HVAC System Solutions Brochure

5 of 12
© 2012 P 10005 - 09/12
How Does Outdoor Temperature Reset Save Energy?
Traditional heating systems do not know
if it is a cool autumn night or the coldest
day in winter.
On average, this extreme temperature is
needed for less than 10 days a year.
tekmar controls with
Outdoor Temperature
Reset
monitor the outdoor temperature.
When the thermostat calls for heat, the
tekmar control operates the boiler to
provide a ‘reset’ water temperature.
On milder days the boiler supply water
temperature is lower.
Without Outdoor Temperature Reset, the
boiler water temperature is the same for
the entire heating season.
With Outdoor Temperature Reset, the
boiler temperature is continually adjusted
to match the heat loss of the building.
Outdoor Temperature Reset saves energy whenever the boiler is operated below the maximum. With modern
condensing boilers, the potential savings increase with the lower minimum operating range.
Because of this, the boiler is always
operated at a temperature calculated to
make up for heat loss on the coldest day
of the year.
On colder days the boiler water temperature
is higher.
Temperature
setting in boiler
Boiler
Maximum
Increasing Outdoor Temperature
°F
70
90
110
130
150
170
190
70 48 26 4 -18
Increasing Boiler Temperature
Heating Load
Days per Heating Season - Toronto, ON 2011
19 days
80 to
100%
60 to
80%
40 to
60%
20 to
40%
0 to
20%
49 days
80 days
69 days
81 days
Temperature
setting in boiler
Boiler
Maximum
Increasing Outdoor Temperature
°F
70
90
110
130
150
170
190
70 48 26 4 -18
Increasing Boiler Temperature
Boiler
Temperature