Upgrade from Mercury to Digital Thermostat 

The amount of understandable knowledge in 12 min is astonishing.

It's great to see people like you who are so passionate about their career.

The few videos I've watched that you've done have truly been tremendously helpful!

My hope is that a digital unit will not let temp fluctuate so much: seems like w/ vertical Mercury it gets pretty cold before heat turns on & pretty hot before turning off which makes for putting on & taking off blankets & poor sleep all night. Further, we use a fireplace which is close to the living room thermostat; so as brick cools overnite, thermostat tries harder & harder to heat the living room until bedrooms are sweltering: now that last kid moved away this summer I'll use this to staple wire between old thermostat's location and our bedroom because in the final analysis all we CARE about is our bedroom now: IT can control the house temp: hey, they must call it a "MASTER bdrm " for a reason. Luckily in our house, only A/C & gas heat, no resistance heating backup or coils, or electric strip, in our house so prolly won't have to figure out some of the finer points. Thanks! Sounds like you have a good heart toward your customers, sir, God bless, Merry Christmas!

Thank you Dave, I am in Tampa it is 3:30 am and I got up feeling warm only to discover I had no display on my Honeywell controller. Mind you it is July 2nd in Florida, we are talking sauna! I watched you connect the wiring to bypass the use of a thermostat, so I did that and I got the unit to start on the cool cycle. This has bought me time to go and buy a new controller in the morning and to get back to sleep.

Wow!!!! Five stars to you and your channel! I wish you lived out by me! I’d call you to service my unit anytime of the week. I respect you honest and loyalty so much! Blessing to you and your business sir!

Most helpful thing I've seen online. Thank you.

THANK YOU , THANK YOU!!!! I had a green wire and a red one for the same set up you've shown here. You explained it so well and so clearly. I replaced it and is running nicely! Your video was so helpful.

Great video! the 50 downvotes must be from 50 competitors angry that someone spent a lot of time and effort making a video to teach homeowners how to do a simple once explained repair instead of paying a couple hundred bucks to a "professional" to hook up a few color coded wires in 10 minutes!

Dude's giving hypothetical reasons why someone might want to change. He's explaining extremely thoroughly how to do that. If you feel the need to defend your knowledge in the comments of a youtube video... you probably are short enough to need the soapbox. Thank you David Jones person for making this incredibly useful video.

Very good video. I removed from service an "old school" White-Rogers mercury bulb thermostat two weeks ago.

You are awesome 👌 Knowledgeable and honest

I'm replacing a vintage thermostat with a Sensi Emerson Thermostat. I've watched all kinds of youtube videos that address swapping out and replacing the old thermostat and I must say this is one of the best for folks with older thermostats. I took the cover off of my thermostat and I still don't see the wires that correspond to R B W Y that I would expect to see so I'm guessing that I actually have to remove it from t he wall and flip it over to see where the various wires connect. Does that sound right or am I missing something? BTW this thermostat is in a mobile home which dates back to the early 1970s. I know that if I call out a service technician to do this it will probably cost me $150 and I don't have that kind of money. I'm 76 years old and want to try and do it myself.

good video, wish it was higher resolution.

Great video! You have a great mechanical aptitude!

THANK YOU for this! It was incredibly helpful.

Help - my current wiring is R,G,B,W,O and Y. I want to replace this old round Honeywell thermostat with a programmable one. I have two zones forced hot air (oil and central ac) My other thermostat is wired as RWY. Any suggestions.

Thanks for the info will clean my mercury bulb thermostat.

I only have a black and white wire and replacing thermostat should I replace wire furnace is just heat.

They are good little trained consumers is why they 'upgrade'.

Thanks for this video but I'd like to ask you the landlord previously used a wiring with only a red/white wire I have a Honeywell CT87N and the heat won't shut off from the thermostat what could be wrong?

david, two questions: If the old mercury has to go to 85 to crank up even to 60, is it hopeless? And also, how do you adjust the bottom dial (room temp) on the old mercury? One last day before I have to replace with a round Honeywell no mercury. Both of my wires seem to be white...

