Pump Performance And Installation - Natco VW Installation And Operating Instructions Manual

leak.
The following suggestions may solve the problem:
1. Replace the installed water pressure reducing
valve with a suitable valve having a back flow
port. These valves have a back flow port which
allows water to flow backwards when the
pressure in the system exceeds the pressure in
the mains.
2. Install a check valve around the pressure
reducing valve to permit reverse flow. This will
allow the expanded water to back flow into the
mains.
Water
Supply
3. Install an auxiliary small relief valve set at 25 psi
less than the main relief valve. The valve must
be piped to a drain and may require occasional
cleaning. It will bleed off the expanded water and
protect the main pressure relief valve from
becoming fouled.
4. Install a properly sized expansion tank.
2H.

Pump Performance and Installation

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 Figure 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:
Model
500 through 850
1010 through 1825
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:
Pressure
Reducing
Valve
To Building
Check
Valve
Pipe Size
2"
2-1/2"
Model
500 through 850
1010 through 1825
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 Figure13, 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:
Model IW
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 (110F).
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).
10
Pipe Size
2-1/2"
3"
Minimum
Reservoir Equivalent Pipe
Gallons* Size and Length