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John Greeb 01-09-2009 01:39 PM

Electric Heat Pump & Programmable Thermostat

I have an older electric heat pump (17 years old) to which I've added a programmable thermostat (Honeywell CT3611). I live in an area with a moderate winter (Baltimore/DC area). Supposedly, the thermostat has "Smart Response" technology. For example, let's say you program the thermostat for 62 degrees overnight and 68 at 8AM. The theory is that the thermostat "learns" to how to automatically adjust the setpoint temperature so that it will reach 68 degrees at 8AM without using the auxillary heat. In this example, it might learn to change the setpoint to 64 at 7AM and then 66 at 7:30 so that it can get to 68 at 8AM without using the auxillary heat.

That's the theory. Here's how mine is programmed- 60 degrees at 9PM, 63 at 6AM then 66 at 8AM. Unfortunately, most of the time when I look at the thermostat at around 8AM, I see the AUX heat light on and I'm worried that the electricity I'm saving overnight is getting burned up in the morning.

Does anyone have any experience with these or similar programmable thermostats? Is the "Smart Technology" a crock & I should just leave the temperature constant? Is the temperature change I have programmed too large? Is the intermediate temperature step at 6AM throwing things off and I should just have the temperature at 6AM be the same as the final temperature (66 degrees)?

On a related issue- To avoid "wasting" money when the auxillary heat comes on, a neighbor disconnected the auxillary heat wire in the thermostat. I've been tempted to do the same thing but I assume this is not a good thing to do because on those really old days, your heatpump can't get to the required temperature without the aux heat & just runs & runs. What is the impact of disconnecting your auxillary heat?

While I'm asking there any reason to replace an older heat pump with a newer and supposedly more efficient heatpump? My 17 year old heat pump is working fine and it passes its yearly checkup with flying colors. However, I assume heat pump efficiency has improved over the past 15 years and I imagine it is just a matter of time before mine will need to be replaced (mine is one of the last "original" heat pumps in our development). Does the improved efficiency & monthly cost savings of a new heat pump justify replacing a functioning albeit less efficient unit?

If you've made though all this- thanks. Any comments/suggestions would be appreciated.


woodchuck 01-09-2009 04:51 PM

If the temp. is the same every day mine will "learn" and the aux heat doesn't come on. On a warmer morning it will reach the desired temp before the set time. On a colder day it will use aux heat in order to reach the temp at the set time. With changing temp it has to learn over and over. My aux heat comes on when the selected temp is over 2 degrees above the actual temp so I would have to program it in 2 degree increments instead of the 3 that you are doing.
Mine is a Hunter and I've had it for maybe 10 years. I've been very pleased with it.

glennjanie 01-09-2009 09:01 PM

Welcome John:
It would be wise to stay with the existing heat pump as long as it is economicaly feasable. The normal life is 12 to 20 years and you are in the middle of that range; maybe a good time to start a replacement savings plan.
Heat pumps are calculated to closer tolerance than gas or oil furnaces were at that time. You are correct in saying the Aux. heat eats up your savings. You are already running at a very efficient temperature and should not try to drop more than 2 degrees for the night and, if there is no one at home through the day, it should be set back again until the house is occupied again.

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