H J K S T

32

30

12

42
32
32
32
32
32
32
32

32
32
32
32

36
36
36
36
36

46
46
46
46

30
30
30
30
30
30
30

30
30
30
30

38
38
38
38
38

44
44
44
44

12
12
12
12
12
12
12

12
12
12
12

16
16
16
16
16

19
19
19
19

42

42

42

42

42

42

42

57

57

57

57

69 1/2
69 1/2
69 1/2
69 1/2
69 1/2

69 1/2
69 1/2
69 1/2
69 1/2

12 1/2
12 1/2
12 1/2
12 1/2
12 1/2
12 1/2
12 1/2
12 1/2

12 1/2
12 1/2
12 1/2
12 1/2

17
17
17
17
17

20
20
20
20

-

-

-

-

-

-

-

-

-

-

-

-

1 1/2
1 1/2
1 1/2
1 1/2
1 1/2

2
2
2
2

17
17
17
17
17

20
20
20
20

-

20

-

20

-

20

-

20

-

20

-

20

-

20

-

20

-

20

-

20

-

20

-

20

22
22
22
22
22

27
27
27
27

Inlet* &

Outlet*

4
4
4
4
4
4
4
4

4
4
4
4

5
5
5
5
5

5 1/2
5 1/2
5 1/2
5 1/2

Boiler

Drain

3
3
2
3
3
3
3
3

3
3
3
3

4
4
4
4
4

5
5
5
5

1
1
1
1
1
1
1
1

1
1
1
1

1 1/4
1 1/4
1 1/4
1 1/4
1 1/4

1 1/2
1 1/2
1 1/2
1 1/2

5

SIZES AND DATA NW220 THRU 670

Model Number

Prex Gal. Cap.

NW
NW
NW
NW
NW
NW
NW

NW
NW
NW
NW
NW
NW

NW
NW
NW
NW

NW
NW
NW
NW

NW
NW
NW
NW
NW
NW

NOTE: For boilers 3400KW to 6000KW, consult factory.
* All ttings under 4” will be threaded type. All ttings 4” and larger will be anged.

** Where overall height is a problem a larger diameter vessel with a reduced height may be furnished.

220
220
220
220
220
220
220

334
334
334
334
334
334

400
400
400
400

500
500
500
500

670
670
670
670
670
670

Std. KW

Input

780K
840K
900K

960K
1020K
1080K
1140K

1200K
1260K
1380K
1500K
1620K
1740K

1800K
1860K
1980K
2100K

2200K
2340K
2460K
2580K

2700K
2820K
2940K
3060K
3180K
3300K

D E F G** H J K S T

60

50

25
60
60
60
60
60
60

60
60
60
60
60
60

66
66
66
66

72
72
72
72

78
78
78
78
78
78

50
50
50
50
50
50

50
50
50
50
50
50

56
56
56
56

62
62
62
62

68
68
68
68
68
68

25

25

25

25

25

25

25

25

25

25

25

25

28

28

28

28

31

31

31

31

34

34

34

34

34

34

71
71
71
71
71
71
71

99
99
99
99
99
99

90 1/2
90 1/2
90 1/2
90 1/2

90 1/2
90 1/2
90 1/2
90 1/2

96 1/2
96 1/2
96 1/2
96 1/2
96 1/2
96 1/2

21
21
21
21
21
21
21

25
25
25
25
25
25

25 1/2
25 1/2
25 1/2
25 1/2

26 1/2
26 1/2
26 1/2
26 1/2

30 1/2
30 1/2
30 1/2
30 1/2
30 1/2
30 1/2

2
2
2
2
2
2
2

2
2
2
2
2
2

2 1/2
2 1/2
2 1/2
2 1/2

2 1/2
2 1/2
2 1/2
2 1/2

2 1/2
2 1/2
2 1/2
2 1/2
2 1/2
2 1/2

25 1/2
25 1/2
25 1/2
25 1/2
25 1/2
25 1/2
25 1/2

25 1/2
25 1/2
25 1/2
25 1/2
25 1/2
25 1/2

30
30
30
30

34
34
34
34

38
38
38
38
38
38

30
30
30
30
30
30
30

30
30
30
30
30
30

33
33
33
33

36
36
36
36

39
39
39
39
39
39

5 1/2
5 1/2
5 1/2
5 1/2
5 1/2
5 1/2
5 1/2

7 1/4
7 1/4
7 1/4
7 1/4
7 1/4
7 1/4

7 3/4
7 3/4
7 3/4
7 3/4

7 3/4
7 3/4
7 3/4
7 3/4

7 3/4
7 3/4
7 3/4
7 3/4
7 3/4
7 3/4

Inlet* &

Outlet*

5
5
5
5
5
5
5

6
6
6
6
6
6

8
8
8
8

8
8
8
8

8
8
8
8
8
8

Boiler

Drain

1 1/2
1 1/2
1 1/2
1 1/2
1 1/2
1 1/2
1 1/2

2
2
2
2
2
2

2
2
2
2

2
2
2
2

2
2
2
2
2
2

6