Heating a Home

[videogames101]

so i have no idea why you'd buy a nest, seems like a 0-value added product


here's an idea i think is way cooler than a bullshit touchscreen: you input your furnace model into this thermostat and using empirical fitting + known boiler efficiency curves it determines the most efficient rate at which to heat/cool your home to a given temperature by given (finite) time

question: obviously instantaneous heating would be the most efficient, if the furnace efficiency curve is flat - however, can someone tell me if this problem is more interesting than waiting till the last possible second then hitting the furnace full blast? are the efficiency curves curved enough to provide a different optimal solution?

i'm an EE and haven't taken thermo so learn to me, any furnace engineers around?

or venture capitalists, i'm assuming google will buy out my company for 3.2 billion USD so this is a big oppurtunity

 

[BarkingGhostar]

NEST only heats homes? Seems like a misfire of a thread title.

 

[videogames101]

NEST only heats homes? Seems like a misfire of a thread title.

i'm sorry if my attempt at framing the question in a comedic manner didn't appeal to you :|

any thoughts on the question at hand though?

 

[Sunrise089]

@OP - Also not an engineer, but I'd expect considering the unavoidable losses from heating/cooling a home too early, this would be a wait to the last minute and then race-to-sleep scenario.

 

[MadScientist]

I'm not an engineer either but Nest's website has a very good explanation of how the Nest will save you money, especially the Heat Pump balance section.https://nest.com/thermostat/saving-energy/

I purchased Honeywell's answer to the Nest it's RTH9580 smart thermostat. It gets better reviews than the Nest, has more features, and it's about $50. cheaper. http://yourhome.honeywell.com/home/Products/Thermostats/7-Day-Programmable/Wi-Fi+Smart+Thermostat.htm

I have a heat pump with a backup electric furnace. This winter I had this thermostat programmed to kick the setpoint temp down from 68F to 63F at 11PM and back up to 68F at 8AM. With a normal thermostat a 2 degree change in the setpoint temp will kick on the auxiliary heat (the electric furnace). This is ~5x more expensive than running the heat pump compressor only. The RTH9580 learns when to turn the heat pump on (compressor only) so the auxiliary heat will not kick in. So instead of the heat pump coming on at 8AM with auxiliary heat, it will come on at ~6:30AM on compressor heat only. Nest calls this feature "Early On". This year's winter has been much colder than last year in TN, but for the same months as last year my electric bill is ~$30.-$40. cheaper per month.

Definitely not a 0-value added product.

 

[herm0016]

i find the Honeywell a much better product as well.

a furnace is generally on or off.
You really can't do what you are proposing. The only thing you may be able to vary is fan speed. heat transfer in the heat exchanger would only be one of many factors such as house volume, vent locations, how insulated are the ducts, etc... that would change the result. time would be a better variable to measure.

The Honeywell will learn how long it takes to heat the house up, so you can set it for a temp, at a time and it will heat it up to that temp, at that time, instead of a traditional scheduler which will turn on the furnace and start heating up the home when it is scheduled. This allows one to be much more precise in the schedule and not have to worry about variations in how long it takes to heat it up. This setup will cause what you are proposing, just in a different manner. It will wait till the last possible time when it knows it can make it to the temp you want at the time you want.

mecheng.