How Mercury Thermostats Work

Рет қаралды 24,693

4 жыл бұрын

Today I discuss how a mercury thermostat works and what the inside of one looks like. I did fail to mention the O and B terminals are for heat pumps, O energizes when it is set in cooling and B energizes in Heating. This will vary depending on what type of system you have.
DISCLAIMER: I AM NOT RESPONSIBLE FOR ANY DAMAGES DONE TO YOUR SYSTEM, IT IS HIGHLY RECOMMENDED THAT YOU HAVE A PROFESSIONAL TO PREVENT DAMAGE THAT MAY BE CAUSED IF DONE IMPROPERLY. I AM ALSO BY NO MEANS A *PROFESSIONAL* HOWEVER, I AM VERY KNOWLEDGEABLE ABOUT HVAC AND I DO WORK FOR A HVAC COMPANY DURING THE SUMMER WHEN IM NOT AT SCHOOL.**PERFORM AT YOUR OWN RISK!**

Пікірлер: 51

@eulaliorodriguez5325 8 ай бұрын

Thank you for this video it has help me a lot.

@j.finesseflights1403 Жыл бұрын

Gr8 info! I have that old mercury unit and was wondering if it could cause my gas valve to click on/off rapidly while the furnace was running?

@michaelmorales3384 2 ай бұрын

4 years ago . Thanks for this informative video anyway .

@sweethoneyicetea6385 2 жыл бұрын

This circle thing broke on mine mine is similar to that one but itsa honeywell ts834 I think my air conditioner won't turn on automatically anymore and my heat don't get warm I have to switch the level down just to turn on the ac

@te2952 2 жыл бұрын

I have this same thermostat, & it is 24 years old. I just now had a problem with it getting stuck on one temp on the heating at 68. When I turn it up above 68 the heat won't shut itself off. If I turn it down below 68, it cycles shutting on and off on the heat normally. I don't know why, but that is my problem. I took the cover off and found some dust. Maybe that is the problem being as the dust might weigh down the mercury bulb a little affecting it's job. Do you have any thoughts to what is going on with it? I do want to thank you for doing the video, you helped me understand a lot. Mine is so old that I can't see the letters in the wiring anymore, so you helped me a lot! This old thermostat sure has been good to me lasting 24 years! I hate the new ones, I went through 6 of those in 4 years. I switched back over, because these old ones work better and last many years. Yep, I am old. Ha.ha.

@ikehvac30 2 жыл бұрын

The dust is unlikely, but it’s possible. I am more thinking that the bimetal strip is causing the issue. I will eventually do an updated video on the stats, hopefully sometime this week or the following week. I am very busy and it’s hard to make videos. Either I forget about making them or I just don’t have the time.

@te2952 2 жыл бұрын

@@ikehvac30....Okay, thank you for answering me back so quickly. I appreciated your input. Blessings.

@marshmower 2 жыл бұрын

No batteries and even when it acts up, you can still use it as an on off switch. I had a hunter programmable and it wouldn't cycle....... it would either stay off or on.

@mickalagould733 9 ай бұрын

@@ikehvac30what if you don’t have the cover for this and you’re using without it? Do you know how to properly move the dial under the mercury? Mine only runs for a little bit then shuts off and won’t turn back on unless we tap our furnace. Thank you in advance.

@aliciazamora2462 6 ай бұрын

To turn on the heater, do both of them have to be at the temperature I want it to be? Ex:I want my home at 75 degrees. Do the red and blue both need to be at 75? Or just the red

@bobandtay7139 Жыл бұрын

I have the same thermometer and it never turns on by itself. Always have to turn the fan from auto to “On” then wait for it to turn on after a minute then turn it back to auto.

@bobandtay7139 Жыл бұрын

@@MyLifeThai371 whoopty fucking doo

@elcues 2 жыл бұрын

I have the exact thermostat. I can not separate the temp and mercury bulb section from the circuit board section. What holds them together ? They do not appear to be screwed together. There are no screws in the horizontal / vertical slots in the bulb plate. There are screws in the circuit board plate in those two slots. I can not separate them to get to the mounting screws. Very Good video. Thank You for you contribution.

@ikehvac30 2 жыл бұрын

It isn’t designed to be separated.

@elcues 2 жыл бұрын

@@ikehvac30 In that case you could not screw the base to the wall. I can see the screws in the base going into the wall but I can not unscrew them with the bulb section in the way.

@ikehvac30 2 жыл бұрын

@@elcues it’s the three copper tabs. They have screws in them. Remove them and it should separate.

@elcues 2 жыл бұрын

@@ikehvac30 Thank You that works. I was afraid to mess with those because of the wires on the tabs. But it worked . Thank You: E.L.

