Heat Pumps After Thermostat Replacement

Discussion in 'HVAC Heating & Cooling' started by dickcarr, Mar 4, 2009.

  1. dickcarr

    dickcarr New Member

    Mar 4, 2009
    Grand Rapids, Michigan
    We are visiting my single sister in Charleston, SC from Grand Rapids, MI. She just bought a new home (with a heat pump) and needed some help in getting things done around the house. Being a handyman type, I packed my tools and headed south. Unfortunately I seem to have brought Michigan weather with me. They've had a slew of freezing or below freezing temps since I've been here, which complicates the matter I write qbout:
    The first project was to replace the old thermostat with a new programmable one since she goes to business each day. The old thermostat was a Honeywell T874R1483 and the new is a Honeywell RTH7500D. I'm a retired telephone dude and am familiar with wiring, but to make sure, I went to the air handler circuit board and copied down the colors and terminals. Here's how my wiring went:
    Air Handler Terminal Wire Color New Thermostat Terminal
    C Brown C
    O Orange O/B
    Y Yellow Y
    W2 White AUX. strapped to E
    G Green G
    Red is connected R
    to another red at
    air handler
    Now here's the problem: With the day temp set for 68 and night to 58, the day comfort is fine, but during the night (and lower outside temps) we have cold air coming out of the vents. We had a HVAC tech come out and he said he found a loose wire on the strip heaters (I guess there's two of them?) He said he tested the heaters and they were okay. He also recharged the outside unit. Could you please verify my wiring and also tell me how I can test to see if the heat strips are functioning? I brought a multimeter with me and know how to use it.
    I'd appreciate whatever help you can be. I've had a guilt trip since there wasn't a problem with the old thermostat, but then again, they hadn't had these lower temps before I came.
    -Dick :confused:
  2. veesubotee

    veesubotee New Member

    Nov 3, 2008
    Turn your thermostat up 5 degrees or so. It should kick in auxiliary heat.

    Perhaps, at night when it gets cold, the balance point may be set too low, or the HP is not super-efficient and is not able to supply enough heat before aux kicks in.

    Does your thermostat have a setting for balance point, or is it set elsewhere. A HP should not require recharging or 'topping off'. If it is low, there is a leak which should be repaired, or if not possible, the unit replaced.

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  4. jimbo

    jimbo Plumber

    Aug 31, 2004
    San Diego, CA
    You have to set up the program on that new thermostat to tell it whether to activate the reversing valve ( O/B wire) for heat or cool. It probably defaulted to opposite of what you need.
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