Can one thermostat operate two line voltage baseboard heaters at once?

Old 12-22-04, 05:51 PM
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Can one thermostat operate two line voltage baseboard heaters at once?

Hi everyone,

As the subject line says, can a single thermostat operate two line voltage baseboard heaters at once?

The front living room of our house has a wood fireplace and two line voltage
baseboard heaters. The previous home owners apparently preferred the
fireplace, as the thermostat box was (i) behind a painting and (ii) the
thermostat itself was taken off. I'd like to have the option of using
either electric or wood.

Inside the box are 3 sets of wires: 1 black (capped), a 2nd black (also
capped), and three copper wires braided together (again, black casing), exposed and uncapped.

With my multitester I can complete a circuit between either black and the 3
braided wires, but not between the two blacks.

How should the connections be made to the thermostat? I'm intending on using a basic, non-programmable like the Honeywell 498A.

At the circuit breaker panel, all of the baseboards feed into double cartridge fuse holders, 2 x 20 amps each. Given that there are only 6 pairings of 20 amp fuses and 11 baseboards in total, more than one baseboard is being protected by each double cartridge. Any problems with that?

Thanks in advance for the help. As a first-time homeowner I want to be handy. But when it comes to the electrical system, I also want to be safe.
Old 12-22-04, 09:52 PM
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Yes, you can tie in two baseboard to one t-stat.. Check your wattage/amp rating and compair to the t-stat.

MAKE SURE you use line voltage t-stat. I looked for the honewell 498a, didn't see anything close to it. I would suggest the honeywell CT1750. It's an electronic t-stat, and has much better temp control than the bi-metal ones.

To wire it. Make sure you have a line coming to the wall from the main panel (220v) That then ties to the t-stat. from the t-stat wire ties to the baseboard.
Old 12-23-04, 08:03 AM
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Thanks Jay,

Okay, so 1 thermostat can run two heaters. Any thoughts on those wires in the box? 1 black (capped), a 2nd black (capped), and 3 exposed end wires braided together.

I can complete a circuit between either single black and the 3 braided, and the single blacks are capped.

Option #1: The single blacks are hot and coming from the main panel. But then, what the heck are the 3 braided? There are only 2 baseboards.

Option #2: The braided wires are hot and the two single blacks run to the baseboard loads. Okay, but then I'm really surprised the braided wires weren't protected by a cap.

Am I missing an Option #3?


p.s. Yes, the Honeywell T498A ( is a line voltage thermostat. The previous owner took it off the wall in order to mount a painting, so I'm going to test it out before buying a new thermostat (like the CT1750).

Thanks again!

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