Hysteresis on the Honeywell old-style bulb thermostat

[Kirk Landaur]

How does the hysteresis work on the Honeywell old-style bulb thermostat?

My house has two of those tan round things, with a dial that has
only two indicators.
1. The desired temperature on top, and......
2. The current temperature on bottom.

I understand that the heat overshoots on the current temperature
and that it lets the current temp go below the set temperature,
so that the gas furnaces are not constantly turning on and off
exactly at the set temperature.

That makes sense (from a wear and tear and noise standpoint).

I call that delayed on and off time the "hysteresis" (but you can
call it whatever it's really called).

Pulling off the cover, I see a mercury bulb inside, which is at the
end of a curved metal strip (bi-metallic perhaps?), which explains
the *initial* on/off mechanism is from the expansion and contraction
of the coiled flat strip kicking the mercury switch on and off.

This can't be the actual on/off of the furnace, because hysteresis
decrees that the on time of the furnace itself is after the mercury
turns it on and so is the off time of the furnace being after the
mercury turns it off.

I can easily test this, simply by turning the thermostat to a
high or low temperature, where the actual on/off of the furnace
blower (and later, the heat) is something like a couple of
minutes delayed.

I get all that - but what I don't understand is *where* the
hysteresis is built in? Is it in the computer? Is there a dial
that sets the temperature range of the hysteresis? Is there
a potentiometer?

How do we *change* or *set* how much hysteresis there is?
Specifically, how do I get *more* hysteresis in my furnace?

 

[Kirk Landaur]

On Sat, 26 Dec 2015 12:49:29 -0800, Uncle Monster wrote:

Inside you'll see a sliding resistor called an "Anticipator"
which provides a tiny amount of heat to fool the thermostat.
ヽ(•‿•)ノ

Is this the anticipator?
http://i63.tinypic.com/280nvqs.jpg

Mine is currently set at 0.55 I think (if I'm reading the right thing).

Notice the distances get spread out non-linearly to the one end:
(1.2, 1.0, .9, .8, .7, .6, .5, .4, .3, .25, .2, .15, .12, .10)

It has a confusingly labeled slider that has "LONGER" and an arrow
indented on it.

The LONGER indent and the arrow fight each other.

On the one hand, the LONGER on one end *implies* that's the end
where the slider makes the hysteresis longer; but, on the other
hand, the arrow points in the opposite direction, which implies
the hysteresis is longer in the other direction?

Do you have experience with this confusing setup?

Mine is currently set to one side, but I want the hysteresis
to be greater.

To increase hysteresis, should I slide the slider toward LONGER?
Or should I slide the slider more towards the direction of the arrow?

 

[whit3rd]

On Saturday, December 26, 2015 at 1:20:38 PM UTC-8, Tony Hwang wrote:

Kirk Landaur wrote:
How does the hysteresis work on the Honeywell old-style bulb thermostat?

My house has two of those tan round things...
Pulling off the cover, I see a mercury bulb inside, which is at the
end of a curved metal strip (bi-metallic perhaps?)

That is just dumb thermostat. Only thing you can set is anticipator.
And remember metal fatigue, bimetal strip calibration goes off with
age. I'd just replace them with decent smart digital programmable ones.

I think this sounds like new-paint disease. No, there's no metal fatigue
going on, and 'decent smart...' devices don't have a half-century MTBF
like a mercury switch mechanism.

Because this IS a dumb thermostat, the timing adjustments that are wanted
might reside in the furnace room, not the thermostat.

 

[Kirk Landaur]

On Sat, 26 Dec 2015 14:20:25 -0700, Tony Hwang wrote:

> What are you trying to accomplish?

I'm simply trying to make the hysteresis of longer duration.

 

[Kirk Landaur]

On Sat, 26 Dec 2015 21:14:41 +0000, Kirk Landaur wrote:

Is this the anticipator?
http://i63.tinypic.com/280nvqs.jpg

This seems to be the correct URL to the picture.
http://oi63.tinypic.com/280nvqs.jpg

Notice the "LONGER" and "<------" fight each other.

 

[John Robertson]

On 12/26/2015 12:37 PM, Kirk Landaur wrote:

How does the hysteresis work on the Honeywell old-style bulb thermostat?

My house has two of those tan round things, with a dial that has
only two indicators.
1. The desired temperature on top, and......
2. The current temperature on bottom.

I understand that the heat overshoots on the current temperature
and that it lets the current temp go below the set temperature,
so that the gas furnaces are not constantly turning on and off
exactly at the set temperature.

