Fitness Manual J Residential Load Calculation Pdf


Friday, May 31, 2019 - Free download as PDF File .pdf), Text File .txt) or read online for free. Load Calculation: Manual J. Equipment Selection: Furnace and Air Conditioner. This example illustrates a permit application packet when the HVAC Contractor. Manual J Load Calculations: Estimates are correct for the amount of heating pdf file. ICC Residential System Review Form K 1 version.

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19, templates to minimize data selection for future load calculations. the Eighth Edition of Manual J. It provides an introduction to residential heat-loss and heat. For more than 40 years, Manual J has been the industry's leading reference tool for performing residential load calculations. With over 30 years of experience. Reduce energy use in new and existing residential buildings. • Promote building .. Manual J Residential Load Calculation Eighth Edition.

The load area for walls and ceilings is equal to the net surface area.

PDF Manual J Residential Load Calculation (8th Edition - Full) Free Books

Line 12 shows the infiltration loads, as copied from Worksheet E. In this case the wall area ratio equals 1.

The heating and sensible load values are equal to the. Exposure Faces Number Htg. West 7. Section 13 product of the load factor and the corresponding Line 14 sub-total. Line 15 shows the effective latent gain ELG. Lines 16 through 19 show the ventilation load and the blower motor load. These values were copied from worksheets H and I..

In this case there is no excursion, so the system designer elected to use a single zone constant volume system. If the peak-hour gain exceeds the average gain by more than 30 percent, the conditioned space is a candidate for the peak load procedure. See MJ8, Section Line 21 shows the total heating load, total sensible load and total latent load equipment sizing loads. Comment and guidance pertaining to the information that appears on Form J1 and the associated work sheets is provided here.

Worksheet A Table 1A provides altitude, latitude values and outdoor design conditions for Worksheet A next page. The system designer provides values for the indoor design conditions.

This is a humid, semi-tropical climate the winter design temperature is above 50 oF. All calculations are made for NFRC labeled fenestration. A sun screen adjustment is applied to the West-facing windows. Lines a through f show the directional calculations for all the windows and the sliding glass door. The values in this column have no insect screen adjustment.

The values in the AHTMD column are adjusted for an insect screen, when this adjustment is applicable. The values in this column have not been adjusted for shading by a sun screen or overhang. Section 13 Ushaft, Apanel, Acurb and Ashaft are used. Note that the panel area Apanel for domed skylights equals the flat panel area multiplied by a 1. Step 3 is used to generate the effective HTM values for the skylights.

Worksheet E Worksheet E next page is used to estimate infiltration loads and to set the ventilation rate.

Step 1 shows that 84 CFM of outdoor air will satisfy the most demanding test, which is the 0. Step 2 uses the default air change method to estimate infiltration loads, but in this case the Table 5A ACH values are replaced by air change values that are compatible with the track record of the builder 0.

Step 3 shows that the system designer has decided to route 50 CFM of outdoor air through the dehumidifying ventilator 50 CFM is required to satisfy the code requirement and that this amount of unbalanced ventilation there is no exhaust air reduces the winter infiltration rate to 24 CFM and completely eliminates summer infiltration.

This results in a Btuh heating load, and no cooling load. Worksheet F Worksheet F page shows that the occupants produce a Btuh sensible load and a Btuh latent load and that default scenario two adds 3, Btuh of sensible load. The home has three televisions and two computers, so the sensible load is increased by Btuh for one television plus another Btuh for one computer. One television is included in the default scenario and the practitioner has decided that one television and one computer will not be used during late afternoons.

Radiant Floors construction Numbers 20, 21 and 22 Note: Use F-value and running feet of exposed edge for slab floors a 22D-5rl b. For rad floor: The fenestration leakage area values in Table 5C do not apply to rated fenestration. The 4-Pascal leakage area of rated fenestration is equivalent to Table 5C information. For example, suppose manufacturer's performance data shows the tested leakage rate was 0.

Then for component leakage area calculations, the 4-Pascal leakage area is 0. Figure provides an example of the data set produced by this type of test. The following equation converts this data to a power-law curve that relates the blower door flow rate CFMbd to the pressure difference PD produced by the blower door. The C and n constants in this equation depend on the size, shape and number of the cracks and openings in the thermal envelope including partition and duct surfaces that leak to an unconditioned space.

