Steam/HW system setback - Energy Savings

Steve Garson_2

My understanding is a 1* set-back for 8-hours will save 3% for those 8-hours. So if you look at 24-hours, that 3% savings is really 1% of the day's fuel consumption.

So a 9* set-back would save 9%. But you need to be sure that the system can bring the building up to normal temp in time for business hours.

Sol

Steam system savings with night setback

Hi,

I work for a district energy supply company. We have a customer who is installing DDC controls in a commercial building.

He runs the steam through a heat exchangeer and then hot water is used for heating througout the building.

He will be replacing the controls since the old pneumatics are shot, but the accounting dept wants to get an idea of the number of years payback this project will be. He plans on using a night setback control to lower the water set point from 180 degF to 90 degF for 9 hours overnight (8pm-5am).

I know there are other savings possibilities, but for this portion, is there a rule of thumb for the % of energy saved? I can then take that percentage and plug it into his historical data and determine a monetary savings for him.

Thank you.

carol_3

I'd plan very carefully to make sure you can recover your water temp in the time you're allowing. I'm not saying you can't---it's just that you want to make sure. Too cold water isn't worth energy savings.