A thermostat with a wide temperature differential is causing a furnace to short cycle excessively. What adjustment would most directly correct this issue on a mechanical thermostat?
- AIncreasing the thermostat's mounting height on the wall
- BSwitching from a heat-only thermostat to a heat/cool thermostat
- CNarrowing the differential or adjusting the anticipator setting closer to the actual current draw of the gas valve circuit
- DIncreasing the heat anticipator setting above the actual amperage draw
Show answer & explanationAnswer & explanation
Correct answer: C. Narrowing the differential or adjusting the anticipator setting closer to the actual current draw of the gas valve circuit
Short cycling from a mechanical thermostat is often corrected by adjusting the heat anticipator to match the actual current draw of the gas valve circuit, which shortens the heat-off delay and evens out cycling, or by physically narrowing the temperature differential. Increasing anticipator setting above actual draw causes the opposite problem (long cycles/undershoot), and mounting height or thermostat type change don't address cycling behavior.
Why the other options are wrong
- A. Mounting height affects sensing location, not cycling behavior directly.
- B. Changing thermostat type doesn't fix a miscalibrated anticipator or differential.
- D. Setting anticipator too high causes long cycles and temperature overshoot, not shorter cycles.
Thermostat Differential & Anticipator
The differential is the temperature swing between on/off points; the heat anticipator adjusts cycle timing by simulating current draw to prevent overshoot or short cycling.
- Anticipator should match actual circuit amperage
- Too low anticipator setting causes short cycling
- Too high anticipator setting causes long cycling
- Narrower differential means tighter temperature control but more cycles
Memory trick: Match the anticipator to the amp draw, or cycling goes haywire.