Nest Wi Fi Thermostats

Wondered the same thing

Quite a sharp little device.  Note cheap, but has the sex appeal of an iPhone.  Here's another article:



http://gigaom.com/cleantech/introducing-a-thermostat-steve-jobs-would-love-nest/



We have two zones of a/c, and only one (main floor) to control the steam radiator heat.  Might have to email the Nest folks at support@nest.com to get their thoughts.

My personal experience...

I am a homeowner, not a heating professional.

I have a mod-con boiler with outdoor reset. My house has gas-filled thermopane windows, a lot of insulation, new roof, not much air infiltration, but not airtight either. My main heating zone (about 24,000 BTU/hr when it is 0F outside and 70F inside) is radiant heat provided by an on-grade slab with copper tubing in it. My other heating zone (about 6,500 BTU/hr) is heated by oversize fin-tubed baseboard. The boiler has three prioritized thermostat inputs, and will provide different temperatures and reset curves for each one. Highest priority is for indirect hot water heater. Middle priority is for the radiant zone, and lowest priority is for the baseboard zone.



For the radiant zone, I have, for historical reasons (mainly ignorance) a very fancy thermostat with 4 different temperatures for each day of the week, so I could have 28 different temperatures set for the radiant zone. But since it is a slab with enormous thermal mass, it does not make sense to use setback at all. I actually set it back 1F for two hours a day for reasons I need not go into here. This does not really change the temperature much, and surely does not save me any money. A cheap round mercury thermostat with no setack would work perfectly fine in this application.



The baseboard zone has a much simpler setback thermometer. Monday through Friday are one class, and Saturday-Sunday are the other. So I could have 8 different temperatures per week in that zone. I have 4F setback in that zone, because I do not use that zone much, especially during the night. That much setback is something of a problem because the reset curve is adjusted so tight that it would take most of the day to recover from that much setback. In fact, I used to use just 2F setback and it took all morning to recover. I have just enabled a boost feature of my boiler's controller and instructed it to boost the temperature of the water 10F if it has not recovered from setback after 2 hours. And if it has still not recovered after another 2 hours, it will add another 10F boost. I will experiment with this for a while. It has not gotten really cold yet, so I am still experimening.



I have experienced a great reduction in heating expenses since I converted from a 60 year old oil burner with primitive controls, to a gas fired mod-con with outdoor reset, and increased the size of the baseboard zone from 6 feet to 28  feet to permit use of lower temperatures to get condensing all the time (except for domestic hot water). Giving the numbers will not mean much, since the temperatures are not the same every year, nor are oil prices or gas prices. And it is probably not fair to compare a 60 year old boiler with a 2 year old (starting its third heating season) new one.



My impression is that the biggest savings come from the outdoor reset, that allows the boiler to run at 75F when heating the radiant zone until it gets down to 52F, when the temperature slopes up to 120F when it is 6F outside. Design temperature around here is 14F. The outdoor reset controls the boiler output temperature directly and the firing rate as a side-effect. The old boiler ran at about 140F all the time. Furthermore, the old boiler was always on (except in the sumemr) and the new one is cold start that undoubtedly saves money too. There seems to be some consensus that you may not want to run an oil fired boiler cold start, but it seems to me it is OK do cold start a gas boiler. For me, there is no savings in the radiant zone due to a fancy thermostat, and the savings for the baseboard zone is probably pretty small. I have 4F setback in the baseboard zone, but it only dropped 2F overnight there, and it went down to about 44F outside. Now it is 61F outside and not much is happening with the heating.

Arduino.cc

Hi,  I'm sure that whatever functionality you want can be set up using an Arduino with an ethernet shield, assuming you already have a home wifi access point. The cost of arduino-compatible microprocessor hardware is very low now and there are libraries to interface it to all the common kinds of sensors out there. You can control relays, which seems to me to be what thermostats do. The starting point for arduino-related stuff is http://arduino.cc  There may be a bit of a learning curve but the flexibility and savings on the components would make it worth it. For example, there are libraries to interface to both the SHT series 1-wire digital humidity and temp sensors from Sensiron and the DHT11 sensors from (I think) Aosoft.