Learning to use classic vintage Honeywell Chronotherm thermostat
Comments
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A digital thermostat could have an anticipator built into it. It's just a very small, adjustable electric heater. You would adjust it in much the same way you do an older anticipator — they are a set it once and forget it setting, unless you change the device to which it is connected, such as a boiler controller or zone valve.
It's not that it couldn't, it's that they don't. I suspect that a good part of the reasoning behind that is that digital thermostats are intended to be "plug and play" with a simple programming menu to set them to the system type. Unfortunately anticipators aren't like that; they take a certain amount of patience and trial and error to get them right — and that is simply not going to happen in today's world.
And this is not to say that with some additional computing power in the thermostat that you couldn't program in anticipator like behaviour, and some "smarter" thermostats do do that, if they incorporate a "learning" mode. In most cases, though, the "learning" mode is related to how long the system takes to recover from a setback than it has anything to do with controlling overshoot.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
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My Chronotherm seems pretty accurate.
My indoor temp is 67.
I slid the red/blue sliders to 68 and boiler turned on.
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My next step is to learn how the setback timer works.
First I need to figure out how to open it and replace the AAA batteries.
I'd also like to calibrate the temperature gauge display
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Vintage Chronotherm Thermostat
Tested the heat today.
Room was 61.
Slid the temp up to 62.
Boiler kicked on.
Slid the temp to desired 64.
At 35 mins., the room was 64.
Boiler ran until 45 mins, when room was 65.
Room eventually reached 67.
Is this correct behavior? I assumed the anticipator logic would have cut the boiler sooner.
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The anticipator logic should have. Check its setting — it may have been set for a previous burner or system.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
All this discussion about a simple thing as a thermostat is like "How many Angels can dance on a head of a pin." discussion of old. I bet most customers don't give a hoot let alone how accurate their thermostats are and set their thermostat for what is comfortable. The set it and forget it, laity.
"When does thermostat trigger boiler to make heat?" Simple, when the contacts close.
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I give a hoot. I don't want to run defective equipment that can be replaced for $20 to $100.
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That old Chronotherm isn't defective — it's just the anticipator isn't set correctly.
Tell you what. If you don't want it, and want to replace it with the latest and greatest whizzy widget, pull it off the wall, package it carefully, and send me a PM and I'll give you a mailing address. I'd love to have it. I'd much rather have that than some plastic from Silicon Valley which may — or may not — still work in five years!
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
As a General Knowledge point, how does one set the anticipator, correctly. hmmm
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Theoretically (yeah, right) the anticipator has a small arrow shaped contact riding on a resistor. It points to a scale and, in theory, you simply (yeah, right again) find the current draw through the thermostat when it's calling for heat and set the arrow there and all will be well.
Usually doesn't work that way… and it's as much a matter of trial and error as anything else.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England1 -
I will keep it in service.
I will try to read the manual and learn how to adjust anticipator.
First I have to figure out how to open it up !! No idea!
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I understand steam (and heating in general) is not an exact science. But, for fun, I've been observing the tolerance/accuracy of my Chronotherm thermostat (which is working great)
There seems to be a +/- 2 degree tolerance in both directions.
TL/DR: Thermostat set for 65, boiler turns off at 67, and turns back on at 63.
Is this normal operation?Does overshoot need to be adjusted?
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Thermostat at 65 is fine by me. Longjohns and 2x layers all winter.
Then 65 goes to 68-69, which is fine.
But, then does not turn back on until 63, which is a bit cold for a few hours11/30
10:30am
31F outside
LR is 61F
Set thermostat to 650:00 - LR temp is 61
10:00 - LR temp is 61
20:00 - LR temp is 62
30:00 - LR temp is 63
40:00 - LR temp is 65
48:00 - LR temp is 67 (Boiler shuts off)
50:00 - LR temp is 67
1:00:00 - LR temp is 68
1:06:00 - LR temp is 69
1:35:00 - LR temp is 68
2:10:00 - LR temp is 67
2:30:00 - LR temp is 67
3:30:00 - LR temp is 65
4:30:00 - LR temp is 65
5:00:00 - LR temp is 64 (36F outside)
6:30:00 - LR temp is 63 (33F outside) Boiler starts back up0 -
Hello CoachBoilermaker,
If the heat anticipator is set correctly it should minimize the dead-band or differential and overshoot. However if you are running on the setback control function the heat anticipator may be minimally or non-functional due to the position of the resistor (Red arrow) in the thermostat. Set back is for energy savings not comfort, the heat anticipator helps with comfort.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
I have no idea how to open the Chronotherm. I don't want to force it and break it. I only know how to flip up the outer faceplate. Any trick to it ?
