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How & Why to Adjust the Heat Anticipator on a Room Thermostat
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• How & Why to Adjust the Heat Anticipator on a Room Thermostat
• How to Use a Mini Ammeter to Check Heat Anticipators and Thermostats for Proper Adjustment
• How Do I Install & Wire Up a Room Thermostat like the Honeywell Round Wall Thermostat?

This article explains what a heat anticipator is on a wall thermostat, where to find it, what it looks like, why we adjust the heat anticipator, how we do so. This article continues discussion of the basics of heating or cooling system thermostats, their use, setting, and adjustment. Here we provide A Guide to Finding, Using, and Adjusting Thermostats for Heating & Air Conditioning Furnaces & Boilers, Heat Pumps or Electric Furnaces or Boilers.

This website answers most questions about central heating system troubleshooting, inspection, diagnosis, and repairs. We describe how to inspect residential heating systems to inform home owners, buyers, and home inspectors of common heating system defects.

The articles at this website describe the basic components of a home heating system, how to find the rated heating capacity of an heating system by examining various data tags and components, how to recognize common heating system operating or safety defects, and how to save money on home heating costs. We include product safety recall and other heating system hazards.

Also see GAS PIPING, VALVES, CONTROLS for more details on how to inspect and test LP and natural gas piping, controls, valves, and tanks. We continue to add to and update this text as new details are provided. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution. © Copyright 2008 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

How & Why to Adjust the Heat Anticipator on a Room Thermostat

Thermostats may also have a "heat anticipator" adjustment which is tuned to the particular heating system to avoid heater on-off oscillating too close to the thermostat's set point.

What is a thermostat heat anticipator? The purpose of a thermostat heat anticipator is to "de-sensitize" the thermostat so that when actual room temperature is hovering close to the set temperature on the thermostat, the thermostat switch won't keep switching the air conditioner or heating system on and off too often - which can damage the equipment.

In our photo you can see our pointer hovering over fine wires wound around a triangular piece of plastic (forming a variable resistor) and you can see at center of the photo a flat copper arm which can be moved to slide a contact to different positions along the wound variable resistor.

The triangular pointer at the top of the copper arm has an opening which helps read the exact position to which the heat anticipator has been set. Behind the pointer you can see a silver scale with different amp readings which are detailed in the table below.

The heat anticipator scale: If you click to enlarge this photo you can see the amperage level to which this heat anticipator had been set when we took this picture. It is below the lowest setting recommended by Honeywell.

A heat anticipator will not work accurately unless the following conditions are met:

• The heating or air conditioning system itself has been adjusted to match the electrical current of the valve or relay which the thermostat is controlling. This is a technical problem for your heating or air conditioning service technician, not something a homeowner can address.
  
  
• The thermostat is installed at a location where voltage and current (amps) fall on or within the limits of the adjustable heat anticipator
  
  
• The thermostat is not installed on a power pile system (don't ask).
  
  
• The heat anticipator on the thermostat is set to match the requirement & electrical characteristics of the particular heating or air conditioning control circuit that it is switching on and off.

Just below we give a table of heat anticipator settings recommended by Honeywell.

Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

THERMOSTATS
  Types of Building & Room Thermostats
  How Thermostats Work
  Detailed Guide to Room Thermostats
  How to Set the Thermostat
  How the Room Thermostat Responds to Temperature
  How Adjust the Heat Anticipator
  Mini Ammeter to Check Heat Anticipators
  Other Switches on a Room Thermostat
  How To Install & Wire Thermostats

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• The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update,
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• Installation Guide for Residential Hydronic Heating Systems
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