Filter
Top Products
28
Inlet and Outlet Connections
For ease of service, install unions on inlet and outlet of the
appliance. The connection to the appliance marked “Inlet” on the
header should be used for return from the system. The
con nec tion on the header marked “Outlet” is to be connected to
the supply side of the system.
Minimum Pipe Size Requirements
Minimum water pipe connections to this appliance is 3 inch
(76.2 mm) pipe for single unit installations installed not more
than 70 equivalent feet (21.3 m) of pipe from the main system
loop or storage tank. The equivalent number of straight feet of
pipe for each valve and fitting in the connecting piping must be
considered to properly arrive at the total equivalent feet of
straight pipe in the field installed piping to the appliance. See
the pip ing requirements in the heating boiler or water heater
section of this manual. Consult factory if longer piping dis tances
are required for a specific application.
PRIMARY HEAT EXCHANGER
FIG. 38 Primary Heat Exchanger
This appliance uses two finned copper tube heat exchangers to
maximize the heat transfer process. The primary heat exchanger
is mounted in the inner jacket on the front side of the ap pli ance.
The primary heat exchanger is composed of two circular glass
lined cast iron headers with 24 vertical finned copper tubes. A
series of “V” shaped baffles are installed between the individual
tubes to control
the movement of the flue products over the finned copper surface
and increase heat transfer. Water enters the primary heat exchanger
and makes four passes over the area exposed to direct heat from
the burner. An internal cir cu lat ing pump ensures proper water flow
over the heat transfer surfaces during burn er operation. Water
temperatures in the primary heat exchanger are con trolled by the
operation of the au to mat ic bypass assembly. Operation of the
bypass maintains water temperatures above 130°F (54.4°C) in the
primary heat exchanger to prevent flue gas condensation on the
primary heat ex chang er surfaces.
SECONDARY HEAT EXCHANGER
FIG. 39 Secondary Heat Exchanger
A secondary heat exchanger is mounted in an inner jacket chamber
at the rear of the appliance. The secondary heat exchanger is
constructed from two glass lined cast iron headers and multiple hor -
i zon tal finned copper tubes. The secondary heat exchanger is
mounted in the dis charge of the flue products from the primary heat
exchanger. This allows additional heat to be absorbed from the flue
products exhausted from the com bus tion process. The return water
from the system passes through the secondary heat exchanger
before it enters the primary heat exchanger. This allows the coolest
return water temperatures to enter the secondary heat exchanger
before proceeding to the primary heat exchanger. When return
water tem per a tures are below approximately 130° F (54.4°C), the
flue products passing over the secondary heat exchanger may be
cooled below their dewpoint re sult ing in the formation of
condensate. The secondary heat exchanger has a special high