Electrical; General; Branch Circuit - A.O. Smith DSE-120-24 Description, Operation, Installation And Maintenance Manual

ELECTRICAL

GENERAL

The installation must conform to these instructions, the local
code authority having jurisdiction, and the requirements of the
power company. In the absence of code requirements follow
the latest version of NFPA-70, The National Electrical Code
which may be ordered from: American National Standards
Institute, 1430 Broadway, New York, NY 10018.
AN ELECTRICAL GROUND IS REQUIRED TO REDUCE RISK
OF ELECTRIC SHOCK OR POSSIBLE ELECTROCUTION.
water heater should be connected to a separate, grounded,
branch circuit with overcurrent protection and disconnect switch.
The water heater should be grounded in accordance with
national and local codes.
Check the heater model and rating plate information against
the characteristics of the branch circuit electrical supply.
CONNECT THE HEATER TO AN IMPROPER SOURCE OF
ELECTRICITY.
Size
60°C
(140°F)
TYPES
RUW, T
AWG TW, UF
MCM
18 ......
16 ......
14 15
12 20
10 30
8 40
6 55
4 70
3 80
2
1
0
00
000
0000
250
300
350
400
500
Ambient
Temp.°C
31-40 .82
41-50 .58
51-60 ......
61-70 ......
71-80 ......
= The load current rating and the overcurrent protection for these conductors shall not exceed 15 amperes for 14 AWG,
20 amperes for 12 AWG, and 30 amperes for 10 AWG copper; or 15 amperes for 12 AWG and 25 amperes for 10 AWG
aluminum and copper-clad aluminum.
* For dry locations only. See 75°C column for wet locations.
WARNING
DO NOT
TABLE 310-16. Allowable Ampacities of Insulated Conductors
Not More Than Three Conductors in Raceway or Cable or Earth
(Directly Buried), Based on Ambient Temperature of 30°C (86°F)
Temperature Rating of Conductor, See table 310-13
75°C 85°C
(167°F) (185°F) (194°F)
TYPES TYPES TYPES
FEPW V, MI TA, TBS
RH,RHW SA, AVB
RUH, SIS, =FEP,
THW, =FEPB,
THWN, =RHH,
XHHW =THHN,
USE, ZW =XHHW*
COPPER
...... ......
...... 22
15 25
20 30
30 40
45 50
65 70
85 90
100 105
115 120
130 140
150 155
175 185
200 210
230 235
255 270
285 300
310 325
335 360
380 405
For ambient temperatures over 30°C, multiply the amacities shown by the appropriate
correction factor to determine the maximum allowable load current.
.88 .90
.75 .80
.58 .67
.35 .52
...... .30
Voltage applied to the heater 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 HEATER TANK IS FILLED WITH WATER. DOING
SO WILL CAUSE THE HEATING ELEMENT TO BURN OUT.
The branch circuit is connected to the heater wiring through an
opening provided on the heater.
The
The branch circuit wire and fuse size should be established
through reference to the latest version of the National Electrical
Code or other locally approved source in conjunction with the
heater amperage rating.
temperature rated. 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 heater
ampere 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 heater.
90°C 60°C 75°C
(140°F) (167°F)
TYPES TYPES
RUW, T RH, RHW
TW, UF RUH
THW,
THWN
XHHW,
USE
ALUMINUM OR COPPER-CLAD ALUMINUM
21 ...... ......
22 ...... ......
25 ...... ......
30 15 15
40 25 25
50 30 40
70 40 50
90 55 65
105 65 75
120 75 90
140 100
155 120
185 135
210 155
235 180
270 205
300 230
325 250
360 270
405 310
CORRECTION FACTORS
.91 .82 .88
.82 .58 .75
.71 ...... .58
.58 ...... .35
.41 ...... ......
13

BRANCH CIRCUIT

Branch circuit wires should be 75°C
Size
85°C 90°C
(185°F) (194°F)
TYPES TYPES
V, MI TA, TBS,
SA, AVB
SIS, AWG
=RHH,
=THHN, MCM
=XHHW*
...... ...... ......
...... ...... ......
...... ...... ......
25 25 12
30 30 10
40 40 8
55 55 6
70 70 4
80 80 3
95 95 2
110 110 1
125 125 0
145 145 00
165 165 000
185 185 0000
215 215 250
240 240 300
260 260 350
290 290 400
330 330 500
Ambient
Temp.°F
.90 .91 86-104
.80 .82 105-122
.67 .71 123-141
.52 .58 142-158
.30 .41 159-176