what is the purpose of the heat anticipator on a Honeywell T87?

Ryan_5

what is the purpose of the heat anticipator on a Honeywell T87?

S Milne

It

anticipats the heat ... and shuts the heat off before it reach's the desired set point.

Scott

Rich W

H/A

When properly adjusted, it reduces temperature swing in the house to a degree-or-so. In effect it controls the cycle rate per hour of the equipment. Fewer cycles equals a larger temperature swing.

Ken D.

Heat ant.

It actually is a little heater that is built into the stat. (you can see it in the form of coil near the bi metal). It adds a little extra heat to the inside of the t-stat to prevent over shooting the room temp. Without it the redidual heat left in the heat exchanger after shut down would increase room temp. to above set point. You set it by matching the HA to the t-stat amperage draw. Hope this helps.

Barry_2

Heat Anticipator

Just to clarify the concept. If you are driving down the street and see a stop sign, you (hopefully) begin to brake before you reach the stop sign so, when you actually reach the stop sign, you are at a complete stop. In the event you wait until you reach the stop sign to apply your brake, you will wind up in the middle of the intersection. Think of the stop sign as the temperature setting on the thermostat. If the system shuts down when the space has reached the desired set point, the residual heat in the system will cause the space temperature to rise above the thermostat's set point.
The heat anticipator causes the system to shut down down before the space temperature is at the setpint so that residual heat in the system will bring the space up to the desired temperature.
The heat anticipator is a variable resistance that generates a small amount of heat resulting from the current flow through it. The more current flow, the more heat generated. This is why the heat anticipator should be set to the amperage draw of the heating control circuit.

John Cockerill

anticipate

means to expext, look forward to, forsee,to be ahead of. The anticipator is a heater within the thermostat which is operated by a resistance to the 24 vt current in the thermostat circuit. The designers of thermostats realized that the heat from across the room was hotter than the desired set point of the room. Looking forward they needed to turn the thermostat to the satisfied condition before the heat reached the thermostat. That was in the days when the temperature of the radiator could not be controled. Today moderation of boiler temperature and increased circulation of moderate temperature heating medium reduce the need for anticipators.

Ken D.

Gene

Good analogy.

Barry_2

Thanks Ken

Twelve years in front of the classroom affords one the opportunity to come up with creative ways to get concepts across. Thanks!

Fred Harwood

Anticipation

The bimetalic actuator in the thermostat requires a bit of energy to expand and cancel the call for heat. It can get that energy from the heating of the space, but the amount of heating required often means temperature overshot. By adding a bit of energy on each call from a small, adjustable heater at the bimetalic actuator, the temperature overshoot can be reduced, without affecting the call set point. On one- and two-pipe steam systems, often the best anticipator setting approximates three to four complete cycles (add the on and off portions of the cycle together) an hour. That simple anticipator works wonders for steam systems.

jim sokolovic

It's like this, officer...

I really wanted to stop at that sign back there, but my anticipator setting was a little off - so, just rip up that silly ticket, and I'll get it set right for next time!

jim_49

Dah , you set the heat anticapator to the amperage coming in from the relay that the t-stat is wired to.Not the stop or yield signs. Without the heat ant. the circuit is not completed through the t-stat. Lets keep it a little simple for some of us out there.Stop making things so complicated with these rediculios responses..

Eugene Silberstein 3

Rediculous?

Jim,
I'm really sorry that you feel the stop sign analogy was rediculous. Your response, unfortunately, reveals a great deal of information about you. The purpose of this site is to afford those who visit us the opportunity to learn from those of us in the industry. In a similar manner, students pay a great deal of money to attend institutions to learn. An integral part of the edcuation process is to associate complicated or confusing concepts with those that we can all relate to. With over 14 years in the classroom teaching HVAC/R (successfully I might add), these "rediculous" responses, as you so refer to them, are the links that bring the "confusing and complicated" into the world of "newly acquired knowledge". If you are not a fan of "real life" analogies, I would definitely recommend that you NOT purchase any my books, as they are full of them. By the way Jim, but was it you that I saw the other day in the middle of the intersection because you failed to see the stop sign?

John (Cockerill), if you're out there.... Do you have anything to add?

Tim Haggerty_2

setting anticipator

I carry a wire coil looped 10 times with alligator clips on ends. Remove T-stat wires and attach in series. Then move the decmil point one space to the left. There won't be any doubt about the amperage going to the T-stat. set HA to that number.

jim_49

Heres to you Eugene, I didn't like your stop sign response. You must be an engineer. I'm a trouble shooter. 20 + yrs.When I wire a unit whatever it may be, I try to make it very simple for the next guy to figure out why and what I did. You must be the kind of person who would put 3 relays to do 1 purpose where I would use only 1, to do the same thing.Go figure...

S Milne

figure this Jim

I thought the analogy was spot on. It made perfect sense.

We're all here to learn and some know more than others.

I don't see what the big deal is.

Scott

Nick W

settings

What are the best settings for baseboard heat, two stage forced air that has to run in low heat 15 minutes to go into high stage? With a T87. At one time someone had posted multiples X amp draw for different equiptment.

John Cockerill

ant circuit

Jim what you say is in the instructions. What the guy who wrote the instruction did not know was the potential comfort adjustment capability of the anticipator. Folks would be more confortable if someone had written the instruction with heating knowledge. As a result there are 80 million T87's in the field which are not adjusted to the building and heating system. It is discussions like these that allow folks to become aware of the designed purpose of the T87 anticipator. They just didn't get into the instruction by the elecrical engineer who wrote them. Obviously the fellow that proof read his work didn't know what he was doing either. It would seem that no one has cared enough to go back and review the instructions. To use another analogy which you seem to get excited about, it's like the fellow who bought an umbrella and took it into church opened. He read the instructions. He simply didn't know how to use it.

John Cockerill Exquisite Heat
www.Exqheat.com

bill_51

baseboard heat.....set the heat anticipator to the amp draw of the boiler control ckt that is being operated by the thermostat.

two stage heating on a time delay.... the best setting on a single stage thermostat anticipator would be the amp draw of the unit running on second stage........remember, if you set that little resistor too low then the amp draw going through it will heat it up too much and make the stat think that the room actually increased in temperature by 5 or 6 degrees in a matter of seconds or burn it out all together making the t-stat useless for heat. the best thing to do for two stage would be to get a two stage t-stat imo

GaryDidier

Stop sign

Eugene,
I liked your analagy/explanation of the heat anticipator so much I'm going to use it when explaining this to my customers. Thanx, Gary from Granville

Barry_2

Thanks Scott

Thanks Scott.

Speaking of engineers, Dan has a great story about a pickle in a bottle and an engineer. To make along story short, there is a pickle in a bottle, but the neck of the bottle is much smaller than the diameter of the pickle. Dan's theory is that if you cannot figure out how the pickle got in the bottle, you are an engineer.

Jim... Sorry... not an engineer myself... just a guy like you... 24 years in the field and umteen years in front of the classroom. I also want to apologize if my response insulted you in any way. We are all on this site to learn and share information, not bicker about the petty things... Remember: Never sweat the petty things and never pet the sweaty things... Regards