HVAC 20:  Thermostat Wiring Rides Again - who has worse documentation? ACIQ Or Resideo?
Channel: Brian Greul
Date: 15/07/2022

One of the challenges in installing the ACIQ unit is that the installation manual is written in what I call Chenglish.  Chinese English.  It was either written in Chinese and translated, or written by someone who has minimal English skills but Fluent Chinese.  Either way, it's English that is difficult to comprehend and make sense of.  Phrases like "Refer to the wiring method of internal and external machine communication and wired controller as follows:" are among the better parts.  

I'm using a Honeywell T9 (Model number 25 digits long) thermostat which has it's own convoluted manual written by someone who wants to make installing a thermostat seem like baking a cake.  98% fluff, last page has the wiring legend.  Lots of "call an HVAC person" sprinkled throughout.

The ACIQ manual starts with a 4 heating 2 cooling scheme (WTF) and graduates to two undifferentiated 1H/1C diagrams, neither of which have strip heat backup (emergency)  or a label explaining that one is for non-heat pump and the other is for heat pump.  I installed with the non-heat pump and this video is correcting that to heat pump.  In addition, there are two heat pump methods out there, heat with cool operation, and cooling with heat operation.  This system is the latter, which is ideal for a cooling climate.

More background on ACIQ:
The system operates as a hybrid.  Communicating air handler and condenser with 24v thermostat control.  24v thermostats are, overwhelmingly, "stupid" by definition.  They simply call for heat/cool, etc.  It's like someone raising their hand when they are hot/cold and then lowering it when satisfied.  Legacy systems had the thermostat simply close a circuit that activated a contactor (relay)..  Modern systems insert some electronics into the process.  By contrast a communicating system has the air handler and condenser share operational data to determine if one or the other should speed up or slow down.  At it's simplest, if the air handler is seeing 25,000 btu of demand at the coil, it will tell the condenser to throttle down.  

ACIQ uses an EEV (electronic evaporator valve) which is like a TXV but electronically actuated for more granularity.  Most American manufacturers are still making 1 or 2 stage compressors.  Imagine having a car with on/off, or off, 60%  and 100% throttle positions.  By contrast, this system is a DC inverter that is rated for 20% to 125% compressor capacity.