Lennox iComfort S30 and E30 smart thermostats (smart hub + HD display): quick sheet

Covers: Lennox iComfort S30 (communicating, also controls conventional equipment) and Lennox E30 (conventional 24 V only). Both use a smart hub mounted near the indoor unit and a separate HD Display on the wall. Lennox S40 is a newer sibling; its settings were not confirmed here.

Single sourceBrands: Lennox3 components

Lennox's dealer-installed smart thermostats. The display on the wall only talks to the smart hub; the hub does the equipment wiring. On the S30 the hub can talk to Lennox communicating furnaces, air handlers and outdoor units over a 4-wire RS-BUS. The E30 cannot communicate with equipment at all, only 24 V conventional wiring. Most calls: magenta (display) or cyan (equipment) communication lights, alert codes that only the dealer menu can clear, and balance-point settings on heat pumps.

Safety first

Turn off power to the indoor unit before moving hub wiring.
Keep communication wiring away from line-voltage wiring and light ballasts.

How it works

Smart hub power is 24 VAC, about 1 A, 60 Hz. The hub feeds the HD Display with 12 VDC on + and -, and talks to it on the A and B communications terminals.

S30 hub terminals toward the equipment are R, i+, i-, C (communicating) plus ACC1 and ACC2 for ventilators or a fresh-air damper. Lennox recommends 18 AWG unshielded cable for power (R, C, 12+ and 12-) and 18-22 AWG shielded cable for the communication pairs, with the shield landed on C at one end only.

E30 hub has conventional terminals (W1, W2, W3, G, Y1, Y2, C, R, O, B and H) plus DS and outdoor-sensor terminals, and jumpers on the hub for unit type and number of heat stages.

The hub's system-status LED shows green for normal, red for a critical HVAC alert, amber for Wi-Fi trouble, magenta when the display is not connected and cyan when the indoor unit is not communicating.

On heat pumps with electric heat or dual fuel, high and low balance points appear once an outdoor temperature is available (field-installed outdoor sensor or a communicating heat pump, which has one built in). They are disabled by default.

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Official manufacturer documentation

Always confirm values against the tech sheet for the exact model.

Lennox residential literature (S30 / E30 installation and setup guides)

OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work. © 2026 OnCall Tech. Original content; not a reproduction of any manufacturer document.Generic part photos (not of this brand): White retro-style refrigerator beside a kitchen sink cabinet by Pavel Danilyuk, Pexels License

Diagnostic guides for this appliance

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5 steps ~15 mineasy

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R, Rh and Rc: when to keep the jumper and when a system has two transformers

Most forced-air systems have one 24 V transformer at the furnace or air handler, and R and Rc are tied together (a factory jumper or an internal link in the thermostat). Some homes, usually a boiler or older furnace for heat plus a separate air handler or add-on AC, have two transformers: one for heat on Rh/R and one for cooling on Rc. Joining two transformers through the thermostat can blow fuses or burn transformers. Decide which you have before landing wires, and pick a thermostat that supports separate Rh and Rc when there are two.

5 steps ~30 minmoderate

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ecobee3 lite retail (EB-STATE3LT-02) and contractor/Pro version (EB-STATE3LTP-02). Now listed as discontinued by several distributors but very common in the field. ecobee Premium/Enhanced have their own sheet.

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