What with all the various eco topics concerning when and how to run your
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...
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.
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
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.
I did the experiment. Put a flapper on a microswitch and stuck it on a
PDA graphs the percentage on-time for each cycle. And keeps a running
Most interesting thing I learned is that the house has a very long time
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.
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
My cumulative (adjusted) readings correspond well with the gas meter
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
If you don't get too nit-picky, you can learn a LOT from relatively
simple measurements with little investment.
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.
On 1/24/2013 8:30 PM, email@example.com 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...
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).
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.