Thermostats with adjustable cycle rates are something any homeowner can install to lower power costs and help an HVAC system last longer.
What is an Adjustable Cycle Rate Differential Thermostat?
All thermostats have a set temperature that will turn on and off an HVAC system.
The temperature difference that a thermostat turns on and off an HVAC unit is called Differential.
For example, a thermostat with a +-1 degree differential that is set at 70 degrees will turn on an air conditioner on at 71 degrees and off at 69 degrees.
It is also sometimes referred to as the cycle rate since it is the cycle that a unit such as an air conditioner turns off and on.
When HVAC units are turned on and off constantly, it takes a toll on the equipment leading to parts wearing out and needing to be replaced.
A unit that cycles often can also lead to larger electric bills.
Why Does Constant Cycling Have Higher Electricity Cost?
When an air conditioner first starts, is when it has the biggest power draw occurs.
This is mainly due to the compressor, which needs a large draw of power to start running.
After a compressor has been running for a few minutes, the power draw drops.
This is the reason that short cycles can run up a power bill.
Short Cycling Wears on Equipment
When an HVAC unit first powers on also is the hardest time on parts.
A units that cycles frequently causes wear and tear on parts which leads to a shorter life span.
For example, an air conditioner at the start must pump refrigerant through a cooling system which takes more work than it does after it has been running.
How to Get an HVAC Unit to Have Longer Cycles
If your HVAC unit is short cycling, it can be caused by several things, including the outside temperature, an oversized unit, a home not well insulated, and more.
Using a differential thermostat that has an adjustable cycle rate is a quick and easy way to solve this problem.
Your current thermostat may be capable of changing the cycle rate, which can be seen in its manual.
Buying a Differential Thermostat
Most thermostats have a built in differential of +-1 degree, while others will have a +-3 degree differential.
For example, a thermostat with a +-1 degree differential that is set at 70 degrees will turn an air conditioner on at 71 degrees and off at 69 degrees.
With a +-3 degree differential it would turn on at 73 degrees and off at 67 degrees.
Most thermostats are rated for +-1 degree differential.
Thermostats that have “Adjustable Temperature Differential” or “Adjustable Cycles” in their product description will usually have a +-3 degree differential.
NOTE: Be sure to verify any thermostat options and features, as software and hardware can change with version updates.
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Adjustable Cycle Rate Differential Thermostats
- Ecobee Smart Thermostat
- Robertshaw RS5110
- Lux Products TX9600TS
Having multiple sensors is good for temperature balancing in many homes.
See here for more information on Ecobee Threshold Differential.
The Robertshaw RS5110 thermostat has a set-point differential feature that prevents an HVAC system from short cycling.
It can be set from 1 degree to as much as 3 degrees in half-degree steps. It also has a 5-minute minimum compressor off-time which is great when power is interrupted as not to damage the compressor.
The Lux Products TX9600TS thermostat is listed has having as adjustable temperature differential (swing).