on/off behavior of Honeywll CT3500/CT3595 thermostat

I recently installed a Honewell programmable thermostat. The manual says "model number CT3500/CT3595". While this device seems to keep the house at the target temperature, I find it odd that it can turns on when the temperatue is already stated as being the target temperature. Note: I have "Smart Response" DISABLED.

A "Hunter" programmable thermostat that I used to own, had a clearly understanable algorithm for turning on/off. The Hunter device would call for cooling if the temperature hit 1 degree above the intended temperature for, say 10 seconds. The Hunter device would then shut off the system if the temperature got 1 degree below the intended temperature for, say, 10 seconds.

I don't understand the algorithm for the Honewell. It seems odd that it would call for cooling if the room temperature is already at the target temperature. I'm just curious if anyone knows why they designed it that way. I'm just hoping that during extreme weather, this Honeywell device isn't going to be causing the system to cycle on/off more than necessary.

J.

Reply to
jay
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I am not familiar with that model thermostat, but it may be turning on with a deviation from set temperature of as little as 1/2 degree. Some of the old mercure thermostats only kept temperature within 2 degrees of set temperature. The digitals are typically much more accurate. The honeywell is apparently high precision. I would not say that about the Hunter thermostats that I have seen.

Stretch

Reply to
stretch

The Honeywell does seem to be designed for precision...but *hopefully* the Honeywell is smart enough to also take amount of time on/off into account so as to not cycle on/off like crazy during extreme weather.

Reply to
jay

Most digital thermostats have cycle timers that prevent more than 4 (or

6) cycles per hour.

Stretch

Reply to
stretch

You can set HW thermostats for a variable number of CPH, depending on the usage. Steam, heat pump, gas, electric, etc.

Reply to
HeatMan

It is because the indicated temperature leans somewhat towards the set temperature if it is within a couple of degrees. Notice that when you change the setting by one degree, it indicates that set point, even though the actual temperature does not change that fast.

However, it has adaptive anticipation that usually controls termperature within less than 1 actual degree. So it does maintain better comfort than cruder thermostats that go one degree from set point before they turn on and a degree the other side of set point before they shut off (2 degree spread plus overshoot).

I was very satisfied with the CT3500 for my steam heat. The only reason I changed that out to CT3600 (7 day vs. 5-1-1) was to monitor boiler run time (current day, previous day, and total), so I can tell how effective setback is. Either was better than a RobertShaw, which was +-1 degree with no anticipator (2 degree spread plus 1-2 degree overshoot).

Reply to
David Efflandt

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