These constants are relatively insensitive to ambient conditions outdoor wind and temperature when test pressures are in the 30 to 60 Pascal range. Testing at pressures that greatly exceed the 4-Pascal pressure caused by natural effects minimizes the "noise" in the measurement. Values for the C and n constants are provided by software that is packaged with the blower door apparatus. This information is generated automatically and presented on a video screen or paper print out.

For example, software-generated values for C and n for the Figure blower door test are Multipoint Blower Door Test The resulting leakage rating Q15 equals the measured leakage Cfm divided by the area of the assembly Cfm leakage per SqFt of assembly.

Q15 values can be converted to a 4 Pascal leakage area for use in the component leakage area method. Effective Leakage Area The C and n constants are used to calculate the effective leakage area for the structure.

This value depends on the density of the air and the reference pressure difference PD. The following equation is used for standard air. This equation can be used for elevations that range from sea level to 2, feet. A 4-Pascal reference pressure that simulates natural conditions is used to produce an effective leakage area value. For C and n values of The equation used to estimate the effective leakage area for any altitude is provided here.

In this case, the altitude ELA4 value depends on the C and n constants, the differential pressure PD and the density of the air d leaking through the cracks. For example, for standard sea level conditions, the density of the air is 0. This guideline is a compromise between accuracy and expediency. It is presented with the understanding that room apportionments may not be sensitive to local differences in the construction detail, exhaust equipment, vent openings and fuel burning equipment.

The accuracy of this guideline is compatible with three methods that are used to estimate the ICFM value. This is a trivial matter when a single family detached home is equipped with a central, single-zone system because the infiltration load for the conditioned space is identical to the infiltration load on the equipment.

A little more thought is required when two or more comfort systems are installed in a home because one infiltration load is shared by two or more pieces of equipment. In this case, the infiltration load on each piece of equipment is estimated by summing the infiltration loads for the rooms served by that equipment. The following conditions are possible: If the flow rate of the outdoor air equals the flow rate of the exhaust air, the ventilation system has no affect on the space pressure or the infiltration rate.

If the flow of outdoor air is greater than the flow of exhaust air, the space will be pressurized and the infiltration is reduced. If the flow of outdoor air is less than the flow of exhaust air, the space will be depressurized and the infiltration is increased.

The following equations estimate the infiltration rate for a dwelling that has an unbalanced ventilation system: For example, suppose a home has an standard infiltration rate of CFM. If 50 CFM of outdoor air is introduced through the return side of the air distribution system with no provision for exhausting this air, the home is pressurized and the infiltration rate is reduced to CFM as demonstrated here: Conversely, if exhaust equipment draws 50 CFM of outdoor air through this home, the thermal envelope will be under a negative pressure.

In this case, the infiltration rate increases to about CFM, as demonstrated here: Infiltration Principles Infiltration rates depend on flow paths and pressure drivers. Some factors cannot be controlled the wind , some factors are controlled by the builder cracks and some factors are controlled by the HVAC contractor engineered ventilation, exhausts and vents.

Understanding infiltration mechanics and related pressure conditions is essential for system design, for trouble-shooting air quality problems and for assuring occupant comfort, health and safety. Air also flows through interior partitions walls, ceilings and floors that have a cavity that is air-coupled to the outdoors or to a leaky unconditioned space. Other flow paths are created by the mechanical systems.

Figure next page summarizes the situation. Section 21 drivers act in concert, so a wide range of pressure conditions and infiltration rates are possible, depending on which drivers are active.

A summary of field study observations is provided below. This information shows that there are many leakage points associated with a dwelling. Walls Exterior walls tend to leak at the top plate and sill plate, around the rough opening of window and door frames, at electrical outlets and at piping penetrations.

Interior walls provide paths that connect the conditioned space with attics, basements and crawl spaces. Studies show that walls can be responsible for 18 to 50 percent of the total leakage area the mean value was 35 percent.

Windows and Doors When closed, windows and doors account for 6 to 22 percent of the total leakage area the mean value was 15 percent. The actual leakage area for a specific assembly depends on the type of window or door and the quality of construction discounted for the age of the unit.

