u/LingonberryNo2744

It truly has been a journey but finally up and running. This is the cooling season so I am going to wait until fall to evaluate automation. My request of Aqara is that they permit me to schedule heat and cool temperatures that are closer than 5º. I mean what if I want to schedule a cooling temperature of 77º and a heating temperature of 74º? It can’t be done right now.

My only other request of Aqara is that they permit a user to choose between a 1º or 2º trigger as to when turn HVAC on or off. Now if I set the cool temperature to 77º the A/C doesn’t turn on until 78º and off until 76º. Our condo is well insulated such that on a 90º+ day it may take several hours to go between 76º and 78º.

Now for the journey. I physically installed the thermostat and when I restored power, configured. Placed in cool mode and HVAC began cooling. Then the smell and a loud pop from the air handler and the thermostat went dark and the HVAC off. I called HVAC service. Several hours and $450 later the 24v transformer was replaced and the HVAC began working again or so I thought.

I realized that the HVAC compressor was not turning back on unless power was shutoff for an hour. HVAC service was called again. After an hour of diagnosis the tech reported that when the cooling temperature was reached the thermostat would turn off the compressor, as it should, but it also turned off 24v to O/B, which is the heat pumps reverse valve, putting the heat pump immediately in heat mode without a 5 minute delay. This created a Freon pressure situation which tripped a sensor in the heat pump, shutting it down. That was $225.

I ordered another W200 from Amazon. At the tech’s suggestion I replaced W200 wiring base as well but when I went to mount thermostat it wouldn’t. I removed wiring base. The old thermostat would mount to old and new base but new thermostat would not mount to new base.

I surrendered, re-installing old wiring base and mounting new thermostat. After configuring everything is now working at the 24 hour mark.

I returned old thermostat and new base to Amazon.

Aqara online chat support was very verbose with no real solution. Email support was a 12 hour response and unhelpful. Would I recommend Aqara W200? Absolutely, but one needs to have more than screwing in a light bulb skills.

I have two design issues that I recommended Aqara resolve:

1. Temperature setting range Is 5º. I use the scheduling feature and prefer my heat set to 73º and my cool to 78º but the W200 won’t permit that. Heat and cool temperatures need to be at least 5º apart. So if you wanted a constant temperature of 75º, whether it be heat or cool modes, you cannot schedule that.
2. Temperature range of 2º between when W200 turns on HVAC and then turns off when temperature is reached. So if your temperature is set for 75º for cooling it won’t turn on A/C until 76º is reached, then it cools until 74º is reached. I would prefer that the user have a choice of 1º or 2º range. Aqara stated they did 2º for energy efficiency but that could be my choice, right?

W200 installed, integrated with HomeKit, and working great or so I thought. I discovered that my heat pump began cooling but soon stopped.

Our local HVAC guy spent over an hour diagnosing what initially looked like a low Freon situation. Turns out it appears to be the W200. Tech confirmed wiring is correct.

The way it’s supposed to work is that in cool mode when the thermostat determines the need for cooling it will turn on the blower and heat pump with the heat pump’s reverse valve set to cool via O/B. That works. However, when the cooling temperature is reached the thermostat will begin the 5 minute cycle down but also turn on heat mode via the O/B causing the reverse valve to be set to heat immediately without waiting for Freon pressures to equalize. This causes freon pressure switch to engage, turning the compressor off and remain off until the pressure equalizes. There was and is no low Freon situation.

I have ordered a new W200, assuming the one I have is defective. It will arrive tomorrow.

I have circumvented the issue by controlling the thermostat with the circuit breaker. I let the A/C run, over cooling the living space, and then power off W200. This prevents W200 from going into the 5 minute cycle down.

I have my temp set for 77º but A/C won’t turn on until 78º and A/C won’t cut off until 76º. Is there any way to adjust to a 1º range rather than a 2º change?

Thus, if I set the temp to 77º A/C will start at 76.5º and stop at 77.5º.

Configured it all with no issue.

Turned temp down and heat pump turned on. After a minute or so a burning smell came from air handler and then a pop. Now there is nothing. AC tech on the way.

***Update***

Fixed! 24v transformer shorted out.

Original installer wired the transformer for 240v when it should have been 208v. It worked for 10 years with a Honeywell thermostat. Was it coincidence? $450 later it’s all fixed. Tech confirmed my wiring was spot on and the Aqara thermostat still works.

I am ready to replace my Honeywell WiFi thermostat but I need to know your opinions on the product for those of you that have already installed it.

FYI - I have an Apple ecosystem

You may find this interesting enough to watch meeting on YouTube. I know I am going to watch the replay the next day.

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