Boiler Reset Control

I'm pretty sure they are referring to installing an ODT (Out Door Temp) detector. An ODT interfaces with the thermostat to provide a PID loop to temperature control

As an example, say the SP (Desired indoor temp) is 72 F, the PV (Actual indoor temp) is 70. There is a call for heat, and a dumb system will usually stage full fire , eg OP 100%, which is pretty wasteful, especially if it's mild outside

I have a Bryant Evolution system at my home, and at my hobby farm. The ODT sensor is always reading the ambient temp, and adjusts A/C and heat accordingly

Eg, say the SP is 72 F, the PV is 71 F, and the ODT is +15 F. The system may only stage at OP 25%, which helps save a lot of gas. If the SP is 72, the PV is 70, and the ODT is -34 F, the OP may very well stage 100%

Compared to my neighbors with similar sized houses, my heating bill is a good 40% lower, despite a much higher setting to accomodate an elderly person.

My summer cooling bill is about 50% lower than my neighbors. I can program Dehumidification Priority so the system always runs on the slowest possible setting. That really helps with our warm and damp summers, keeps the interior very dry

With a boiler and infloor heat, not sure how much an ODT interface would help. Any more details?

 

Rereading your first post, my error. You do NOT have a boiler but a regular furnace. I assumed you had a boiler

I think the gains will be minor if you have an older furnace with single speed blower and single stage gas valve. My Bryant has an ECM variable speed motor and two stage gas valve

 

Is it condensing or the older style? That is, are a couple of ABS or PVC pipes run from the furnace out the sidewall, or is there a regular chimney?

Most furnaces that old had a single stage gas valve, the fancier ones had two stage.

 

If you wish, I can go into more detail regarding condensing furnaces with two-stage gas valves. Eg

http://i653.photobucket.com/albums/uu256/jayman_photo/HVAC photos/DSCF0185.jpg

 

Back in the 1970's when I worked for my family business, which was a industrial/commercial heating wholesaler, a boiler reset control for residential use became popular called "Entertrol". This control was a big seller during the 1970's Arab oil embargo, which was the first real increase in fuel costs we experienced.
What this control does is, an outdoor sensor is installed along with the boiler reset controller. This reset controller replaces the aquastat controller on your boiler and depending on the outside temperature the reset controller automaticaly resets the boiler water temperature both up and down and typically runs your boiler circulator all the time at only the boiler water temperature required to heat the house to save fuel costs.
I've been out of the business since 1983 and don't know if this "Entertrol" or other devices like it still fly off the shelves, but a boiler reset does save a considerable amount of money.
Be advised this boiler reset is really for hot water heating systems only.

 

That is vaguely how my Bryant Evolution hot air system works.

The ODT sensor is used to modify the PID loop for the indoor temp control, which will control staging for heat, and cycles for cool.

Eg: If the setpoint is 74 F, the ODT is 12 F, the PID may only use low fire to heat the home. If the ODT is -35 F, the PID will then ramp to high fire - two stage gas valve

For cooling, especially with priority dehumidification, the outdoor scroll compressor will run at its low speed, and the indoor ECM fan motor at its slowest speed. Especially on a cooler but very damp day, this will keep the house comfortable without turning it into a walk-in freezer

If you have a "smart" condensing gas furnace (Two stage gas valve, ECM blower motor) an ODT with an appropriate control network, eg Bryant Evolution, can result in considerable savings

 

You have a two stage gas valve. If the factory manual is around - it is supposed to be by code - there should be a section on how to wire up the thermostat and ODT

Eg: my Bryant Evolution furnace. If used with a conventional thermostat, a separate two-wire plug is used for an ODT sensor. You have to fiddle with DIP switches to properly do the staging

If you go for the Evolution control network, like mine has, a single four wire connector bypasses all of that. The ODT is wired in as above, but instead of using DIP switches the configuration is through the Evolution panel.

You have a lot more control over SP tracking, staging, time delays, etc, with the networked control. However, even a regular thermostat combined with an ODT sensor on a supported furnace, can save considerable amount in a cold climate

 

I'm sure Carrier offers a specific ODT with the correct plug already terminated. The one for my Bryant came with around 20 ft of cable, and cost a whopping $45

 

Reset controls come in three versions.

1. Outdoor reset. been arounbd for 30+ years.

2. Outdoor/Indoor resets. A compromise to tame outdoor resets.

3. Indoor reset. These analyse thermostat information to reset the boiler for optimum temperature supply with high rate of circulation for even comfort. These work on all heating and cooling systems as a retrofit for new and old systems. They work well with geothermal, solar hydronic, and steam systems.

 

Of course, we've bent the proper terminology as the OP didn't have a boiler system, but a hot air system.

My Bryant Evolution network uses a form of outdoor reset. You can program the system to stage based on outdoor temp, which is supplied by a thermister that plugs into the furnace control board

You can also use that outdoor temp control to monitor when to heat/cool, and to lockout cooling below 55 F. The control loop then functions as a PID loop, which is a lot more efficient than on/off style room thermostats

For similar sized homes on my street, my heating and A/C costs are 30-55% lower