Outdoor Reset Question

jb9

Hello,

I have a basic question about Outdoor Reset Controls. Isn't this concept essentially an outdoor thermostat? Why don't all boilers support an ODR? I guess I don't really understand if and/or why an ODR is more sophisticated than a regular thermostat. I am assuming it is definitely an advancement in boiler technology, but since I don't have a lot of experience with them (or with equipment that doesn't support them), I don't have a solid appreciation of their history and why they are so valuable in a system design.

Thanks.

Gordy

The outdoor reset takes the outdoor temp, and matches the water temps your system needs for a specific outdoor temperature to off set the heat loss at a given outdoor temp.
A,curve programed by the installer/user.

CI boilers have a some what limited ability to gain the most efficiency from it verses a condensing/ modulating boiler. Given that return water temps in the sub 135'region for a ci boiler is bad for it, and a modulating/condensing boiler thrives on return temps below 130 the lower the more efficiency gained.

Emitter types play big roles in how far outdoor reset can take efficiency. In a sense bigger is better. It allows lower water temps gaining efficiency.

Gordy

As for why don't all boilers have it. All mod/cons do that I know of. Ci boilers can have it, but usually do not come with the feature.

SWEI

Outdoor Reset allows the heating or cooling system to anticipate demand, before the indoor air temperature has changed even a fraction of a degree. When properly utilized it can produce a level of comfort that is simply impossible using a conventional thermostat.

jb9

These are really helpful responses. I think I have a better understanding. I see how the "anticipation" of the demand via the heat loss produces that level of comfort. Do electric resistance or air-to-water heat pumps have support for ODR as standard? And, is the ODR a configurable setting/interface? If so, how does one "tune" it? Again, thanks in advance... I am learning a lot. Sorry for all the questions.

SWEI

Modern air to water heatpumps include built-in ODR control. SWTs drive COP so they need it to get their seasonal performance numbers up.

Electric resistance boilers with built-in ODR are available from Thermolec (3kW and up) Electro (10 kW and up) and NextGen (4kw and up.) There are undoubtedly others as well.

Adjustment of the ODR parameters varies from brand to brand. Some are very basic (a single pot) and others have 4-point or ratio-based settings.

Gordy

To add to Kurts input. The thermostat becomes redundant high limit device. When properly setup the ODR calls the shots, and as Kurt noted provides excellent comfort when properly setup.

Big Ed_4

A out door reset is nothing new , in the early 1900's there was option to add an ODR on gravity hot water coil fired systems . mechanical ,manual set with lever and chain controlling air damper . One would check the outdoor thermometer on the back porch , go to the same chart we use today and move a weight along the lever to the desired water temperature.
In the early 50's there was an automatic version using vacuum tubes . They been around . They work , saves fuel adjusting the supply temperature for what is needed . Lower the the system temperature less system loss and less fuel burn . Around 20% savings. Comfort as far as less temperture swing .