# Wiring an "override" thermostat



## aNYCdb (Dec 5, 2016)

I had another idea I wanted to float by folks. Currently in my house in upstate New York I have two zones of heat each with an old style mechanical thermostat (not line voltage). One of the potential issues I'm facing is we occasionally intend to let friends stay with us and I'm worried that if they turn the heat down in one of the zones and forget about it it may result in pipe freezing issues. I recently picked up two new standard 7 day thermostats and a similar wifi enabled version and I was wondering if I could do the following.

1. Replace the two existing thermostats with the 7 day programmable one.
2. Wire the wifi enabled thermostat to both zones and place it in the basement so that I could set it to turn on both zones if the basement went below 35 or so and if needed remotely raise the temperature of the hole house.

My though is that this would enable guests to play with the thermostats upstairs to their hearts content, but give me the piece of mind of having a backup.


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## Chris (Dec 5, 2016)

I just did this with a house I have out of state just so I could monitor it and also turn the heat up before I got there. I only had one zone though but I have a great peace of mind that I can click on an app to check the temp in the house and outside. I had some problems with wiring because my house was built with 4 wires and no Common (Power) wire to the thermostat because back in 2001 they didn't have these wifi ones. I had to steal my fan wire and convert to common and change it in the furnace. I lost the ability to have the fan only on but it still works like normal with the heat and AC. I am not sure how the two zones works as that is above my abilities.


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## aNYCdb (Dec 5, 2016)

Chris said:


> I just did this with a house I have out of state just so I could monitor it and also turn the heat up before I got there. I only had one zone though but I have a great peace of mind that I can click on an app to check the temp in the house and outside. I had some problems with wiring because my house was built with 4 wires and no Common (Power) wire to the thermostat because back in 2001 they didn't have these wifi ones. I had to steal my fan wire and convert to common and change it in the furnace. I lost the ability to have the fan only on but it still works like normal with the heat and AC. I am not sure how the two zones works as that is above my abilities.



Good to know. I just tore down a bunch of fake paneling on many of the walls, so I think I'm going to rewire anyway.


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## kok328 (Dec 5, 2016)

Chris said:


> I just did this with a house I have out of state just so I could monitor it and also turn the heat up before I got there. I only had one zone though but I have a great peace of mind that I can click on an app to check the temp in the house and outside. I had some problems with wiring because my house was built with 4 wires and no Common (Power) wire to the thermostat because back in 2001 they didn't have these wifi ones. I had to steal my fan wire and convert to common and change it in the furnace. I lost the ability to have the fan only on but it still works like normal with the heat and AC. I am not sure how the two zones works as that is above my abilities.



One member had the same issue of not having that common wire.
I tipped him off that sometimes when all wires are not needed, they will be cut back and to reveal a little insulation, you may find excess wires.  Other times, they ran the exact number of conductors they needed and there is no other option than to rob the fan wire.  check it out if you want to get your fan back.


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## kok328 (Dec 5, 2016)

aNYCdb said:


> I had another idea I wanted to float by folks. Currently in my house in upstate New York I have two zones of heat each with an old style mechanical thermostat (not line voltage). One of the potential issues I'm facing is we occasionally intend to let friends stay with us and I'm worried that if they turn the heat down in one of the zones and forget about it it may result in pipe freezing issues. I recently picked up two new standard 7 day thermostats and a similar wifi enabled version and I was wondering if I could do the following.
> 
> 1. Replace the two existing thermostats with the 7 day programmable one.
> 2. Wire the wifi enabled thermostat to both zones and place it in the basement so that I could set it to turn on both zones if the basement went below 35 or so and if needed remotely raise the temperature of the hole house.
> ...



My :2cents:?  I think your over-thinking this. If wiring allows, replace the mechanical thermostats with programmables that have a password feature but, still allows for a few degrees of adjustment and your all set.
Guest will be able to adjust the temp a few degrees but, will not be allowed to drop the temp so far to allow for freezing.  You'll also want the ON/OFF feature to be passworded also.


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## Chris (Dec 5, 2016)

kok328 said:


> One member had the same issue of not having that common wire.
> I tipped him off that sometimes when all wires are not needed, they will be cut back and to reveal a little insulation, you may find excess wires.  Other times, they ran the exact number of conductors they needed and there is no other option than to rob the fan wire.  check it out if you want to get your fan back.



Already checked that, was hoping to find a wire hidden in there but no luck. They cheaped out on this one and only ran the 4.


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## nealtw (Dec 5, 2016)

Chris said:


> Already checked that, was hoping to find a wire hidden in there but no luck. They cheaped out on this one and only ran the 4.



Can you not just add a bypass switch at the furnace for the fan?


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## Chris (Dec 5, 2016)

nealtw said:


> Can you not just add a bypass switch at the furnace for the fan?



What do you mean by bypass switch?


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## nealtw (Dec 5, 2016)

Chris said:


> What do you mean by bypass switch?



You must have disconnected the fan wire at the furnace so if you take another power wire thru a switch and back to where the fan was hooked up.
Years ago that is all we had with the old thermostats.
Keep in mind I am only asking.


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## Chris (Dec 5, 2016)

I had to jump a wire to the fan switch in the furnace so it would come on with the heat. I guess I could put a manual switch for fan only but I don't think I have ever run just the fan by itself before.


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## nealtw (Dec 5, 2016)

Chris said:


> I had to jump a wire to the fan switch in the furnace so it would come on with the heat. I guess I could put a manual switch for fan only but I don't think I have ever run just the fan by itself before.



Before anyone had AC that was common here to pull cooler air from the basement.


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## kok328 (Dec 5, 2016)

Chris said:


> I had to jump a wire to the fan switch in the furnace so it would come on with the heat. I guess I could put a manual switch for fan only but I don't think I have ever run just the fan by itself before.



Didn't realize you jumper the fan to the heat, I thought you just stole the fan wire and left G open.
Won't your fan come on via control board relays in heat mode?

You'll be blowing cold air while the system is proofing the safetys (~1min), coming up to temp.
If your fan runs after burner shuts down then the control board is running the fan.
This is good to cool down the heat exchanger and get the most out of the warm ducts.


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## Chris (Dec 5, 2016)

Makes sense I never had a basement before and we just used regular fans because I grew up with wall heaters


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## slownsteady (Dec 10, 2016)

Getting off topic here. The OP never mentioned anything about fan switches. It sounds like he wants a master t-stat to control two downstream t-stats for override ability.


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## buffalo (Dec 11, 2016)

Or set a program on a program able tstat,  when you bump the temp up or down , it will go back to the program at the next programmed temp change. 

 And cris , how long of a tstat wire run is it . Somtimes nobody stapled it in the wall and you can tie a new wire to it and pull it through. Or if the existing wire drop straight to the basement you can use a long tiny chain , shove it in the hole in the drywall , jigel it around and it falls through the hole in the floor , tie a new wire to it .


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## Chris (Dec 11, 2016)

It goes down then over about 20 feet then down again. I might try and pull a new wore but I will wait until I am living in the house and it is summer so I have time.


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