The mechanical thermostat: how it works.
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- เผยแพร่เมื่อ 14 ก.ย. 2012
- I describe the mechanical thermostats used for many years in residences. I show how they work and some tips on problems.
This video is part of the heating and cooling series of training videos made to accompany my websites: www.graycoolingman.com and www.grayfurnaceman.com to pass on what I have learned in many years of service and repair. If you have suggestions or comments they are welcome.
If you are a homeowner looking to repair your own appliance, understand that the voltages can be lethal, the fuels are highly flammable and high pressures are used. Know your limits. - แนวปฏิบัติและการใช้ชีวิต
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Great video GFM! Watching your videos is like having an instructor in my own home. Thanks again for all your teachings.
Of all the mechanical thermostats out there, my favorites are the Honeywell thermostats (in particular the CT51/CT55 rectangular ones, and of course the CT87N round), since they are very popular, well made, and easy to see and use. I too am fond of the GE/Trane Bay-Stat thermostats, since they were easy to see/use and very well made, as well as the Robertshaw TX400 Cube (which bears a close resemblance to the Honeywell CT87N).
Thanks for the videos. I'm an electronics tech myself and used to work at a hostel that had a few of these mechanical ones. We replaced them with digital programmable ones. They are good for if you could set it and forget it, but I find many people have way too many rooms on a zone and so the programmables don't seem to work so well in those situations. The room at the end of the zone will be the coldest. So I had to be constantly adjusting the one in my room that worked for several rooms anyway. Would have been easier to have a manual one as I was home most of the time anyway.
I'm downgrading a programmable one in my landlady's house tomorrow to either a digital non-programmable or an analog one. They find it hard to use the programmable one. Its not very user-friendly to elderly folks. They always have to get out a booklet when they want to change any setting. So I'm helping them go back to what they're comfortable with. There is lots of information for upgrading from analog to digital but virtually none for going the other way. This is a two wire one (r and w) so I'm thinking any old analog Honeywell should do. I will admit that some of the programmable ones I've encountered, I would have liked to launch it off the end of my steel toe boot into the stratosphere. But I digress... :)
I kinda liked the ones with mercury switches. As long as its contained inside the bulb, they're pretty safe. Its when they break and get into the environment they're bad. But if they're on the wall and operating properly, how are they going to break? All those CFL bulbs they were touting as successors to the incandescents come with mercury too, and any money savings you wind up paying for when you have to pay to recycle the bulbs.
My "Industrial Electronics" instructor once told me he believed programmable thermostats were great in new houses with good insulation and little air flow, but in old houses with lots of drafts, he thought the analog kind were better. I think its all a matter of laziness, myself. I have no trouble getting up and turning down the thermostat at night and turning it back up during the day whenever I need it. I grew up in a remote area in Canada where energy prices are through the roof. So we never wasted energy. Now I'm equipping my parents with some LED bulbs (9 watts to replace 60) and this will save them even more money. They don't have a programmable thermostat, either. Dad wouldn't be long getting rid of it if he did buy one. :)
Once again, thanks for the great video and insight! All the best!
+privatear2001 You should have seen the programmable ones in the 1980s. They make the newer ones look easy. I have never seen a programmable last longer than 10 years. Those old mechanicals easily do 50 or more. As a service tech, I never installed programmables in an elderly person's home. I don't think the age of the house makes any difference. Thanks for the thoughts.
GFM
Thank you for explanation how mechanical thermostats works :-)
Your video is going to be useful for my engineering thesis!
Welcome
GFM
Thank you for showing how to adjust high quality non electronic thermostats
Welcome
GFM
You got it. No sandpaper as it removes the plating.
GFM
When you first show the bimetal--at about 2 min, there are two wires. Are these grounds? I took apart a thermostat and now I'm trying to figure out where they're supposed to go
Great video! By the way, that dual lever thermostat will NOT work for our house because the boss of the house needs 78 in winter and 65 in summer! I do not argue with her. In our house, I will need those levers on the opposite side.
I don't either. Happy wife, happy life.
GFM
I'm doing some updates on a small house that uses two millivolt wall furnaces for heat. How can I control both furnaces with one thermostat?? I'm afraid that installing two thermostats is going to result in "short cycling" on the furnace that is near all the bedroom doors as that thermostat will be too close to the furnace. On the other hand, I don't want to open a gas valve on a furnace where the pilot has gone out because I'm getting a millivolt signal from the other furnace. Seems like I need a 2 pole thermostat but I don't know if one exists.
On an older CT87N1001 Honeywell thermostat, how does the automatic side of the fan switch work. Is the automatic function part of the thermostat or does it connect to a extra lead to the furnace for the automatic feature to run?
If it has a mercury switch, the fan in auto leaves fan control to the furnace. The newer style without the mercury switch has a F "fuel" and E "electric" switch that allows the furnace to control the fan in the F position. E position energizes the fan on a call for heat.
GFM
I have the first type of thermostat. Part of the thermostat is getting hot enough to melt part of the plastic housing. The contact seems ok
Interesting. Does the unit short cycle?
GFM
Please how many degrees does the coil end rotate in a 5°C difference?
That is not something could answer. It depends on the design of the thermostat.
GFM
Thanks ...
Merry Christmas
GFM
Merry Christmas too you .. :-)
I just need to know how to turn it on.
If there is a heat-cool-off switch, turn it to heat, set the temp lever above the temperature in the structure.
GFM
I wonder if you still answer to comments. Cool vid btw!
I do.
GFM
I don't know i can get the help I need here. I have the EMERSON 1F56N-444 at home and it doesn't go off or come on when it's on automatic. It is stressful leaving my bed at night trying to turn it off or on. My question is how to I set it to automatically come on or go off at particular temperature ? Thank you
Are you using the heat or cool?
GFM