Pressure Enthalpy without Tears Eugene Silberstein, M.S., CMHE, BEAP Presented by Eugene Silberstein, M.S., CMHE, BEAP Suffolk County Community College Cengage Learning HVAC EXCELLENCE EDUCATORS CONFERENCE SOUTH POINT HOTEL & CASINO MARCH 31 – APRIL 2, 2014

If we change the way we look at things, the things we look at change

S IX

Chocolate Pudding

74 39 28 23 19 18 22 17 15 14 13 1 x 1 x 72 2 x 2 x 18 1 x 2 x 36 2 x 3 x 12 1 x 3 x 24 2 x 4 x 9 1 x 4 x 18 2 x 6 x 6 1 x 6 x 12 3 x 4 x 6 1 x 8 x 9 3 x 3 x 8

LINES OF CONSTANT ENTHALPY LINES OF CONSTANT PRESSURE Pressure (psia) PRESSURE DROPS PRESSURE RISES HEAT CONTENT DECREASES HEAT CONTENT INCREASES Heat Content Btu/lb

Pressure (psia) SATURATION CURVE Heat Content Btu/lb Btu/lb

THE SATURATION CURVE Under the curve, the refrigerant follows the pressure-temperature relationship The left side of the saturation curve represents 100% liquid The right side of the saturation curve represents 100% vapor For non-blended refrigerants, one pressure corresponds to one temperature

LINES OF CONSTANT TEMPERATURE Pressure (psia) LINES OF CONSTANT TEMPERATURE Heat Content Btu/lb

Pressure (psia) LINES OF CONSTANT VOLUME (ft3/lb) Heat Content Btu/lb

Pressure (psia) LINES OF CONSTANT ENTROPY Heat Content Btu/lb

Pressure (psia) LINES OF CONSTANT QUALITY Heat Content Btu/lb

PUT IT ALL TOGETHER… Pressure (psia) Heat Content Btu/lb

Pressure-Enthalpy (p-h) Diagram for R-12 (Simplified) Pressure (psia) 160°F 140°F 221 120°F 172 100°F 132 80°F 99 60°F 72 40°F 52 20°F 36 0°F 24 12 20 25 31 35 8 8 8 8 8 9 9 9 9 9 1 1 1 1 1 0 2 4 6 8 0 2 4 6 8 0 0 0 0 0 Enthalpy in btu/lb (Heat Content) 0 2 4 6 8

Pressure-Enthalpy (p-h) Diagram for R-22 (Simplified) Pressure (psia) 160°F 140°F 352 120°F 275 100°F 211 80°F 159 60°F 117 40°F 84 20°F 58 0°F 39 15 24 31 40 46 110 112 119 123 Enthalpy in btu/lb (Heat Content)

Pressure-Enthalpy (p-h) Diagram for R-410A (Simplified) Pressure (psia) 160°F 140°F 557 120°F 434 100°F 334 80°F 251 60°F 186 40°F 133 20°F 93 0°F 63 13 28 45 123 133 140 143 148 152 21 37 53 Enthalpy in btu/lb (Heat Content)

REPEATING vs. NON-REPEATING CYCLES

High Pressure High Temperature CONDENSER Liquid Vapor High Pressure High Temperature METERING DEVICE COMPRESSOR Low Pressure Low Temperature EVAPORATOR

Subcooled Liquid Saturated Refrigerant Superheated Vapor CONDENSER METERING DEVICE COMPRESSOR EVAPORATOR

Pressure Subcooled Region Superheated Region Saturated Region Heat Content

Pressure Heat Content

Pressure (psia) Heat Content Btu/lb

Height Above Saturation VAPOR LIQUID

Saturation VAPOR LIQUID Distance Below Saturation

Pressure (psia) Heat Content Btu/lb

PUT IT ALL TOGETHER… Pressure (psia) A E B C D Heat Content Btu/lb

E to A: CONDENSER (Including discharge and liquid line) Pressure Heat Content (psia) Btu/lb PUT IT ALL TOGETHER… A B C D E E to A: CONDENSER (Including discharge and liquid line) A to B: METERING DEVICE B to C: EVAPORATOR C to D: SUCTION LINE D to E: COMPRESSOR A B C D E

NET REFRIGERATION EFFECT The portion of the system that provides the desired cooling or conditioning of the space or products being treated. A E D B C

NET REFRIGERATION EFFECT The larger the NRE, the greater the heat transfer rate per pound of refrigerant circulated NRE is in the units of btu/lb Cooling effect can be increased by increasing the NRE or by increasing the mass flow rate The cooling effect can be decreased by decreasing the NRE or by decreasing the rate of refrigerant circulation through the system

NRE Example Heat Content at point B = 35 btu/lb Heat Content at point C = 85 btu/lb NRE = C – B = 85 btu/lb – 35 btu/lb NRE = 50 btu/lb Each pound of refrigerant can therefore hold 50 btu of heat energy How many btu does it take to make 1 ton?