That makes sense (from a wear and tear and noise standpoint).

I call that delayed on and off time the "hysteresis" (but you can
call it whatever it's really called).

Pulling off the cover, I see a mercury bulb inside, which is at the
end of a curved metal strip (bi-metallic perhaps?), which explains
the *initial* on/off mechanism is from the expansion and contraction
of the coiled flat strip kicking the mercury switch on and off.

This can't be the actual on/off of the furnace, because hysteresis
decrees that the on time of the furnace itself is after the mercury
turns it on and so is the off time of the furnace being after the
mercury turns it off.

I can easily test this, simply by turning the thermostat to a
high or low temperature, where the actual on/off of the furnace
blower (and later, the heat) is something like a couple of
minutes delayed.

I get all that - but what I don't understand is *where* the
hysteresis is built in? Is it in the computer? Is there a dial
that sets the temperature range of the hysteresis? Is there
a potentiometer?

How do we *change* or *set* how much hysteresis there is?
Specifically, how do I get *more* hysteresis in my furnace?

The hysteresis is set on the thermostat. I used to have one of those old
Honeywell units and as I recall it had a calibrated sub-dial that set
the hysteresis temperature range. Something like 0.5 degrees to around 3
degrees (F). You simply moved this sub-dial to the over/undershoot range
you desired.

Of course this info may well be searchable, rather than depending on
memory...

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[Dave M]

It's the weight of the mercury that moves the bimetal coil spring such that
it takes a higher temperature to bend the bimetal coil spring so that the
mercury flows back to the other end of the bulb. When the mercury moves to
one end of the bulb, it makes the spring reposition itself so that it takes
a much higher (or lower, depending on heat or cool mode) for the spring to
return back to its original position.
Here's a link to a web page that describes the operation very well, saving
me a lot of typing.
http://inspectapedia.com/heat/Thermostat_Temperature_Response.php

Cheers,
Dave M

Kirk Landaur wrote:

How does the hysteresis work on the Honeywell old-style bulb
thermostat?

My house has two of those tan round things, with a dial that has
only two indicators.
1. The desired temperature on top, and......
2. The current temperature on bottom.

I understand that the heat overshoots on the current temperature
and that it lets the current temp go below the set temperature,
so that the gas furnaces are not constantly turning on and off
exactly at the set temperature.

That makes sense (from a wear and tear and noise standpoint).

I call that delayed on and off time the "hysteresis" (but you can
call it whatever it's really called).

Pulling off the cover, I see a mercury bulb inside, which is at the
end of a curved metal strip (bi-metallic perhaps?), which explains
the *initial* on/off mechanism is from the expansion and contraction
of the coiled flat strip kicking the mercury switch on and off.

This can't be the actual on/off of the furnace, because hysteresis
decrees that the on time of the furnace itself is after the mercury
turns it on and so is the off time of the furnace being after the
mercury turns it off.

I can easily test this, simply by turning the thermostat to a
high or low temperature, where the actual on/off of the furnace
blower (and later, the heat) is something like a couple of
minutes delayed.

I get all that - but what I don't understand is *where* the
hysteresis is built in? Is it in the computer? Is there a dial
that sets the temperature range of the hysteresis? Is there
a potentiometer?

How do we *change* or *set* how much hysteresis there is?
Specifically, how do I get *more* hysteresis in my furnace?

 

Zus fucking Christ all the misinformation here.

First of all you start talking anticipators on December we are going to assume you mean on a heating thermostat. now for one, I disagree with going digital, digital is shit. In fact I am looking for appliances like microwaves, stoves and fridges that have the old style dial and no IC to go bad that you can't get once the thing is six months old. On the old stuff we can go to a plumbing supply (not DIY, where the real plumbers go, I have been there many times) and still even get parts for old steam controlled systems. now on tho9se the anticipator was a whole different story. But back to the lectric now -

In the heating mode, the anticipator heats the thermostat to delay the furnace from turning on. Every time a forced air furnace cyles on and off it wastes energy. the anticipator delays the turn on by heating, by a SPECIFIC caloric amount, the thing that turns the furnace on, in most cases on old stuff, a bimetallic strip rolled into a coil.

the mercury in the switch is heavy in relation to everything else and when it flops to the other side it creates its own hysteresis. That is the minimum. They want more.

They want more because it saves money to overshoot the temperature called for and let it have longer to cool down, and it also helps to not have it kick in too soon either. These cycles throw energy away, in most cases. Some systems are actually throttled but they are expensive. So since we have a binary input - on or off - we must use it wisely.

