Author Topic: Nest thermostat power charged (c-wire) through usb?  (Read 11050 times)

Offline hellovn

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Nest thermostat power charged (c-wire) through usb?
« on: March 30, 2014, 07:11:13 pm »
Hi All,

Thermostats in my house has only 2 wires (W & Rh). I have been doing some research about wifi thermostats and have a question.

1. It seems that nest thermostat may work with 2 wire systems. Do you think if it is a good idea if I can run a usb from a wall charger to my nest and have a z-wave power outlet to auto schedule my nest thermostat usb charing from 02:00 AM to 03:00 AM? The reason I do that is because nest will not be working if it is being charged by the usb port.

Running a c wire from my furnace to my thermostat will cost me around 300$ so that is not an option.

Let me know if my hack will work?

Thanks,

Offline watou

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Re: Nest thermostat power charged (c-wire) through usb?
« Reply #1 on: March 31, 2014, 04:04:26 am »
Hi All,

Thermostats in my house has only 2 wires (W & Rh). I have been doing some research about wifi thermostats and have a question.

1. It seems that nest thermostat may work with 2 wire systems....

You are correct that the Nest thermostat does not require the "C" wire.  They have a "compatibility checker" on their site that should help you review whether the Nest will work with your system. https://nest.com/thermostat/installation/#works/?mode=buy

watou

Offline qwen3579

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Re: Nest thermostat power charged (c-wire) through usb?
« Reply #2 on: March 31, 2014, 07:05:25 am »
Are you wanting to run a USB charger for charging the Nest battery? I don't think you'll have to do that. I think the voltage from your Rh wire (12 volts?) charges the Nest battery.

I have a common wire in my system, but Nest support had me disconnect due to an issue I had. My system has been running fine, and charging my 2 Nests fine without it.
« Last Edit: March 31, 2014, 07:08:42 am by qwen3579 »

Offline TheGadgetGuy

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Re: Nest thermostat power charged (c-wire) through usb?
« Reply #3 on: March 31, 2014, 10:42:20 am »
The Nest will NOT accept anything significantly lower than 24v AC through the HVAC wiring to power and charge itself. 

Without major modification, you would not be able to charge the Nest via its USB connector, because the backing plate obstructs the USB connector when installed.  I had considered that myself when installing my Nest units in my motorhome, but decided against the needed modifications.



"Lots of Z wave switches by various companies", 8 Panasonic IP cameras, 4 Schlage locks, 2 Kwikset locks, 3 Z-wave thermometers, 2 5 button Cooper scene controllers, etc.

Offline jimpapa

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Re: Nest thermostat power charged (c-wire) through usb?
« Reply #4 on: March 31, 2014, 01:16:58 pm »
I'm sitting in the Dr. Office.  So I don't have the details.  But how about if you use a separate 24v power supply and give the nest what it wants in place if the USB wiring you where going to do?



Offline jimpapa

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Re: Nest thermostat power charged (c-wire) through usb?
« Reply #6 on: March 31, 2014, 09:02:49 pm »
I think Hellovn said he only has 2 wires on his current T-stats


Offline TC1

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Re: Nest thermostat power charged (c-wire) through usb?
« Reply #7 on: March 31, 2014, 09:51:57 pm »
If you don't want to go down the Nest route for your 2-wire thermostat, you could use the RTOA 101 available from Lowes (sold as an Iris thermostat), I have two of them, one working with a c-wire,  and one working with 2-wires and strictly off the batteries.

-TC

Offline qwen3579

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Re: Nest thermostat power charged (c-wire) through usb?
« Reply #8 on: April 03, 2014, 10:42:14 am »
If you don't want to go down the Nest route for your 2-wire thermostat, you could use the RTOA 101 available from Lowes (sold as an Iris thermostat), I have two of them, one working with a c-wire,  and one working with 2-wires and strictly off the batteries.