How Many btu = 1 Ton? 12,000 btu/hour = 1 Ton = 200 btu/min From the previous example, how many lb/min do we have to move through the system to get 1 ton? 200 btu/min/ton ÷ 50 btu/lb = 4 lb/min We must circulate 4 pounds of refrigerant through the system every minute to obtain one ton of refrigeration Mass Flow Rate Per Ton

NRE and MFR/ton The NRE determines the number of btu that a pound of refrigerant can hold The larger the NRE the more btu can be held by the pound of refrigerant As the NRE increases, the MFR/ton decreases As the NRE decreases, the MFR/ton increases NRE = Heat content at C – Heat content at B MFR/ton = 200 ÷ NRE Cool, huh?

THE SUCTION LINE The line that connects the outlet of the evaporator to the inlet of the compressor. This line is field installed on split-type air conditioning systems. A E B D C

SUCTION LINE The suction line should be as short as possible The amount of heat introduced to the system through the suction line should be minimized Damaged suction line insulation increases the amount of heat added to the system and decreases the system’s operating efficiency Never remove suction line insulation without replacing Seal the point where insulation sections meet

A E E B D D C

HEAT OF WORK The quantity, in btu/lb that represents the amount of heat that is added to the refrigerant during the compression process. A E B C D

HEAT OF WORK (HOW) The HOW indicates the amount of heat added to a pound of refrigerant during compression As the pressure of the refrigerant increases, the heat content of the refrigerant increases as well Heat gets concentrated in the compressor As HOW increases, efficiency decreases As HOW decreases, system efficiency increases HOW = Heat content at E – Heat content at D

HEAT OF COMPRESSION The quantity, in btu/lb that represents the amount of heat that is added to the system, outside of the evaporator A E B C D

HEAT OF COMPRESSION (HOC) The HOW indicates the amount of heat added to a pound of refrigerant outside the evaporator Comprised of the HOW and the suction line As HOC increases, efficiency decreases As HOC decreases, system efficiency increases HOW = Heat content at E – Heat content at C

TOTAL HEAT OF REJECTION The quantity, in btu/lb that represents the amount of heat that is removed from the system. THOR includes the discharge line, condenser and liquid line. A E B C D

TOTAL HEAT OF REJECTION (THOR) THOR indicates the total amount of heat rejected from a system Refrigerant (hot gas) desuperheats when it leaves the compressor (sensible heat transfer) Once the refrigerant has cooled down to the condensing temperature, a change of state begins to occur (latent heat transfer) After condensing, refrigerant subcools THOR = Heat content at E – Heat content at A THOR = NRE + HOC

SUBCOOLING & FLASH GAS Subcooling is a good thing, right? Flash gas is a good thing, right? Are flash gas and subcooling related? How can we tell? Stay tuned...

(Only a slight Exaggeration) HIGH SUBCOOLING.... (Only a slight Exaggeration) A B C D E What happened to the amount of flash gas?

LARGE AMOUNT OF FLASH GAS.... (Only a slight Exaggeration) B C D What happened to the subcooling?

SUBCOOLING & FLASH GAS Subcooling and flash gas are inversely related to each other As the amount of subcooling increases, the percentage of flash gas decreases As the percentage of flash gas increases, the amount of subcooling decreases

COMPRESSION RATIO Determined by dividing the high side pressure (psia) by the low side pressure (psia) A E High-side pressure Low-side pressure B C D

COMPRESSION RATIO Represents the ratio of the high side pressure to the low side pressure Directly related to the amount of work done by the compressor to accomplish the compression process The larger the compression ratio, the larger the HOW and HOC and the lower the system MFR The larger the HOW and HOC, the lower the system efficiency Absolute pressures must be used