Thank you for sharing this video.

I live in Phoenix, have the old round Honeywell t-stat. Want to replace with my digital touch screen Honeywell. The old t-stat has red to r, green to g, what appears to be blue to O, white to w and yellow to y however w&y are jumped/connected. Confused as to why it is set up this way and wonder how to set up my digital

All your videos are great. Thank you for making and posting them.

Hello and thanks for the videos. I am replacing an old mercury based Dayton thermostat with a White Rodgers 1F78. It appears the wiring scheme is unorthodox for this old thermostat but it worked perfectly, I just wanted to convert to digital. Anyway, the blue wire was connected to R5, White wire to Y6 and Red wire to W4. I am trying to figure out which ports are equivalent on the 1F78 because it seems to simply stay on. I have heat only; a Weil-McLain boiler

The old mercury were the best thing. "less moving parts???' A bimetal strip and a dial! Inefficient?? Anything that turns on the furnace when it is too cold and turns it off when the temp is good, is completely efficient. They last virtually forever; the reason they use mercury is because a mercury contact never fails. The new ones need constant power. If you cannot add a third wire in the wall, you have to use a battery... It works hard to hold a relay the whole time your furnace is running. It will fail on the coldest day of the year, when you have no spare batteries. And they go out of calibration much more often than the mercury design, except you cannot recalibrate them like the mercury type.

Safer..how much land fill space used with those batteries..

I am trying to install a Honeywell programmable thermostat and there are only 3 wires coming out of the wall. The white wire has been spliced to a green and a yellow wire. Can you help?

Old junk i update one with honeywell round digital mutch better now i have a new boiler and now with round modulation from honeywell love it ^^

Funny. I’m a tech guy at a big computer company and I rip out these smart thermostats and go out of my way to install mercury thermostats.

Hi David, I am planning to replace my old thermostat to digital, but I am confuse of the wiring. There is a line voltage (Off-High-Medium-Low) and low voltage (Numeric Dial) wiring that connects to my old thermostat. Need help please.

I would like to replace 3 Automag Mercury thermostats with 3 basic digital Emerson thermostats. The boiler is a brunham heat only furnace with 3 separate zones and valves. The current Automag mercury thermostats have 3 wires and are connected w-w, r-r and g-b. I have not been able to find any information on how to hook those 3 wires to 3 basic non programable digital Emerson thermostats. Any help would be appreciated.

Thank you, your presentation was most helpful!

Great job explaining this!

Great job David 👍🏻

thanks, I'll try the thermostat. I changed the relay, capacitor and the control board. When I push the in the contact or the fan runs and the compressor runs. In heat mode or cooling mode the heat pump won't start. Could you give me any ideas what to do? One other thing the reversing valve coil clicks but the whips have sound is not happening.

I didn't take note of the wires connected to my old thermostat. Now I have a red, white, green and BLACK wire. I assume that red goes on R, green goes on G and white goes on W. I don't know where the black wire goes (I had assumed that it was all self explanatory). Any suggestions how I can get my air cond working?

Hello, i got some trouble about my thermostat wire, I don’t know if you can help, there color are different from many normal wire, they are only 4 colors, black, blue, green, and red, i would to install to nest thermostat, thank you 🙏

Great video David👍👍👍

My only suggestion is that you do an actual “how to” video and have someone film you as you replace one and just do a voice over explaining what your doing at the time. But this was very helpful thanks!

Afternoon David, I hope you can help me. My issue is I currently have a mercury thermostat for the cooling unit in my home (the heat is controlled by another thermostat downstairs). The mercury thermostat only has (3) wires connected to it. (yellow, green & red). I hooked the (3) existing wires up to the new Honeywell Lyric T-5, and no response. It says that I need a “common”. At the cooling unit in the attack there are only the (3) wires connected (same color) what should I do? Am I able to upgrade my thermostat with only the 3 wires? Please advise if you can.

