John Wood Electric Water Heaters - Manual (Page 5)

Electrical
1. Check to see that the element marking and nameplate
data correspond with the electric service available. The
junction box where electrical connections are made is
located near the top of the heater, near the upper access
door.
2. Install a circuit directly from the main fuse box. This cir-
cuit must be the right size for the length of run and the
load (see Table 1).
3. A ground wire must run from the green ground screw
provided at the electrical connection point in the heater
junction box to the ground connection at the service
panel.
4. Adequate fusing must be provided at the service
entrance as required by local codes and/or electric utility
having jurisdiction. This can be accomplished with either
a circuit breaker or fuse block in the service panel or a
separate disconnect switch, so that electric power can be
shut off easily when working on the heater.
5. Final connections are made at the junction box in the
heater. Access to the junction box is obtained by remov-
ing the cover near the knockouts.
6. The heater you have received is internally wired. A spe-
cific wiring diagram is located inside the upper door or for
certain models on the rating plate. All wiring is colour-
coded and connections must be made as shown in the
wiring diagram.
Wiring
TWO WIRE CIRCUIT FOR NON-SIMULTANEOUS OPER-
ATION. SINGLE HIGH LIMIT.
The basic operation of a two-thermostat system (upper and
lower) on an electric water heater of 240 volts is as follows:
Only one element will come on at any one time. This is
known as a flip/flop system. On a 240 volt water heater,
there will always be 120 volts to both elements. The ther-
mostat will direct the second leg of the 120 volts to the ele-
ment to complete the 240 volts required for energizing the
element.
Initial Start Up: When the tank is full of cold water, the
upper thermostat will take priority and the top portion of the
water will heat up to the setting of the thermostat. Once that
temperature has been reached, the thermostat will then flip
down the 120 volts to the lower thermostat. The thermostat
switch closes and the bottom portion of the tank heats up
until the water reaches the setting on that thermostat. At this
point the tank will be full of hot water.
TWO WIRE CIRCUIT FOR SINGLE (1) ELEMENT HEATERS EQUIPPED WITH
SINGLE (1) HIGH-LIMIT CONTROL. SPACESAVER TM MODELS ONLY.
INCOMING
SUPPLY
ELEMENT
BLACK
BLACK
JUNCTION
BOX
208/240V SUPPLY: RED
120/277V SUPPLY: WHITE
RED BUTTON
RESETS BOTH
CIRCUITS
HIGH-LIMIT CONTROL:
BOTH N/C’s OPEN AT
180°F
THERMOSTAT:
N/C - OPENS WHEN
TEMPERATURE
REACHES SET POINT
WATER HEATER MUST
BE GROUNDED TO THE
ELECTRICAL SUPPLY
SERVICE.
Figure 1 Single Element Wiring
TWO WIRE CIRCUIT FOR DUAL (2) ELEMENT HEATERS EQUIPPED WITH A
SINGLE (1) HIGH-LIMIT CONTROL. NON-SIMULTANEOUS OPERATION.
INCOMING
SUPPLY
LOWER
ELEMENT
UPPER
ELEMENT
BLACK
BLACK
JUNCTION
BOX
208/240V SUPPLY: RED
120/277V SUPPLY: WHITE
HIGH-LIMIT CONTROL:
BOTH N/C’s OPEN AT
180°F. RED BUTTON
RESETS BOTH CIRCUITS
UPPER THERMOSTAT:
N/C - OPENS, N/O CLOSES
WHEN TEMPERATURE
REACHES SET POINT
LOWER THERMOSTAT:
N/C - OPENS WHEN
TEMPERATURE
REACHES SET POINT
WATER HEATER MUST
BE GROUNDED TO THE
ELECTRICAL SUPPLY
SERVICE.
Figure 2 Double Element Wiring
MAX.
WATTS 120 V 208 V 240 V
1500 20 A 10 A 10 A
3000 35 A 20 A 20 A
3500 40 A 20 A 20 A
4500 30 A 25 A
5500 35 A 35 A
MAX. VOLTS
Table 1 Power Requirements
NOTE: Water heater must be well grounded to the elec-
trical supply service.
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