You can make a system that will keep the temperature within like a half a degree, but that costs more in energy.

The anticipator is usually set to the draw of the gas valve, but that is in older systems. In older systems, the thermostat directly controlled the gas valve and then another thermostat in the plenum controlled the blower. That was a good system.

However, now that we have induced draft systems, the thermostat turns on the induction motor and the computer checks for presssure in the flue. After blowing for a while and not seeing any significant pressure it will turn on the gas and the tubular heat exchanger will get hot, at a certain calculated rate. After a timer in the computer says it is long enough, the main blower turns on.

Once the thermostat is satisfied, meaning its setpoint has been reached, the computer turns the gas off and the blower runs for a predetermined period to keep putting the heat into the house rather than the chimney. This is usually settable by DIP switches on the PC board in the furnace.

That means more than the anticipator really, as it is set based on how long the ductwork is. On a smaller system you might want to set the afterrun shorter but on a bigger system maybe longer.

If you have an induced draft furnace, the anticipator only counts for the turn on really. The timer on the board controls when the blower shuts off. Many of them run the blower too long and put out cold air. People bitch about it and the guy comes and sets it shorter.

The control set really did work better, but those tubular heat exchangers with induced draft are marginally more efficient. Really, the difference is NOT night and day like the furnace guy tells you. The old ones could easily be 80 % efficient and many were. Even some gravity furnaces, if the dampers are set right. But people today do not want to fuck with it, this unit does it all, it is easy. There is only one advertising word better than easy in this world.

The tubular heat exchangers are really good in a few wways. first of all their recovery is like lightning, and second of all as long as the system is working properly you CANNOT get carbon monoxide poisoning in the house. The pressure where the fuel is burned is always below atmospheric, so if it is putting out CO it is going up the chimney or flue, not into the house.

The problem with that system is that because of how it works with the temp changes and all that, There is no effective way to quickly and accurately measure the temperature, otherwise that would control the blower, maybe albeit from the computer, but still that would be the optimum way.

But those things are stainless steel and being used under those conditions should not have any holes drilled into it or things welded to it because that would compromise its long term integrity. Even if it won't kill you, you still don't want any leaks. (some of them do leak but nobody really notices)

Anyway, just set the anticipator to mid range. Sure you can go down there and get the rating of the gas valve but that does not always result in the optimum setting anyway. That depends on the house, and not just the square footage, the shape of it, the position of the furnace relative to the entire perimiter and what parts of the house are important to you to heat.

That is why those guy made the money. I say made because I doubt anyone gives alot of thought to it anymore.

Like installing a single heat and air system in a two story house. I must be the only motherfucker out there who can really balance one right, and I have never been to school for this shit. People in the business are like any business, get er done and get out. handle the problems later, and if not, call our lawyer.

Set it in the middle. If the house gets too hot before the furnace kicks off, move the anticipator in the direction to close the shunt across the resistor they hang under the bimetallic strip.

It is the opposite with cooling. In the cooling mode the anticipator is in series with the adjustment and the resistor is of a higher value. What it does them is heats the thermostat while the AC is running to make it run longer, and then it will stay off longer. The net energy is almost the same except for the starts.

Money is spent when you start and stop, that is why it is good to use the cruise control on long trips if possible. whenever you use the brakes you are wasting the gasoline you used to get the car moving. You convert it to heat.

With climate control, in the winter, once you get the walls warm it is cheap unless you got no insulation and those winds really blow. In the summer, once the place is cooled off it is not that hard to keep it that way unless there is a hell of alot of sun.

Like they said - keep an even keel. though it seems to be the opposite here, once you understand the principles involved, the anticipator does that, in a backwards kind of way.

 

[Tony Hwang]

Kirk Landaur wrote:

How does the hysteresis work on the Honeywell old-style bulb thermostat?

My house has two of those tan round things, with a dial that has
only two indicators.
1. The desired temperature on top, and......
2. The current temperature on bottom.

I understand that the heat overshoots on the current temperature
and that it lets the current temp go below the set temperature,
so that the gas furnaces are not constantly turning on and off
exactly at the set temperature.

That makes sense (from a wear and tear and noise standpoint).

I call that delayed on and off time the "hysteresis" (but you can
call it whatever it's really called).