I have HONEYWELL T8195B-1009 thermostat and want to replace it with a digital. I have two thermostats on my system. Any recommendations ?

I truly appreciate this video. Thank you kindly sir!!

This was excellent. Helped out alot

Good Tutorial. I have a motor home with furnace only. AC is separate. The old thermostat has two wires. One is white and one is red. I put white on the W terminal and red on the R terminal and nothing. Any suggestions would be appreciated.

There is no white wire coming out of my wall. I have a black, green, yellow, and red. Not sure where the black is supposed to go. Any ideas?

I have the Honeywell t87f and when I took it off I only see two wires a red and a white is that all I need to hook up to my new electronic thermostat which is a Honeywell home rth2300b thermostat? I have this thermostat for my oil baseboard heat

If you program your new programmable digital thermostat to 65degrees when you are not home for ten hours a day Monday thru Friday then 74 degrees when your home.If you use an old thermostat latched on 74 degrees all the time costs more money to operate.

What if I have an old thermostat for only ac and only 3 wires?????????

is it more efficient to turn the heat down when not needed or keep the same temperature?

Energizing on cool?

I have a universal parts thermostat heat will not work on auto but on fan what CLD be the problem

Thank you

Question: I have an old Honeywell round thermostat (Mercury) with a Heat/cool switch and a fan switch that has 2 positions, On and Auto. How is the fan energized when on Auto. Is it an internal function of the thermostat (Green wire energized when the thermostat calls for heat) or is it some kind of function of the furnace.

Hello, great video but I have a question. I have a digital thermostat for my a/c and a round Mercury thermostat for heat. I want to put the heat in the digital thermostat. Now my heat is a boiler with hot water base board heat. Can I hope this up to the digital

I just spent a lot of money on E-bay for a mercury thermostat. I am going the other way and getting rid of this digital rubbish. Was hoping to see how exactly it was mounted, as I ran into a snafu. I am sick of this digital garbage when the old stuff got the job done, without batteries, and was more precise. I like mechanical knobs and switches that respond to me, not to a computer chip that detects something. I get that with the vintage, round Honeywell Thermostat with mercury switches. And this bunk about mercury being poisonous is B.S. Unless you swallow it, it is not a problem. And in a thermostat, it is sealed in a glass vial that is highly unlikely to leak or break. I live in a country that bans things adhawk because they think its dangerous. Meanwhile, alcohol, tobacco, and firearms are flying off the shelves and stockpiled by nut jobs, and no one says a word. Our food is poisoned with cancer causing ingredients from fertilizers to pesticides, causing the cancer, and health crises of diseases, illnesses, and deaths, and NO ONE says a word, but BY GOD, we MUST ban mercury thermometers, thermostats and chemistry kits, because some stupid kid poisoned themselves by drinking it. Totally ridiculous !

Ok. I only have 2 wires coming out of my wall and want to install a digital wifi thermostat. How the hell am I gonna do this?

But what about a simple two wire bulb type? I only have two wires, bulb opens when temperature is reached, and closes when it gets cold. On the old existing thermo stat I only have two terminals, it is not on a heat pump and doesn’t have any of the numbered terminals you show but of course the new t’stat has those terminals and requires batteries to run. All the t’stat does is close a contact and applies 24 volt Ac to a solenoid.

i really appreciate you making this video and wanted some advice if you can pass it down. Im trying to upgrade my mothers thermostat to a modern one and found that her White Ridge 1f56w-444 wiring does not have a yellow wire. I took a picture of the original wiring before i took everything off and copied the picture to reinstall the thermostat. It does not turn on anymore. Ive tried to fix it and looked over the original manual but to no avail. I did your test tying the red green and white wire together and the system did not turn on. Any advice you can give me to get her ac unit back up and running again. Were down in Texas and its getting hot.

