reducing temperature swings for hot water heat (also, what's anticipation exactly?)

Moved into a new house this summer, my first experience with hot water heat. Ran it for the first time today. Took nearly an hour to go up 3 deg. to the set point, but after the thermostat switched the heat off, temperature continued to go up another 4 deg.
Admittedly it is not so cold yet, 50F today, so that's one reason it is flabby. Still, the previous owners used Honeywell MagicStats (two for to jones with separate pumps but one furnace), and I'd like to upgrade to something that might give me more settings to control. I can't find a thermostat on the web where the description indicates that it might be good for precise control of a slow, 'massive' hydronic heating system.
I have read about controlling temperature using PID (proportional, integral, differential). But home thermostats for non-electrical-heat seem to be just on/off based on set point...or am I wrong? Some of them do have something called "anticipation". To me, anticipation means that the controller looks at HOW FAST the temperature is changing, and if it is going up at a good clip, stops heating early in anticipation of continued temperature rise (differential control). In HVAC usage, however, it seems to mean the same thing as cycles/hour. Why is cycles/hour called anticipation?
Many thanks,
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Chuckles wrote:

The "anticipators" I remember from the days of non-electronic thermostats were just a little very low resistance wirewound heating element inside the thermostat housing which was electrically connected in series with the thermostat contacts and the coil of the heating system's on-off relay.
The theory of operation was that while the thermostat was "calling for heat" that little heater warmed things up in the vicinity of the thermostat's temperature sensing element and faked the thermostat into killing the heater before the room temperature got to the thermostat's set point. That helped compensate for the overshoot of the heating system.
Some of those anticipators were adjustable by means of a sliding tap which adjusted how much of the little heater was actually in the circuit, to accomodate a variety of possible relays with diffent current draws. Those adjusters could also be used to tweak the anticipation function a bit.
Jeff
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Yes, those I understand. But here is an article from someone who works at Honeywell:
http://www.pmmag.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2379,101234,00.html
"If you remember back to the purpose of an anticipator, it's there to determine cycle rate. An electronic thermostat skips the anticipator and goes directly to cycle rate. It makes the job easier for us, too, because it figures the amp draw of the load and adjusts accordingly, rather than having us do it (not that we did it all that much anyway)."
This makes no sense to me, hence my original question.
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Adjusting your anticipator will help. The anticipator setting is determined by your heating equipment. (Digital meter required) If you have the old round t-stat, the anicipator simply changes the angle of the mercury switch to either come on sooner and shut off later or come on later and shut off sooner. With a hydronic system you will still get this swing during your shoulder seasons. You can control this to a larger degree by adding an outdoor reset control to your system. This adjusts the boiler water temp to meet demand based on outdoor temp. Whether you wish to spend the money to add this will depend on (outdoor reset will increase system efficiency... but...) the type of boiler you have, how old it is, and if you will live in the house long enough to justify the expense. Have fun!
TAB Dude
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Hot water heating systems are fairly difficult to control to a tight set point do to thermal lag and thermal inertia or wind-up. A good thermostat/controller will require some intelligence in that it can register when it started the system, when the temperature reached set point and how much overshoot there was. Then the controller needs to be able to calculate a new energize/de-energize time in relation to set point times for tighter control. This is called adaptive control among other things. This is actually true for any type of heating/cooling system to maintain +/- 1/2 deg. at set point time/temperature. Most thermostats that are not electronic have what's call heat anticipation (and some have it for cooling also) and it is just a resister that is located next to the bi-metal that heats up when a small amount of current passes through it (heat on). This heat given off by the resister affects the actual temperature inside the thermostat making it think its warmer than it actually is thereby shutting off the system early. The amount of current is usually adjustable with a little slide switch.
It is fairly tough to get PID (proportional, integral, derivative) when you don't have the proportional part. A typical home thermostat is a two position device, on or off. However, some of the newer home thermostats do have the ability to learn. I have a Honeywell t'stat that has this ability - it is about 8 years old and I'm sure the newer electronic t'stats are much better.
I did a lookup on Consumers reports and they recommend a LUX TX9000 among others, and they say it is compatible with HW heating. I don't know if it has all the features you are looking for but it's a good place to start.
Good luck,
ELAhrens

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Lux......Hummmmmmm...
I personally wouldn't own a Lux stat, they are junk in my opinion. They cause a lot of service calls.......and are just a problem waiting to happen.
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After following some very useful leads in this thread, and reading up on "outdoor reset", I turned the water temperature high limit down from 180 to 140 (the lowest possible). This helped very noticeably! It is not the same as an automatic reset, but the boiler is old and doesn't warrant a big investment now. As far as I can tell, 140F should be OK until the temperature hits the twenties (depends on the house, of course). I'll have to remember to turn the water temperature up when it gets colder than that, and when we get a new boiler I'll get a system similiar to the one you describe.
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You have solved your problem it seems. The outdoor reset is used quite often on hydronic systems due to their flywheel effect. With a good outdoor reset, simple stats can handle the job in each zone. You may want to check out the following supply of very reputable controllers if you are so inclined to upgrade some day.
Tekmar makes a simple single stage boiler control model: A256-1 or A256-2 http://www.tekmarcontrols.com/products.html
Regards
Kevin
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