ABSOLUTE PRESSURE Absolute pressure = Gauge pressure + 14.7 Round off to 15, for ease of calculation Example 1 High side pressure (psig) = 225 psig High side pressure (psia) = 225 + 15 = 240 psia Low side pressure (psig) = 65 psig Low side pressure (psia) = 65 + 15 = 80 psia Compression ratio = 240 psia ÷ 80 psia = 3:1

Low Side Pressure in a Vacuum? First, convert the low side vacuum pressure in inches of mercury to psia Use the following formula  (30” Hg – vacuum reading) ÷ 2 Example High side pressure = 245 psig High side pressure (psia) = 245 + 15 = 260 psia Low side pressure = 4”Hg Low side (psia) = (30”hg – 4”Hg) ÷ 2 = 13 psia Compression ratio = 260 ÷ 13 = 20:1

Meet Tammy…

90th Floor 2 Lawyers + 1 Tammy = Wasted Time 2nd Floor

Tammy’s 8-Hour Day 9am – 10 am Work on 2nd Floor 10am – 11am Walk up 11am – 12 noon Work on 90th Floor 12 noon – 1pm Walk down 1 pm – 2pm Lunch 2pm – 3 pm Work on 2nd Floor 3 pm – 4 pm Walk up 4pm – 5 pm Work on 90th Floor

Hmmmmmmmmmmmm What if the law firm moves its 90th floor office to the 3rd floor? How will this affect Tammy’s productivity? Will she do more work? Less? What the heck does this have to do with air conditioning? How many licks does it take to get to the chocolaty center of a Tootsie Pop?

If Tammy’s office moves from the 90th floor to the 3rd floor, we get something like this….

Tammy’s 8-Hour Day 9:00 am – 10:00 am Work on 2nd Floor 10:00 am – 10:05 am Walk up to 3rd Floor 10:05 am – 11:05 noon Work on 3rd Floor 11:05 am – 11:10 am Walk down to 2nd Floor 11:10 am – 12:10 pm Work on 2nd Floor 12:10 pm – 1:10 pm Lunch 1:10 pm – 1:15 pm Walk up to 3rd Floor 1:15 pm – 2:15 pm Work on 3rd Floor 2:15 pm – 2:20 pm Walk down to 2nd Floor 2:20 pm – 3:20 pm Work on 2nd Floor 3:20 pm – 3:25 pm Walk up to 3rd Floor 3:25 pm – 4:25 pm Work on 3rd Floor 4:25 pm – 4:30 pm Walk down to 2nd Floor 4:30 pm – 5:00 pm Work on 2nd Floor

Office Comparison Which is better? 2nd Floor  90th Floor 4 hours of work 3 hours of walking up and down the stairs 1 hour lunch Day ends on the 90th Floor 2nd Floor  3rd Floor 6 ½ hours of work 30 minutes of walking up and down the stairs 1 hour lunch Day ends on the 2nd Floor Which is better?

COMPRESSION RATIO Lower compression ratios  higher system efficiency Higher compression ratios  lower system efficiency The closer the head pressure is to the suction pressure, the higher the system efficiency, all other things being equal and operational

Causes of High Compression Ratio (High Side Issues) Dirty or blocked condenser coil Recirculating air through the condenser coil Defective condenser fan motor Defective condenser fan motor blade Defective wiring at the condenser fan motor Defective motor starting components (capacitor) at the condenser fan motor

Causes of High Compression Ratio (Low Side Issues) Dirty or blocked evaporator coil Dirty air filter Defective evaporator fan motor Dirty blower wheel (squirrel cage) Defective wiring at the evaporator fan motor Closed supply registers Blocked return grill Loose duct liner Belt/pulley issues

THEORETICAL HORSEPOWER PER TON Determines how much compressor horsepower is required to obtain 1 ton of cooling The ft-lb is a unit of work The ft-lb/min is a unit of power 33,000 ft-lb/min = 1 Horsepower The conversion factor between work and heat is 778 ft-lb/btu 33,000 ft-lb/min/hp ÷ 778 ft-lb/btu = 42.42 btu/min/hp

THEORETICAL HORSEPOWER PER TON THp/ton = (MFR/ton x HOW) ÷ 42.42 For example, if we had a system that had an NRE of 50 and a HOW of 10, the THp/ton would be: THp/ton = (200/NRE) x HOW ÷ 42.42 THp/ton = (200/50) x 10 ÷ 42.42 THp/ton = 4 x 10 ÷ 42.42 THp/ton = 40 ÷ 42.42 THp/ton = 0.94

THp/ton Example If we had a 20-Hp reciprocating compressor and the THp/ton calculation yielded a result of 2 hp/ton, what would the expected cooling capability of the system be? 16 TONS 5 TONS 25 TONS 1 TON 3.8 TONS 20 TONS 3,492 TONS 10 TONS

What Affects the THp/ton Number? The Net Refrigeration Effect (NRE) The Heat of Work (HOW) What Affects the NRE and HOW? Suction pressure Discharge pressure Compression Ratio Airflow through the coils Blowers and fans And so on, and so on, and so on, and so on….