@MichaelLeeHensel Жыл бұрын

@ikehvac30 @elcues thank you guys so much I had the same problem, couldn't figure out how to separate them! I'm hoping I can use the same wiring and upgrade to a smart thermostat 🤞🏻

@franklinemerson6331 2 жыл бұрын

I have the same one my heat will not cut on and it’s only blowing out cold air through air vents in my home what do I need to set the 2 clicks to in order to get heat going in my house to stay warm???

@ikehvac30 2 жыл бұрын

if the stat is set to heat and the desired temperature is above the inside temperature, and you don’t have any heat, it sounds like an equipment issue not so much a thermostat issue

@Pass179 5 ай бұрын

I was interested in the white dial inside?

@kumardinesh1990 2 жыл бұрын

2nd thermostat wiring tell me

@kristen5312 Ай бұрын

We have one of these old mercury thermostats and for some reason the A/C stopped turning on. The outside unit was thoroughly checked and is in great order. I found when I turned on the A/C on the thermostat and press the cover in against the wall with some pressure, it kicks on for a few minutes and then shuts off. Is this a short in the wiring? The bad news is, if I was willing to stand in front of it and push, it would work. 🙄🙄😏😏

@ikehvac30 Ай бұрын

Sounds like the stat is having an issue with the connection, check and make sure everything is tight. If everything is indeed tight, time to replace it.

@kristen5312 Ай бұрын

@@ikehvac30 Thank you for answering. So turn the breaker off, remove the plate and check the connections for the wires, etc??

@ikehvac30 Ай бұрын

@@kristen5312 yes

@joebrown72 2 жыл бұрын

Ever hear tell of anyone having trouble with their furnace coming on working but then maybe shutting off a little early probably and then when it does it keeps cutting back on and of and on and off but when I turn the thermostat down it will stay off. It seems to heat to the temperature but then when it shuts off its like ots not picking up on it being that wamr there but it is. Could be the furnace itself I guess only reason I'm thinking thermostat is because it doenst do it all the time any thoughts man?

@ikehvac30 2 жыл бұрын

Sounds like the heat anticipator, if you have an old mechanical thermostat, I would say it would be a good idea to replace it due to its age. If it is a digital one that is old, I would also say it is time to replace it. It sounds like it is keeping too tight of tolerance when it comes to heating.

@joebrown72 2 жыл бұрын

@@ikehvac30 I just noticed the needle was stuck on 24 on the thermostat. Id say when I trip the breaker would that ruin the heat anticipator there's one in the furnace too right what could hurt that? Hopefully with a new thermostat it will be ok

@haroldabbot7763 3 жыл бұрын

how do you test this mercury switch with a multi meter to prove that it works

@ikehvac30 3 жыл бұрын

In most cases, if it doesn’t work, you just replace it. They are obsolete now a days. If you insist in checking one, check between R and all the terminals. If these stats were still used today I would make a video on testing them, but since they are not, there is no reason to make a video on it. It is cheap enough to replace them.

@elcues 2 жыл бұрын

@@ikehvac30 Use an ohm meter

@Jeph629 Жыл бұрын

Simple components, etc. Why do they fail?.......contact points oxide? (they appear to be made of aluminum)..........bimetal strip corrodes??

@luluinterrupted9213 2 жыл бұрын

My heat anticipator isnt set right and my air conditioning won't blow cold air at all

@ikehvac30 2 жыл бұрын

So, the heat anticipator doesn't affect the cooling part, it sounds like it is an unrelated problem.

@yaznorwood9514 10 ай бұрын

I have this same thermostat! Unfortunately I don’t know if it’s working because when I turn it on nothing comes on. No AC or heat but my fan located in the backyard is spinning as if the AC is working. I also noticed a spark that happens when I touch the mercury glass bulb. Other than that nothing, do you have any ideas?? Would be greatly appreciated if u could give some insight

@khmergodhobbies 3 жыл бұрын

what is that wheel cycle below the mercury for? what do those numbers mean?

@ikehvac30 3 жыл бұрын

That is the heat anticipator. It helps to prevent the furnace from overshooting the set point. Most stats have it built in electronically.

@khmergodhobbies 3 жыл бұрын

@@ikehvac30 my ac stopped working but fan still turns on if I turn it to heat instead of cool. Compressor and condensor fan still works if I turn it to cool, but interior a/c doesn't make a sound. Do you think the anticipator or thermostat is the issue?

@ikehvac30 3 жыл бұрын

@@khmergodhobbies I doubt it has to do with a thermostat. I would suggest calling someone out to take a look.

@khmergodhobbies 3 жыл бұрын

@@ikehvac30 thanks

@HBSGaming 2 жыл бұрын

what is the wheel cycle they should be on?? ive pushed it around it and im still cold.

@sadnbluelady Жыл бұрын

how do you fix one of these?

@ikehvac30 Жыл бұрын

Do not attempt to repair these. It contains Mercury. New ones are cheap enough to buy and are a whole lot better. If yours has failed, it is likely that you can't repair it even if I told you how.