Wiring 2 Baseboard Heaters to One Thermostat

[Indio Bravo]

I have 2 baseboard heaters currently connected to a rotary thermostat. I am replacing the thermostat with a programmable digital thermostat which can be wired either as single pole (L1 only) or double pole (L1 and L2). There were 2 black wires from the load and 2 red wires from the line in the wiring diagram for the existing installation. I assumed the 2 black wires were L1 and L2 so I connected them to the matching L1 and L2 wires on the new thermostat, a Lux ELV4 model (The old rotary thermostat was a TPI TR202-1/TW242 model).

The installation worked, but I noticed that the room is always hot. The actual reading is 73 degrees no matter how low I set the thermostat. Apparently, only one heater is cycling or switching on and off while the other heater is on all the time. It seems to me that I should have wired it only as single pole (L1 only) and just left the second black wire disconnected. The instructions for the new thermostat say that only L1 is switched during normal operation.

But then, doesn't that mean that only 1 baseboard heater is connected? How do I connect the wires so that my single thermostat will control the 2 heaters?

Thanks foe any help.

IB

[Tony Hwang]

Think two black wires are L1 and two reds are L2. You connected only one heater thinking that way.

[John Grabowski]

*It is quite possible that one pair of black and red is the line and the other pair is the load. Look inside the box and see if there is a red and black for each cable. To wire it as a single pole you would need to splice two wires together. You should confirm which wires are your hots with a tester or lightbulb. Also double check the wiring diagram for the thermostat.

[RBM]

You need to identify the 240 volt feed wires in the box, and connect those two wires to the two "line" wires on the thermostat. Then identify the two "load" wires, which are the ones that go to the two heaters, and connect them to the two load wires of the stat. You may have two sets of load wires in the box, one for each heater, in which case just parallel them onto the load wires from the stat.

[Existential Angst]

I would add:

Make a test load from two light bulbs in two pigtails, connected in series, for the 240 V switching, to see whats what on the thermostat. These two bulbs in series will glow at normal brightness on 240 V, and much much dimmer on 120 V. Really very handy.

Also, baseboard heaters draw substantial power. It seems to me that the relays found on thermostats, circuit boards, etc, if mechanical, are built for toy trains, not 1,000-2,000 watt loads. If solid state relays are used, then mebbe they not so fragile. I believe SCR-solidstate relays never click, and mechanicals always have a "click".

But an external mechanical relay never hurts.for longevity of things like circuit boards, thermostats, etc, and alls you do is connect the coil of the relay to the thermo just as you would the baseboard heater. Then run your line and load wires to the relay contacts. You can also connect an external solid state relay in the same way.

[hrhofmann]

.

Make sure that the two light bulbs you use are the same wattage.

[Existential Angst]

Make sure that the two light bulbs you use are the same wattage. =================================================

Good point. And, they can be any wattage, and any base, altho pigtails are usually edison base. As long as they are both the same watts, and 120 V. And if there is any doubt, they should be checked on a known live circuit, just to make sure a filament didn't break.

[Michael B]

About 30 years ago, when I lived in the country with all rooms on baseboard heaters, I wanted to put them all on setback for when we were gone to work during the day. Found the prospect very expensive and kind of uncertain at that time. Maybe things have changed nowadays.

But I made a setback unit that cost about 12 dollars and my time. I used a single timer for the system, and a

7 1/2 watt night-light bulb alongside each heater thermostat. And I had a dimmer to the string, so that the bulbs were running slightly lower voltage, and they did indeed seem to last forever.

Adjusting the spacing of the bulbs for the bulbs was the tricky part, and I considered ceramic wirewound resistors later, but it was working so well I left it alone. And the dimmer could have been replaced with an appropriate resistor, but it gave some setback temperature range adjustment.

From what I heard a few years ago, the owners of that house are still us> I have 2 baseboard heaters currently connected to a rotary thermostat.

[Existential Angst]

But I made a setback unit that cost about 12 dollars and my time. I used a single timer for the system, and a

7 1/2 watt night-light bulb alongside each heater thermostat. And I had a dimmer to the string, so that the bulbs were running slightly lower voltage, and they did indeed seem to last forever.

Adjusting the spacing of the bulbs for the bulbs was the tricky part, and I considered ceramic wirewound resistors later, but it was working so well I left it alone. And the dimmer could have been replaced with an appropriate resistor, but it gave some setback temperature range adjustment.

From what I heard a few years ago, the owners of that house are still using the same setup. ===================================================

Inneresting. Can you elaborate a little more? What do the lites have to do with "setback"? What is "setback"? Purpose of dimmer? etc.

[hrhofmann]

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ide quoted text -

Setback refers to setting the thermostat temperature ower during unoccupied times, like when everyone is at work, and late at night to reduce the heat loss while everyhone is in bed with their electric blankets. He/she was putting the bilbs near the thermostats to fool the thermostats into thinking the temoerature was higher so tha the furnace did not run as much. Regular setback thermostats are now available in Home Depot, Lowes, etc for well under 20.00 USD so no one would do anything like he said anymore.

[Tony]

quoted text -

Reminds me about what I did at my old watering hole. It was hot and humid in the bar area so I moved a small lighted display to the other end of the cigarette machine... right under the locked thermostat. :-) I let a few people in on the secret, sometimes it got freezing in there so we moved the light to *adjust* the thermostat.

[Existential Angst]

Setback refers to setting the thermostat temperature ower during unoccupied times, like when everyone is at work, and late at night to reduce the heat loss while everyhone is in bed with their electric blankets. He/she was putting the bilbs near the thermostats to fool the thermostats into thinking the temoerature was higher so tha the furnace did not run as much. Regular setback thermostats are now available in Home Depot, Lowes, etc for well under 20.00 USD so no one would do anything like he said anymore. =======================================

Perty ingenious! I'da never figgered that out from his description, but now it makes sense! And apparently it works!