Optimal Keen Vent Control

Introduction and acknowledgments.

Home Assistant and Node-RED automation system for Keen vents control. Ecobee thermostat is used.

This repository is inspired by, structured, and built partially upon the work of Daniel M. Zimmerman. However, the changes to some operational concepts are significant enough for this not to be a branch of the original repository.

Why it's different.

While I initially used the HomeAssistantKeenVentsEcobeeAutomation with minor modifications, over time, some critical aspects of the operation were changed to better fit my needs, also significantly improve the functionality of the system. These changes make the system more flexible and work better in more situations:

• houses with less than ideal insulation;
• improperly sized or unbalanced HVAC system;
• great temperature spread across the rooms with Keen Vents installed.

Advantages:

My aim is to document every single aspect of this system. This includes the installation guidance and comments throughout the Node_RED nodes, flows, code, HA automation, and configuration files. This will allow you to modify the system to fit your needs better.

Thresholds are no longer used.

I moved away from using the thresholds as they allow for situations where multiple vents can be closed to the degree that significantly increases air duct pressure. This causes strain on the system, resulting in air leaks to unconditioned space and excessive noise in the system and at the vents' exits. The common belief is that at most 40% of all vents in a forced air system should be closed at any time¹.

Weighted mean average vent position is utilized.

This further lowers the chance of overpressure in the system.¹ The function will always attempt to keep the weighted position of all the vents above 60.

Vent position changes are ranked.

Node-RED flow will ensure that the vents that get more opened are controlled first so that there is no unnecessary pressure increase in the system.

Operation of vents is staggered.

There are no substantial changes to the airflow or sudden changes to pressure, further increasing the system's stability and lowering the noise.

Per room climate control.

With the aid of the Home Assistant automation, instead of using the target offsets in the HA interface, you can now define an absolute temperature. This will change the offsets used by the Node-RED flow and calculate and send to the thermostat a new temperature that would allow for greater comfort overall. So instead of adjusting the input number for the dining room to ‘-2’, you can set it to ‘68ºF’.²

Control for backlash.

The backlash is the issue affecting some larger Keen vents, especially those that are installed on a ceiling when the vent reverts its position from the defined one to a more open position (or a more closed one, depending on the orientation of the installation) once the actuator stops applying force. This is due to poor velocity control for maximum open and maximum closed positions in Keen vents hardware.

Disclaimer.

All opinions are my own and are not material other than to illustrate my experimentation with Keen vents, Ecobee thermostat, and the Home Assistant. These opinions cannot be considered endorsements, disapproval, or condemnations of any product, service, company, or person. There are no expressed guarantees of functionality or fitness for any application.

https://github.com/dkitsov/optimal-keen-vent-control/wiki

Footnotes

1. I am not an HVAC professional, nor do I play one on TV. ↩ ↩²

2. This is not weighted at this time. There is no control for occupancy either at this time. ↩