Old thermostat has 2 wires. how to I wire my honeywell rth111/rth221? thanks, Rich

You need to contact Honeywell customer support on this.

Look here for the manual:
http://www.honeywellconsumerstore.com/store/images/pdf/rth111b-vertical-digital-non-programmable-thermostat-installation-manual.pdf

R & H

did you get this stat installed?

First things first. What type of system? Heat only, boiler or furnace? Central cooling.
Do NOT take wires off the old thermostat yet, or mark the color wire, to the terminal letter. Most times W,Y,G,R, terminals and maybe even a C terminal.

Your new thermostat should have the same letters. Sometimes they mix up color wire with terminal letters...... example (yellow wire to w terminal)
Also turn off power to equipment it is controlling. It is not high volts but you can short out the transformer. Hook uo wire color to same letter terminal on old stat, to new stat. Thats it.

If you just have two wires and it controls heat only put black wire on W, or W1 if there is no plain W

HONEYWELL WEBSITE:
Go to honeywell.com
Under red welcome sign
Bottom red highlighted box literature/image search
Type in thermostat model number
Click on arrow to right
Then click on the PDF files owners manual / installation instructions
If you can’t find what you want, the bottom left and bottom of web
Page, they have homeowners assistance and Home products to get the help you need.

The red does go to RC, but the yellow should go to the W terminal, in HVAC W=heat Y=Cool, so aslong as the same wire is on RC on the t-stat, and RC on the unit, and same wire to the W on the t-stat as to W on the unit it should work!

rh goes on red, this is what will provide power to the heat

rc is red if you want to power the ac unit