Pulling off the cover, I see a mercury bulb inside, which is at the
end of a curved metal strip (bi-metallic perhaps?), which explains
the *initial* on/off mechanism is from the expansion and contraction
of the coiled flat strip kicking the mercury switch on and off.

This can't be the actual on/off of the furnace, because hysteresis
decrees that the on time of the furnace itself is after the mercury
turns it on and so is the off time of the furnace being after the
mercury turns it off.

I can easily test this, simply by turning the thermostat to a
high or low temperature, where the actual on/off of the furnace
blower (and later, the heat) is something like a couple of
minutes delayed.

I get all that - but what I don't understand is *where* the
hysteresis is built in? Is it in the computer? Is there a dial
that sets the temperature range of the hysteresis? Is there
a potentiometer?

How do we *change* or *set* how much hysteresis there is?
Specifically, how do I get *more* hysteresis in my furnace?

What are you trying to accomplish? To make things worse?
That is just dumb thermostat. Only thing you can set is anticipator.
And remember metal fatigue, bimetal strip calibration goes off with
age. I'd just replace them with decent smart digital programmable ones.
With this you can adjust some things in the service mode at initial
installation.

 

[Tony Hwang]

Kirk Landaur wrote:

On Sat, 26 Dec 2015 12:49:29 -0800, Uncle Monster wrote:

Inside you'll see a sliding resistor called an "Anticipator"
which provides a tiny amount of heat to fool the thermostat.
ヽ(•‿•)ノ

Is this the anticipator?
http://i63.tinypic.com/280nvqs.jpg

Mine is currently set at 0.55 I think (if I'm reading the right thing).

Notice the distances get spread out non-linearly to the one end:
(1.2, 1.0, .9, .8, .7, .6, .5, .4, .3, .25, .2, .15, .12, .10)

It has a confusingly labeled slider that has "LONGER" and an arrow
indented on it.

The LONGER indent and the arrow fight each other.

On the one hand, the LONGER on one end *implies* that's the end
where the slider makes the hysteresis longer; but, on the other
hand, the arrow points in the opposite direction, which implies
the hysteresis is longer in the other direction?

Do you have experience with this confusing setup?

Mine is currently set to one side, but I want the hysteresis
to be greater.

To increase hysteresis, should I slide the slider toward LONGER?
Or should I slide the slider more towards the direction of the arrow?

General rule of thumb on anticipator is matching the number on dial same
as current draw on your gas valve. You can play with setting it
little higher or lower. I used to set it slightly higher than gas valve
rating considering the length of wiring from furnace to thermostat.
Again go digital.

 

[Tony Hwang]

Dave M wrote:

It's the weight of the mercury that moves the bimetal coil spring such that
it takes a higher temperature to bend the bimetal coil spring so that the
mercury flows back to the other end of the bulb. When the mercury moves to
one end of the bulb, it makes the spring reposition itself so that it takes
a much higher (or lower, depending on heat or cool mode) for the spring to
return back to its original position.
Here's a link to a web page that describes the operation very well, saving
me a lot of typing.
http://inspectapedia.com/heat/Thermostat_Temperature_Response.php

Cheers,

Dave M

I think you are thinking backward. Spring controls the position of bulb
depending on temperature. Not the other way around.

Kirk Landaur wrote:
How does the hysteresis work on the Honeywell old-style bulb
thermostat?

My house has two of those tan round things, with a dial that has
only two indicators.
1. The desired temperature on top, and......
2. The current temperature on bottom.

I understand that the heat overshoots on the current temperature
and that it lets the current temp go below the set temperature,
so that the gas furnaces are not constantly turning on and off
exactly at the set temperature.

That makes sense (from a wear and tear and noise standpoint).

I call that delayed on and off time the "hysteresis" (but you can
call it whatever it's really called).

Pulling off the cover, I see a mercury bulb inside, which is at the
end of a curved metal strip (bi-metallic perhaps?), which explains
the *initial* on/off mechanism is from the expansion and contraction
of the coiled flat strip kicking the mercury switch on and off.

This can't be the actual on/off of the furnace, because hysteresis
decrees that the on time of the furnace itself is after the mercury
turns it on and so is the off time of the furnace being after the
mercury turns it off.

I can easily test this, simply by turning the thermostat to a
high or low temperature, where the actual on/off of the furnace
blower (and later, the heat) is something like a couple of
minutes delayed.

I get all that - but what I don't understand is *where* the
hysteresis is built in? Is it in the computer? Is there a dial
that sets the temperature range of the hysteresis? Is there
a potentiometer?

