house thermostat w/ elapsed timer

What with all the various eco topics concerning when and how to run your heating/cooling, I have yet to see a home electronic thermostat with the added feature of - - an elapsed run timer -
ie - how long has the system run since timer reset ?
This would be great to see if setting the temp higher in summer, or a little lower in winter actually changes anything while being able to record the amount of time the furnace or A/C runs...
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On Thu, 24 Jan 2013 17:32:54 -0600, "ps56k"

My relatively plain jane, 5 yr old Hunter does that. I thank I paid $50 for it- it has a couple programmable features and flashes me when the elapsed time reaches a preset. [I use 75 hours] Then I know it is time to change the air filter.

I take it on faith that it saves a little. The math involved in figuring all the heating/cooling degree days, traffic in and out, relative humidity, wind direction, etc would make my head explode.
If the heater/cooler runs less it will save money.
Jim
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Yes, I was thinking that too. Some of them have an elapsed time counter for changing the filter.

And agree that the timer would not tell you much because there are the other factors, like weather, so it would be hard to compare and draw meaningful conclusions. Similar info is already available on the gas or oil bill. Mine also shows the degree days for this year and last with usage. Another problem with the simple timer would be if you had a two stage furnace you would not know which rate it was firing on.
The way I look at it, heat loss is going to be roughly proportional to temperature difference. So, if it's 20 outside and you have it at 70F vs 60F inside, the difference is either 50 or 40. Since 40 is 20% less than 50, you'd be saving maybe 20% on energy. However if you set it back at say midnight for 7 hours, it won't get down to 60F for many hours. So, you're probably going from 70F to more like 65F average, which would be more like a saving of 10%. And then you're saving 10% for just 7 hours, which reduces it to maybe 3% overall savings for the day. The amount may be in question, but there isn't any doubt that it does save some energy.
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I had one I bought about 8 years ago. It was good for me so I could compute oil use at 3/4 gallon per hour. I got gas and the device went bad. Not more than three years old.
Greg
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On 1/24/2013 3:32 PM, ps56k wrote:

I did the experiment. Put a flapper on a microswitch and stuck it on a register. PDA graphs the percentage on-time for each cycle. And keeps a running average.
http://imageshack.us/photo/my-images/69/furnmondisplay.jpg
Most interesting thing I learned is that the house has a very long time constant. I turned the thermostat from 65F back to 60F and went to bed. Was in the low 30's outside. 7 hours later, the furnace still hadn't come back on. When I added up the run-minutes to get the house back up to 65F and compared to what it would have used keeping the place at 65F, the difference was in the noise level.
Another interesting observation is that when I wake up and turn on the computer, there's an observable drop in furnace output. Kinda interesting to watch for the first week. After that, not so much.
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-snip-

Let me be the first to observe that you aren't measuring how long the burner is running- but how long the *fan* is running. They will be similar-- but variable.

While the computers will add a bit to your heat output-- I'll bet the sun helps more. To test my theory- work nights for a week and see what happens.
Jim
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On 1/25/2013 7:19 AM, Jim Elbrecht wrote:

You're at least the SECOND. While I am indeed measuring the fan time, they invented math to calculate a good approximation of the burner time. For the limited temperature range over which relative measurements are relevant, the time to heat the heat exchanger to operating temp is relatively constant. And the fan turnoff delay is a timer. My cumulative (adjusted) readings correspond well with the gas meter readings.
It don't vary enough to affect the conclusions.

You're certainly correct that the sun adds more heat than the computer. And I can see that too. According to my measurements, my computer is currently supplying about 10% of my space heating energy. Don't matter if it's day or night. And you see the same relative effect from the air-conditioner run time in summer.
That simple measurement influenced me to set the computer's sleep timer much shorter so it's running less. Heating with gas is cheaper than heating with computer.
FWIW, I have another PDA program that uses the IR port to "watch" the led on the electric meter and plot electrical consumption. Kinda neat to watch the water heater or the fridge or the furnace fan go on and off and calculate the energy consumption. I can get a fairly accurate measurement of what a hot shower or washing a load of clothes costs me.
If you don't get too nit-picky, you can learn a LOT from relatively simple measurements with little investment.

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My old oil burner took 5-6 minutes before the fan came on. Temps at register were high. The fan turn on was at the lowest possible setting.
Greg
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On Thu, 24 Jan 2013 17:32:54 -0600, "ps56k"

The Nest thermostat does this. The web site will show you time used for every day in the last month and they send an email each month with all of the details. I certainly wouldn't spend the money just for that but it really is a nice thermostat, particularly to monitor a vacant or vacation house.
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On 1/24/2013 8:30 PM, snipped-for-privacy@attt.bizz wrote:

Honeywell was about to release one of their own then there were the lawsuits against or from Nest. Honeywell delayed thier's.
For those of us in Canada Costco Canada was selling an Ecobee that was similar to the Nest although with more bells and whistles. I think it was $399 at Costco but I may be wrong. Nest might be $200 or $250 I think at least in Canuckistan...
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There are two models of the Nest. The first generation can be had for $200 and the second generation is $250. The only difference, AIUI, is the support for different HVAC setups (the second generation is more sophisticated and will support more HVAC options).
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