Water Pressure; Tank Installation - Natco VW Installation And Operating Instructions Manual

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 IV
include allowance for 30 feet of piping and normal
fittings between heater and tank.
Table IV. Pump Performance Requirements
Water
Model Category
Soft
500 Normal
Hard
Soft
600 Normal
Hard
Soft
715 Normal
Hard
Soft
850 Normal
Hard
Soft
1010 Normal
Hard
Soft**
1200 Normal
Hard
Soft**
1430 Normal
Hard
Soft**
1670 Normal
Hard
Soft**
1825 Normal**
Hard
Water Category
Soft
Normal
Hard
* 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 (500-850) and 2 1/2" on Models (1010-1825)
** To prevent erosion, these models must be ordered with cupro-nickel heat
exchanger tubes.
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 2J.
Flow Head* Temp. Rise
Rate Loss Across
(GPM) (ft.) Heater, (F)
45 5.0 17
68 9.9 11
90 15.7 8
45 5.1 20
68 10.0 14
90 15.9 10
45 5.3 24
68 11.0 16
90 17.8 12
45 5.4 30
68 11.1 20
90 18.1 15
45 3.9 35
68 7.5 23
90 11.7 18
68 7.8 27
68 7.8 27
90 12.2 21
68 8.1 32
68 8.1 32
90 12.6 24
68 8.3 37
68 8.3 37
90 13.0 28
90 13.5 30
90 13.5 30
90 13.5 30
Grain Hardness per Gal.
1 through 7.5
7.6 through 17
Over 17
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.
2I.

Water Pressure

It is very important that water pressure in the
system be maintained above 30 psi. If the
system pressure should drop below this, the
vapor pressure of water in the suction side of the
pump can cause hammer and cavitation in the
pump and damage the heater through lack of
water circulation. If for any reason the water
supply is turned off temporarily to service a
piece of equipment, the manual gas valve on
the Model IW should be closed until the water
pressure has been restored and the lines bled of
accumulated air. If the heater fails to fire when it
is turned back on, it may be airlocked. To
eliminate the airlock, open the pressure relief
valve and allow air to bleed out until water flows.
As soon as full circulation is resumed, the
entrained air will be carried out through the hot
water faucets.
2J.

Tank Installation

1. Be sure the floor is waterproof and structurally
capable of supporting the tank when it is filled
with water.
2. The tank should be placed so that manholes,
inspection covers, nameplates and drain valves
are accessible.
3. Be sure the tank is suitable for the water in the
system. Some water is corrosive and requires a
protected tank with a special lining.
14