Amazing isn’t it? I can’t be satisfied with the existing system, I had to try to control it automatically. That would be OK if not for the problems I cause.
The first project was just to connect the system to its boost control with the NEST thermostat. Boost runs the system at full speed and is usually controlled by a humistat or CO2 sensor. With the NEST connection I can set up a schedule throughout the day to run continuously or for a certain number of minutes per hour.
I reused the old two wire thermostat wire and ran it from the Recouperator to the NEST in the living room. I wired the Boost to the NEST Common and to G to the fan control. Unfortunately it is not yet possible to just turn on the fan by asking Alexa although the temperature can be set.
I explained the control made possible by the Foobot air quality monitor. The Foobot can use IFTTT to have the NEST turn on the fan for a preset number of minutes. I have the NEST set to 30 minutes. Of course if air quality is lower than ideal, the Foobot will send the signal constantly until air quality improves so the 30 minutes is reset without manual intervention.
The system is designed to also be controlled by a 0-10v signal from a home automation system. This would allow use of the variable flow other than through the manual dial that comes with the system.
Unfortunately I did not understand the difference between an analog 0-10v system and an electronic PWM or MLV 0-10v signal type. Pulse width modulation PWM is often used with LED lights. Instead of sending a straight voltage to the lights, the PWM sends a variable voltage that makes incandescent lights flicker but somehow works better with LED. The MLV signal is used with florescent ballasts for large lighting systems especially.
My first experiment was to purchase an inexpensive PWM LED driver. It takes analog voltage input and converts it to PWM. Of course when I purchased it I did not realize it needed analog and output PWM. Actually the opposite of what I needed. That is because I should have known LED usually uses PWM output. Also notice that this controller requires 24v direct current while the Recouperator has 24v alternating current at the auxiliary outputs. That was a distinction I had failed to make. I could use a 24v plug in transformer to control the LED driver but the output doesn’t match what the control on the Recouperator needs.
I needed to find a variable control that outputs 0-10v and can be managed through an internet interface. Lutron makes several variable controls for various types of lighting and fans.
From this list only the Caseta Wireless operates with the Lutron Connected Home system that uses a smartphone to set the signal and dim lights or control a motor. The Caseta comes both in an electronic low voltage version (ELV) and 120 volt AC. Although the ELV is new and I didn’t see it on their documentation.
Several of the Lutron switches can create a 0-10 VDC signal. But they require a TVI which is a 0-10VDC interface also made by Lutron. I purchased I purchased the PRO 120 VAC version of the Caseta Wireless switch and the TVI that was recommended in the charts, the Grafix-TVI, but later found out it puts out magnetic low voltage 0-10v which the system cannot use either.
Unfortunately I can find no way to translate an electronic low voltage (ELV is AC or DC) or magnetic low voltage to analog DC voltage. That doesn’t mean I didn’t try.
The MLV transformer the Grafix-TVI puts out 0-10vdc with no load but when I attached it to the analog 0-10 the signal dropped to 2.34v. The Grafix can’t take the 0-10 load from the ERV. There is also sink and source sides for 0-10v. The Grafix-TVI is a sink device which means the ERV needs to have a source control. I don’t know what the ERV is but I think I can assume it is also a sink control.
I also have a small circuit board that will translate PWM into analog 0-10v but that would require a driver that puts out 0-10v PWM signal.
Sometime during my tests, although I always had the ERV off during connections, one of them was not right enough to blow the internal 120 to 24 VAC transformer. At least I’m not getting the 24v power through the transformer now. So I’m getting a new part and hopefully that will fix the problem.