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I am less concerned about the overshoot from 65 to 68-69. I want to adjust the fact that boiler does not turn on until temps drop to 63. What is this called? Can I adjust it to 1 degree? I have both red/blue sliders at 65. It would be good if boiler fired up again at 64, and not 63, for example
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National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
The Chronotherm is a mercury bulb thermostat. All mercury bulb thermostats are VERY sensitive to being off level. In your situation, I make the same recommendation I have to others: see if (in this case) you can tilt the thermostat a little to the left (counterclockwise — down on the left) and see if that causes it to turn on closer to the temperature number you want (if that makes it worse, tip it the other way…).
The overshoot is controlled by the anticipator. As the instructions above say, try moving the anticipator index one notch and see if that makes a difference — but be patient and observe it for several cycles. If it makes it worse, go the other way. Getting it right may take quite some time — a week or so — which is one reason why these thermostats aren't popular any more.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
I'll try tilting and see if there is play.
I want to see the anticipator setting
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@109A_5 I don't know how to lift the cover. Does it hinge? Does it slide up? or off/away? I don't want to break it, esp. now that it's freezing temps. I need to see a video, but could not find one
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I don't know, is an out of calibration thermometer a defective thermometer? Is a car that reads 100 miles on the odometer after actually traveling 101 miles on oversized tires defective? Is a human body that over thinks everything when others don't overthink stuff like this defective? Only the Coach can answer that question!
As far as removing the plastic cover from the Chronotherm thermostat is concerned. you just hold the sides of the cover and pull gently. Nothing to it. it should take about as much force as it would to lift the lock button on a 1964 Chevrolet car door
No hinge… just tension clips.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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the heck am I doing?
how do I delete my junk comments?
known to beat dead horses0 -
there is no delete, only edit
NJ Steam Homeowner.
Free NJ and remote steam advice: https://heatinghelp.com/find-a-contractor/detail/new-jersey-steam-help/
See my sight glass boiler videos: https://bit.ly/3sZW1el0 -
@EdTheHeaterMan Thanks. I got the cover off. Next, I need to adjust the anticipator b/c setting to 65F overshoots to 68-69F. Can you explain (as you excellently do) what I need to press, and in what direction?
Note the cover has two hook on the top edge. So you pull the bottom edge away from the base and then slide cover upwards. To reinstall, hook the top edge then press bottom edge
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Hello neilc,
Edit junk with something of value, don't click on "Post Comment" so fast.
" watch a cycle on your gage and see if you're cutting out at 2, or higher? those scales aren't their most accurate,
is your pigtail clear? "
As far as I know the Coach does not have a functional gauge, and no pigtail, but there is a water trap on the Pressuretoll type device.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
Sorry, I'm ot @EdTheHeaterMan , but perhaps I can help?
In answer to what to adjust on your thermostat. In the lower left corner of that first picture there is a sort of wiggly black arrow which points to about .42 on a scale. That is the anticipator which you are looking for. Try adjusting it to .30 for a first try. If that improves things, but not enough, adjust it lower. If it improves things, but too much, pick it up a bit. If it makes things worse, adjust it the other way to, perhaps .46 or so.
But don't rush it. Make an adjustment and then pay attention to it for a few cycles. And put the cover back on after you adjust it — the adjustment with the cover off and the adjustment with the cover on will be different.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
Thanks jamie!
GPT suggests I increase the amps to get the boiler to turn off sooner? I bumped it from .42 to .44.
Recall, the issue is that if I set the thermostat to 65, the boiler runs until 66, rads heat to 68, and then the boiler does not start again until it drops to 63
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Did .42 to .44 make the overshoot better? Or worse? If it made it better, but not good enough, go further. If it made it worse, you went the wrong way…
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
I believe the Red arrow pointing to the Triangle or Index Arrow recessed in the plastic is the indicator of which temperature adjustment lever (Blue or Red) is presently active. Also it appears there is a button or leaver (Orange arrow) to manually change to the other temperature control, Blue or Red (see the instruction manual).
