Heat pump best schedule?

[Charlie Velasquez]

…… My position is that any amount of setback will save energy as long as we are talking about single speed heat pumps with heat strips turned off or fossil fuel furnaces. There is no penalty for "catching up" in the morning for those units, they don't work any harder just longer. It takes more energy to keep the downstairs warmer through the night than it takes to warm it back up in the morning. . . .

After retiring from the classroom I headed our school district’s newly formed energy conservation program. We studied our various systems and had engineers consult and study our systems. There are several buildings with all electric, geothermal, and mixed air handling systems.

Allan’s comments above pretty much summed up the conclusions. You always saved energy with a setback; pretty much just a matter of physics. However, that did not correlate to a savings in expenses. Because of our utility’s billing method, electricity after about 7:00 am was more expensive. Our elementary students arrived at 8:00 and it generally took about an hour to get our buildings from our 55° setback to our 68° occupied set point. But, that was the most expensive time for energy. It was cheaper to start heating the building about 5:30 to about 71°, maintain that from 7:00 to 8:00, then drop it to 68° when the kids were opening and closing outside doors when they arrived.

As suggested in a previous post, let your building get colder and see how long it takes to heat with various outside conditions. Then you can make calculations on any energy and money savings.

[Allan Dozier]

Thanks for the report Charlie. That is a caveat I left out. We don't have different rate periods where I am but it is an important factor especially for those recharging an electric vehicle.

[Dick Strauss]

During what hours do people occupy the space? This is a big question that maybe I missed.

[Aaron Rosenthal]

Ah, yes Dick. Mornings are full occupied at 06:45, ending at about 07:30, and afternoons vary from 20 minutes before astronomic sunset until 1 1/2 hours after astronomic sunset. Other hours the space is sparsely used.
We had unusually cold weather this winter, so I had the system start at 05:30. Settings for unoccupied are 15 deg. C, for automatic make up heat.
Because we just had the unit installed, I don’t have the electricity cost over any period I can analyze. I can see by to app on my devices that the heat reaches set temps now the outside temperature has moderated.

[Jim Becker]

Aaron, I'll suggest that you keep your overnight setbacks reasonable so that the required rise is less taxing on the system and that should help conserve energy. I don't think I'd use one between the morning activities and those before and after dusk.

[Bill George]

The Only way you Setback folks are really going to know is get a recording wattmeter and then do the math. I have a recording one for my solar panels and 120 volt but trying to find a 240 volt loads. Low cost that is, some are going for $300.

Ok I found on Amazon a 0-50 Amp current transducer that outputs 0-10 vdc for less than $25 USD that will let me use my existing 0-30 vdc Data logger that cost me $110, about as low cost as you can get and simple. The logged data is downloaded via USB to my computer and will let me create charts amps and time.

[Chris Parks]

Having data is the key, without it you are guessing and data logging/collection can be done pretty cheaply these days. Different settings will give different answers and data is the only way to nail that down.

[Bill George]

Yes the Current transducer is 0-50 amp and the out put is 0-10 vdc which is one of the more common interfaces. It can be 0-10 or 0-20 amp depending on what range you would prefer, my logger is 0-30 vdc and it can be scaled also. This is not my first rodeo.