Think about running the heat tonight

[joe the plumber]

Originally Posted by Saltheart

How does this "outdoor reset control" dohickey work? I never heard of one but it sounds very logical. How would it work on a hot water heating system like I use to heat my house?

Saltheart,
An outdoor reset contol is a mini computer that wires to your boiler's high limit.It uses sensors (usually about 10,000 ohm) that monitor outdoor temp(located on the cold side of the dwelling)and 2 others that are on the boiler supply and return.They wire to the control with ordinary tsat wire.The control measures the resistance of each sensor and is equipt with computor logic that can now modulate the boiler's high limit in accordance to a heating curve within the contol.This heating curve can be adjusted to work on any hydronic heating system.
The heating curve is a "reset ratio".Simply put....If your house requires 180Degree water to keep your home 68 on a 0 degree day,then when the temp outside is 10,the boiler's high limit is now 170.A 40degree outside temp would "reset" your boiler's high limit to 140.Your circ runs 24/7 untill the contol scenses something called "warm weather shutdown"usually 65Degrees outside.The circ now shuts down.
If your boiler makes domestic hot water the reset contol scenses the call and the boiler goes out of modulation and fires up to its normal 180 degree high limit to satisfie the demand.
The return sensor monitors your return water temps and maintains a minimum temp on the boiler to prevent dangerous condensation which can lead to internal corrosion of the boiler.
These controls are made by TACO,TEKMAR,and many others.I also want to add that starting 2012 ALL new heating equiptment MUST be equipt with some kind of "weather responsive control"In the meantime,the control I describe will cost between 350 and 500 dollars.They pay for themselves quickly.
Please contact me with a PM if I can further help you.
Joe