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.

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

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.

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

Most digital thermostats have cycle timers that prevent more than 4 (or
6) cycles per hour.

Stretch

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

"stretch" wrote in message
ups.com...
Most digital thermostats have cycle timers that prevent more than 4 (or
6) cycles per hour.

Stretch

On Thu, 12 May 2005 01:08:45 GMT, jay wrote:
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.

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).