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Trane HVAC

Posted by sclancy (My Page) on
Wed, Jul 25, 12 at 11:29

We have a Trane system installed in our new house by the builder/HVAC contractor. I have gotten conflicting info from the HVAC contractor.

We have 2 independent zones each with gas heat/ac.

Lower zone is an XR95 heater and is mechanically split between 1st flr and basement although the mechanical dampers on the 2 air trunks are not split between basement and 1st floor - each branch has basement and 1st floor registers on it. It is controlled with a basic Honeywell nonprogrammable thermostat.

The upper zone is electronically split into 3 subzones (electronic dampers) and is controlled by a ComfortLinkII thermostat. The upper zone works perfectly and the 3 subzones ensure that the 2d and 3rd floors are temperature balanced.

My questions and confusion are:

1. What programmable thermostat (Trane or otherwise) can I use to get control over the 4 fan speeds on the lower zone? (I love fan speed control of the comfortlink II and the ability to program recirculate for part of every hour)

2. Was/Is Trane offering this year in zip 23059 free comfortlink II thermostats with purchases of qualifying systems? If so, should I have gotten them for both my upper and lower systems?

3. Can my lower zone be better balanced without redoing the ducting given that basement and 1st level registers are shared on both main trunks? The cooling temp differential between the 2 floors is 4-6 degrees.

4. Is it typical to split basement and 1st floor on separate trunks and/or to use electronic dampers like they did for the 2d and 3rd floors?


Follow-Up Postings:

RE: Trane HVAC

I am not a Trane expert, but I will give you my comments:

1. If the ComfortLinkII thermostat is working well for then second floor, then consider it for the first floor. Honeywell has many programmable thermostats which are either a homeowner can install or Pro installed.

2. The major brands run promotions in the Spring and Fall seasons. You will have to log onto the Trane web site to see what is currently offered.

3. It is hard to keep an even temperature between the first floor and basement without true zoning. I have this problem in my house.

4. It is not typical unless people want to use the basement for living space and want good temperature control.

RE: Trane HVAC

I am not sure about questions 1 and 2.
Question 3
I am assuming that all of your exterior walls on your first floor are exposed to the ambient (outside)temperature and sun, or to the garage temperature. I am also assuming that at least some of your basement exterior walls are at least partially below grade and that at least some of these below grade walls far enough beneath the grade that no windows have been installed.
The differences between the heat transfer rates
of your 1st floor walls and your basement walls are so great that for you to maintain a temperature balance between these two floors, you will need to either install 1 system per floor or install at least 1 motorized zone damper per floor. Unfortunately with existing houses, modifying the ductwork in a way that is compatible with a motorized zone damper system is usually not an easy feat to accomplish.
Question 4
Is it typical, no. Is it correctly designed absolutely not. Do some HVAC contractors do this, absolutely. What you have probably noticed, if the thermostat is located on the 1st floor is that during the winter, the basement stays much cooler unless you raise the temperature set-point on the thermostat; which of course causes the temperature on the first floor to be too warm. In the summer, you will notice that the basement temperature remains cooler than the set-point on the thermostat.
In some states/municipalities, like Raleigh NC, it is against the building code to install a system that does not allow you to independently control the temperature on each conditioned floor.

While I assume you'd rather not hear this, the only way that you can correct this problem is to have a room by room manual j load calculation performed so that you can design and install a new duct system, regardless of whether you end up adding a separate unit for each floor or if you plan to use automatic zone dampers.

Here is a link that might be useful: Manual J Load Calculation and Duct Design Information

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