Ceilings Ceiling leakage can occur at wall-ceiling intersections that are not sealed and which may be hidden by molding , at recessed lighting fixtures, attic access doors, electrical penetrations and piping penetrations. Ceiling leakage can account for 3 to 30 percent of the total leakage area the mean value was 18 percent. A foam encapsulated attic reduces ceiling leakage and may reduce leakage through wall cavities. Attic Exhaust Fans Attic exhaust fans were not mentioned in the study, but they can cause a dramatic increase in ceiling leakage and interior wall leakage.

Attic exhaust fans also affect the leakage rate of attic duct runs. Manual J has no procedure for adjusting infiltration Cfm for negative attic pressure produced by an exhaust fan. The net affect depends on the power of the fan, the amount of relief provided by the attic vent openings, the amount of leakage from the conditioned space and the affect on duct leakage. In some cases its possible for the reduction in ceiling load to be smaller than the increase in the sensible and.

It may even be possible to produce a condition that would cause a combustion appliance to backdraft. It is possible for the operating cost of an attic exhaust fan to greater than the associated reduction in cooling energy cost.

Attic exhaust fans are sized by attic ceiling area. Sizes range from 0. Fan capacity is typically 1, Cfm or more. A small 50 cfm or so fan is not classified as an attic exhaust fan. Vent Openings Exhaust vents may have no damper or a leaky damper. The leakage area for vent openings can vary from 2 to 12 percent of the total leakage area the mean value was 5 percent.

Fireplaces The leakage produced by inoperative fireplaces depends on the source of combustion air. If the combustion air comes from the conditioned space, the leakage depends on the quality of the flue damper and the seal at the glass doors when installed.

The leakage area associated with fireplaces can vary between 0 percent and 30 percent the mean was equal to 12 percent. Comfort System The leakage attributed to comfort systems can range from 0 percent to 28 percent the mean was 18 percent. The total amount of leakage area depends on the type of equipment, the location of the equipment and duct runs, and the amount of exposed duct-wall area.

This benefit could be provided by an external wrap infiltration barrier , a plastic vapor retarder location depends on climate , insulating panels that have a foil facing or dry wall sheet rock. In all cases, the effectiveness of the membrane depends on methods, materials and workmanship as it pertains to sequencing, cutting, fitting, lapping, taping and caulking and quality of workmanship.

Leakage points not sealed by a membrane must be sealed on an local basis. Tapes, caulking materials, mastics, aerosol foams, gaskets and dampers are used for this purpose. Section 23 runs are not sealed 0. When risers or drops are located in an exposed wall, the duct load factor or latent load is added to the system load values. This will increase the system load factors and latent gain value for the previous example. Software solutions are only as good as the input data.

If the duct surface area is off by percent the duct load error will be in the neighborhood of percent. If the leakage estimate is way off the mark, the duct load will be incorrect. Also expect extremely large load factors for R-0 scenarios, especially if there is a lot of exposed surface area. One page of tables and equations is required to summarize the performance of one duct system scenario.

Since there are a large number of possible scenarios depending on duct-run locations, supply-side geometry, return-side geometry, insulation R-value and leakage class , a comprehensive library of duct factor tables is impossible to produce and would be to large to be of practical use.

Fortunately, this is no problem when "Powered by Manual J" software evaluates duct loads. Software implementation of the Manual J duct load model accepts practitioner input for:. Manual J duct tables provide performance values for the entire duct system that is described in the table's heading. When these values are processed by Manual J Worksheet G, the worksheet returns a heat loss factor, a sensible gain factor and a latent cooling load value for the entire duct system.

However, Worksheet G may also be used to generate load factors and a latent load value for the return side of the system. The location of the duct runs. The surface area of the supply system. The surface area of the return system. The duct wall R-value or values. Weather data and altitude correction from Worksheet A.

The indoor design conditions. Envelope loads and envelope infiltration rate. Many types of roof-attic construction. The temperature of supply air heating. The blower CFM heating and cooling. For existing duct systems, this information is gathered by inspection and testing. Or, the practitioner provides the information for duct systems that are on the drawing board.

Return Side Load Factors Figure next page shows the Worksheet G calculation for a radial duct system in a vented attic under a dark shingle roof duct table 7B-R for a 2, SqFt floor area. The duct has R-4 insulation and is not sealed 0. The installed supply duct surface area is SqFt, and the installed return duct surface area is SqFt as measured or estimated by the practitioner.