Get the Picture?

MASS FLOW RATE OF THE SYSTEM The amount of refrigerant that flows past any given point in the system every minute Not to be confused with MFR/ton MFR/system is the actual refrigerant flow, while MFR/ton is the flow per ton MFR/system can be found by multiplying the MFR/ton by the number of tons of system capacity, or MFR/system = (42.42 x Compressor HP) ÷ HOW

COOL STUFF As the HOW increases, the MFR/system decreases, and vice versa As the Compression Ratio increases, the HOW increases As head pressure increases, or as suction pressure decreases, the Compression Ratio increases As the MFR/system decreases, the capacity of the evaporator, condenser and compressor all decrease Let’s take a closer look…

Evaporator Capacity = MFR/system x NRE x 60 A function of the MFR/system and the NRE The MFR/system is in lb/min, the NRE is in btu/lb and the capacity of the evaporator is in btu/hour Evaporator Capacity = MFR/system x NRE x 60 Btu Lb Btu 60 Min Hour Min Lb Hour

EVAPORATOR CAPACITY If the NRE or the MFR/system decreases, the evaporator capacity also decreases The “60” is a conversion factor from btu/min to btu/hour, given that there are 60 minutes in an hour Divide the evaporator capacity in btu/hour by 12,000 to obtain the evaporator capacity in tons

Condenser Capacity = MFR/system x THOR x 60 A function of the MFR/system and the THOR The MFR/system is in lb/min, the THOR is in btu/lb and the capacity of the condenser is in btu/hour Condenser Capacity = MFR/system x THOR x 60 Btu Lb Btu 60 Min Hour Min Lb Hour

Compresser Capacity = MFR/system x Specific Volume COMPRESSOR CAPACITY A function of the MFR/system and the Specific volume of the refrigerant at the inlet of the compressor Calculated in cubic feet per minute, ft3/min Compresser Capacity = MFR/system x Specific Volume ft3 Lb ft3 Min Min Lb

COEFFICIENT OF PERFORMANCE (COP) The ratio of the NRE compared to the HOC If the HOC remains constant, any increases in NRE will increase the COP If the NRE remains constant, any decrease in HOC will increase the COP The COP is a contributing factor to the EER of an air conditioning system COP is a unitless value

COP EXAMPLE Heat content at point B = 35 btu/lb Heat content at point C = 104 btu/lb Heat content at point E = 127 btu/lb NRE = 104 btu/lb – 35 btu/lb = 69 btu/lb HOC = 127 btu/lb – 104 btu/lb = 23 btu/lb COP = 69 btu/lb ÷ 23 btu/lb = 3 Notice that the “3” has no units

ENERGY EFFICIENCY RATIO (EER) A ratio of the amount of btus transferred to the amount of power used In the units of btu/watt The conversion between btus and watts is 3.413 One watt of power generates 3.413 btu For example, if a system required 50,000 btu of heat, 14,650 watts of electric heat (14.65 kw) can be used

ENERGY EFFICIENCY RATIO (EER), Cont’d. The efficiency rating of an air conditioning system is the COP For each btu/lb introduced to the system in the suction line and the compressor, a number of btus equal to the NRE are absorbed into the system via the evaporator To convert the COP to energy usage, we multiply the COP by 3.413

EER EXAMPLE The NRE of a system is 70 btu/lb The HOC of the same system is 20 btu/lb The COP is 70 btu/lb ÷ 20 btu/lb = 3.5 The EER = COP x 3.413 EER = 3.5 x 3.413 EER = 11.95

SEASONAL EER (SEER) Takes the entire conditioning system into account Varies depending on the geographic location of the equipment Ranges from 10% t0 30% higher than EER So, if the EER is 10, the SEER will range from 11 to 13

From the P-H Chart, We Can Find Compression Ratio NRE HOC HOW THOR COP MFR/ton THp/ton MFR/system Evaporator Capacity Condenser Capacity Compressor Capacity EER of the System SEER Okay, Okay, Okay… How do I plot one of these things?

