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BT

wrote:

I have line volt thermostats for each of the baseboard heaters in my
condo. The thermostats are old analog and ugly. I want to replace
them with electronic thermostats. I pulled one of the old thermostats
off the wall to check the wiring. A single pole should have 2 wires,
while a double pole has four. My thermostats have 3 wires plus a
ground. One red, one black and one white. On the electrical panel,
there are 2 breakers for the heat, so I'm assuming it's 240 volts to
the heaters. I've looked for hours on the web, and I can't find an
example wiring diagram that matches what I have. Any ideas or
suggestions? The mini wiring diagram on the old thermostat shows it to
be a single pole with one wire to line and one to load. No mention of
the third wire at all, making it rather useless

You mentioned that there are two breakers for the heat, I assume that you
mean there is one double pole breaker, and the poles are tied together so
that they both shut off together. One pole of the breaker is connected to
one bus of the breaker box, the other pole is connected to the other bus.

Typical wiring for 240 volt circuit would be:
Black = HOT (first bus)
Red = HOT (second bus) (other bus or leg from the BLACK)
White = Neutral

There are 120 volts between Black and White
There are 120 volts between Red and White
There are 240 volts between Black and Red.

For strict 240 volt applications, the neutral is not needed. Not sure why
your thermostat would need a neutral, unless it uses 120 volts for some
reason. Perhaps you can find out the thermostat model number and work back
from there. As somebody else suggested, it is possible that it uses 120
volts for a heat anticipator. If you know how to use a volt meter SAFELY,
perhaps you can try that as well to verify.