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Programmable Thermostats on Furnaces |
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rev. 2008-12-07
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Programmable Thermostats on Furnaces |
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rev. 2008-12-07
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Existing Conditions
There are several natural gas fired furnaces located throughout the xxx building. These furnaces are controlled by simple wall mounted thermostats, which control to a single setpoint all the times.
Retrofit Conditions
It is recommended that electronic setback thermostats be installed, to reset the space temperature of the shop areas to 15°C during unoccupied times. Typically, space temperature during occupied periods would be set at 21°F for heating and 24°F for cooling. During unoccupied periods temperature would be allowed to drift within a wider range (e.g. 18°C to 27°C).
<The supply fan would operate continuously during occupied periods. It would cycle off in the unoccupied mode, only coming on when either heating or cooling were needed.>
<Because this unit has economizer damper control, we recommend using a thermostat that has 'damper override' capability. This feature disables economizer damper operation during unoccupied mode, so that the dampers remain fully shut and the air handler does not bring in ventilation air.>
We recommend using a commercial grade "heating only" setback thermostat that takes power from a low-voltage control transformer. Residential grade thermostats are typically less expensive, but they are less rugged, require battery replacement and are prone to corrosion of the battery contacts.
In most cases we would recommend allowing occupant access for fine-tuning of the setback schedule. However, if occupant adjustment is not desirable, consider a thermostat with a password lockout to prevent undesired access.
Further Benefits
Application Details
If conditioning cannot be turned off during unoccupied hours, install temperature setback.
A basic energy conservation measure that saves energy during unoccupied periods. A standard feature in most electronic control systems. With other types of controls, it requires special thermostats.
Issues and Concerns
References
This recommendation is in accordance with Measure HV10 of the CMHC manual on Energy and Water Efficiency in Multi-Unit Residential Buildings and with Section 6.3 Heating Ventilating and Air Conditioning Systems of the ASHRAE Standard on Energy Conservation in Existing Buildings.
Analysis
Sample bin analysis
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Natural Gas Consumption |
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LOADS |
Setback Bin Hours |
Existing GJ Gas Consumption |
Retrofit Consumption |
Savings |
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Average F |
Average C |
DeltaT |
Setback DeltaT |
Total Bin Hours |
Base |
Winter |
Total |
Ngas Heating Load - GJ/h |
Setback Heating Load - GJ/h |
7a-8p |
8p-7a |
7a-8p |
8p-7a |
Heating 8p-7a - GJ Gas |
Heating GJ Gas Saved |
23 |
-5 |
22 |
20 |
3 |
1 |
1 |
2 |
0.27 |
0.25 |
1.2 |
1.6 |
0 |
0 |
0 |
0 |
28 |
-3 |
20 |
18 |
97 |
18 |
23 |
52 |
0.24 |
0.22 |
21.3 |
75.6 |
5 |
18 |
16 |
2 |
33 |
0 |
17 |
15 |
551 |
101 |
118 |
266 |
0.21 |
0.19 |
167.9 |
383.4 |
36 |
82 |
72 |
10 |
38 |
3 |
14 |
12 |
1,034 |
189 |
191 |
447 |
0.19 |
0.16 |
435.6 |
597.9 |
81 |
111 |
95 |
16 |
43 |
6 |
11 |
9 |
1,503 |
275 |
235 |
575 |
0.16 |
0.13 |
744.7 |
758.4 |
117 |
119 |
98 |
21 |
48 |
9 |
8 |
6 |
1,539 |
282 |
197 |
513 |
0.13 |
0.10 |
751.8 |
787.3 |
96 |
101 |
77 |
24 |
53 |
11 |
6 |
4 |
1,503 |
275 |
150 |
426 |
0.10 |
0.06 |
707.6 |
795.3 |
71 |
79 |
51 |
28 |
58 |
14 |
3 |
1 |
1,202 |
220 |
86 |
281 |
0.07 |
0.02 |
713.8 |
488.6 |
51 |
35 |
10 |
25 |
63 |
17 |
0 |
-2 |
752 |
138 |
32 |
138 |
0.04 |
0.00 |
640.1 |
112.0 |
27 |
5 |
0 |
5 |
68 |
20 |
-3 |
-5 |
381 |
70 |
5 |
70 |
0.01 |
0.00 |
367.0 |
13.5 |
5 |
0 |
0 |
0 |
73 |
23 |
-6 |
-8 |
148 |
27 |
0 |
27 |
0.00 |
0.00 |
146.4 |
1.3 |
0 |
0 |
0 |
0 |
78 |
25 |
-8 |
-10 |
32 |
6 |
0 |
6 |
0.00 |
0.00 |
31.7 |
0.0 |
0 |
0 |
0 |
0 |
83 |
28 |
-11 |
-13 |
15 |
3 |
0 |
3 |
0.00 |
0.00 |
15.0 |
0.0 |
0 |
0 |
0 |
0 |
88 |
31 |
-14 |
-16 |
1 |
0 |
0 |
0 |
0.00 |
0.00 |
1.0 |
0.0 |
0 |
0 |
0 |
0 |
93 |
34 |
-17 |
-19 |
0 |
0 |
0 |
0 |
0.00 |
0.00 |
0.0 |
0.0 |
0 |
0 |
0 |
0 |
98 |
36 |
-19 |
-21 |
0 |
0 |
0 |
0 |
0.00 |
0.00 |
0.0 |
0.0 |
0 |
0 |
0 |
0 |
0 |
0 |
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8,760 |
1,604 |
1,039 |
2,806 |
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4,745 |
4,015 |
489 |
550 |
419 |
131 |