An R-22 A/C System… Condenser saturation temperature 120°F Condenser outlet temperature 100°F Evaporator saturation temperature 40°F Evaporator outlet temperature 50°F Compressor inlet temperature 60°F Compressor Horsepower: 4 hp

Pressure-Enthalpy (p-h) Diagram for R-22 (Simplified) Pressure (psia) 180°F 160°F 140°F 352 0.7 120°F 275 100°F 211 80°F 159 60°F 117 40°F 84 20°F 58 0°F 39 -20°F 25 -40°F 3 4 4 5 1 1 1 1 1 2 0 6 3 1 1 1 2 2 0 2 7 1 5 Enthalpy in btu/lb (Heat Content)

Pressure-Enthalpy (p-h) Diagram for R-22 (Simplified) Pressure (psia) 180°F 160°F 140°F 352 0.7 120°F 275 100°F 211 80°F 159 60°F 117 40°F 84 20°F 58 0°F 39 -20°F 25 -40°F 3 4 4 5 1 1 1 1 1 2 0 6 3 1 1 1 2 2 0 2 7 1 5 Enthalpy in btu/lb (Heat Content)

Pressure-Enthalpy (p-h) Diagram for R-22 (Simplified) Pressure (psia) 180°F 160°F 140°F 352 A B 0.7 120°F 275 100°F 211 80°F 159 60°F 117 40°F 84 C 20°F 58 0°F 39 -20°F 25 -40°F 3 4 4 5 1 1 1 1 1 2 0 6 3 1 1 1 2 2 0 2 7 1 5 Enthalpy in btu/lb (Heat Content)

Pressure-Enthalpy (p-h) Diagram for R-22 (Simplified) Pressure (psia) 180°F 160°F 140°F 352 A B 0.7 120°F 275 100°F 211 80°F 159 60°F 117 40°F 84 C D 20°F 58 0°F 39 -20°F 25 -40°F 3 4 4 5 1 1 1 1 1 2 0 6 3 1 1 1 2 2 0 2 7 1 5 Enthalpy in btu/lb (Heat Content)

Pressure-Enthalpy (p-h) Diagram for R-22 (Simplified) Pressure (psia) 180°F 160°F 140°F 352 A B 0.7 120°F 275 100°F 211 80°F 159 60°F 117 40°F 84 C D 20°F 58 0°F 39 -20°F 25 -40°F 3 4 4 5 1 1 1 1 1 2 0 6 3 1 1 1 2 2 0 2 7 1 5 Enthalpy in btu/lb (Heat Content)

Pressure-Enthalpy (p-h) Diagram for R-22 (Simplified) Pressure (psia) 180°F 160°F 140°F 352 A B E 0.7 120°F 275 100°F 211 80°F 159 60°F 117 40°F 84 C D 20°F 58 0°F 39 -20°F 25 -40°F 3 4 4 5 1 1 1 1 1 2 0 6 3 1 1 1 2 2 0 2 7 1 5 Enthalpy in btu/lb (Heat Content)

Pressure-Enthalpy (p-h) Diagram for R-22 (Simplified) Pressure (psia) 180°F 160°F 140°F 352 A B E 0.7 120°F 275 100°F 211 80°F 159 60°F 117 40°F 84 C D 20°F 58 High: 275 psia Low: 84 psia “A”: 40 btu/lb “B”: 40 btu/lb “C”: 110 btu/lb “D”: 112 btu/lb “E”: 125 btu/lb 0°F 39 -20°F 25 -40°F 3 4 4 5 1 1 1 1 1 2 0 6 3 1 1 1 2 2 0 2 7 1 5 Enthalpy in btu/lb (Heat Content)

COMPRESSION RATIO = 275 psia ÷ 84 psia = 3.27:1 High: 275 psia Low: 84 psia “A”: 40 btu/lb “B”: 40 btu/lb “C”: 110 btu/lb “D”: 112 btu/lb “E”: 125 btu/lb COMPRESSION RATIO HIGH SIDE PRESSURE (psia) LOW SIDE PRESSURE (psia) COMPRESSION RATIO = 275 psia ÷ 84 psia = 3.27:1

