TR
OUBLE
SHOO
TING
TR
OUBLE
SHOO
TING
24 • On-Demand Water Heater Service Handbook for 240, 340 & 540 Condensing Models
The 540 Indoor (T-H3-DV) model uses the same computer board
as the 540 Outdoor (T-H3-OS) model. There are two banks of DIP
switches (upper and lower bank) on the computer board. The upper
bank has certain special functions as shown on the following table
and generally should not need adjustment.
Verify the functions of each DIP switch carefully before changing
any settings. If you have questions, contact the technical service
department.
Table 6: 540 (T-H3) model
Upper bank of DIP switches (Figure 10)
NOTE: Dark squares represents DIP switches
Lower bank of
DIP switches
Upper bank of
DIP switches
Figure 10 : 540 (T-H3) Model
DIP SWITCH SETTINGS (CONTINUED)
No.
Functions
ON
position
OFF
position
1
Gas type
Propane
Disable
2
Natural gas
Disable
3
4
Installa
tion
se
ttings
5
N/
A (Do not change switch position.)
N/A
N/A
(Def
ault)
6*
Deacti
va
tion
of the exhaust temperature control
(This
swi
tch
is
for a
speciali
z
ed
purpose
only)
Enable
Disable
(Def
ault)
7
N/A (Do not change switch position.)
N/A
N/A
(Def
ault)
8
Deacti
va
tion
of the freeze prot
ection
firing
system
Enable
Disable
(Def
ault)
Out
door
models
No.
3 : OFF
No.
4 : ON
OFF
ON 1 2 3 4 5 6 7 8
V
e
nt
settings
(
Indoo
r m
odel
only)
3" v
e
n
tings
5 to 20
ft
(DEFAUL
T)
21 to 40
ft
41 to 70
ft
4" v
e
n
tings
5 to 50
ft
(DEFAUL
T)
51 to 100
ft
N/A
No.
3 : ON
No.
4: OFF
No.
3 : OFF
No.
4 : OFF
No.
3 : ON
No.
4 : ON
Set DIP switches shown in the table above depending on the vent leng
th.
OFF
ON 1 2 3 4 5 6 7 8
OFF
ON 1 2 3 4 5 6 7 8
OFF
ON 1 2 3 4 5 6 7 8
Set DIP switches shown
in the table below
.
Propane
OFF
ON
1 2 3 4 5 6 7 8
Natural
Gas
OFF
ON
1 2 3 4 5 6 7 8
WARNING:
Do not adjust DIP switch No. 6 without guidance from the technical service department. The
only time DIP switch 6 should be set to ON is when your unit is being hooked up to CAT III/IV metal vent
with a maximum temp. rating of 480° F. The No. 6 DIP switch deactivates the exhaust temperature control
when set to the ON position.
Failure to follow this warning can lead to personal injury, carbon monoxide poisoning, or death.
*
Continued on the next page.