-TC

Do these thermostats support controlling both from location (ie - any changes you make on one are pushed to the other)? Or have you been able to write Lua/PLEG to accomplish this?

I love my Nests, but I would like to be able to make changes from one and have it pushed to the other.

Offline watou

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Re: Nest thermostat power charged (c-wire) through usb?
« Reply #9 on: April 03, 2014, 11:43:06 am »
I love my Nests, but I would like to be able to make changes from one and have it pushed to the other.

I think there has to be a way with Lua or PLEG to achieve what you're after, but in case it's too far out of reach, the Ecobee thermostat supports this feature natively (as in, using their web console), and I wrote a plugin for that thermostat as well (http://cocu.la/vera/ecobee/README.md).  Ecobee makes a nice range of web-accessible thermostats.

Offline qwen3579

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Re: Nest thermostat power charged (c-wire) through usb?
« Reply #10 on: April 03, 2014, 12:11:08 pm »
I love my Nests, but I would like to be able to make changes from one and have it pushed to the other.

I think there has to be a way with Lua or PLEG to achieve what you're after, but in case it's too far out of reach, the Ecobee thermostat supports this feature natively (as in, using their web console), and I wrote a plugin for that thermostat as well (http://cocu.la/vera/ecobee/README.md).  Ecobee makes a nice range of web-accessible thermostats.

Thanks for that info - those are pretty slick.

I have the temperature updates working on my Nests with PLEG (see here: http://forum.micasaverde.com/index.php/topic,24127.msg167381.html#msg167381) However, luup restarts when I adjust the mode (heat, cool, auto).

Should probably move the discussion there - I didn't realize that I hijacked hellovn's thread. Sorry!  :-\
« Last Edit: April 03, 2014, 12:14:08 pm by qwen3579 »

Offline watou

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Re: Nest thermostat power charged (c-wire) through usb?
« Reply #11 on: April 03, 2014, 12:18:08 pm »
I have the temperature updates working on my Nests with PLEG ... However, luup restarts when I adjust the mode (heat, cool, auto).

I wouldn't know why this is happening, but if you are doing back-to-back actions or variable changes, this might be overwhelming some aspect of Luup, socket I/O, or something else.  Would there be some way to insert a brief delay (say, 2-6 seconds) between actions that might send multiple commands off your Vera?  This is just a complete SWAG, but it's what I would try.

Offline hellovn

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Re: Nest thermostat power charged (c-wire) through usb?
« Reply #12 on: December 09, 2014, 06:12:01 pm »
I just forgot to reply this thread :). I have bought 2 z-wave 2gig CT 100 and they work great. Although they are not as luxury as Nest :)

Offline RoChess

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Re: Nest thermostat power charged (c-wire) through usb?
« Reply #13 on: December 09, 2014, 06:55:29 pm »
I'm in an old home with only 2-wires as well, but I risked trying to see if Nest would work, and it has been performing spectacular.

My only issue is with the Vera Nest plugin not yet fully supporting UI7, so I have to settle for only having automatic scene control of the Home/Away function. That supprisingly has been working out well though, the moment I get out of bed the Nest is switched to Home mode via a Vera scene, and heats the downstairs up to a comfortable temperature already before I even make it downstairs (Home set to 69F). When I go to bed it goes into Away mode and keeps temp above 50F.

Have it running for little over a month now, and already see savings on my utility bills. Am on weird ever changing schedules, so programming a regular thermostat would never have worked for me, and it would happen quite often where I had forgotten to turn the thermostat down. Having Z-Wave sensors now do that fully automatic is easy to get used to, and at this rate it should have all paid for itself in less then 6 months.

Offline hellovn

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Re: Nest thermostat power charged (c-wire) through usb?
« Reply #14 on: December 10, 2014, 12:00:01 pm »
Thanks Rochess for your information. After reading many weird problems that are reported with 2-wire NEST, i have decided to go with Z-wave battery thermostats :(. I am still a fan of NEST though so I will consider upgrading in the future.