anyone help with t-stat wiring?

tony hill

i am replacing a white-rodgers 1e30-910. old model with mercury. it only has 2 usable terminals. there was a white wire hooked to the R5 and a black to a 4.

i purchased a honeywell 7400 to replace it and the instructions seem to indicate the 4 should go to the R on the honeywell but i am unsure about the R5. i would think that would go to RC, but i don't know. Any insight? honeywell isn't available until tomorrow........

Anthony Menafro

Heating or cooling

Is this just for heating or heating and cooling? If for heating, you only hook two wires and they normally go to R and W terminals.

Anthony

tony hill

heat only

sorry--heat only, one pipe steam oil furnace.

i just looked at the furnace and it appears the R and the G are connected???? only thing is the color of the wires are red and white, so they must change wires somewhere in the house.

on edit: just traced it and white wire goes to G terminal on furnace (also honeywell control on my furnace) and black in my tstat turns to red wire which goes to R. so i assume i hook R to R and G to G????

Glenn Harrison_2

On a standard modern day thermostat...

R is the power coming into the thermostat, and the W terminal is your heating terminal. The reason you have a G in the boileris the boiler manufacturer cheated a little by using a fan relay center, which would nomally be used on a forced air furnace with central A/C, to enegize ther boiler. By making R and G you are energizing the relay next to the transformer. In a forced air furnace G would go to G, and would be controlled by the fan switch on the T-stat. So in your case, R goes to R, and G in the boiler goes to W on the thermostat.

tony hill

thanks!

i have a pretty standard boiler--burnham model. wierd that they would "cut corners", they seemed to have a reliable reputation!

but anyway, thanks for the knowledge!