HEAT OF WORK = 125 btu/lb – 112 btu/lb = 13 btu/lb High: 275 psia Low: 84 psia “A”: 40 btu/lb “B”: 40 btu/lb “C”: 110 btu/lb “D”: 112 btu/lb “E”: 125 btu/lb HEAT OF WORK HEAT CONTENT AT “E” – HEAT CONTENT AT “D” HEAT OF WORK = 125 btu/lb – 112 btu/lb = 13 btu/lb

HEAT OF COMPRESSION= 125 btu/lb – 110 btu/lb = 15 btu/lb High: 275 psia Low: 84 psia “A”: 40 btu/lb “B”: 40 btu/lb “C”: 110 btu/lb “D”: 112 btu/lb “E”: 125 btu/lb HEAT OF COMPRESSION HEAT CONTENT AT “E” – HEAT CONTENT AT “C” HEAT OF COMPRESSION= 125 btu/lb – 110 btu/lb = 15 btu/lb

NRE = 110 btu/lb – 40 btu/lb = 70 btu/lb High: 275 psia Low: 84 psia “A”: 40 btu/lb “B”: 40 btu/lb “C”: 110 btu/lb “D”: 112 btu/lb “E”: 125 btu/lb NET REFRIGERATION EFFECT HEAT CONTENT AT “C” – HEAT CONTENT AT “B” NRE = 110 btu/lb – 40 btu/lb = 70 btu/lb

MFR/ton = 200 ÷ NRE =200 ÷ 70 btu/lb = 2.86 lb/min/ton High: 275 psia Low: 84 psia “A”: 40 btu/lb “B”: 40 btu/lb “C”: 110 btu/lb “D”: 112 btu/lb “E”: 125 btu/lb MASS FLOW RATE PER TON 200 ÷ NRE MFR/ton = 200 ÷ NRE =200 ÷ 70 btu/lb = 2.86 lb/min/ton

THOR = 125 btu/lb – 40 btu/lb = 85 btu/lb High: 275 psia Low: 84 psia “A”: 40 btu/lb “B”: 40 btu/lb “C”: 110 btu/lb “D”: 112 btu/lb “E”: 125 btu/lb TOTAL HEAT OF REJECTION HEAT CONTENT AT “E” – HEAT CONTENT AT “A” THOR = 125 btu/lb – 40 btu/lb = 85 btu/lb

THp/ton = 2.86 lb/min/ton x 13 btu/lb ÷ 42.42 = 0.88 Hp/ton High: 275 psia Low: 84 psia “A”: 40 btu/lb “B”: 40 btu/lb “C”: 110 btu/lb “D”: 112 btu/lb “E”: 125 btu/lb THEORETICAL HORSEPOWER PER TON [MFR/ton x HOW] ÷ 42.42 THp/ton = 2.86 lb/min/ton x 13 btu/lb ÷ 42.42 = 0.88 Hp/ton

COEFFICIENT OF PERFORMANCE High: 275 psia Low: 84 psia “A”: 40 btu/lb “B”: 40 btu/lb “C”: 110 btu/lb “D”: 112 btu/lb “E”: 125 btu/lb COEFFICIENT OF PERFORMANCE NRE ÷ HOC COP = 70 btu/lb ÷ 15 btu/lb = 4.67

MASS FLOW RATE OF THE SYSTEM High: 275 psia Low: 84 psia “A”: 40 btu/lb “B”: 40 btu/lb “C”: 110 btu/lb “D”: 112 btu/lb “E”: 125 btu/lb MASS FLOW RATE OF THE SYSTEM [42.42 x Compressor HP] ÷ HOW MFR/system = [42.42 x 4] ÷ 13 btu/lb = 13.05 lb/min

CAPACITY OF THE EVAPORATOR High: 275 psia Low: 84 psia “A”: 40 btu/lb “B”: 40 btu/lb “C”: 110 btu/lb “D”: 112 btu/lb “E”: 125 btu/lb CAPACITY OF THE EVAPORATOR NRE x MFR/system x 60 CAP/evap = 70 btu/lb x 13.05 x 60 = 54,810 btu/hour CAP/evap = 54,810 btu/hour ÷ 12,000 btu/hour/ton = 4.57 tons

