Installation & Operation Manual
58
8
Domestic water heaters
Pump operation
1. The water heater must have a properly sized circulating
pump. This pump is sized to circulate water between
the heater and the storage tank only.
2. The pump is sized to the heater input and water
chemistry specifications noted in the Water Chemistry
section
on page 53.
3. The diameter and length of the piping installed between
the storage tank(s) and water heater must be properly
sized based on the capacity of the circulating pump.
4. The pump must run continuously when the water
heater is energized. This is the standard operating
system for a water heater.
A pump delay control function with an all bronze pump is
installed as standard equipment on all water heater systems.
The pump will operate only while there is a “Call for Heat”
and for a timed period after the water temperature setpoint
is satisfied to remove any residual heat from the combustion
chamber.
5. Lubricate pump to manufacturer’s recommendations.
Pump
damage
due
to
inadequate
lubrication
is
non-warrantable.
The tank sensor must be installed in the tapping provided in
the lower 25% of the storage tank to achieve proper operation.
As shipped from the factory, the tank sensor is in the literature
package shipped with the unit. Placing the sensor in the tapping
provided on the storage tank will improve temperature response
and prevent short cycles of operation.
TABLE 8D
MINIMUM PUMP PERFORMANCE
Based on heating potable water with a hardness of 5 to 25
grains per gallon and total dissolved solids not exceeding
350 ppm. See
Water Chemistry
section on page 53.
Model
GPM
Ft. Hd.
400 - 750
55
10
1000 - 2100
90
15
When installing multiple water heaters and/or multiple storage
tanks, the diameter of the inter-connecting pipe and all fittings
must be increased. An increase in pipe diameter will decrease
head loss in the system piping and ensure proper flow. Proper
pipe size between the heater and storage tank
MUST
be
maintained to ensure that the standard pump supplied on the
water heater will maintain desired flow.
TABLE 8C
COMMON WATER MANIFOLD SIZE FOR
MULTIPLE WATER HEATER INSTALLATIONS
Pipe sizing chart provides minimum pipe size for common
manifold piping to ensure adequate flow.
Number of Water Heaters
Common Manifold Size (Min.)
Models
400 - 750
1000 - 2100
1
2"
2 1/2"
2
3"
4"
3
3 1/2"
5"
4
4"
6"
5
5"
6"
6
5"
6"
7
6"
7"
8
6"
7"
The standard circulating pump on this water heater is sized
based on installation of a single storage tank and heater in close
proximity. If the number of fittings and straight pipe exceeds
the specified maximum equivalent number of straight feet
for a specified diameter of pipe, non-warrantable operational
problems may be experienced.
400 - 750 Models
1/4 HP, 120 VAC, 5.8 Amps
1000 - 2100 Models
1/2 HP, 120 VAC, 7.4 Amps
The standard pump selection is based on the following pipe and
fittings from the water heater to the storage tank:
6 - 90° elbows
2 - ball valves
2 - unions
1 - cold water tee
Not more than 45 feet of straight pipe.
For every elbow and tee in excess of those shown above,
DEDUCT 6.5 FEET from the maximum allowable straight pipe
in the heater to tank circulating loop.
NOTICE
The factory supplied pump allowas enough
feet of head to accommodate pressure drop
of the unit and up to approximately 45
equivalent feet of piping with some limited
reserve. If additional lengths of piping are
required, it may be necessary to upgrade the
factory pump. Please refer to the pressure
drop curves in
Section 4
of this manual for
the respective model’s heat exchanger to
determine pump requirements.
NOTICE
The factory supplied pump will
accommodate pressure drop of the unit plus
up to approximately 45 equivalent feet of
piping with some limited amount of reserve
capacity. If additional lengths of piping are
required beyond 45 equivalent feet, it may
be necessary to either upsize the piping or
upgrade from the factory pump. Consult the
respective pressure drop charts in
Section 4
of
this manual for respective units.
