Ask Experts Questions for FREE Help !
    kw8n's Avatar
    kw8n Posts: 1, Reputation: 1
    New Member

    Dec 12, 2009, 04:46 PM
    Mears m21
    I have M21 SP thermostats through the house here (built in 1978). Single pole switch.
    Of course the two heavy leads (Blk and Red) are for the source and the load for one side of the 220 V circuit.
    There is also a lighter gauge white wire. Where should that be connected in this configuration? Right now it is on the other side (the unswitched side) of the 220 V line.
    Or is this some sort of "ground" and really should be connected to something neutral (such as the earth ground or at least the neutral)?
    hvac1000's Avatar
    hvac1000 Posts: 14,540, Reputation: 435
    Heating & Air Conditioning Expert

    Dec 12, 2009, 05:23 PM

    You might also have to search Google for a wiring diagram for that thermostat or post a picture of the one you have.
    headpin8's Avatar
    headpin8 Posts: 1, Reputation: 1
    New Member

    Feb 5, 2015, 09:49 PM
    I also need help wiring a Mears M21 SP thermostat.

    ma0641's Avatar
    ma0641 Posts: 15,681, Reputation: 1012
    Uber Member

    Feb 6, 2015, 07:30 PM
    See the post above your's

Not your question? Ask your question View similar questions


Question Tools Search this Question
Search this Question:

Advanced Search

Add your answer here.

Check out some similar questions!

Mears m600s [ 0 Answers ]

I have a Mears M400s 2 circuit thermostat that I want to replace. There are two 8 ft electric baseboard heaters on one circuit, and one baseboard on another, one thermostat. I can't find anyone who sells a two circuit thermostat. I found a Mears webpage, that shows the mears M600s 2 circuit, but...

Mears Thermostat [ 0 Answers ]

I have a Mears M611WT single line thermostat with thermometer. The old thermostat had a black and white wire and a copper neutral coming from the electrical box in the wall which was connected to a single pole 120/240 20 amp thermostat. The new Mears thermostat has a black and red wire and a...

Mears thermostat [ 1 Answers ]

I have mears 240 volt double pole thermostats in my house for my celling heat.They have been in for 23 years. They work great.except they have become very hard to turn the dial.Any

Mears thermostat [ 3 Answers ]

I have a late 60's home with electric coil heating in my ceilings. Each room has their own thermostat, my master b. room came on unexpectingly last week. What kind of thermostat will I need to get? It is heat only. I will tell you I am ignorant to any kind of electric problems. I just don't know...

Mears thermostat [ 1 Answers ]

We have mears thermostats controlling ceiling heat - of the 11 in the house some work marginally- the mears number on the thermostats is M22-DP - 22amp/double pole - Is there a programmable replacement for the mears antiques? If so a purchase site? Thanks

View more questions Search