CAPACITY OF THE CONDENSER High: 275 psia Low: 84 psia “A”: 40 btu/lb “B”: 40 btu/lb “C”: 110 btu/lb “D”: 112 btu/lb “E”: 125 btu/lb CAPACITY OF THE CONDENSER THOR x MFR/system x 60 CAP/cond = 85 btu/lb x 13.05 x 60 = 66,555 btu/hour CAP/cond = 66,555 btu/hour ÷ 12,000 btu/hour/ton = 5.55 tons

CAPACITY OF THE COMPRESSOR High: 275 psia Low: 84 psia “A”: 40 btu/lb “B”: 40 btu/lb “C”: 110 btu/lb “D”: 112 btu/lb “E”: 125 btu/lb CAPACITY OF THE COMPRESSOR MFR/system x Specific Volume CAP/comp = 13.05 x 0.7 = 9.13 ft3/min

ENERGY EFFICIENCY RATIO High: 275 psia Low: 84 psia “A”: 40 btu/lb “B”: 40 btu/lb “C”: 110 btu/lb “D”: 112 btu/lb “E”: 125 btu/lb ENERGY EFFICIENCY RATIO COP x 3.413 EER = 4.67 x 3.413 = 15.94 SEER (low end) = 1.1 x EER = 1.1 x 15.94 = 17.5 SEER (high end) = 1.3 x EER = 1.3 x 15.94 = 20.7

275 psia 84 psia 61 psia 40 110 112 125 100 111

Let’s See What Happened… CR = 4.5 HOW = 14 HOC = 25 NRE = 60 MFR/ton = 3.33 lb/min THp/ton = 1.1 COP = 2.4 MFR/system = 12.12 CAP/evap = 43,632 btu EER = 8.19 CR = 3.27 HOW = 13 HOC = 15 NRE = 70 MFR/ton = 2.86 lb/min THp/ton = 0.88 COP = 4.67 MFR/system = 13.05 CAP/evap = 66,555 btu EER = 15.9

Properly Operating System Heat Content “A” = 40 btu/lb Heat Content “B” = 40 btu/lb Heat Content “C” = 109 btu/lb Heat Content “D” = 111 btu/lb Heat Content “E” = 125 btu/lb High side pressure = 267 psig High side pressure = 282 psia Low side pressure = 70 psig Low side pressure = 85 psia Compressor Hp = 2.5 Hp Specific Volume = 0.7 NRE = 69 btu/lb HOW = 14 btu/lb HOC = 16 btu/lb THOR = 85 btu/lb Comp. Ratio = 3.32 MFR/ton = 2.9 lb/min/ton THp/ton = 0.96 Hp/ton COP = 4.3 MFR/system = 7.58 lb/min CAP/evap = 31,381 btuh CAP/cond = 38,658 btuh CAP/comp = 5.3 ft3/min EER = 14.68 SEER = 16.15 – 19.1 A/B C D E

Clogged Cap Tube System Heat Content “A” = 39 btu/lb Heat Content “B” = 39 btu/lb Heat Content “C” = 112 btu/lb Heat Content “D” = 118 btu/lb Heat Content “E” = 134 btu/lb High side pressure = 226 psig High side pressure = 241 psia Low side pressure = 59 psig Low side pressure = 74 psia Compressor Hp = 2.5 Hp Specific Volume = 0.9 NRE = 73 btu/lb HOW = 16 btu/lb HOC = 22 btu/lb THOR = 95 btu/lb Comp. Ratio = 3.26 MFR/ton = 2.74 lb/min/ton THp/ton = 1.03 Hp/ton COP = 3.3 MFR/system = 6.63 lb/min CAP/evap = 29,039 btuh CAP/cond = 37,791 btuh CAP/comp = 5.97 ft3/min EER = 11.26 SEER = 12.39 – 14.64 A/B C D E

System Okay System Clogged Increase/Decrease NRE 69 73 Increase HOW 14 16 HOC 22 THOR 85 95 Comp. Ratio 3.32 3.26 Decrease MFR/ton 2.9 2.74 THp/ton 0.96 1.03 COP 4.3 3.3 MFR/system 7.58 6.63 CAP/evap 31,381 (2.62) 29,039 (2.42) CAP/cond 38,658 (3.22) 37,791 (3.15) CAP/comp 5.3 5.97 EER 14.68 11.26 SEER 16.15 – 19.1 12.39 – 14.64

Contact Information... Eugene Silberstein Suffolk County Community College 1001 Crooked Hill Road Brentwood, NY 11717 (631) 851-6897 E-mail: silbere@sunysuffolk.edu