Hi David, i have a question. I have 3 wires coming out of my wall and only my black wire is marked green and red is red on my mercury thermostat..... wired it like i saw it on my new digital thermostat and now all it does, is tell mw the temp and wont turn my heat up or down. (My a/c is controlled by qnother mercury thermostat on another wall). I matched it like you said but i still have to control the heat from the furnace its self. I have water heated floorboards.

Can you please help me??? I have an old round mercury thermostat that I want to replace with a Sensi. I have central AC and my heat is baseboard hot water recirculating pipes. I have two sets of wires coming into my thermostat. The first set are red and white. Red going to the R terminal on the thermostat and White going to the W. The second set of wires have red, white, and blue. The red going to the B terminal, white going to Y, and the blue going to G. There is also a jumper wire connecting the R and B terminals in addition to the wires going there. Everything works fine as is but wife wants digital. In the sensi app, when I put in the letters for the terminals I have wires going to it tells me it’s no a valid configuration. Please help! Thanks!

I have a LUXPRO PSDO1OBF non-programmable heat only,with fan. Trying to install it to a baseboard heating. I am ??? Not to sure I have the right thermostat.

Can an old mercury thermostat be used on a 6 wire set up! Another words thiers 6 wires coming out of wall. I just got a house. It has a Goodman furnace and some kind of electric heat pump outside for A/C It actually has an old style fuse instead of breaker on side of house. I'm gonna test the hot wire with my volt meter. Are you in Alabama

My home has old cloth “potentially asbestos wiring”. I was actually looking to upgrade my digital thermostat to a smart thermostat however the wiring in my house only have 2 wires. They are also wrapped in “asbestos”. Are there any videos on how to handle this?

Help! My old thermostat has a blue wire that goes from W to A?

Hi David, My old Thermostat only have 2 wires (Yellow/Green) The wire was Yellow on R and Green on W for the old thermostat. My old thermostats look like 2:30

Good Job

I have a mercury 1620 30V that I want to change out with a digital... my trane xl 2100 is a furnace and has only 4 wires going to it..... i did not mark the wires and I don’t have a wrench to see what the wires are plugged in.... I guess I will have to get a wrench won’t I??? Haha.... does any body know already the four wire red blue green white......

Good job, very helpful. Thank you

What if my mercury thermostat has only two wires?

How do I know if I have a heat pump ?

Thank you!! Great video!

SirThe thermostat in my condo has only 3 wiresHeatCoolCommonIt control old McQuay fan coilI need to replace it with a non-programmable digital thermostat But they have so many port (Y, W, O, R, etc.)Can you just name one model for my case that’s easy to install?Thank you

Does this work with a boiler/ radiant heat?

david jones thank you nice

Good info

Great job thanks

Good stuff.

Here is some advice to all those who plan to replace their old mechanical thermostats: rather than dispose of them, have them resold somehow. Or perhaps donate them. My aunt and her husband gave me their old mechanical thermostat (which I prefer over a digital one), and I plan to use it.

Less moving parts but they last 1/10 as long as a good old reliable mercury thermostat.

Well I've only got 2 wires, red and white.

Thank you Kindly

nice informitio

I have two old Honeywell mercury thermostats and one new Honeywell digital (T-87) in my house. The old mercury ones are MUCH more accurate and work better than the digital. The Honeywell digital T-87 is garbage. Because it's digital, it's an all-or-nothing propostion. Either it's on or it's off -- there's no in-between that you'd get with an analog like the mercury thermostats.

