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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 7599
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Thank you time and consideration! I've run into an ABCD

Customer Question

Thank you for your time and consideration!
I've run into an ABCD wiring puzzle!  I have a Carrier WeatherMaker infinity 58MVP100-F-1720 system with all Carrier parts including a 2 stage (supposed to be, but don't see this per wiring diagram) furnace, a single stage AC, humidifier, dehumidification capability, and variable speed fan control.  This was hooked up to an old Carrier "stock" WeatherMaker Infinity Thermidistat (controlled everything from auto switch heating and cooling to humidification, dehumidification, fan control, and coordinating with outdoor temperatures).  The entire system was installed in 2004.
The wiring for the Carrier 58MVP WeatherMaker Infinity System to the old Carrier WeatherMaker Infinity Thermidistat are:
W/W1:  White wire (heating)
Y/Y2:  Yellow wire (cooling)
G:  Green wire (indoor fan control)
R:  Red wire (24 vac) "live wire"
S1:  Blue wire (outdoor sensor)
S2:  Brown wire (outdoor sensor)
HUM:  Orange wire (humidifier)
DEHUM:  Pink wire (dehumification)
C (COM):  Black wire (24 vac) Neutral wire
The original old Carrier Infinity Thermidistat broke down.
Now, I bought a Carrier Infinity Touch Control (SYSTXCCITC01-A), thinking that this unit would come "wire ready" to automatically control and regulate the furnace, AC, humidifier, dehumidification, and allow for continuous fan operation (I have UV and MERV 16 filters that I like to keep running to purify the air continuously).
The new Infinity Touch Control is supposed to take care of all of this, and since all of the components are Carrier WeatherMaker Infinity components, I thought that this would be a "no-brainer".
However, the new Carrier Infinity Touch has only 6 wire terminals (ABCD + S1 and S2).
The ABCD interface is:
A:  Green wire (Data A wire)
B:  Yellow wire (Data B wire)
C:  White wire (COM wire)
D:  Red wire (24 vac wire)
S1:  Optional Remote Room Sensor
S2:  Optional Remote Room Sensor
There is also some sort of "Accessory Port" with very thinly spaced prongs which I am not familiar with.
I am not sure how to proceed.  I have read and researched many installation manuals and checked blogs, but could not find the answers that I need.
I was thinking of attaching the "Black wire; COM wire" to the "C Terminal White COM", the "Red wire; 24 vac wire" to the "D Terminal Red 24 vac", but I do not know which wire to attach to the "A Green Data A Terminal" and the "B Yellow Data B Terminal".  Also, I do not know if I should attach the Outdoor Sensor S1 and S2 wires to the "S1" and "S2" user interface terminals.  Sounds like these may be remote indoor sensors.
Also, with just a simple ABCD user interface on the new Carrier Infinity Touch Control, how will it be able to control humidification, dehumidification, and fan control?
It's all still a Carrier Infinity System, but I am going from 9 wires (5 control wires + 2 hot and neutral 24 vac wires + 2 outdoor sensor wires) down to a new Carrier Infinity Touch Control with only 6 terminals (2 control terminals + 2 hot and neutral 24 vac terminals + 2 Optional Remote Room Sensor Terminals)!  Wish Carrier maintained compatibility with their WeatherMaker Infinity Ideal Comfort older units, or at least give instructions on how to do it!  I would like to have back the ability for the User Control to regulate everything, including heating, cooling, humidification, defumidification, and fan control.
Any assistance would be greatly appreciated!
- Adrian
- Adrian
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.


Please attach a well focused, close up photo of the wiring diagram glued inside the service panel,you can use the paper clip icon at the right end of the toolbar at the top of this dialog box,Include a picture of the thermostat wire connections to the printed circuit board in the same area.

If there is no paper clip icon, look for the '+attach files' link at left of your send button.

We can go from there.

Customer: replied 1 year ago.
Hi Phil,I am attaching not only the photos that you have requested of the furnace board, wiring for the old thermidistat, and backplates for the old and new thermidistats, but I also drew a wiring diagram sketch for your review.In addition, there are PDF files for:
1. System component and model numbers
2. The wiring diagram sketch that I drew on the computer
3. Single file containing excerpts of wiring diagrams for the Carrier 58MVP gas furnace, the old Carrier Thermidistat, and the new Carrier Infinity Touch Control
4. Full version of the Furnace Manual
5. Full version of the old thermidistat manual, and
6. Full version of the new Infinity Touch Control.Thank you so much. I truly appreciate your time and help!Sincerely,Adrian Karatnycky***@******.***P.S.: Unfortunately, the File for the Carrier Infinity Touch Control SYSTXCCITC01-A Installation Manual was too large to upload!
Expert:  Phil replied 1 year ago.

Hello again,

Thanks for all that data.

The situation is this... there are two entirely different types of thermostats.... communicating thermostats that talk in two directions to the furnace and can report on furnace conditions back to the screen on the thermostat... those have the ABCD wire connections.

The other type of thermostat is not a communicating type, it sends signals to the furnace only, it does not receive any feed back. It has the R,Y, y2, w, w2, G, C and hum and dhum etc terminals.

