2441TH Insteon Thermostat with heated floor

[thedishking]

Hello!

I have a question on the 2441TH Insteon thermostat.

 

I'd like the ability to set it to a temperature, and have a script in the ISY know when it has reached the set point, and turn off.

 

I am using this thermostat to control a heated floor, with a 240V normally open Insteon load controller, and it works great, with one exception.

 

The thermostat and the load controller are in the same scene in the ISY, and the thermostat is the controller of the scene.

 

The problem is the thermostat is very "precise". In other words, the floor sensor (hard wired in place of the factory thermistor in the thermostat) varies a bit, especially at 73 degrees F.

 

So, if the floor is at 62 degrees, and I tell it to heat to 73, it does function as expected.

 

The problem is once the floor reaches 73 degrees, the thermistor seems to vary a bit (wanders from 71 to 73, within seconds) and the thermostat turns the load controller back on, and off, etc. This takes place many times over the course of a minute, turning on and off, and back on, and off.

 

Two questions:

 

1. Can the ISY detect when the thermostat has reached the set point? Since this is a heated ceramic floor, it holds the temperature for a long time, and does not need to turn on and off so often. Once an hour would be acceptable.

 

2. Can the thermostat be told a "range"? In other words, heat to 73, and turn off. Don't call for heat until you reach a -3 degree change (70 degrees) or so.

 

Any advice would be greatly appreciated!

 

Thanks!

 

thedishking

[KMan]

According to the 2441TH manual, there doesn't appear to be way to adjust the "swing" (swing is the range of temperature that it will control to). If you could adjust it, you'd just change that to 3 deg and be all set.

 

Instead, I believe you'll have to use ISY programs to achieve what you want. The following programs should come close:

 

If
       Status  'Thermostat- Main' < 69° (Temperature)

Then
       Set 'Thermostat - Main' Mode Heat

Else
  - No Actions - (To add one, press 'Action')

 

If
       Status  'Thermostat- Main' > 72° (Temperature)

Then
       Set 'Thermostat - Main' Mode Off

Else
  - No Actions - (To add one, press 'Action')

 

If you want the programs to dynamically adjust if someone manually changes the setpoint at the tstat, it becomes more complex. I think Michael has mentioned that version 5.0 will have some enhancements that will help solve these types of problems.

[larryllix]

Another possibility that works well for radiators with large thermal mass and therefore slow response is proportional or PWM control.

 

To do this with crude method you could set up three programmed each with different on times that give a "pulses" to the heating elements.

 

Let's say one has an On time of 14 minutes, one with 8 minutes, and one with 2 minutes. Now you evaluate your floor temp against your desired temp set point and run the desired gradient of heat programmers every 15 minutes. This would give you almost 100, 50, and 15 percent heat settings so your ceramic floor doesn't overshoot and undershoot your temperature setpoint

 

If the Wait timer is ever allowed to use a variable the PWM (pulse width modulation) times could be varied infinitely with just a calculation.

 

Off would be a 4th level of heat.

 

I certainly hope there is some high temperature limit for this to override a stuck on module contact or triac.