RTH7400 old Trane help - http://www.hvacmechanic.com/ Forums

Original message

john84

97.100.54.130

"RTH7400 old Trane help" , posted Sun 14 Sep 22:06

I have an old Seco TA 7060 mercury two stage thermostat with a Honeywell RTH7400.
The AC system is old Trane w/ heat pump
AirHandler: TWV036B140A
Compressor: TWD736B100A

The old thermostat wasn't floating correctly, but the house would get very cold. I replaced the Thermostat 2 nights ago and at night it maintained the 78 I set it to, but during the day, and now into the second night the temp is remaining at 81.

The Wiring is set as follows:
Old --> New

O (Orange)-> O/B
X (Blue)-> C
Y (Yellow)->Y
G (Green)-> G
R (Red)-> R (jumped to RC)
E (Black, jumped to W2)-> jumped E to Aux
W2 (White)-> White
W3 (Brown)-> taped

There is also a black taped off, which already had been.
I was told by the Home Inspector the Heating Strips were missing.
Honeywell told me to use these settings:
170->7
190->0
270->9

I tried changing 170 to 2
My Family is sweating, and I need any help given, thank you.

Replies:

john84

97.100.54.130

"Re(1):RTH7400 old Trane help" , posted Sun 14 Sep 22:15

sorry,
W2(white)->Aux

john84

97.100.54.130

"Re(2):RTH7400 old Trane help" , posted Mon 15 Sep 16:43

I had a tech come out and he said the thermostat looked like it was wired ok, the freon was low, 50 and the high was at 320. It has been 2 hours since he left and I am still at 82 degrees. It is 90 degrees outside and I know it takes a while to cool but, has not dropped even a degree.

JayB

75.8.36.59

"Re(3):RTH7400 old Trane help" , posted Tue 16 Sep 18:45

Are you saying the head pressure was 320 when the suction pressure was 50? Your condensor coils are plugged or the fan motor is barely running.

john84

97.100.54.130

"Re(4):RTH7400 old Trane help" , posted Sun 21 Sep 11:25

Yes those were the readings, he cleaned the coils and recharged. I took more than a day seems to be working now. Thank you