The Table 1 values for the location are 0F for heating, 95F for sensible cooling and 40 grains for latent cooling. Th e left side of Figure shows Worksheet G calculations for the entire duct system. Note that the default supply and return areas from Table 7B-R are SqFt and 95 SqFt the practitioner may use these defaults for the installed surface areas if more accurate values are not available. For leakage values, the practitioner has to make a decision pertaining to expected tightness of the supply runs and the return runs.

Manual J provides the following options: Use the Table 7 default values for sealed 0. Or use Figure or Figures and to generate leakage rate values. Or use values that are compatible with a code requirement. The heat loss factor for the entire duct system is 0. The sensible gain factor for the entire duct system is 0. The latent cooling load value for the entire duct system is 3, Btuh.

Th e right side of Figure shows Worksheet G calculations for the return side of the duct system. Note that the supply side surface areas have been set to zero. The heat loss factor for the return-side of the duct system is 0. The sensible gain factor for the return-side of the duct system is 0. The latent cooling load value for the return-side of the duct system is 3, Btuh. Refer to Section For multiple locations use a separate worksheet for each location.

See Section Step 1 Enter base-case load factors and latent heat value from Table 7 eyeball interpolation is acceptable Existing Construction R-Value 1 2 3. The return side loads for this example are as follows: The heating load for the space served by the duct system converts the return side heat loss factor to a heating load.

For example, if the space heating load is 52, Btuh per line 14 on the J1 form , the heating load for the return-side of the duct system is 0. The sensible cooling load for the space served by the duct system converts the return side sensible gain factor to a sensible cooling load.

For example, if the sensible space load is 22, Btuh per line 14 on the J1 form , the sensible cooling load for the return-side of the duct system is 0. The return side latent load is provided by Worksheet G. Then the dry-bulb temperature DB of the air that exits the return duct equals the indoor dry-bulb temperature plus the return duct gain. Return air Cfm may be equal to the blower Cfm, or may be somewhat larger or smaller. For the purpose of this calculation, Rcfm defaults to blower Cfm.

An indoor humidity ratio grains of moisture per pound of air value is provided by altitude sensitive psychometrics based on the indoor dry-bulb and relative humidity values. Then the latent heat equation below , converts a latent return duct load latent Btuh to a grains of moisture gain DGR.

Altitude sensitive psychometrics converts an exiting dry-bulb temperature and grains value to a exiting wet-bulb temperature, and converts an indoor dry-bulb temperature and relative humidity value to an entering wet-bulb temperature.

Manual J Residential Load Calculation (8th Edition - Full) Solutions Manual

The wet-bulb rise DWB equals the difference between the two wet-bulb values. Duct System Efficiency The heating and sensible cooling loads generated by duct systems are sensitive to a collection of variables and interactions such as piping geometry, the location of the duct runs, the condition of the air in the duct runs, the condition of the air surrounding the duct runs, the tightness of seams and joints, and the amount of duct-wall insulation.

Duct loads also depend on the size of the dwelling and construction details because equipment size, blower CFM, the size of the duct airways and the total surface area of the duct system depend on the size of the heating and sensible cooling loads. Leakage at seams and joints produces a latent cooling load and creates pressure differentials that affect the dwellings infiltration rate.

Duct load calculations are complex and recursive, and should be performed on a case by case basis by "Powered by Manual J" software.

This manual provides solutions for a collection of default scenarios see Table 7. As demonstrated by Sections 7, 8 and 9, these solutions reduce to a heat loss factor, a sensible heat gain factor and a latent gain value. The loss and gain multipliers for heating and sensible cooling loads are expressed as a percentage of the envelope load.

The latent heat gain value is expressed in Btuh units. The information presented here pertains to the duct loss and gain models used to generate the Table 7 values.

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Alternatively, performance is noticeably improved when the wall insulation is upgraded to R Depending on the circumstances, replacing R-6 with R-8 produces a 3 to 6 percent reduction in the sensible duct load and a 2 to 9 percent reduction in the duct heating load. In addition, the absolute humidity in a properly vented attic is approximately equal to the outdoor humidity.

Open crawlspaces are undesirable because there is little difference between the crawlspace temperature and humidity and the condition of the outdoor air. Enclosed crawlspaces and unconditioned spaces produce environments that range from benign to hostile, depending on construction details tightness, insulation placement and insulation R-value.

