Laarsen Associates PW Manual Do Utilizador

Page 10

1.

The factory provided pump on PW heaters and
the recommended field provided pump for
model VW heaters are sized to provide proper
circulation through the heater and heater-to-
tank circulation loop (see Figures 11 and 12). If
the heater-to-tank circulating loop does not
contain more than 6 elbows or 30 feet of
pipe, use pipe fittings in the loop no smaller
than the following:

500 through 850

2"

1010 through 1825

2-1/2"

If the heater-to-tank circulating loop contains
more than 6 elbows or 30 feet of pipe, use pipe
or fittings in the loop no smaller than the
following:

500 through 850

2-1/2"

1010 through 1825

3"

To assure free circulation, do not use globe
valves, side outlet tee connections or other
restrictive fittings in heater-to-tank loop.

2.

The Model IW heater is designed for use in a
system without a hot water storage tank. The hot
water supply line to usage point must have a
return leg to the heater (see Figure 13, 14 and
15). A built-in circulating pump and internal heat
exchanger bypass maintains the heater in a
standby condition. It also maintains the
temperature at the controller setting of the water
in the entire building circulating loop whether or
not there is any use of hot water.

A separate circulating pump is required for
circulation of water in the building loop. The
control system provides variable heat inputs to
match periods of higher or lower water
consumption.

3.

The Model IW heater requires a minimum of
circulating hot water in the building circulation
loop. To prevent excessive temperature
fluctuations in the delivered water, the whole
building system, including the return loop, must
have the equivalent volume of pipe shown
below:

500 through 850 ............... 6.3 ................. 1 1/4" x 100 ft.
1010 through 1220 ......... 10.2 ................. 1 1/2" x 100 ft.
1430 through 1670 ......... 17.0 ....................... 2" x 100 ft.
1825 ................................ 27.0 ................. 2 1/2" x 100 ft.

* The gallons shown are the calculated volumes of the pipes.

4.

Model VW, PW and IW heaters are 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 2045 (Submittal Data).

5.

Pump Sizing: A suitable pump must be field-
provided for circulation of water between Model
VW heaters and the storage tank. This pump
must be sized to avoid excessive temperature rise
and to provide correct flow for water hardness
conditions. Specifications in Table 4 include
allowance for 30 feet of piping and normal
fittings between heater and tank.

6.

Install pump in a cool location. When pump is
installed where it is subjected to excessive heat,
the life of the pump will be shortened. Heat will
embrittle motor insulation and dry out bearing
lubricants. If the pump motor is equipped with
thermal protection, excessive heat may trip the
thermal switch and shut down the pump
intermittently. This could result in rapid scaling
of the heater.

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.

7.

The pump should be accessible for lubrication,
inspection and service.

8.

If pump is designed for floor mounting, install
securely on concrete block or pad at least six (6)
inches above floor level. This will prevent
flooding of motor when floor is washed. Be sure
that floor mounted pumps are not suspended
from piping and that piping is plumbed to avoid
strain on the pump casing.