I'm doing the obligatory "build your own thermostat" Arduino project. Can I use one of these to control an HVAC that is connected to a 24VAC relay?
638233
They are rated to handle up to 250VAC at 10A, so your 24VAC should not be an issue.
638234
It depends... as long as the current requirements don't exceed the rating of the relay contacts... you can control anything. Generally speaking if you are interfacing to the low voltage side of the HVAC control, you will 'likely' be in good shape. If you are trying to directly control the fan motor and have a need for a much higher current loads, then you will need to use a different relay, or a down-stream relay with higher current rated contacts.
707285
The manual for the RC840 (without transformer) shows how to do this using an external transformer. http://www.aubetech.com/manuel/2/RC840.pdf transformer below or most local suppliers: http://www.amazon.com/Honeywell-AT150A1007-Transformer-universal-knockout/dp/B00096SJ1W/ref=sr_1_5?ie=UTF8&qid=1410107869&sr=8-5&keywords=24+v+thermostat+transformer However, I did not see the RC840 listed on Amazon. If it is not availiable you should be able to use the RC840T-240 using the same diagram in the RC840 manual, just by disregarding the "R" terminal. product info or RC840T-240 says " Low current consumption means multiple relays can be controlled by a single thermostat " suggesting that most thermostats should be OK, but it looks like the built in transformer is only big enough for one relay. I would not recommend parallelling the transformers to increase capacity, this could could cause a dangerous feedback loop.
1290664
No, this thermostat requires constant power - you will need a 24V "common" wire connected to the thermostat's "C" terminal. You would either need to run additional wires from your furnace to this thermostat, or there is an adapter you may be able to install into your current setup, but I'm not sure if you can make it work with only two wires. Either way you will need to modify your current configuration to include the common wire. See Venstar ACC0410 Add-A-Wire for all 24VAC Thermostats
922371
Doubt it. Thermostats are low voltage. Cost would be high but you can use a step down transformer. In real life - just turn the stupid thing on or off!
973886
It's a relay that has a timer and thermostat connected to it. As long as you respect the load rating of the relay (thermostat), you can switch anything.
251485
As long as your air conditioner is not controlled through the furnace thermostat. Mine are separate and this is exactly what i use mine for, my rv furnace. Good luck!
1206015
You have to supply 12V for Vcc and ground to the relays. The in1-4 can be triggered directly from Arduino outputs as long as your 5V and 12V supplies share a common ground.
1267662
i dont believe the thermostat can read the remote "thermostat" or remote "sensors", unless it has the 12 volt power from the 4th wire to operate that part of the system
1390922
It's a relay, designed to use the low voltage signal from a typical thermostat to switch a 240 volt circuit e.g. a 240v baseboard heater. The unit is designed to provide the 24v power to the thermostat as a step-down from the incoming 240v main, so no need to separately power the "smart" thermostat. I've installed it for exactly that use-case, and it's working fine. Unless you REALLY know what you are doing on the high voltage side, I wouldn't recommend this as a DIY project, but the product itself works fine for it's intended purpose.
121657
You're on your own for the control cable. You need a light gauge 3-conductor cable (thermostat cable will work), the power supply is only one Amp.
383570
P.S. You can power it off the R & C terminals where your thermostat ties into your furnace if your thermostat is 24V.
1855221
I used mine to interface to a zone controller so that would not be available as an option. I did not see any options on the programming of the stat. to control speed any way. My best guess from not seeing that option is that the thermostat would not control the speed but cant say for sure, I am not sure if your air handler has any sensors in it to detect if it needs to change fan speeds without a signal to do so from the thermostat, you could check on what actually controls the speed of the fan your equipment. This thermostat has tons of programming options and is the very best I have ever had or seen, but again I did not see programming options for speed control. I used mine to interface to a zone controller so that would not be available as an option. I did not see any options on the programming of the stat. to control speed any way. My best guess from not seeing that option is that the thermostat would not control the speed but cant say for sure, I am not sure if your air handler has any sensors in it to detect if it needs to change fan speeds without a signal to do so from the thermostat, you could check on what actually controls the speed of the fan your equipment. This thermostat has tons of programming options and is the very best I have ever... » Read More I used mine to interface to a zone controller so that would not be available as an option. I did not see any options on the programming of the stat. to control speed any way. My best guess from not seeing that option is that the thermostat would not control the speed but cant say for sure, I am not sure if your air handler has any sensors in it to detect if it needs to change fan speeds without a signal to do so from the thermostat, you could check on what actually controls the speed of the fan your equipment. This thermostat has tons of programming options and is the very best I have ever had or seen, but again I did not see programming options for speed control. « Show Less
376663
No. The switch is rated for the low voltage (24v) and current associated with a room thermostat. Although this device could be used to control an intermediate device which in turn could turn a light on or off.
1493654
Yes you can. I use this but I also purchased the separate relay. This tells my furnace when the fan kicks on so it calls for the water.
2001859
No, but why spend the money on a "connected" thermostat if you're not going to connect it? Just buy a cheaper programmable one.
1889336
It worked for me. There are instructions about where to put the 2 wires. It's just a relay closure. But, when I asked Honeywell about it I got an answer from someone who apparently was clueless about electronics. But, I used it on a system with ~ 15 volts to the relay and it was fine. That was about 6 or 7 years ago. Now there are "millivolt" thermostats. Some systems have a very low voltage sent to the relay. I don't know if the (thermo)stat you're asking about will be used in in such a system. If so, better check. My system was very old. But, basically, yes, only two wires are needed.
616494
If there are 2 leads, it should work. You will need to install a GIF prior to the thermostat.