Steam Setback

Brad White_200

That suggestion for a "Smart Recovery" thermostat would be a simpler way to get you there starting today.

My only reservations (and in no way negates the suggestion), is that, to my understanding, these thermostats focus on the "optimum start time", not the degree or depth of the setback.

To expand on how these work (I have one), the controller will measure the time it takes to make occupied setpoint and if it falls short on a given day, the next day or cycle it starts earlier. It does this until the space is at temperature at the time that is set.

This means that you set the target temperature AT a target time, not assuming to start the boiler "an hour ahead of time". That early time is up to the controller.

However, whenever you change that start time, the controller also has to start anew with all new information over time. You will spend a bit more time trying deeper setbacks but this suggestion still gets the nod in my book.

Good call, KC!

Brad

Bart_8

What would you recomend for the maxium setback on an old steam system in a church, for the most energy savings

Brad White_201

Age-Old Question....

If the church is stone with thick walls, once the heat is lost, recovery can take a while. There is a seasonal ramp-up with old stone buildings.

If the church is frame-built (hey, insulation opportunity here!), there is less thermal mass of course, usually a faster drop-off after heat is removed, but a faster recovery. Oh, those thrifty Lutherans....

With either of these, but especially the stone building, (conductive, but high in mass, slow to heat, slow to cool down), there is the capacity issue: How much radiation compared to the heat loss?

A surplus of radiation is what you will have most of the year because it is so rarely at design temperatures outside. This is a decided asset.

I have tried studies and models and found too many variables and dependencies to give a direct, absolute answer.

But I will suggest investing in some data loggers (I use HOBO loggers from Onset Computer as one brand), to see how quickly a warm-up occurs from a colder setback. At the same time, monitor the outside air temperature and the inside WALL temperature.

After a few rounds of that, you might find an optimum start point, either the lower limit of your setback or the latest start time for your boiler. Either of which will save you energy of course- you have to decide which to use, limit on drop or early time on.

Unknown

Install a thermostat like a honeywell visionpro 8000. This t-stat will "get to know" your system. Program it for 60-65 degrees @ night(to prevent pipes from freezing), & whatever time you want to set it @ for the day. The t-stat will learn your system & fire the boiler accordingly.