Our 15 year old mixed vendor A/C failed on us. The main failure was multiple leaks in the evaporate coil. Looking at the repair costs, rebates available, tax credits, and age of the system, I felt it was best to replace it with a new system rather than repair the old system in patchwork fashion.
Based on what I have read here many times, it is more important to focus on the install contractor and less on the brand of the equipment. Using the local installers that were available and decent (based on reviews, ratings, recommendations, gut feel, etc.), we were down to the choice of a Trane or Lennox replacement system.
For summary information, we live in mid-central Florida, non-coastal, have cheap natural gas available, and all of the Florida normal items apply (high humidity, summer heat, light winters, etc.) The house is 15 years old, 2250 square feet, has decent duct work (inspected by utility company and several contractors), has decent insulation (R30 in the attic and also inspected), and the heat/cooling load calculations show the load between 52k to 57k BTUs. As probably expected, our needs are driven more by the cooling load than anything else.
Our old system was the following:
- Goodman CLJ60-1 one stage condenser (replaced Carrier 38CKB060 condenser in 2004 due to repair costs exceeding replacement costs)
- Carrier 58UHV100-1-20 variable speed furnace
- Carrier CK3BXA060 evaporator coil
- Carrier TSTATCCPRH01-B thermostat (thermidistat)
The replacement system that was selected is as follows:
- Trane 4TTX6060E1000B (XL16i) condenser
- Trane TUD2D120B9V5VB (XV80) furnace
- Trane 4TXCD063BC3H evaporate coil
- Trane TCONT802AS32DA (802) thermostat
The install contractor did a great job during the install, and the follow-up visit the next day. I have verified that DIP switches are set and equipment is wired for 2 stage cooling, 2 stage heating, and Comfort R is on. It has been several weeks since the unit was installed, and I have a couple of questions:
1) The unit cools the house in 1st stage adequately so far. April has been a great weather month for us, but that also means it has been mild compared to the summer (humidity is lower, outdoor temps lower, etc.) For cooling, the unit cycles on for about 6 to 8 minutes and then back off. This happens 2 to 3 times per hour at the most during the hottest parts of the day (thermostat cycles per hours is set for a maximum number of 3 runs per hour). The old unit seemed to come on for longer periods of time, but since it was older, low on refrigerant, etc. I thought that may have been it. Since it has been mild weather, my thought is that the short run times was due to the mild weather and would get longer as we get into the heat of the summer. Is this OK for the new unit or would it be considered short cycling?
2) The new thermostat seems to maintain the temperature within a .5 to 1 degree of the set point only, and does nothing about the humidity. The old thermostat maintain the temperature as well but also factored in the humidity, and would overcool by a few degrees (think it was 2 or 3 degrees) as needed to maintain humidity levels. Could the new thermostat be the reason behind the 6 to 8 minute run times as compared to the longer run times on the old equipment?