Honeywell Home T834L1004/U Cool Only Thermostat- Dual Scale Fahrenheit and Celsius

The T834L1004 is a non-programmable thermostat from Honeywell Home, cool-only.

A non-programmable thermostat holds one setpoint until someone changes it. That is the whole design, and it is the right design more often than the market admits: in a shop, a rental, a spare room or anywhere occupancy has no schedule, a programmable stat gets overridden permanently within a week and then behaves like this one with extra steps.

Cool-only covers the reverse case: a space with air conditioning and no heat, where a combination stat leaves a heat setting that should never be used.

The dial is marked in both Fahrenheit and Celsius.

Where it hangs decides what it reads. A thermostat measures the air touching it and nothing else, so an interior wall about five feet up, out of direct sun, away from supply registers and doorway drafts, and clear of the back of a wall carrying hot water or flue pipe. Most complaints that a stat is “off by three degrees” are placement, not calibration — the stat is reading the truth about a spot nobody lives in.

These are also the straightforward answer to the C-wire problem. A smart thermostat needs a common wire to power itself continuously, and in an older house that wire is often not in the bundle — which turns a thermostat swap into a wire pull. A non-programmable stat does not draw a continuous 24 V supply for itself, so the wires already on the wall are usually the wires it needs.

If the stat has an adjustable heat anticipator, set it to the current stamped on the primary control rather than leaving it where it arrived. Too low and the burner shuts off early and the room never reaches setpoint; too high and it overshoots and then coasts cold. It is the one adjustment on a stat like this that changes comfort, and the one most often skipped.

Confirm the system type before ordering — low voltage, line voltage and millivolt thermostats look similar and are not interchangeable.

• Brand: Honeywell Home
• Manufacturer Part #: T834L1004/U
• Type: Non-programmable thermostat
• Stages: Cool-only
• Scale: Fahrenheit and Celsius
• UPC: 085267271363
• Category: Thermostats