So just dust the coils off if they are not as accurate as you need., Don't remove the mercury thermostats, they are far superior to what is made today, and left in place are not an environmental problem the mercury is incased in glass and cannot go anyhere. “an estimated 310,000 mercury thermostats are disposed of every year just in New York, but only slightly more than 1 percent of those are recycled. The vast majority of them are being dumped into our enveronment and each one contains approx 2.8 grams of mercury which can poison about 150 million gallons of water each. ”They require no batteries and unlike modern thermostats almost never break and will not shut down your system in the middle of winter when you are on vacation because of a weak battery, causing your pipes to freeze and flood the place. (happened to me) The energy savings from a electronic thermostat is greatly overrated to in fact in my actual real life studies, I can detect almost no difference. As a landlord, I used to replace mercury thermostats routinely, However, after spending over a thousand dollars in cost of replacements, troubleshooting, parts and labor for techs to troubleshoot Hvac units only to discover malfunctioning electronic thermostats, I reinstalled the old mercury ones that i had on hand, and they just keep functioning decade after decade. Finally, there is no programing required which is time consuming to have to keep reprogramming them constantly for various reasons.

I will tell you since PSEG changed my mercury thermostat to modern one it never worked good more than 5 to ten degrees inacurate

How could a different thermostat possibly save you any money at all on heating or cooling costs, let alone $200 a year? All it is, is an on/off switch. It's going to take the same amount of fuel to heat a house from e.g., 65 degrees to 70 degrees, regardless of what you are using for a switch to turn the furnace on when it reaches 65 degrees and turn it off when it reaches 70 degrees. If you're claiming that a digital thermostat is more accurate and accuracy translates to savings, then that's false. If an old thermostat causes the furnace to heat the house to say, 72 degrees when you only wanted it to heat to 70 degrees, then it will be that much longer before the furnace has to come on again; it evens out. Furthermore, the old style of thermostat is nothing more than a mercury switch (which is just a glass bulb with metal contacts on each end, and a pool of mercury in the middle) on the end of a coiled bimetallic strip. Mercury switches don't wear out or otherwise fail; bimetallic strips don't wear out or otherwise fail, which means, those old thermostats don't wear out or otherwise fail. On the other hand, all microchip-based electronics (digital thermostats) are prone to failure. There's been a White-Rodgers rectangular thermostat in my house since about 1971, and it's never had an issue (obviously; there's nothing that can go wrong with them). I'd never even cleaned it until tonight. Out of curiosity, I took the front off it and there was decades' worth of dust bunnies in there, but due to the design, very little dust was on the coiled bimetallic strip. There was a small spot of dust on top of it just under the mercury switch, not enough to cause any significant insulating effect. The thermostat manufacturers must be desperate to sell new thermostats (which, like many new products, are a downgrade compared to old products). They know the old ones never wear out or otherwise fail under normal conditions, so first, they play the comical "MERCURY IS SCARY!" card (as if the mercury is going to magically teleport out of its glass bulb), then they spin a yarn about energy savings.

thank you sir!!!!

Your a beautiful soul. Thank you.

Jeez 240p, but it was helpful.

I collect different types of mercury switches make things out of it

Hey David, here’s my problem as brief as I can make it. Thermostat went blank, put new batteries in and it came on. Problem is that it does not turn anything on. So I followed your instructions and connected all the colored variations together and nothing comes on. I checked the transformer and both high and low sides seem to be good on both sides. So now I went pc board where the relay is located. Having trouble testing the no and nc terminals on it but it does not click when I put the breaker on and adjust thermostat . Could this board with the relay be bad or is there anything I should check on the outside condenser , could I be low on Freon . It is a unit with heat pump and emergency electric heat that I switch to manually on the thermostat.

Think I'm more confused now than I was. Lol

Lol my current thermostat has two black wires…no labels

RC?

Look I like the content... but did you really upload a 240p video in 2017....come on now.

Too confusing with the different brands

A mercury thermostat will last near forever. Not so much with a digital.

"What I want to talk about today is mercury thermostats how they're more energy-efficient and can allow you to save up to $200 a year on cooling or heating costs." So, the old mercury thermostat is better for the environment and can save me money? Why would I change it out?