Takagi T-H3J-DV, Service Handbook

Page: 65 / 80

MAINTENANCE
MAINTENANCE
On-Demand Water Heater Service Handbook for 240, 340 & 540 Condensing Models • 65
13.2.3 Remove the eight screws
that hold the primary and
secondary heat exchangers
together. (There are two
screws on each of the four
sides. Save them for future
use.)
NOTICE: The primary and
secondary heat exchangers are
identified on page 49 or
50.
13.3 IF you are replacing the
primary heat exchanger
assembly, go to “Preparing
the New PRIMARY Heat
Exchanger for Installation.”
IF you are replacing the
secondary heat exchanger
assembly, go to “Preparing
the New SECONDARY Heat
Exchanger for Installation.”
Preparing the
New PRIMARY
Heat Exchanger
for Installation
●
The primary heat exchanger is the
same assembly for both indoor
and outdoor models.
●
240 and 340 models use primary
heat exchanger 100074698.
●
540 models use primary heat
exchanger 100074699.
●
The new primary heat exchanger
comes with:
◦
A combustion chamber
attached to the bottom of
the heat exchanger. (See
“Combustion Chamber,”
page 73.)
◦
A plate attached at the top
with a gasket surrounding
the flue gas connection to the
secondary heat exchanger.
See item 401, page 74.
1. Make sure the gasket on top of
the primary heat exchanger is
not compromised. If it is, contact
technical support.
2. Remove the following items from
the primary heat exchanger and
INSTALL THEM IN THE SAME
LOCATIONS ON THE NEW
PRIMARY HEAT EXCHANGER:
•
High limit switch on the left side
(item 412, page 74).
•
Over-heat Cutoff Fuse (OHCF) and
its six clips. See Figure 64, Figure
65, and item 413 on page 74.
See also “Over-heat Cutoff Fuse” in
Figure 41, page 49.
•
Air tube and its connector/nipple
on the bottom of the combustion
chamber. (See Figure 58, p. 63.)
•
Pipe heater at the front of the
primary heat exchanger. See
Figure 64. See also page 74.
•
O-Rings on the connection tubes:
◦
See item 458, page 74,
at connection point “E.”
This O-ring is attached to
the connection tube that
travels to the secondary heat
exchanger.
◦
See item 458, page 74, at
connection point “C.” This
O-ring is attached where the
outlet water tube connects to
the outlet water connection.
3. Complete the steps in the next section:
“Preparing the New SECONDARY Heat
Exchanger for Installation.”
Preparing the
New SECONDARY
Heat Exchanger
for Installation
1. INDOOR MODELS ONLY:
Remove the following items from
the secondary heat exchanger,
then INSTALL THEM IN THE
SAME LOCATIONS ON THE NEW
SECONDARY HEAT EXCHANGER:
•
Silicon ring (item 154, page 74)
which is located around the
Pipe Heater
OHCF Plug
OHCF goes across front and
wraps around right side.
Figure 64.
Bypass
Valve
OHCF goes across back....
...reverses direction,...
...then terminates
here.
NOTE: The bypass valve shown above is
included with 540 models only.
Figure 65.