Saturday, September 1, 2012

Competition: Nest: Airwave: Fail

Spent the summer with Nest installed in my workshop for benchmarking. Whereas I'm not quite impressed with general performance, there's one thing I'm sorely disappointed with: Airwave.

Let's start with the fact that it is advertised as "an exclusive feature of Nest Learning Thermostat". Well, it's not. It existed for ages - don't know about thermostats, but one of my 10+ old HVAC units has it implemented in hardware.

Then come claims that it can "reduce A/C runtime up to 30%". I really doubt it. Except, maybe, the "up to" part - you see, technically, 1% falls under "up to 30%" as well.

Now, "I doubt it" is not a scientific proof, but here's the facts that make me come forward with this claim, and some more.

  • Under some circumstances, Airwave will backfire. Trivial example: volumetric heat capacity of the inner coil is too small for the amount of time Nest lets the air handler run. I do not know how they calculate this amount, but in either case, it fails for my specific configuration, 'cause it starts blowing warm air shortly after condenser is shut off.
  • To add insult to an injury, this makes the A/C to turn on sooner than it would otherwise have, causing short cycling.
  • Apparently, the decision to activate Airwave doesn't really take latent heat into consideration [to proper extent], and I end up with a clammy workshop which makes me put the temperature down two degrees - my normal comfortable working temperature is 28°C, but at the end of this summer, as monsoon came and brought humidity with it, I had to drop it to 26°C.
  • In addition, it appears that the inner coil's temperature rises above the dew point quite fast, and air stream starts blowing the condensate back into the air it just finished working hard on extracting humidity out of.
As a result, let me use Nests' marketspeak, "I may have ended up with electric bill up to 30% higher than last summer", when a dumb thermostat was in exactly the same location.

  • Can you fine-tune Airwave? No.
  • Can you disable Airwave? No Yes. You have to convince it first that you really want it off, Dave. (see update below)

So, either I have to put up with Nest's inefficiency, or I will have to take it off and eat the $250 + shipping as a cost of curiosity, or just sell it to someone fascinated with it. I suspect the latter will be the case, for Nest is surely falling short of its advertised virtues.

Disclaimer: The above is a personal opinion, based on subjective feelings and objective measurements. Your mileage may vary.

UPDATE (2012/10/02): Since about a couple of days ago, it is possible to disable it. However, as of the moment of writing, this is not yet reflected anywhere on Nest support site.

UPDATE (2012/10/03): Automagically, Airwave turned back on without my interference. So if it annoys you as much as it annoys me, you'll have to watch it for a while and make sure that it is really off. A similar issue came up with Auto-Away - it turns back on without being told to. Looks like a telltale sign of not saving a flag state when a device firmware update is happening.