A.O. Smith On Demand 305 Series 100 Design Manual page 27

For this application:
Pump should be controlled by an Aquastat,
Timer or Combination Aquastat and Timer.
Pump to be sized to maintain circulation
loop temperature.
A minimum of 3 GPM flow is recommended
for the circulation system.
The pump should be sized to overcome the
pressure loss through the on demand water
heater, optional storage tank, and supply
and return plumbing in the circulation loop.
Reference the section Pump Sizing for
Circulation.
Pump to be of bronze or stainless construc-
tion.
Key
3/4" Ball Valve
3/4" Union
NOTE: This drawing is not intended to describe a complete system and is not a replacement for a pro-
fessional engineering drawing. It is intended only as a guide and does not imply compliance with local
building code requirements. Confer with local building officials before installation
engineer is to determine the necessary components and configuration of the particular system to be in-
stalled. It is the responsibility of the engineer or contractor to ensure that the installation is in accordance
with all local building codes.
Minimum 3/4 " Hot
Water Supply Line
(Optional)
2-10 Gallon
Storage Tank
(To eliminate cold water
sandwich e ect caused by
fre quent On/O operation)
Building Outlets
Domestic Hot Water - Circulation Systems
2 On-Demand Water Heater
Optional Piping Installation
Check Valve
Pressure Relief Valve
On-Demand
Water Heater
Primary
Pressure Regulator
Circulating Pump
. The Contractor or
27
On-Demand
Equipment List
On-Demand
Water Heaters
Electronic Connection *
* Refer to On-Demand Accessories
and Model Applicability for
electronic connection details.
On-Demand
Water Heater
Sub 1
Gas Supply Line
Aquastat Connection
Boiler Drain Valve
S
Solenoid Valve
Drawing Date:
September 07, 2008
Drawing Number:
QTY
2
Minimum 3/4 " Cold
Water Supply Line
Expansion Tank
Mixing Valve
H-2-RO