Re: [GBlist] Setback Thermostats, basic question

["Robert Jordan" <rwjordan@charter.net>]

Jim,

For hot water heat, there are sensors that take the outdoor temperature as input and modulate the water temperature based on the heat load determined by the outside conditions.  Tekmar has the most varied product line.  It will probably cost $400 to $500 for the control and a like amount for the electrician to put it in, if he can figure it out.

They work well.

Bob Jordan

----- Original Message -----

From: JNH2@aol.com

To: greenbuilding@crest.org

Sent: Wednesday, January 02, 2002 10:54 PM

Subject: Re: [GBlist] Setback Thermostats, basic question

Sounds like a good question for all these experts to tangle with.

We have set-back thermostats (in a residence) that allow for 4 different time/temperature settings during the week (day 1 through day 5) and another set of 4 time/temperature settings for the weekend (Day 5 & 6) 

We have found that in a heating situation a setback of between 5 and 8 degrees works pretty well, and is able to compensate (at least to our perception) in the morning and late afternoon when it is programmed to come back up to a comfort level.

In a cooling situation, 5 degrees seems to be the maximum for a reasonable transition in the morning and afternoon, allowing the building to get warmer than that takes much longer to cool down.

With an entire weekend and a full 10 hours each night, you could rather easily set the t-stat to start ramping up somtime around 5:00am - so that for weekends you could tolerate a much cooler/warmer temperature with several hours to get up to comfortable temperature Monday morning. 

The way to determine just where you want to set the thermosats back to is to start with a reasonable guess (8 degrees, 10 degrees, ?) and using a separate thermometer, check to see on similar weather days how long it takes the occupied spaces to get to a comfortable level.  A good guess would be to set-back 10 degrees and expect the system to take roughly 2 1/2 to 3 hours to compensate.

There are much more complicated formulae, and figuring that could work up the ideal times and set-back numbers, but that would mean a constant monitoring and adjusting of the set-back numbers and times.

Actually what I am hoping to come across someday is a piece of software that will take the input from external temperature sensors and coordinate the building's systems to avoid over cooling/heating while still maintaining the maximum amount of set-back - of course that is not prohibitively expensive.

my thoughts, for what they are worth.

good luck,

Jim Holdcraft
Saint Louis