How do we *change* or *set* how much hysteresis there is?
Specifically, how do I get *more* hysteresis in my furnace?

 

[Tony Hwang]

Ralph Mowery wrote:

"Kirk Landaur" <kirk@example.com> wrote in message
news:n5mtr6$8v0$1@news.mixmin.net...
How does the hysteresis work on the Honeywell old-style bulb thermostat?

My house has two of those tan round things, with a dial that has
only two indicators.
1. The desired temperature on top, and......
2. The current temperature on bottom.

I understand that the heat overshoots on the current temperature
and that it lets the current temp go below the set temperature,
so that the gas furnaces are not constantly turning on and off
exactly at the set temperature.

That makes sense (from a wear and tear and noise standpoint).

I call that delayed on and off time the "hysteresis" (but you can
call it whatever it's really called).
and
Pulling off the cover, I see a mercury bulb inside, which is at the
end of a curved metal strip (bi-metallic perhaps?), which explains
the *initial* on/off mechanism is from the expansion and contraction
of the coiled flat strip kicking the mercury switch on and off.

This can't be the actual on/off of the furnace, because hysteresis
decrees that the on time of the furnace itself is after the mercury
turns it on and so is the off time of the furnace being after the
mercury turns it off.

I can easily test this, simply by turning the thermostat to a
high or low temperature, where the actual on/off of the furnace
blower (and later, the heat) is something like a couple of
minutes delayed.

I get all that - but what I don't understand is *where* the
hysteresis is built in? Is it in the computer? Is there a dial
that sets the temperature range of the hysteresis? Is there
a potentiometer?

How do we *change* or *set* how much hysteresis there is?
Specifically, how do I get *more* hysteresis in my furnace?


Part of it is in the house its self. It takes a while for the air and walls
in the house to heat up. Then the thermostat cuts off, but the air handler
will blow for a while to cool off the frunace heat chamber. The furnace
should have a control for this near the heat chamber. Say the house over
shoots 2 degrees during all of this. Then it cools down and the furnace
starts back up.

That is why blower does not come on with flame on, does not go off with
flame off(this going off delay is usually adjustable at the control board)

 

[Ralph Mowery]

"Kirk Landaur" <kirk@example.com> wrote in message
news:n5mtr6$8v0$1@news.mixmin.net...

How does the hysteresis work on the Honeywell old-style bulb thermostat?

My house has two of those tan round things, with a dial that has
only two indicators.
1. The desired temperature on top, and......
2. The current temperature on bottom.

I understand that the heat overshoots on the current temperature
and that it lets the current temp go below the set temperature,
so that the gas furnaces are not constantly turning on and off
exactly at the set temperature.

That makes sense (from a wear and tear and noise standpoint).

I call that delayed on and off time the "hysteresis" (but you can
call it whatever it's really called).

Pulling off the cover, I see a mercury bulb inside, which is at the
end of a curved metal strip (bi-metallic perhaps?), which explains
the *initial* on/off mechanism is from the expansion and contraction
of the coiled flat strip kicking the mercury switch on and off.

This can't be the actual on/off of the furnace, because hysteresis
decrees that the on time of the furnace itself is after the mercury
turns it on and so is the off time of the furnace being after the
mercury turns it off.

I can easily test this, simply by turning the thermostat to a
high or low temperature, where the actual on/off of the furnace
blower (and later, the heat) is something like a couple of
minutes delayed.

I get all that - but what I don't understand is *where* the
hysteresis is built in? Is it in the computer? Is there a dial
that sets the temperature range of the hysteresis? Is there
a potentiometer?

How do we *change* or *set* how much hysteresis there is?
Specifically, how do I get *more* hysteresis in my furnace?

Part of it is in the house its self. It takes a while for the air and walls
in the house to heat up. Then the thermostat cuts off, but the air handler
will blow for a while to cool off the frunace heat chamber. The furnace
should have a control for this near the heat chamber. Say the house over
shoots 2 degrees during all of this. Then it cools down and the furnace
starts back up.

 

[Bob Engelhardt]

On 12/26/2015 3:55 PM, John Robertson wrote:

The hysteresis is set on the thermostat. I used to have one of those old
Honeywell units and as I recall it had a calibrated sub-dial that set
the hysteresis temperature range. Something like 0.5 degrees to around 3
degrees (F). You simply moved this sub-dial to the over/undershoot range
you desired.
...

That is the "anticipator", not hysteresis setting. It is actually a
heater that warms the thermostat in anticipation of the room heating up
and minimizing overshoot.

