I am trying to replace an acient honeywell thermostat w a new honeywell HTR221. The old thermostat has a black wire going to a TR terminal a red wire going to a TR terminal a black wire to a b terminal and a white wire to a W terminal.

The terminals on the new thermostat are Y, G, Rh, Rc, and W.


Where do the old wires hook onto the new thermostat?

This is a gas fired furnace/boiler manufactured by Weil-Mclane

Forget the color code. Back track the wires you have to the components they operate. In your install instructions for your new t-stat it will tell you where to place them once you know exactly what they do. All else is guess work.

BTW the number you supplied for your new stat does not compute!

The number you posted is for a Modutrol IV Motor. LOOK AGAIN for the correct number.