Information gained by a limited effort to investigate the affect of location is summarized by Figure This figure shows that the loads for open crawlspaces. The crawlspace system has more exposed duct wall area than the attic system because the crawlspace runouts extend to the perimeter of the floor plan and attic runouts only ran to the center of a room. This figure also indicates that radiant barriers or white shingles or tile roofs reduce the cooling load for attic duct systems.

Duct heat transfer to an unconditioned space can be significantly reduced if the surface area of the system is minimized. In this regard, research performed at the National Renewable Energy Laboratory NREL indicates that when the thermal envelope is efficient, an acceptable level of comfort can be provided by an attic duct system that features a central air handler and short supply runs that feed supply air diffusers located near the interior walls of the rooms.

Duct loads are eliminated when duct runs are in a conditioned space, and significantly reduced when in an encapsulated attic. This is important because duct surface area estimates are based on the assumption that the blower CFM is compatible with the calculated loads and that duct airway sizes are compatible with the blower performance and the total effective length of the duct system.

In other words, default surface areas for Manual J duct tables do not apply to duct systems that have been designed by using whimsical guidelines and unreliable rules of thumb the surface area correction procedure adjusts for these cases. Section 27 humidity level that produces condensation on a visible surface. The following equation is used to evaluate the temperature distribution across a structural panel.

This equation shows that the temperature at a concealed surface Tc depends on the R-value for the layers of material between the surface of interest and the outdoors Rc , the total R-value across the sandwich Rt , the outdoor design temperature To , and the indoor temperature Ti.

For example, the following guidance compares the condensation potential at the inside surface of a cinder block wall that has insulation on the indoor side of the block with the condensation potential of a block wall with the same amount of insulation installed on the outdoor side of the block.

These calculations are based on data provided by Figure , which shows the thermal resistance of the path between the concealed surface and the outdoor air is R-2 for indoor insulation and R for outdoor insulation.

Figure also shows that the total thermal resistance for both walls is R and the indoor and outdoor temperatures are 70 oF and -5 oF. For a 57 oF dew point, the psychometric chart for normal temperatures indicates that indoor air with. Overall resistance of both walls is R with Interior finish and air films. Insulation on Outside Surface This equation provides the value for the temperature at indoor surface of the cinder block if the insulation is installed on the outdoor surface of the wall.

Insulation on Inside Surface This equation provides the temperature at indoor surface of the block under the insulation if the insulation is on the indoor side of the wall. For a 7. These calculations show that concealed condensation is almost certain if the insulation is installed on the inside surface of the block wall.

These calculations show that concealed condensation is prevented or will be unusual if the insulation is installed on the outdoor side of the block wall. Section 27 following equation shows that airway surface temperature Ts depends on duct air temperature Ti and ambient temperature To , the overall R-value Rt of the duct wall duct material, insulation and air film resistence , and the resistance of the inside air film Ri.

If the ambient temperature is 0F and the duct air temperature is F, the temperature for the duct airway surface is about A similar calculation shows that return duct condensation will not occur. Ri equals the air film coefficient for airway air: Ri is about 0. For example, sea level dwelling has winter humidification added to supply air, and the dew-point of space air is If the blower is off, space air may siphon through an attic duct system.

Uninsulated metal duct is used to demonstrate the calculation procedure. If the blower is off, the total R-value of a sealed metal duct that has no insulation is about 1. If the ambient air temperature To is 0F and the duct air temperature Ti is 70F, the temperature for the duct airway surface is about 35F, so condensation is possible.

When the blower operates, 1, CFM of F air moves through the supply side of the duct system. The Manual J humidification load was determined to be 4, Btuh for the winter design condition, so the humidifier must add 4. But the furnace only operates for 42 minutes per hour because it is oversized, so the humidifier must add moisture at a rate of 6.

This means that return air enters the return duct at 70F and If the blower runs, the total R-value of a sealed metal duct that has no insulation is about 0. In general, duct runs installed outside of the conditioned space should be insulated R4 is common, R6 or R8 is good practice, and ma be a code requirement. For winter humidification, the amount of duct wall insulation must assure that the duct airway surfaces will be warmer than the dew-point of ducted air.

