pfodApp™ and pfodDevice™ for Home Climate Control

Greg emailed with this outline of how he is using pfodApp to control the circulation, ventilation and humidity in his house.

Circulation Ventilation Humidity Control (CVHC)

Intent:

Control the air circulation, ventilation and humidity in a more sophisticated manner than the current configuration.

Original Control Scheme:

Circulation

• Furnace fan manual switch.

• Static timer on furnace fan after burner shutdown.

Ventilation

• 5 inch duct from cold air plenum to outside – manual damper.

• Exhaust fan manual switch.

Humidity

• Humidifier – Wall mounted humidistat controller with manual setpoint activated when furnace burner runs.

Modified Control Scheme:

Circulation

• Compare upstairs temperature with basement temperature and activate furnace fan to equalize temperatures.

• Control furnace fan based on hot plenum temperature rather than a simple furnace timer.

Ventilation

• 24 VAC damper controlled based on humidity level.

• Activate exhaust fan to draw in outside air if outside temperature is below inside temperature when cooling is desired.

Humidity

• Humidifier – Activated when furnace fan runs. Humidity setpoint is automatically adjusted based on outside temperature.

• Interlock humidifier if excessive condensation forms on windows.

Instrumentation Requirement:

• Monitor temperature in multiple locations including each level of the house.

• Monitor the humidity.

• Monitor window condensation.

• Control the furnace fan.

• Control the humidifier.

• Installation and control of a fresh air inlet damper.

• Control the plenum exhaust fan.

Interface Specification

• Graphical interface via a tablet or phone accessible via internet.

• Alerting of extreme or abnormal conditions via text messaging.

• Long term history collection of all pertinent parameters.

• A flexible means of plotting measured variables and system states for analysis.

Hardware

• Arduino Uno with 32K of program memory.

• Ethernet shield.

• 7 DS18S20 One-wire temperature sensors.

• 1 Honeywell HIH-4000 humidity sensor.

• 1 HDS10 condensation sensor.

• 1 PowerSwitch Tail II 5 VDC/120 VAC solid state relay.

• 4 channel 5 volt relay board.

• 1 AC Sensor Split Core Current Transformer SCT-013-000 0-100A.

• 1 24 VAC relay.

• 1 small breadboard.

• 7805 linear voltage regulator.

• LM324 general purpose opamp.

• Assorted resistors, capacitors, diodes etc.

Software

• pfodApp android app.

• Python 3.3

• Arduino IDE.

pfod Interface Overview – Sample Screenshots

Main Menu	Sensors – Current Value	Sensors – Rate of Change
Sensors – Minimum	Sensor – Maximum	Actuators
Recirculation Fan	Recirculation Fan - Setpoints	Recirculation Fan – Mode
Humidifier – Setpoints	Time	Charts
Charts – Configure	Charts – Plot
Charts – Configure	Charts - Plot
Charts – Configure	Charts – Plot

Android^TM is a trademark of Google Inc, For use of the Arduino name see http://arduino.cc/en/Main/FAQ

Matthew Ford 1^st January 2015
© Forward Computing and Control Pty. Ltd. NSW Australia
All rights reserved.

The General Purpose Android/Arduino Control App.
pfodDevice™ and pfodApp™ are trade marks of Forward Computing and Control Pty. Ltd.

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