Upgrading to a smart thermostat.

[acer66]

Hi there,

This is an older 2 story house which originally only had a boiler with radiators for heating which might be not as old as the house itself but it is also pretty old.

The reason for the second thermostat is for the more recent 10+ years maybe ac in the attic.

Friend wants to upgrade to a smart thermostat mainly for the heating.

Reading up about it I came across the c wire which older systems may or not have but is needed for a smart device.

Is that something, life long remodeler here, easy to do or is that more a pro endevour?

The other question is are there devices that could control both systems?

Thank you.

 

[jlv03]

Is the attic system A/C only? Or A/C and heat?

How many wires are on each thermostat?

Yes, you can combine thermostats, but you'll need a thermostat that has a separate Rc and Rh.

 

[acer66]

Yes the attic is ac only.

Big ole nc boiler doing the heating only is in the basement.

I will get back about the wires tomorrow.

Thank you.

 

[Jsf721]

I have these and they are great. They hook up by wifi and are easily controlled.

 

[P0234]

I'm pretty sure the Ecobee stuff will run both setups using one unit. You might have to pull a C wire if neither of the existing units has one, but if its a 10YO AC unit. chances are good it has one, you can use that to power both systems.

 

[David Paul]

An Ecobee can control both systems. Thats what I have. Oil fired boiler for heat, completely separate ac unit.

 

[PoorUB]

Pretty much any currently made heat/cool thermostat can handle two systems. There maybe a few that will not, but I am not aware of any.

As for a common terminal, you need a common from only one of the systems to power the thermostat. Pretty sure it can be either, but I will not bet on that!

 

[BSWS]

The C wire has been a blue wire on my last 2 thermostat projects. Neither thermostat had a blue wire in it, but if you pull the cable out of the wall you'll likely find extra wires that are not used, the blue is there. The next step is to determine where it needs to be connected at the furnace/boiler/AC. It's been easy to determine the common terminal on my furnaces.

 

[RalphInCA]

If you do not have a C wire, you can get an adapter.

Something like this.

 

[Shiftless]

but if you pull the cable out of the wall you'll likely find extra wires that are not used

Don’t bet on it.
When I pulled the cable to upgrade the thermostat in my vintage 1950 house, there were only 2 wires In the jacket. I ended up getting a new furnace and new ductwork to go with a new thermostat and new connecting cable. My new upgraded thermostat works great now.

 

[PoorUB]

The C wire has been a blue wire on my last 2 thermostat projects. Neither thermostat had a blue wire in it, but if you pull the cable out of the wall you'll likely find extra wires that are not used, the blue is there. The next step is to determine where it needs to be connected at the furnace/boiler/AC. It's been easy to determine the common terminal on my furnaces.

Don’t bet on it.
When I pulled the cable to upgrade the thermostat in my vintage 1950 house, there were only 2 wires In the jacket. I ended up getting a new furnace and new ductwork to go with a new thermostat and new connecting cable. My new upgraded thermostat works great now.

I was going to comment on this too. Newer homes likely have a C wire. Older homes with a boiler and attic air there is a good chance there will not be enough wiring to connect a C wire.

As far as running a common, it can be hit or miss. Unfinished basement, single story it should be fairly simple. Finished basement, all bets are off. I have pulled thermostat wire that required cutting holes in finished walls and ceilings and someone came in after to repair the mess I left.

Many companies manufacture thermostats that use a remote sensor, plus you can run the thermostat from the app on your phone, and have multiple users. You can mount the thermostat anywhere, right by the heating equipment and use two of the old thermostat wires to connect to the temps sensor that can be mounted where the thermostat was.

Honeywell sell a Prestige and also a 8000 thermostats that only needs two wires for power and a control board mounted by the heating equipment. They will also run to separate units like a boiler in the basement and attic air.

 

[acer66]

Took a bit longer but the first one is the ac and the second one is the boiler.

Thank you.

 

[P0234]

Took a bit longer but the first one is the ac and the second one is the boiler.

Thank you.

Looks like you have a C wire!

 

[dogdog]

Yes look like you have c wire all you need to do is verify the 24Vac between C and R.. C is there purely to work with R to power the thermostats and it operates the relays to provided R powers to what ever W, Y G or what other nots.

Next thing you need to verify is the transformer have enough power to power the new “smart” thermostat you get.

Also I wouldn’t combine the thermostats into one unless pulling wires is easy.

 

[75gmck25]

I've concluded that my HVAC guy must have been really good when he installed my new gas boiler in the basement in 2012 and my attic A/C in 2013. He set it up for both units to be controlled by one Honeywell programmable thermostat. I just move the switch from heat to cool in the summer and back the other direction in the winter.

 

[dave*99]

Many thermostats will do what you need. I installed 3 Honeywell T-9 recently. They came with a remote temperature sensor. Nice product.

Pay attention to the Rc and R terminals. Your AC system has likely has the C wire. You will use the Rc terminal for the red wire from the AC unit, along with Y, B and G.

Use the R terminal for the red wire from the heater and the white wire goes to W.

The old thermostat could have done this too. By removing the jumper between R and Rc. Newer thermostats sometimes have the jumper or that function is sometimes set programmatically in a menu. Sometimes the terminals are labeled Rc and Rh.

 

[acer66]

Thank you for all the suggestions and the owner choose the ecobee with video door bell etc because of them.

My friend will have the hvac guy over anyway and will let him deal with it.

Thanks again.