These are *not interchangeable... unless your furnace printed circuit board is wired to accept either type of thermostat, if that is the case it will have both of these terminal strips on the printed circuit card.

The diagram you sent does not show the ABCD communicating terminal strip so that type of thermostat will not work on your furnace........... unless.... the printed circuit card inside the furnace has the two different thermostat terminal strips.

If you can send me a photo of the printed circuit card I can take a look for that... the communicating control systems are fairly recent however and the odds are that it will not have that communicating terminal strip.

I know this is a bit complex, let me know if this makes any sense to you on your end, we can go from there... don't forget to send me a photo of the card. We can go from there.

Thanks for letting me work with you. When we are finished, if my answer has been polite, professional,and thorough, please click one of the ratings . If you still need help let me know!. Expert is not paid for assisting you until you rate answer. Feel free to follow up for30 days at no additional cost.

Customer: replied 1 year ago.
Thanks for the reply. I will take a photo of the circuit board and upload it to too you. I will likely need to dismount it (if possible) as it is in a small bay and can't be fully visualized.Thanks!- Adrian
Expert:  Phil replied 1 year ago.

Before you do that, get me a photo of actual wiring diagram thats actually glued to the blower access door... that will show the alternative wiring that the one you sent in color apparently from the manual.

There is some degree of risk in removing the card, it can be damaged or it can be reconnected improperly.

Customer: replied 1 year ago.
Hi Phil,Thank you so much for the explanation! The Carrier circuit board is Model CEPL130456-01. I have attached a revised Wiring Diagram and photos of the board up close.There may be hope! There is an ABCD connector already on the board in the area labeled "PL 7". The Infinity Touch came with a green ABCD adapter plug which fits in nicely into the board's connector. I didn't remove the connections or wires from the board.I guess the question now is how should I rewire the board? And, how to integrate the Humidifier and AC components? Also, can the outside temp sensors be attached to the board? And, will the variable speed heat, single stage cooling, dehumidify, humidify, and fan controls be successful?The manual states that I should still use a N.O. power relay with the humidifier, which is already installed. Should the "Orange-to-Red" wire be spliced into a female prong and connected to the "HUM" male prong on the board? Also, there are 2 wire ports on the board labeled OAT. Could these be the attachments for the outdoor temperature sensor wires labeled S1 (Blue) and S2 (Brown)?Not sure where the other wires are rewired and if wires should be disconnected due to the ABCD interface?Thank you so much for your patience and time!I truly appreciate it!!!Sincerely,Adrian Karatnycky***@******.***
Expert:  Phil replied 1 year ago.

Hello, it will take some heroics to get your new communcating thermostat wired to the existing system, it will be infinitely easier to order a drop in replacement for the existing thermostat... exact same thermostat functions to wire directly to what you have.

There are two reasons, current time required and risks of getting the communicating thermostat to work... many hours at best.... then later when there are problems in one of the circuits it will take team of rocket scientists flown in from MIT to sort out what went wrong and how to fix it.

Call them on the phone, tell them you need a drop in replacement thermostat, with the same terminal strip and wire connections as are in the existing thermostat.

Let me know how that goes,

Thanks for letting me work with you. When we are finished, if my answer has been polite, professional,and thorough, please click one of the ratings . If you still need help let me know!. Expert is not paid for assisting you until you rate answer. Feel free to follow up for 30 days at no additional cost.

Customer: replied 1 year ago.
Hi Phil,Just wanted to run this by you before trying to find a drop-in TSTAT. I have attached the current Original Wiring and a Proposal for ABCD wiring. The Carrier furnace circuit board CEPL130456-01 looks like it can communicate with ABCD connections with the Infinity Touch Control. I found a wiring diagram from the Infinity Touch manual that is for the Infinity TSTAT with ABCD connection to the furnace board along with Non-Communicating connections for the Air Conditioner and the Humidifier. This is in the file named page 72. The ABCD rewiring diagram utilizes existing wires. I would have to manually input during TSTAT setup the specifics for the AC. I am not sure about the Fan Control as this looks like it is already built into the circuit board. There is a "G" fan wire that hooks into the old TSAT along with the 24 VAC live "R" wire. I believe that the Data wires ("A" and "B") on the ABCD connection should be able to control fan control. However, there is a diagram on Page 77 and 78 for "G Input Wiring for Blower Operation" which I included as a separate file.Please let me know what you think about this. I could try this, but would be sure to get a spare 3 amp fuse and hope the circuit board handles this okay without burning out!Thanks!- Adrian***@******.***
Expert:  Phil replied 1 year ago.

Hello Adrian, you demonstrate a good understanding of the circuits involved, I do not see any shorts that you might have created that would damage the card... but assuming that I am correct in that is a long shot, to protect the card put a 2 amp fuse in the 24v circuit at the transformer as well.... if that does not blow instantly but does blow later in the testing as you measure the amperage to be sure there is not a dead short, fit a 3 amp fuse.

Stay in touch.

Thanks for letting me work with you. When we are finished, if my answer has been polite, professional,and thorough, please click one of the ratings . If you still need help let me know!. Expert is not paid for assisting you until you rate answer. Feel free to follow up for30 days at no additional cost.