TS86A T-Stat

al leone

I'm dealing with a millivolt steam sys. There are 3 terminals , R Y W, with two should the wires be on and does it make a differance as to the system operation?
As of now the wires are on R and Y .If I set the t-stat at 70 the bioler turn off a 68. Is the t-stat antisipating the room temp creeping up to 70 as the rads are still hot?

All the other t-stats I've put in like the T87-s 24v. have always been wired R and W.

Is this a steam thing?

Dale

No, it's a millivolt thing

The t86 is a millivolt stat that can be used with either the old 250MV generators or what passes for modern 750 powerpiles. R to Y has no heat anticipator and therefor drops very little ( 10 or less) of the millivoltage available. R to W is for the 750 millivolt powerpiles and it does have a heat anticipator and drops nearer 100 mv. which usually isn't too much for the 750mv powerpile. If you have at least 135mv at the gas valve coil when the system is running you should be fine. Maybe Timmie will comment he's the best I know on these.

al leone

If I leave R and Y the way it is on this t stat can it over fire the boiler?

Unknown

With a Powerpile System

using that thermostat you should wire to "R" and "W", that puts a fixed anticipator in the circuit which will give you a more accurate cycle. The TS86 is a dedicated millivolt thermostat and even though it drops between 110 to 135 millivolts across the thermostat it will not cause any problems with operation. Make sure you do not have more than 30 feet of 18 gauge wire from the thermostat to the controls. Do not use any wire smaller than 18 gauge as it will cause problems with cycle and in some cases too many millivolts are dropped across the wire and it will run erratically.

If you are interested I sell a complete manual on Powerpile Systems.