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V12Tech, HVAC Technician
Category: HVAC
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Experience:  A.A.S. MET, E.P.A cert, Certificate of Excellence HVAC/R
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Have 2 x Tempstar DC90 furnaces installed Dec 1996. One does

Customer Question

Have 2 x Tempstar DC90 furnaces installed Dec 1996. One does upstairs, one does downstairs. Replaced older honeywell thermostats with new honeywell thermostats. Each furnaces is controlled by its own T-stat. Renovation required new pull of wires (insufficent # XXXXX on old install for new T-stats) which also required Honeywell Wiring Module (THP9045). Problem is this, inducer blower will not shut-off on one of the furnaces - runs continuously while other furnace operates normally. If a simple thermostat is installed in lieu (cobbled in beside the furnace), then inducer blower works OK. Go figure! Any insightd? Bad T-stat? bad wiring Module? bad furnace control board? bad furnace sensor?
Submitted: 4 years ago.
Category: HVAC
Expert:  wwhac1985 replied 4 years ago.

wwhac1985 :

Do you have a volt ohm meter

wwhac1985 :

Is your furnace flashing any fault codes

JACUSTOMER-fl289470- :

Checking

JACUSTOMER-fl289470- :

No multimeter.

JACUSTOMER-fl289470- :

no codes

wwhac1985 :

have you disconnected jsut the W wire on the furnace control board and left all others in place

JACUSTOMER-fl289470- :

Checked with Multi-meter previously and T-stat voltages (including call) were fine

wwhac1985 :

sorry Just

wwhac1985 :

Have you reset the power to the furnace

JACUSTOMER-fl289470- :

dissconnect W? on wiring terminal board or furnace control board?

wwhac1985 :

Yes

JACUSTOMER-fl289470- :

not sure on disconeecting power (just via switch)

wwhac1985 :

yes or breaker

JACUSTOMER-fl289470- :

then power was reset multiple times

wwhac1985 :

Does the furnace start up normal and heat

JACUSTOMER-fl289470- :

Normal start and heat (fresh air blower cycles normally) but inducer motor keeps running

wwhac1985 :

Have you removed the control board to see if there is any burn marks on it

JACUSTOMER-fl289470- :

no burns

wwhac1985 :

If you have all thermostat wires disconnected from furnace and the Inducer motor is still running then it is a faulty control board there is a relay in the board that when it gets a connection from r-w it energizes a relay on the control board that closes a circuit passing 120 volts to the inducer motor.

wwhac1985 :

If there is no wires on the low voltage terminals and you check across r-w there should be 24 volts

JACUSTOMER-fl289470- :

used simple T-stat and looks to run A-OK; use new T-stat and is NG

wwhac1985 :

How do you currently have the new thermostat and contol module wired up

JACUSTOMER-fl289470- :

AS per honeywell instructions

JACUSTOMER-fl289470- :

both furnaces done identically, 1 OK 1 is not

wwhac1985 :

Have you checked the continuity between r-w with a multimeter

wwhac1985 :

coming from thermostat

JACUSTOMER-fl289470- :

T-stat voltages OK

wwhac1985 :

Do you have a furnace only or is there a a/c unit also

JACUSTOMER-fl289470- :

No a/c, just furnace

wwhac1985 :

How many wires did the existing thermostat have

JACUSTOMER-fl289470- :

2

wwhac1985 :

what kind of thermostat do you currently have on the wall

JACUSTOMER-fl289470- :

new wire pull has 4

wwhac1985 :

what are you using the wire module thp9045 for

JACUSTOMER-fl289470- :

T-Stat is a Honeywell OEM for Lutron (wireless) Previous T-Stat was an older Honeywell programmable version

JACUSTOMER-fl289470- :

New T-stat requires 2 pair of wires - module allows shared common.

wwhac1985 :

Is your current thermostat wireless

wwhac1985 :

Do you have the model number of the thermostat

JACUSTOMER-fl289470- :

New T-stat wireless settings control, but all T-stats are hardwired on wall

JACUSTOMER-fl289470- :

T-Stat is LR-HWLV-HVAC

wwhac1985 :

Does the thermostat still have the r-rc jumper still installed

JACUSTOMER-fl289470- :

just checked, no jumper

wwhac1985 :

The thermostat comes with a factory installed jumper check your other thermostat to see if it still has the jumper installed

wwhac1985 :

Install factory jumper between r-rc after turning off power then go into installer setup and check install option 900

JACUSTOMER-fl289470- :

no jumper on other furnace T-stat

wwhac1985 :

it is a brass flat piece of metal between them have you checked option 900 in the installer setup

JACUSTOMER-fl289470- :

sorry, rechecked and found small jumper on both T-stats from R to Rc

wwhac1985 :

ok I was looking at the wiring diagrams and application use for the module it is used for a fan and compressor to be run off 1 wire if you only have 2 wires what terminals do you have them hooked up to

wwhac1985 :

is the thermostat recognizing the module

JACUSTOMER-fl289470- :

goes to R, W, K, and C (with jumpered R-Rc)

wwhac1985 :

so you have 4 wires at the thermostat and they go to the module then only 2 wires that go to the furnace and module

JACUSTOMER-fl289470- :

yes

wwhac1985 :

Have you tried switching the two modules around to see if you still have the same problem as i recall you dont have a multimeter

wwhac1985 :

also when you disconnect the r and w wires to the furnace the furnace should just stay off no inducer motor running

JACUSTOMER-fl289470- :

not yet. Can also swap t-stat heads on the bases. Can we pick this up later please? Time zone here has me up too late

wwhac1985 :

yes that is fine

JACUSTOMER-fl289470- :

thanks

Expert:  V12Tech replied 4 years ago.
Have you checked the continuity between r-w with a multimeter
wwhac1985 : coming from thermostat
JACUSTOMER-fl289470- : T-stat voltages OK
......................................................

used simple T-stat and looks to run A-OK; use new T-stat and is NG
.............................................................
You said induced draft runs, so it is a gas furnace.K is for a compressor!

