Products

Smart thermostats

The thermostat is not an accessory. On a modulating system it is what decides how finely the equipment can run — and the wrong one cancels what you paid for.

The part chosen last, that decides everything

People spend weeks choosing a furnace or heat pump, then pick the thermostat in thirty seconds at the end of the contract. That is the reverse of its actual importance.

On single-stage equipment the thermostat really is just a switch. But on modulating equipment — an SLP99V furnace, an SL25XPV heat pump — the thermostat drives the modulation. Without a control that can communicate with the unit, it runs flat out or not at all, exactly like an entry-level model.

Put plainly: the wrong thermostat erases the difference you just paid for.

Compatibility before features

The connected features — mobile app, geofencing, usage reports — are nice. Compatibility is structural.

Lennox’s iComfort platform is built to communicate with the modulating equipment in the range. That is what lets a furnace step its flame in fine increments and a heat pump vary its capacity continuously.

This does not mean only one option is valid. It means the question is not “which thermostat do you like” but “which one gets full use out of the equipment I am installing”.

The heat pump setting worth knowing

One habit carried over from furnaces quietly runs up bills: setting the temperature back sharply overnight.

With a furnace, recovery is fast and cheap. With a heat pump, jumping the setpoint in the morning triggers the electric backup heat — the most expensive mode the system has. A moderate setback, or a gradual recovery managed by the thermostat, costs less than a big swing.

That is the kind of detail we explain at commissioning, rather than letting you discover it on the February bill.

At a glance

Compatibility: decisive — a non-communicating thermostat throttles modulating equipment
Remote control: mobile app on connected models
Zoning: possible with motorised dampers, assessed case by case
Power: common wire (C-wire) required on most models

The Lennox lines

Series Signature

iComfort

Lennox's control platform, built to communicate with the modulating equipment in the range. It is what lets an SLP99V furnace or an SL25XPV heat pump actually use their modulation.

Model line-ups change from year to year. We confirm what is available at the time of your quote.

Frequently asked questions

Can I put an off-the-shelf thermostat on my new system?

Technically, often yes — and that is exactly the problem. Modulating equipment talks to its thermostat to adjust output continuously. Wired to an ordinary thermostat it behaves like a single-stage unit: you paid for modulation and never see it. Check compatibility before you buy.

What is the common wire?

The "C" wire supplies continuous power to the thermostat. Older battery models did without it, but nearly every connected thermostat needs one. In an older house that wire is sometimes missing — it is solvable, but better known in advance.

Does it actually save money?

The savings come mostly from scheduling: setting back overnight and during working hours. A connected thermostat makes that easy and automatic. Be careful with a heat pump, though — deep setbacks force the backup heat on recovery, which costs more than you saved. We show you the right settings.

Do I need a thermostat on each floor?

That is a zoning question, not a thermostat question. If your upstairs overheats in summer, a second thermostat alone changes nothing; you need motorised dampers that can actually direct the air. It is doable, and it gets assessed on site.