In general, duct runs installed outside of the conditioned space should be comprehensively sealed this is good practice, and may be a code requirement. For winter humidification, exposed duct runs must be as tight as possible much better than the 0.

Reactively humid air leaking out of a supply duct may condense and possibly freeze on a nearby surface. Cold air leaking into a return duct can cause condensation and possible freezing at the leakage point. Therefore, the maximum acceptable non condensing humidity level in any room or zone depends on the construction of the room or zone. Also note that moisture can be mechanically dispersed throughout a home, by a forced-air heating system.

For example, if return air is drawn from a room that contains a pool or hot tub, the entire home will be humidified. Even if the blower is not operating, moisture will migrate through any duct run supply or return that connects a humid room with the other rooms served by the air distribution system.

Condensation also can occur inside of air distribution systems located in unconditioned spaces. For example, homes equipped with baseboard heat and a cooling.

Section 27 system installed in the attic may have problems with duct wall condensation or air handler cabinet condensation during cold weather. In extreme cases water may drip from the ceiling supply outlets or returns. This moisture is generated when humid, buoyant room air migrates to the attic duct system through a supply or return , loses sensible heat and moisture the water vapor in the air condenses on cold surfaces , loses buoyancy and falls back into the room through a supply or return , which draws more room air into the duct system.

This continuous, gravity-driven circulation process is called thermosiphoning see Section Because the infiltration and ventilation loads are similar, they are combined into a single outdoor air load.

Provide a comprehensive vapor retarding membrane for structural surfaces. Duct runs and equipment cabinets in an unconditioned space must be tightly sealed. Section guidance pertains to the moisture migration load for winter humidification. Section provides guidance for calculating humidification loads caused by duct leakage. The following equations show that the default humidification load depends on the total flow of outdoor air infiltration CFM plus the ventilation CFM , the absolute humidity difference between the indoor air at the indoor design condition and the outdoor air at the winter design temperature and 80 percent RH , and the altitude correction factor ACF from Table 10A.

Figure provides moisture content values for a range of outdoor air temperatures and moisture content values for a variety of indoor humidity values.

This information is used when the elevation is 2, feet or less. For higher elevations, moisture content values are read from Table 12, a psychometric chart for the altitude of concern, or they can be obtained by using altitude sensitive psychometric software.

Figure For example, sea level calculations show that 4. For convenience, Figure summarizes the result of a similar set calculations for a range of outdoor temperatures and indoor humidities.

The following equation converts pounds of water per hour to gallons of water per day: Section 27 Therefore, the 1.

Manual J Residential Load Calculation (8th Edition - Full) Solutions Manual

If a humidification device has its own self contained source of heat, there is no humidification load on the central equipment. If a humidification device does not have a source of heat, the heat of evaporation is a load on the central heating equipment.

This equation determines the humidification heating load HHL generated by evaporative humidification devices. For example, an evaporative device that processes 1. The following equation provides a value for the heating load produced by evaporative humidification devices. For this equation, CFMoa is the total flow of outdoor air infiltration plus ventilation and Grains Added is the grains of moisture added to the flow of outdoor air.

For example, adding 15 Grains of moisture to CFM of outdoor air produces a 1, Btuh humidification load at sea level. It is offered as investigative-demonstrative tool.

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His attention to detail, knowledge, experience, and respectful manner were much appreciated. Customer service is clearly important with this company. Find a contractor. Communities Library View Entry. Downloads - Public Files. Back to Library. Richard Mogridge.

ACCA Membership. Manual J Load Calculations: Estimates are correct for the amount of heating and cooling required for a residence. Manual S Equipment Selection: The selection of equipment was based on the heating and cooling loads and OEM performance data; the equipment is within the maximum sizing requirements. Manual D Duct Systems:The associated heating and sensible cooling loads are determined by multiplying the HTM values by the load areas. The duct wall R-value or values. Some of this resistance is generated as moving air rubs against a duct wall or any other surface the blower vanes, the fins of a coil or the plates of a heat exchanger, for example , the remainder of the resistance is caused by turbulence produced by fittings and air-side devices.

Encapsulated Attic: The consequence of this can be an uncomfortable environment, increased operating costs and can lead to unexpected repair costs. Pubudu Charaka Kudahetti. THL is the total latent heating load.

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