Greenway

 

 Ventilation Control System Finished  Map to the following dashboard in Hubitat Independent control of 6 fans. Two boost fans individual relays and same 25Khz speed demand 

  As ever on a budget waste not want not approach. mostly stuff I had in stock Code ERV Code Six individually fused channels Power board shown in place. 35 Amp Hall effect current sensor. Driver code here  ERV Code Dashboard for ERV fan control and testing      Six controlled channels with 25Khz PWM fan speed control The first layer of the system. Two Arduinos one for control one for networking, Code here  ERV Code

  Simple loft fan rule

  New dual rotor fans slower and quieter, lower power with better static pressure. Testing shows these to be as good in terms of flow as the faster fans but with more static pressure. I suppose they are designed for use in ducting in a car.  ERV Sensors looking good revised location to get them, deeper into the airflows. All looks good, there is a throttle valve on the bypass now with a single servo. After testing the 4 port valve is not good enough it seems, no surprise. I'm looking at a simple bypass mode with a mixed fresh and conditioned inlet stream.

 

Live data feed from Hubitat Cloud   

Smart control: - reduces power costs of air handling units - adjusts ventilation to your everyday needs - provides a wide range of control options It has been estimated that smart control allows to half the average cost of electricity for ventilation.

 We get around a 1C boost to the fresh air from loft heat exchange with the duct. The loft is consistently between 4 and 15 C hotter than the outside air and even at night boosts heat in the fresh air duct to the living room. An unanticipated benifit

  This is a rough break down of materials costs NZ$28 1 X 60 litre Sistema box NZ$30 3 X 7500CPM main fans NZ$20 4 X 6500RPM booster fans NZ$3.50 4 X Fan speed controllers NZ$30 1 X 30 Amp PSU NZ$104 5 X diffusers with 3M of duct and Y junction NZ$21 4 X 150mm 3M ducts NZ$14 2 X 150mm 1M ducts NZ$1.00 12 X 150mm PVC flower pots NZ$15 6 X 6mm Corroplast sheet 900 X 1200 NZ$ 50 Arduinos and breakouts for project NZ$!00 Wire plugs sockets misc electrical NZ$60 New tools NZ$150 Tape screws wood sundry hardware Hot glue sticks NZ$30 2 X Sitema filer boxes NZ$12 2 X Foam exercise mats NZ$30 PC Servos NZ$100 Experiments breakages re-work Total NZ$1,510

  Hubitat allows development of custom drivers in Groovy. Its pretty easy to learn and the Hubitat framework allows connection and management of devices not supported by Hubitat officially like all your home-brew Arduino devices. You can also create custom applications to extend the capabilities of the devices. e.g Calculate dew point app:1153 2020-09-04 22:39:02.775 info Rho = 1.2405 kg/m3 app:1153 2020-09-04 22:39:02.771 info outsidetemp = 11.1 °C app:1153 2020-09-04 22:39:02.767 info Pressure = 100.8 Kpa app:1153 2020-09-04 22:39:02.763 info Absolute Humidity = 125.0 kg/m3 app:1153 2020-09-04 22:39:02.759 info Dew point temperature = 3.5 °C Still haven't finished the absolute Humidity calculation Credit to Bruce Ravenel for the original app code I based this on definition( name: "Calculate dew point", namespace: "hubitat", author: "Bruce Ravenel", description: "Calculate dew point", category: "Convenience"

  I wanted to avoid having the Arduino generate the 25 KHz PWM signal for the fan seed control pilot signal. Here ia a cheap as chip's wee board that I have modified to allow the Arduino to send an analogue voltage as fan speed demand. The modification is simply lifting the leg of the two trimmer pots for fans 2 and 3 and connecting that leg to the Arduino output.

 Looking at the specifications of propitiatory systems it seems that the fans are nothing special. They typically use Axial flow fans with AC voltage motors around 60 Watts seems suitable for our house. In order to allow me to do this without an electrical certificate my system is entirely 12 volt.  The fans I have are pretty quiet to so it seems like win win to me less that US$30 each for the 60 W devices and US$16 for the boost fans. Computer fans are a good low cost option. Quiet long lived and they have built in speed controllers too. I am using two fan types in the system. I bought them cheapef than this Specifications : -- Size: approx. 120*120*38 mm -- Voltage: 12(V) -- Blast Capacity: 280.38CFM -- Current: 5.0A -- Rotate Speed: 7500CPM(r/min) -- Noise Level: 64DBA -- Wind Pressure: 24.60 mmH2O -- Bearing: High precision double ball bearing -- Operating Temperature: -10℃ ~ + 70℃ -- Storage Temperature: -40℃~+70℃ -- Power range: Plus or minus 15% of rated power supply -- Insulati