Even though I now see there is actually two heat anticipator resistors, looking at the mechanical layout the bi-metal springs and the placement to the mercury switches the dead-band, differential or hysteresis may differ between Blue (energy savings mode) and Red (comfort mode).
It appears you are presently in the Blue temperature control mode, I would try the Red temperature control mode, the differential may be narrower by design.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System1 -
Increasing the resistance of the heat anticipator resistor, the lower numbers on the scale should make the boiler cut off sooner, more added heat inside the thermostat housing. The more resistance in the circuit (inside the thermostat housing) the more heat is generated in there.
The scale represents the nominal current (a starting point) through the thermostat circuit not the resistance of the variable resistor.
Actually the scale is to make the heat output of the anticipator resistor the same with various systems that have different system currents. The other advantage of the design is you also can also use it as a fine tune method. The higher the number on the scale (lower added heat) the longer the system will run.
BTW for it all to function correctly you probably need the cover re-installed.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
Try .35 first and be sure to operate the system with the thermostat cover in place. Wait 24 hours before your next adjustment. Also @109A_5 has a good point about the red and the blue adjustment. Try to snap to the Red adjustment, to see if that has a smaller differential. I never knew that was a thing, but it might be!
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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The battery is dead.
The clock is dead.
There are no pins in the clock.
I currently keep both blue and red slider together to set the temperature.
No idea yet how the setback stuff works
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I see. I did it backwards. In this video, it says "longer cycle" goes with higher number. So, for shorter cycle, I need lower number? I changed it from .42 to now at .35 Thanks
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A while back I mentioned that the clock motor generates some heat inside that thermostat and that thermostat is clibrated to account for that additional heat. When you say "The battery is dead…. The clock is dead." that tells me two things.
- the motor is not operating so the heat generated by that motor is not there. so the thermostat is by design out of calibration.
- You didn't read or remember that I already told you this fact.
I said this back in October on this discussion.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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It's the same, just looks different 1.2 longest run time (least added resistor heat ), .15 shortest runtime (most added resistor heat). Don't confuse the indexing pointer with the electrical wiper of the variable resistor (180 degree difference).
And yes I do understand the present state of the thermostat.
" The battery is dead.
The clock is dead.
There are no pins in the clock.
I currently keep both blue and red slider together to set the temperature. "
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
" I currently keep both blue and red slider together to set the temperature. "
Yes but even so there may be a functional difference.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
I believe the mechanical hysteresis is different between the Red and Blue slider mode functions (even if they are set at the same set point). The Mercury switch is above the pivot point of the bi-metal spring on one and below on the other, pendulum versus tipping mechanics. I would think running the system with the Red slider active would provide better comfort. And the heat anticipator should be fine tuned in the Red mode.
The clock, when set up and functional just switches between what is basically to different thermostats in one housing.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
Ed, thanks for the repost. I installed 2 fresh AAA batteries and set the clock.
Tested it out. Seems pretty close.
34F outside
LR is 61F
Set thermostat to 640:00 - LR temp is 61
10:00 - LR temp is 61
20:00 - LR temp is 62
30:00 - LR temp is 63
35:00 - LR temp is 64
40:00 - LR temp is 65 (Boiler shuts off)
50:00 - LR temp is 67Next task is below.
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I think I want to learn to use the blue/red override switch to have manual setback without moving the sliders every day. Pressing the button toggles the pie wheel between blue and red wedge.
Does the following seem correct? Set BLUE=60 and set RED=65. When I go to bed, push manual program advance button #11 to show BLUE. Leave it all day when away at work. Get home 5pm, push manual program advance button #11 to show RED. Is that the right idea?
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Sure, if that schedule works for you. It sounds like you got the clock working, you could insert the pins and automate the process so you don't forget (I forget). Also many claim with steam heat using the setback does not save much. I only set back when I will be away for about 8 hours or more, this place heats up fairly quickly.
National - U.S. Gas Boiler 45+ Years Old
Steam 300 SQ. FT. - EDR 347
One Pipe System0 -
The toggle button works as described. Last night, I set BLUE=58, and RED=64. When I get home after work today, I will toggle button to red, to have 64F from 5pm-10pm.
I'm sure keeping it down at 58-60 for 10pm to 5pm (19 hours setback) has to save some oil. Those house can go from 60 to 68 in 40 mins. of boiler operation. Setback probably saves 2-3 boiler cycles in that 19 hours. Takes 40 mins. even just to raise it 1-2 degrees, with cold main, and overshoot.
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