Last November I was assisted by Jay11j with the install of a Vision Pro IAQ Thermostat on my Trane XL80 furnace, Trane 12SEER A/C and Honeywell HE365 Humidifier. Everything was working great and the "Frost Protection" mode of the IAQ kept my humidity perfect (no condensation on windows). This summer I decided to replace my furnace with a more efficient one and chose the Trane XC95 which is the communicating model. The contractor told me he could use the IAQ thermostat on this system, however, to get the full benefit of the modulating furnace, I should replace the IAQ with the Trane TCONT900A Communicating thermostat, which I did. This new thermostat also has a feature the IAQ doesn't have and that is the ability to set the "continuous fan airflow by percentage to take advantage of the variable speed fan in this furnace. [url=http://www.bayareaservice.com/Tcont900.htm]TRANE XL900 Series 7-day Communicating comfort control thermostats[/url] The new thermostat [B]does[/B] control my humidifier, however, I cannot use the "Frost Protection" mode of this new thermostat because there is no way to connect an outdoor temp sensor to the system as there is with the Vision Pro IAQ. The contractor connected my humidifier installing a 110v outlet on the side of the furnace powered from the power box inside the furnace. They ran another apparent 110v line from the furnace power box to a small brown "switch" that has two connectors for the 110v in and then 3 other connectors with two wires running to the two yellow wires on the humidifier. This doesn't appear to be a 24v transformer, don't know if it's a switch or what. The problem is that this new thermostat is a 3 wire hook up D=data, R=24 volt hot and B=24volt common. The contractor informed me there was no way to connect an outdoor temp sensor to the system because this "communicating system" has the outdoor temp sensor installed inside the new models of Communicating A/C outdoor units. Everything is controlled by the Thermostat via the Furnace through the "Data" connection from the compressor to the furnace. There are no direct connections to either the thermostat or the Furnace board for an outdoor temp sensor. This doesn't make a lot of sense that they would design it this way as I am sure there are a lot of people who have a furnace and don't even have A/C. How do they take advantage of the "Frost Protection" feature of the Trane Communicating thermostat if they cannot connect an outside temp sensor without buying a new A/C compressor? Is my contractor wrong on this? Now after that long winded explanation, which I apologize for, my questions are: Is there any way to connect a outdoor temp sensor to this system or do I need to add one of the new Humidistats like the Aprilaire #58 [url=http://www.aprilairehumidifierparts.com/product.php?p=aprilaire_58&product=171318]Buy Aprilaire #58 Humidistat | Aprilaire 58[/url] or possibly the Honeywell IAQ Digital Humidistat since my humidifier is a Honeywell HE365? [url=http://www.aprilairehumidifierparts.com/product.php?p=honeywell_dg115eziaq&product=171859&category=1692]Buy Honeywell TrueIAQ Digital Humidistat, Dehumidistat, Fresh Air Control | Honeywell DG115EZIAQ[/url] The Aprilaire #58 literature makes it appear the wiring would be simple, however, it indicates an A/B switch on the control that must be in a particular position for specific models of Aprilaire humidifiers or damage could occur. since I have a Honeywell Humidifier, this is confusing. Have read in forums that they fried them wiring them incorrectly. In the case of the IAQ humidistat, I cannot determine from the literature if it can be wired directly to the furnace terminal board without going through the furnace thermostat which I cannot do as it is 3 terminal wiring as indicated above. Wiring this one appears even more confusing but it does have more features like indoor/outdoor temps, etc. Once again I apologize for the length of my post and would appreciate any advice or suggestions you might provide. Colorado Winter is coming and I don't want to spend it adjusting the thermostat up and down daily to avoid the condensation. Thanks, Depdad

I have a Florida ground source heat pump GTO36 with auxiliary built in electric heat element, and a Hunter 44428 thermostat for 1 or 2 stage heat pumps with 1 or 2 stages of auxiliary heat. This is a new install. What would be the appropriate wiring? The unit has markings for R,Y,O,W2, E, G, and C. The thermostat has R, Y, W, W2, G, E, O, and C. Here is a quess: Therm Heat pump R-----------red------R Y---------yellow-----Y O---------Orange----O W2-------white ----W2 E-------- ----E G---------Green------G C--------- -----C Thanks Have also blue, black