JACUSTOMER-fl289470- : No a/c, just furnace

You have no compressor or AC!!!!


JACUSTOMER-fl289470- : New T-stat requires 2 pair of wires - module allows shared common.


No you dont need this for heat only with a gas furnace!
The sared common you describe is to run the green fan circuit with the compressor, just as a thermostat will in auto position, the yellow is jumped internally to green in auto!
This will simply run the compressor and fan together rather than using green and yellow!


.................................................................

The THP9045 Wiring Module is designed to be used with applicable thermostats in 1 Heat/1
Cool retrofit applications where only 4 wires are available. The K terminal on the thermostat
can be used to operate both the fan and compressor on a single wire, and the module is
designed to receive the signal from the K terminal, split that signal and reroute it to operate
the compressor, and/or fan for normal operation. See the THP9045 manual for further details
Technical Assistance | 24 hours a day, 7 days a week | www.lutron.com
U.S.A. / Canada: 1.800.523.9466 | Mexico: +1.888.235.2910
Other Countries: +1.610.282.3800
........................................
You do not need that K terminal or the kit!
JACUSTOMER-fl289470- : No a/c, just furnace
..............................................................



Programming by a Lutron Factory Trained Installer
For full functionality, the HVAC Controller must be programmed to a Repeater and PC software
must be used by a Lutron factory-trained installer. For questions on how to become a qualified
installer, please contact your local Lutron representative.
To add the thermostat to a Lutron system:
Use the Lutron PC software to start activation
mode. When a Lutron system is in activation mode,
an unaddressed thermostat will show “Device Is
Unaddressed” at the top of the screen.

...........................................

Heat Only System (Series 20)
Rc [R+Rc joined by jumper]
R Series 20 valve terminal “R” [1]
W Series 20 valve terminal “B”
Y Series 20 valve terminal “W”
C 24 V common [3]
S1/S2 Optional remote sensor

THE "K" terminal is not used in Heat only.
in fact the whole thing is not required!

JACUSTOMER-fl289470- : New T-stat requires 2 pair of wires - module allows shared common.

........................................
Heat Only System With Fan
Rc Power [1]
R [R+Rc joined by jumper]
W Heat relay
G Fan relay
C 24 V common [3]
S1/S2 Optional remote sensor

................................................
Heat Only System
Rc Power [1]
R [R+Rc joined by jumper]
W Heat relay
C 24 V common [3]
S1/S2 Optional remote sensor
.........................................
http://resi.lutron.com/LinkClick.aspx?fileticket=iIRX1F8NMpk%3D&tabid=585&mid=1452

Advanced Functions Getting Started
2. Press and hold
blank center key
until the display
changes.
1. Press SYSTEM.
Press s/t to
select function
Function Setting
Press s/t to
change setting
SUN
SYSTEM
HEAT
M33008
M33009
DONE
0280 0
DONE CANCEL
AM
6:01
HEAT SUN
M32755
3. Change settings as
required
4. Press DONE to exit &
save changes.


perating Manual
P/N 041-339 Rev. A 14 69-2656EFS—01
Advanced Functions
Backlight Settings
Function 0280 Press s/t to change the backlight settings:
Options: 0 Backlight ON for approx. 8 seconds after keypress
1 Backlight always on low intensity, with full brightness after keypress
Temperature format (°F/°C)
Function 0320 Press s/t to set the temperature display format:
Options: 0 Fahrenheit
1 Celsius
Furnace Filter Change Reminder
Function 0500 Press s/t to change the furnace filter change reminder:
Options: 0 Disabled
1 10 R.T. Day
2 30 R.T. Day
3 60 R.T. Day
4 90 R.T. Day
5 120 R.T. Day
6 180 R.T. Day
7 270 R.T. Day
8 365 R.T. Day
9 30 C Days
10 60 C Days
11 90 C Days
12 120 C Days
13 180 C Days
14 365 C Days

Advanced Functions
Humidifier Pad Replacement Reminder
Function 0510 Press s/t to set the humidifier pad replacement reminder:
Options: 0 Disabled
1 90 C Days, 30 R.T. Days
2 180 C Days, 60 R.T. Days
3 365 C Days, 90R.T. Days
UV Lamp Replacement Reminder
Function 0520 Press s/t to set the UV lamp replacement reminder:
Options: 0 Disabled
1 365 Days
2 730 Days (2 years)
Clock format
Function 0640 Press s/t to choose a clock format:
Options: 12 12-hour time (i.e., “3:30 pm”)
24 24-hour time (i.e., “15:30”)
Screen lock
Function 0670 Press s/t to choose a screen lock setting (see page 10):
Options: 0 Screen is unlocked (fully functional)
1 All functions locked except temperature controls and CANCEL key
2 Screen is fully locked



APPLICATION
The THP9045 Wiring Module is designed to be used with
applicable thermostats in 1 Heat/1 Cool retrofit applications
where only 4 wires are available. The K terminal on the
thermostat can be used to operate both the fan and
compressor on a single wire, and the module is designed to
receive the signal from the K terminal, split that signal and reroute it to operate the compressor, and/or fan for normal
operation.
Use with the following thermostats:
— THX9321R
— T2060F3080

ACUSTOMER-fl289470- : No a/c, just furnace

THIS IS NOT EVEN REQUIRED NO AC!
Not yelling, just wanted to not blend in.