Honeywell TH1100DV1000 vs Honeywell RLV3120A1005 Thermostat: Which Heat-Only Unit Fits

The Honeywell TH1100DV1000 and the Honeywell RLV3120A1005 are both heat-only thermostats, but they are built for different wiring systems. The TH1100DV1000 is a 2-wire unit for conventional heating systems, while the RLV3120A1005 is a line-voltage unit for electric heat. The choice comes down to what is behind the wall, not which one looks better, so the first job is identifying the existing wiring and the heat source before ordering either.

Both are simple, non-programmable digital thermostats aimed at replacing an old dial or worn-out unit without rewiring a home. Neither offers scheduling or smart features, and that is the point: they are cheap, reliable controls for a single heating zone. The comparison below covers the wiring, the display and controls, the installation realities, and who each one is wrong for.

Honeywell TH1100DV1000 Pro-Digital 2-Wire Heat Only

Type: Digital heat-only thermostat
Wiring: 2-wire
System: Conventional heating
Programming: Non-programmable
Display: Digital
Brand: Honeywell

The TH1100DV1000 is a direct replacement for a basic two-wire heating control. It uses the two wires already running to the old thermostat to draw power and to switch the heat, which means no common wire and no new cable run in most cases. The digital display replaces the guessing game of a mechanical dial, and the unit reads room temperature while holding a setpoint.

This is the pick for gas furnaces, boilers, and other conventional systems where the thermostat is a simple on-off switch. The 2-wire design keeps installation close to a like-for-like swap, which suits older homes and anyone who wants the job done without calling an electrician. It is a heat-only control, so homes with central air need a different model.

Trade-off: The 2-wire design is convenient on the wall but limiting on features, and this unit cannot run cooling or a multi-stage system, so it only fits homes with a dedicated conventional heat circuit.

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Honeywell RLV3120A1005 Digital Non-Programmable Thermostat for Electric Heat Only

Type: Digital non-programmable thermostat
Wiring: Line-voltage
System: Electric heat only
Programming: Non-programmable
Display: Digital
Brand: Honeywell Home

The RLV3120A1005 is built for electric heat, which in practice means baseboard heaters, radiant panels, and similar line-voltage loads. It switches the higher-current circuit directly rather than sending a low-voltage signal to a furnace board, so it is not interchangeable with the TH1100DV1000. The digital display and buttons give precise setpoints compared with a bimetallic dial.

This is the unit for a room with an electric baseboard heater and a tired old dial on the wall. It handles one heating zone, keeps a steady temperature, and does so at the lowest price of the two. Buyers with a gas furnace or a heat pump should stop here and look at the other unit instead.

Trade-off: Line-voltage wiring carries real current, so installation demands confidence and a breaker that is actually off, and this thermostat has no scheduling, so every setback is manual.

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Side-by-Side Comparison

Feature	Honeywell TH1100DV1000	Honeywell RLV3120A1005
Type	Digital heat-only thermostat	Digital non-programmable thermostat
Wiring	2-wire	Line-voltage
System	Conventional heating	Electric heat only
Programming	Non-programmable	Non-programmable
Display	Digital	Digital
Brand	Honeywell	Honeywell Home
Best Use	Gas furnace or boiler zone	Baseboard or radiant electric heat

The table settles the main question in one row: wiring. The TH1100DV1000 expects two low-voltage wires from a conventional heating system, while the RLV3120A1005 sits on the line-voltage circuit that feeds electric heat. A buyer who gets this wrong will either be holding a thermostat that cannot be wired in or, worse, one that is unsafe for the circuit.

The second row that matters is the heat source. Conventional systems, meaning gas furnaces and boilers, pair with the TH1100DV1000. Electric baseboard and radiant heat pair with the RLV3120A1005. There is no crossover here; the two products are not competitors so much as two answers to different questions.

Beyond that, the units are close. Both are non-programmable, both have digital displays, and both come from Honeywell. The RLV3120A1005 is the cheaper of the two, but only for the buyer whose home actually has electric heat. Price is the tiebreaker only after the wiring question is answered.

Which Should You Buy?

Choose the Honeywell TH1100DV1000 if the home has a conventional heating system, the old thermostat has two low-voltage wires, and the goal is a simple like-for-like swap with a digital readout. It is the right call for gas furnaces, boilers, and single-zone conventional heat.

Choose the Honeywell RLV3120A1005 if the room has electric baseboard or radiant heat and the existing control is a line-voltage dial. It is the budget option of the pair and the correct one for electric heat, provided the buyer is comfortable working safely around line voltage or is hiring someone who is.

FAQ

1. Can the Honeywell TH1100DV1000 replace the RLV3120A1005?
   No. They are built for different circuits. The TH1100DV1000 uses 2-wire low-voltage connections, while the RLV3120A1005 is a line-voltage unit for electric heat.

2. Which thermostat is better for electric baseboard heat?
   The RLV3120A1005. It is designed specifically for electric heat, so it is the correct match for baseboard and radiant panels.

3. Does either thermostat support cooling?
   No. Both are heat-only models. A home with central air needs a different thermostat.

4. Are either of these programmable?
   No. Both are non-programmable, so temperature setbacks have to be done by hand.

5. Which one is cheaper?
   The RLV3120A1005 sits at the lower price point, but it only fits electric heat systems, so the lower price is not available to every buyer.

6. Can these thermostats work with a heat pump?
   No. Both are designed for their specific heat sources, and a heat pump requires a compatible thermostat built for it.

7. How hard is installation?
   The TH1100DV1000 is close to a direct swap on an existing 2-wire setup. The RLV3120A1005 involves line-voltage wiring, which calls for care and, for many buyers, a professional.

Bottom Line

The wiring decides this one, and the Honeywell TH1100DV1000 is the better all-around pick for the conventional gas or boiler systems most homes with a two-wire thermostat actually have. Buyers with electric baseboard heat should take the RLV3120A1005 instead and treat the lower price as a bonus rather than the reason. Either way, confirm the heat source and the wires at the wall before ordering.