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This paper introduces the analysis of thermostat activity over time to determine the BTU replacement requirement for HVAC equipment. This analysis allows HVAC equipment to operate for precise delivery of BTU’s dynamically with the heat loss characteristics of an enclosed environment. PRESENT METHODS Most heating and cooling systems operate to bring a fixed temperature transfer medium to the controlled enclosed environment by means of a thermostat. Some systems enhance the delivery of needed transfer medium with source temperature adjustment accomplished by means of an outside sensor reset process. Outside reset devices do not adapt well to leads and lags due to piping loss or the changing aspects of the various heat loss characteristics of enclosed occupied space. Outside reset systems do not consider even comfort circulation needs. At best outdoor reset devices approximate actual demand by means of adjustable compensation rates. THE PROBLEM Building structures experience variable factors, which cause changing BTU loss characteristics. Thermostat activity needs a way to direct the Source HVAC equipment to provide precise BTU replacement for maximum comfort and minimum energy use. THERMOSTAT DEMAND ANALYSIS Thermostat activity is an information base for demand analysis in addition to circulation demand activity
This paper introduces the analysis of thermostat activity over time to determine the BTU replacement requirement for HVAC equipment. This analysis allows HVAC equipment to operate for precise delivery of BTU’s dynamically with the heat loss characteristics of an enclosed environment.
PRESENT METHODS
Most heating and cooling systems operate to bring a fixed temperature transfer medium to the controlled enclosed environment by means of a thermostat. Some systems enhance the delivery of needed transfer medium with source temperature adjustment accomplished by means of an outside sensor reset process. Outside reset devices do not adapt well to leads and lags due to piping loss or the changing aspects of the various heat loss characteristics of enclosed occupied space. Outside reset systems do not consider even comfort circulation needs. At best outdoor reset devices approximate actual demand by means of adjustable compensation rates.
THE PROBLEM
Building structures experience variable factors, which cause changing BTU loss characteristics. Thermostat activity needs a way to direct the Source HVAC equipment to provide precise BTU replacement for maximum comfort and minimum energy use.
THERMOSTAT DEMAND ANALYSIS
Thermostat activity is an information base for demand analysis in addition to circulation demand activity
. Thermostat data gathering By polling a thermostat periodically (every second) for demand status over time (one hour) actual demand activity can be determined. By comparing actual demand to an Ideal demand value (.60), the variation of demand value from ideal demand value will determine the need for raising or lowering the transfer medium supply temperatures. A microcontroller containing an algorithm can control the source output to adjust the transfer medium temperatures upward or downward. BTU supply temperature adjustment Correction of BTU source temperature, hour to hour provides a smooth transition of BTU supply in close proximity with changing heat loss/gain characteristics on the enclosed environment. Analysis periods, Ideal demand factors and temperature change increments can be determined and preset in software by the heat loss behavior of the structure and the given outer environment. Geography and structure will vary. Example Ideal thermostat demand factor = .60 Actual thermostat demand factor = .83 Temp Change factor = ((.83-.60) x10)= +2.3 Temp Change Increment 2Far 2.3 x 2F = + 4.6Far Current High Temp set Point 150 degrees Far 150F + 4.6 F = 154.6 F New High temp limit = 154.6 F Higher for the next hour
Thermostat data gathering
By polling a thermostat periodically (every second) for demand status over time (one hour) actual demand activity can be determined. By comparing actual demand to an Ideal demand value (.60), the variation of demand value from ideal demand value will determine the need for raising or lowering the transfer medium supply temperatures. A microcontroller containing an algorithm can control the source output to adjust the transfer medium temperatures upward or downward.
BTU supply temperature adjustment
Correction of BTU source temperature, hour to hour provides a smooth transition of BTU supply in close proximity with changing heat loss/gain characteristics on the enclosed environment. Analysis periods, Ideal demand factors and temperature change increments can be determined and preset in software by the heat loss behavior of the structure and the given outer environment. Geography and structure will vary.
Example
Ideal thermostat demand factor = .60
Actual thermostat demand factor = .83
Temp Change factor = ((.83-.60) x10)= +2.3
Temp Change Increment 2Far
2.3 x 2F = + 4.6Far
Current High Temp set Point 150 degrees Far
150F + 4.6 F = 154.6 F
New High temp limit = 154.6 F
Higher for the next hour
How are the 'Ideal thermostat demand factor' and the 'Actual thermostat demand factor' calculated? A more thorough explanation of this and a comparison to a typical outdoor temp reset would help me understand this more clearly and why it is more advantageous. Is the polled thermostat that's used for BTU supply temp adjustment measuring discharge air temp compared to discharge setpoint, space temperature compared to space setpoint or return air temperature compared to return air setpoint? Or is it something else altogether?
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In Hydronics we compare the actual thermostat demand ADR activity over time. That is a comparison of calls over total samples within an hour. We then campare that to a circulation Ideal demand constant IDR, say 60%. If the actual is higher than the constant then we are to increase temp limits. If the actual is lower then constant then we lower limits. In the case of steam and AC, or ventilation CO2, we would use a time cycle adjustment, as temperature is more difficult to measure, yet time periods are measurable as ( steam increasing or decreasing cycle time generates more or less BTU to the system.)
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