LAARS Mighty Therm LO-NOx PW (Sizes 500-1825) - Install and Operating Manual - Manual (Page 13)

Mighty Therm Lo-NOx Page 13
2. Model PW heater is not suitable for heating
swimming pools or any other application where
temperature of the water flowing through the
heater remains below the dew point (110°F).
In applications requiring the rapid use of
measured volumes of water, the recovery of the
heater between the time intervals of use must
equal the volume used. See the recovery table in
the current Document 2129 (Submittal Data).
3. Pump Sizing: the heater circulating pump is
sized to provide enough flow to prevent damage
to the heat exchanger. Specifications in Table 4
include allowance for 30 feet of piping and 6
elbows between heater and tank.
IMPORTANT: Check oil level in pump before
starting. Oil pump every three (3) months. Fill
bearing assembly to lower level of overflow
vent. Add five (5) or six (6) drops of oil to front
and rear of motor. Use 20W non-detergent oil.
Pumps located in excessively hot or dusty
locations should be oiled once a month. Self
lubricating pumps do not require oiling.
4. The pump should be accessible for lubrication,
inspection and service.
Figure 14. Hot Water Supply System Using Dual Tanks.
NOTES:
1. Heavy line
indicates Heater to Tank Circulating Loop.
2. When a very large volume of water is circulated in the building
loop with the use of a separate pump, tee building loop into cold
water supply and return to storage tank.
Flow Head* Temp. Rise
Water Rate Loss Across
Model Category (GPM) (ft.) Heater, (°F)
Soft 45 5.0 17
500 Normal 68 9.9 11
Hard 90 15.7 8
Soft 45 5.3 24
715 Normal 68 11.0 16
Hard 90 17.8 12
999 Soft 45 3.9 35
and Normal 68 7.5 23
1010 Hard 90 11.7 18
Soft 68 7.8 27
1200 Normal 68 7.8 27
Hard 90 12.2 21
Soft** 68 8.1 32
1430 Normal 68 8.1 32
Hard 90 12.6 24
Soft** 90 13.5 30
1825 Normal** 90 13.5 30
Hard 90 13.5 30
Water Category Grain Hardness per Gal.
Soft 1 through 7.5
Normal 7.6 through 17
Hard
Over 17
* Pressure drop includes loss through 30 feet of pipe and normal fittings when
heater is installed with storage tank. Pipe and fittings are assumed to be 2" on
Models (500-715) and 2 1/2" on Models (1010-1825)
** To prevent erosion, these models must be ordered with cupro-nickel heat
exchanger tubes.
Table 4. Pump Performance Requirements.