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Steve Z · Dec 28, 2006, 12:44 PM

I just replaced a MEARS thermostat for my electric baseboard heat that would only operate in the full on or full off position. In other words "all or nothing".

I put in a new MEARS M 612 and wired it the same way the old thermostat was wired. This also agreed with the schematic that came with the new thermostat.

I'm having the same symptoms. All or nothing. Is it possible that I may have another defective thermostat?

I checked the lines at the baseboard unit and when the thermostat clicks at about 65 degrees nothing comes through to the heating unit. When I put it up to the maximum, I then have 240 watts at the baseboard unit.

labman · Dec 28, 2006, 01:24 PM

That is how most thermostats work, like a light switch. When the temperature falls below the set point, it turns it on like turning on a light. When it reaches the high temperature, it turn off like a light. Thus the temperature fluctuates over a small range.

There are controls for baseboard heater that do work like a dimmer switch. I once had an office with one. I hated it. If the weather changed over the weekend, I came in to a freezing office or a stiflingly hot one.

Steve Z · Dec 28, 2006, 02:06 PM

Originally Posted by labman

That is how most thermostats work, like a light switch. When the temperature falls below the set point, it turns it on like turning on a light. When it reaches the high temperature, it turn off like a light. Thus the temperature fluctuates over a small range.

There are controls for baseboard heater that do work like a dimmer switch. I once had an office with one. I hated it. If the weather changed over the weekend, I came in to a freezing office or a stiflingly hot one.

I understand how the thermostat works but on bth of those I have recently wotked with there is no thermostatic action. It's only full on without stop or completely off.

Does this sound like another faulty thermostat or am I missing something?

tkrussell · Dec 28, 2006, 03:01 PM

IS the stat you have a single pole or double pole, and what voltage are yuou trying to control? I cannot find Mears stats on the web.

Steve Z · Dec 28, 2006, 03:14 PM

It's a MEARS M 612 Double Pole 240 Volts.

labman · Dec 28, 2006, 05:21 PM

Originally Posted by Steve Z

I understand how the thermostat works but on bth of those I have recently wotked with there is no thermostatic action. It's only full on without stop or completely off.

Does this sound like another faulty thermostat or am I missing something?

As I tried to explain, if it heats at full capacity, and then shuts off completely, when it reaches the set temperature, that is how most thermostats work. That is why it doesn't do any good to turn the thermostat up if the heat is already on.

Steve Z · Dec 28, 2006, 06:50 PM

Once again,

I realize how a thermostat works. The problem with this one is that if the room temperature is about 60 degrees, for example, even though the thermostat actually clicks at 60 degrees; nothing happens until I put it all the way up to 75 degrees. At that point, it won't shut off. Automatically, no matter how warm the room gets.

I believe it's a defective thermostat. It's doing the same thing that the one did that I replaced. I'm just looking to see if it's something I did wrong before I take the thermostat back.

Thanks for your help.

labman · Dec 28, 2006, 07:02 PM

Before you give up on them, check to see if you have wired them up exactly like the diagram here, https://www.askmehelpdesk.com/electr...ers-50274.html

tkrussell · Dec 29, 2006, 03:45 AM

Sure sounds like the stat is defective. On a duoble pole stat, one pole closes as sos as it is truned from off to the lowest setting, the second pole closes a degree or two just above the room temperature.

So, when you first turn the stat on, you should hear a click, then as you raise the setting, say the room is 68 and you want 72, you should hear a click at 69, and the heat should then be on. Once the room gets to 72, the second pole should click again as it is opening.

Each 2 pole stat is marked with two wires as LINE and two wires as LOAD. Be sure you have the feed to LINE and the wiring going to the heater on LOAD, and you should have no problem.

If you have it wired correctly, then it must be defective.

mikb1957 · Dec 30, 2006, 05:55 PM

Originally Posted by Steve Z

I just replaced a MEARS thermostat for my electric baseboard heat that would only operate in the full on or full off position. In other words "all or nothing".

I put in a new MEARS M 612 and wired it the same way the old thermostat was wired. This also agreed with the schematic that came with the new thermostat.

I'm having the same symptoms. All or nothing. Is it possible that I may have another defective thermostat?

I checked the lines at the baseboard unit and when the thermostat clicks at about 65 degrees nothing comes through to the heating unit. When I put it up to the maximum, I then have 240 watts at the baseboard unit.

I had the same problem with a Mears M4 11. I swithced it with another identical thermostat from another room in the house and it worked fine. The other location where I put the bad stat had the same symptoms. I didn't buy a new one yet. If yours is wired right and it's a compatible unit, then it sounds like it's defective. Check it with a continuity tester and a hair dryer.

badgirl68 · Sep 10, 2011, 08:25 AM

We moved into a house with Mears heating and no one can tell us how it works. Can you please help me?

jerseytech82 · Oct 7, 2012, 01:38 PM

These stats do have 2 hex-head (allen key) screws that can adjust the temp on/off and swing (between temp) size 3/32 I've had to "calibrate" every single mears I've ever used... honeywell has a digital thermostat for electric baseboard $20-$25 a piece though and with 9 stats in my house, I replace them a few at a time... well worth the $$$ though as they have multiple heating levels no matter what the temp. say you set at 75 and its 60 in your room, the stat will demand full heat as it nears the set temp (75) it begins backing down the power/heat demand and baseboard begins to cool a bit while still heating the room, once room reaches set temp, the temp can be sustained with minimal energy consumption as the therm. Only needs low or med heat to sustain temp... definitely well worth the $$$!! I've saved a good bit of $$$ each year with these thermostats and they work with any electric baseboard system