 

[Bob Engelhardt]

On 12/26/2015 3:58 PM, Dave M wrote:

It's the weight of the mercury that moves the bimetal coil spring such that
it takes a higher temperature to bend the bimetal coil spring so that the
mercury flows back to the other end of the bulb. When the mercury moves to
one end of the bulb, it makes the spring reposition itself so that it takes
a much higher (or lower, depending on heat or cool mode) for the spring to
return back to its original position. ...

Yes!

 

[Bob Engelhardt]

On 12/26/2015 4:14 PM, Kirk Landaur wrote:

On Sat, 26 Dec 2015 12:49:29 -0800, Uncle Monster wrote:

Inside you'll see a sliding resistor called an "Anticipator"
which provides a tiny amount of heat to fool the thermostat.
ヽ(•‿•)ノ

Is this the anticipator?
http://i63.tinypic.com/280nvqs.jpg

Yes

...
On the one hand, the LONGER on one end *implies* that's the end
where the slider makes the hysteresis longer; but, on the other
hand, the arrow points in the opposite direction, which implies
the hysteresis is longer in the other direction?
...

The anticipator has nothing to do with hysteresis. It's adjustable to
account for different currents that are drawn by different "heaters".
Once adjusted to the current that your heater draws, it will put heat
into the thermostat to anticipate the room heating up.

 

[Michael A. Terrell]

Tony Hwang wrote:

Dave M wrote:
It's the weight of the mercury that moves the bimetal coil spring such that
it takes a higher temperature to bend the bimetal coil spring so that the
mercury flows back to the other end of the bulb. When the mercury moves to
one end of the bulb, it makes the spring reposition itself so that it takes
a much higher (or lower, depending on heat or cool mode) for the spring to
return back to its original position.
Here's a link to a web page that describes the operation very well, saving
me a lot of typing.
http://inspectapedia.com/heat/Thermostat_Temperature_Response.php

Cheers,

Dave M

I think you are thinking backward. Spring controls the position of bulb
depending on temperature. Not the other way around.

They are interactive.

 

[Michael A. Terrell]

Kirk Landaur wrote:

How does the hysteresis work on the Honeywell old-style bulb thermostat?

My house has two of those tan round things, with a dial that has
only two indicators.
1. The desired temperature on top, and......
2. The current temperature on bottom.

I understand that the heat overshoots on the current temperature
and that it lets the current temp go below the set temperature,
so that the gas furnaces are not constantly turning on and off
exactly at the set temperature.

That makes sense (from a wear and tear and noise standpoint).

I call that delayed on and off time the "hysteresis" (but you can
call it whatever it's really called).

Pulling off the cover, I see a mercury bulb inside, which is at the
end of a curved metal strip (bi-metallic perhaps?), which explains
the *initial* on/off mechanism is from the expansion and contraction
of the coiled flat strip kicking the mercury switch on and off.

This can't be the actual on/off of the furnace, because hysteresis
decrees that the on time of the furnace itself is after the mercury
turns it on and so is the off time of the furnace being after the
mercury turns it off.

I can easily test this, simply by turning the thermostat to a
high or low temperature, where the actual on/off of the furnace
blower (and later, the heat) is something like a couple of
minutes delayed.

I get all that - but what I don't understand is *where* the
hysteresis is built in? Is it in the computer? Is there a dial
that sets the temperature range of the hysteresis? Is there
a potentiometer?

How do we *change* or *set* how much hysteresis there is?
Specifically, how do I get *more* hysteresis in my furnace?

Have you read the instructions for the thermostat?

<https://customer.honeywell.com/resources/techlit/TechLitDocuments/60-0000s/60-0830.pdf>

 

Bob Engelhardt wrote: "That is the "anticipator", not hysteresis setting. "

Yes! Digital programmables have replaced
the heat anticipator with a set of "firing length"
options: 1 for shorter firing time, 2 for normal,
and 3 for longer.

 

[Tony Hwang]

Kirk Landaur wrote:

On Sat, 26 Dec 2015 14:20:25 -0700, Tony Hwang wrote:

What are you trying to accomplish?

I'm simply trying to make the hysteresis of longer duration.

Then move the anticipator to higher number from what it is now.
When we were running 4 stores in the past, one store had that
old thermostat, I played with it during summer cooling, winter heating
months.
After all that time spent, I drew a conclusion original setting was best
optimized setting. Eventually I replaced it with digital 7 day
programmable thermostat which realized some savings on utility bill.