How to adjust honeywell round thermostat (mercury switch) to the right temperature

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On Feb 22, 11:07 pm, Glenda Copeland <gscopel...@Use-Author-Supplied- Address.invalid> wrote:

The problem you have is called hysteresis. When the temperature rises the 'stat switches off & the temp. falls but the stat does not close at the same temperature as when it was rising. The hysteresis should only be a couple of degrees but now it's obviously a lot more. This is due to ancient technology and probably wear and tear and lack of lubrication. The mercury bulb is indestructable but the rest of the 'stat wears. Get a new themostat. It will pay for itself in a year. http://en.wikipedia.org/wiki/Hysteresis
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On Feb 22, 11:07 pm, Glenda Copeland <gscopel...@Use-Author-Supplied- Address.invalid> wrote:

I don't know if such things are available in America but in Europe you can get an "intelligent thermostat." There is an additional outside sensor and the heating is switched on earlier in cold weather and later in warmer weather. The exact amounts depend on the insulation of your house (nonexistant I expect in America). The thermostat determines this for itself after the first run. Dependant on your lifestyle, between 10 and 20% can be knocked off your heating bill. Some of these devices also compensate for wind . A digital thermostat can save 10%. It's important that the thermostat is correctly sited. In Europe every room is independently controlled in new buildings.
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It's important that the thermostat

That may be an exaggeration. I recently lived in Europe several years.
The heating I encountered was all hot water radiator (or hydronic - it is SO nice to step on a heated tile bathroom floor on a cold morning).
Every radiator had its own thermostat, mounted on the radiator. That's really not an ideal location. The furnace did have an outdoor sensor with reset and a time schedule.
Energy was expensive so houses were very well insulated and very tight.
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Yes nearly all heating over here is by means of hot water circulation, even in very large buildings.The boiler(furnace in your parlance) can be far more efficient, exceeding 100% in some cases.. Also water is far easier to mix and control than air. The hot water pipes can be much smaller diameter than air ducts & therefor can be better insulated. Domestic hot water can be produced from the same boiler, as and when required. (No need to store it hence reduced losses.) Things are expremely primitive in the USA compared with Europe.
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.The boiler(furnace in your parlance) can

I call it a boiler, too. But it doesn't actually boil anything, so to avoid confusion I used the word furnace. Sorry if I confused.
Also water is

Well, I'm talking mostly residential, though the office buildings I saw all had the same kind of hot water heat. There was no air conditioning except maybe in a computer server room.
Primitive? That's relative. In Germany I saw no VAV, no DDC, no control systems to speak of, thermostatic control valves on the radiator where the heat from the unit masks the room conditions, thermostatic valves that you have to disassemble monthly because they scale up and always fail to "no heat" condition. No smoke detectors, heat detectors, CO alarms.
On the other hand, I saw first class furnace/boiler systems in residential that were well maintained by law, including semiannual combustion tests and chimney cleaning. And as I mentioned, well insulated and well sealed; you can get infiltration down to near zero if you use plaster over masonry and very very expensive double pane tiltable-closable windows. I wish I could get those in the US but I couldn't afford it if I could. Even the doors are built with a lip to seal against the jamb. I was paying 27 cents a kWhr so you can see why they work hard to save energy.
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I live in the UK. My house hase quadruple glazing and 4" insulated shutters, There's 2' of insulation in the walls and roof. This means we need no central heating. I have done all the work myself, I used to be an energy efficiency engineer working for the government.
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quad glazing, 4" shutters, post a photo, is the quad glazing LowEArgon
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On Fri, 26 Feb 2010 11:58:45 -0800 (PST), harry

It has nothing to do with the USA being "primitive". There are plenty of hydronic heating systems in the US, particularly in the Northeast (fueled by oil, natural gas, or propane), and they do give a nice heat (though they do take up wall space for radiators or baseboard convectors). However, you don't get air conditioning with that distribution system, so forced air is more common anywhere AC is desirable, now or in the future. Some houses (like the one I grew up in) do have both, but that's usually the result of retrofitting AC; a new home is likely to have only one HVAC system.
Josh
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harry wrote:

Well, you know how those darn colonies are. They rebel and go their own way.
TDD
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The Daring Dufas wrote:

That's revolting.
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Bob F wrote:

It's revolutionary.
TDD
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No gas boiler can exceed 100% efficency, I know of none over 98%.
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On Mon, 22 Feb 2010 23:07:14 +0000 (UTC), Glenda Copeland

I'd yell at you too. Who needs 75? Set at 78 and be happy with 68. Wear a sweater.

Don't pull that cover off. There are electical forces there that will make your cold cream run.

In that case you could risk bending the spring or some other part that is holding the mercury capsule, but two major concerns. 1) Being a Mercury Capsule, it might head for earth orbit. 2) A good chance you'll bend it in the wrong direction (it's confusing) or bend it in the right direction but so much that the offset pointer won't be able to correct it. And you only get to bend it once or twice and soon it will break off. Plus you probably need TWO needlenosses to bend it.

You can try to tip the house while holding the thermostat in place.
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wrote:

Bad advice by me. I was actually closer with my last line. See below.

This advice was somewhat sarcastic, but it modified just a little, it was the best advice in my post. If the adjustment with the copper pointer is insufficient, you can rotate the entire thermostat. The amount you want to rotate it is the amount it takes to make the number for example 75 to show up in the same place that currently the number 85 is in. Plus a little more if you want to recenter the copper pointer. (You now know better than I do how many degrees it is from end of the scale to the middle with the copper pointer) That would matter if you want to finish this job with the copper pointer, instead of remounting the thermostat a bunch of times. You could use two-sided tape so remounting would go quickly, or you could use screwws and finish off with the copper pointer.
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On Mon, 22 Feb 2010 23:07:14 +0000 (UTC), Glenda Copeland
As to buying a new thermostat, people here are often ready to buy new, to throw money at a problem.
As to accuracy, what does accuracy matter when people don't know if they want 74.4 or 74.7, or 75.3? And much moreso is it not important when they want something around 75 and their husband wants something around 68. Improved accuracy isn't going to help.
Temperature stabilty is adjustable iirc on the round Honeywell thermostats. It's called cycle delay or something. But one can't lower it too much because of the furnace, not because of the thermostat. It's not good for many furnaces to turn off and then turn on again when the temp drops 0.1 degrees. This is all the more true for ACs which need time for pressure to go down where it the refrigerant is compressed. The thermostat comes set for a reasonable value and it can be lessened if wanted with most furnaces. If it is also an AC thermostat, either there are two cycle delay adjustments, the cycle delay applies to the furnace only, or it can't be lowered more than is safe for the AC.
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