Talk:Thermostat
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[edit] History?
Is it possible to have some material about the history of the thermostat? Thanks A.S. Brown 04:23, 17 August 2005 (UTC)
[edit] H.L. Mencken
Here is an essay commenting on the history from January 1931. Maybe some of this should be placed into the article.--Kalmia 20:59, 16 November 2006 (UTC)
http://www.bizbag.com/mencken/menktherm.htm
THE THERMOSTAT
….Of all the great inventions of modern times the one that has given me most comfort and joy is one that is seldom heard of, to wit, the thermostat. I was amazed, some time ago, to hear that it was invented at least a generation ago. I first heard of it during the War of 1914-18, when some kind friend suggested that I throw out the coal furnace that was making steam in my house and put in a gas furnace. Naturally enough, I hesitated, for the human mind is so constituted. But the day I finally succumbed must remain ever memorable in my annals, for it saw me move at one leap from an inferno into a sort of paradise. Everyone will recall how bad the coal was in those heroic days. The patriotic anthracite men loaded their culm-piles on cars, and sold them to householders all over the East. Not a furnaceman was in practise in my neighborhood: all of them were working in the shipyards at $15 a day. So I had to shovel coal myself, and not only shovel coal, but sift ashes. It was a truly dreadful experience. Worse, my house was always either too hot or too cold. When a few pieces of actual coal appeared in the mass of slate the temperature leaped up to 85 degrees, but most of the time it was between 45 and 50.
The thermostat changed all that, and in an instant. I simply set it at 68 degrees, and then went about my business. Whenever the temperature in the house went up to 70 it automatically turned off the gas under the furnace in the cellar, and there was an immediate return to 68. And if the mercury, keeping on, dropped to 66, then the gas went on again, and the temperature was soon 68 once more. I began to feel like a man liberated from the death-house. I was never too hot or too cold. I had no coal to heave, no ashes to sift. My house became so clean that I could wear a shirt five days. I began to feel like work, and rapidly turned out a series of imperishable contributions to the national letters. My temper improved so vastly that my family began to suspect senile changes. Moreover, my cellar became as clean as the rest of the house, and as roomy as a barn. I enlarged my wine-room by 1000 cubic metres. I put in a cedar closet big enough to hold my whole wardrobe. I added a vault for papers, a carpenter shop, and a praying chamber.
[edit] Fancy units operating from 24vac
I've changed the article to state that some digital units can operate directly from the 24vac thermostat circuit and do not require batteries (except possibly to provide backup against power failures). This is true and was also true of good-old mechanical "clock thermostats" before the fancy digital units. This is accomplished one of three ways that I'm aware of:
- An additional wire provides a return path for the 24vac, allowing the thermostat to have a constant source of power whether it is calling for heating/cooling or not.
- A rechargeable battery is charged from the circuit when the thermostat is not calling for heating/cooling and powers the unit when the thermostat is calling (and has therefore shorted its two input wires).
- The thermostat is powered from the voltage on the circuit when the transformer isn't calling and is powered from the current flowing in the circuit when the thermostat is calling. (Yes, I've actually seen this!)
Atlant 17:08, 9 February 2006 (UTC)
[edit] But what IS a Thermostat??
Do you think that we could possibly have a better, simple explanation of what a thermostat is before the article goes on to explain various types of thermostat and how they work? Which, frankly most people who want to know what it is won't be interested in?
What defines an object as being a thermostat? What does an object have to have/do to be a thermostat? Is the timer control on my central heating a thermostat?
Imagine an 11 year old kid was wanting to make a thermostat for a science project - what would they need to do? Must it control a system to be a thermostat or can it simply act alone measuring temperature?
These are questions I would still like answered after looking the word up.
Cheers
I'm afraid he (the kid) can't do it, since there;s welding involved in making one
[edit] drake and josh
I was wondering which kind was the thermostat in one mummii i love you of the drake and josh episodes ? cuz in that one we see the inside of it and cables were prominent since they were being welded, at first I thought it was a bimetallic thermostat since the cable maybe was a bimetallic strip and was getting modified ur the bestto only cool, but maybe it was a heat pump and the cool wires were being joined with other cool wires instead of heat wires thus making the heat uneffective therefore causing turning up the heat impossible. But maybe it had only two wires, or it had a thermocouple, but surely the thermometer was in one way blocked to keep from heating and it defintely couldn not have been a digital thermostat
[edit] Karl
I have a millivolt thermostat controlling a freestanding (fireplace like) gas stove. I need to know how to test the thermostat, and/or the power coming from the stove thermopile, to see which item is defective. The behavior I am getting is that turning up the thermostat, till you hear the "click" (contact with a holding magnet that holds the circuit closed), results in no usual lighting of the stove. Yet, when I go over to the stove and flip the on switch, it lights right up. How does one tell whther the thermostat is defective?
- Use an ohmmeter. Disconnect the thermostat from the heater and connect the ohmmeter to the thermostat instead. When the thermostat is not calling for heat, the meter should read infinite resistance. When the thermostat is calling, the ohmmter should read zero resistance.
- You could also place a "clip lead" (or any other short) across the thermostat (while it's wired into the heater). The heater should turn on. If it does, the thermostat is defective or miswired. If it still doesn't turn on, move your clip lead (short) to the terminals at the heater where the thermostat connects. If the heater now turns on, the wiring (cabling) to the thermostat is defective. If it still doesn't turn on, then it's a mystery ;-).
- Atlant 01:25, 29 November 2006 (UTC)
Thank you. Your suggestion conforms to a telephone call I got from the tech rep at Lux (maker of unit in question), just this morning. Now, in answer to athe question of what a thermostat is, in simple terms: "It is a switch, operated by changes in temperature."
Karl C Kelley 17:45, 29 November 2006 (UTC)
- Yes, that's a good, brief definition for an electrical thermostat. There are other kinds, of course ;-). Good luck with your continued troubleshooting!
- Atlant 17:50, 29 November 2006 (UTC)
[edit] Comment about oil heating
I think it would be a good idea to mention on Oil Furnaces that use hotwater to heat the house, the thermostat operates an electric valve to get water flowing. —The preceding unsigned comment was added by 172.164.79.146 (talk) 19:35, 7 January 2007 (UTC).
[edit] Use of Bi-metal thermostats
They are still widely used at least in The Netherlands. I edited a bit and slapped on a {{{globalize}}} template. László 13:01, 25 January 2007 (UTC)
- I think it's safe to say they're still widely used everywhere. There are still plenty of folks worldwide who aren't cutting-edge technologists and Wikipedians ;-).
- Atlant 13:15, 25 January 2007 (UTC)
[edit] Suggestions
I am certain there is good deal more information about thermostats available. Discussions of the manufacturing of bimetallic elements such as dimpling disks, various schemes of using this phenomena, disk hysteresis, designing temperature ranges, and methods of power circit activation. The thermostat description "The power through the thermostat is provided by the heating device and may range from..." is unclear to me. Please revise.
—The preceding unsigned comment was added by Drkeene (talk • contribs).
[edit] Removed Sections
I removed the 'Chronothermostat' and 'Phone Interface' sections, because both lacked any... content. Both simply said "This section is a stub". Just posting here, in case anybody was using those as placeholders for future content. Ahanix1989 13:24, 22 April 2007 (UTC)
[edit] PID Controller
The explanation of how a PID controller works is not correct.
A standard thermostat is "P". The heating or cooling action is turned on based on whether the temperature is less than or greater than the set point.
With a PID system, the actual set point of the thermostat is modified slightly to improve the accuracy (reduce the error) with which the temperature matches the temperature which the user has set.
This is done by generation of two functions of the temperature.
I stands for intergal which is simply described as the error multiplied by the time the error has occurred. This is (algebraically) subtracted from the set point which will move the set point in the opposite direction from the error. The effect is that after a small error has occurred for a period of time that the system will be run to correct it.
D stands for differential which is simply described as the rate which the temperature is changing -- how much it changed during a measuring period. This is also (algebraically) subtracted from the set point. The effect is to turn the system off earlier than a standard thermostat would and by doing so to prevent overshoot.
The stability of a non-proportional system (on/off or staged) is improved by not operating I while the system is running and only operating D while the system is running.
Tyrerj 16:23, 6 June 2007 (UTC)
