Conversions,
SI Systems, Tables, Pressure Temp/Chart
| Power | Mass | ||
| BTU/hr x 0.292 8 | = W (J/s) | kg x 2.205 0 | = lb |
| BTU/hr x 251.996 | = cal/hr | lb x 2 240 | = ton (long) |
| kW x 1.341 0 | = hp | lb x 2 000 | = ton (short) |
| hp (electrical) x 746.00 | = W | kg x 1000 | = ton (metric) |
| hp x 2 546.699 | = Btu/hr | lb x 2 204.623 | = ton (metric) |
| Pressure | lb x 14 | = stone | |
| atm x 101.325 | = kPa | gram x 0.2 | = carat |
| atm x 1.013 25 | = bar | Mass Flow | |
| atm x 1 013.25 | = mbar | kg/s x 132.277 3 | = lb/m |
| atm x 14.696 | = PSI | Volume | |
| Bar x 100 | = kPa | m3 x 264.172 1 | = gal (US) |
| Bar x 29.53 | = in Hg | m3 x 219.969 2 | = gal (UK) |
| Bar x 14.504 | = PSI | m3 x 35.314 7 | = ft3 |
| mbar x 0.750 0 | = torr | gal (US) x 3.785 4 | = litre |
| mbar x 750 | = µ | gal (UK) x 4.546 1 | = litre |
| mbar x 100 | = Pa | pint (US) x 0.473 2 | = litre |
| Pa x 7.5 | = µ | pint (UK) x 0.568 3 | = litre |
| Pa x 0.0075 | = torr | quart x 2 | = pint |
| kPa x 10 | = mbar | quart (US) x 0.946 4 | = litre |
| kPa x 7.500 6 | = mmHg | quart (UK) x 1.136 5 | = litre |
| PSI x 6.894 8 | = kPa | litre x 33.814 0 | = oz (US) |
| PSI x 27.71 | = in WG | litre x 35.195 1 | = oz (UK) |
| PSI x 703.6 | = mm WG | ft3 x 6.228 8 | = gal (UK) |
| PSI x 2.401 6 | = in Hg | ft3 x 7.480 5 | = gal (US) |
| PSI x 51.8 | = mm Hg | litre x 28.316 85 | = ft3 |
| kgf/cm2 x 0.980 7 | = bar | cc x 4.928 922 | = teaspoon |
| kgf/cm2 x 98.0 7 | = kPa | cc x 14.928 922 | = tablespoon |
| kgf/cm2 x 14.223 | = PSI | cc x 236.588 2 | = cup |
| mm WG x 9.806 4 | = Pa | drops x 15.419 63 | = cc |
| in WG x 249.08 | = Pa | ml x 1 | = cc |
| in Hg x 3.376 85 | = kPa | Volume Flow | |
| in Hg x 0.491 2 | = PSI | m3/s x 2 118.88 | = cfm |
| in Hg x 25.4 | = torr | m3/hr x 0.588 6 | = cfm |
| mm Hg x 133.322 4 | = Pa | l/s x 15.850 3 | = gpm (US) |
| mm Hg x 1000 | = µ | l/s x 13.198 2 | = gpm (UK) |
| mm Hg x 1 | = torr | l/s x 3.6 | = m3/hr |
| Energy | Specific Heat | ||
| Btu x 1 055.056 | = J | Btu/lb.ºF x 4.186 8 | = kJ/kg.K |
| Btu x 0.252 0 | = kcal | kcal/kg.K x 4.186 8 | = kJ/kg.K |
| cal x 4.186 8 | = J | Temperature | |
| kJ x 0.947 8 | = Btu | (ºC x 1.8) + 32 | = º F |
| kJ x 238.845 9 | = cal | (ºF - 32) ~ 1.8 | = º C |
| Heat Flow | Absolute temperate (K) | = º C + 273.15 | |
| Btu/hr/ft2 x 3.154 6 | = W/m2 | Absolute temperature (R) | = º F + 459.67 |
| Heat content/enthalpy | Temperature difference | ||
| Btu/lb x 2.326 0 | = kJ/kg | 1 K (deg.C?T) | = 1.8R (deg.F?T) |
| Heat Transfer | 1 R (deg.F?T) | = 0.555 6 K (deg.C?T) | |
| kW x 3 412 | = Btu/hr | Torque | |
| Btu/hr.ft2.ºF x 5.678 3 | = W/m2.K | N.m. x 0.737 6 | = ft.lb force |
| Btu/hr x 0.293 1 | = W | kgf.m x 9.81 | = N.m. |
| Btu/ft2 x 11 356.53 | = J/m2 | Velocity/Speed | |
| Btu/ft2.ºF x 4.874 0 | = kcal/m2.K | km/hr x 0.277 8 | = m/s |
| Btu/ft2.ºF x 20.407 7 | = kJ/m2.K | m/s x 196.850 4 | = fpm |
| ton refrigeration x 12 000 | = Btu/hr | knot x 1.852 | = km/hr |
| ton refrigeration x 3.516 8 | = kW | mile/hr x 1.609 3 | = km/hr |
| Distance | km/hr x 1 193.256 | = mach | |
| m x 1.093 6 | = yard | m/hr x 741.454 9 | = mach |
| m x 3.280 9 | = ft | Angle | |
| m x 39.37 | = in | 360 degrees | = revolution |
| yard x 1 093.613 | = km | 57.295 8 degrees | = radian |
| ft x 3 280.83 | = km | 6.283 184 radian | = revolution |
| m x 1 000 | = km | Area | |
| ft x 12 | = in | m2 x 10.746 | = ft2 |
| mile x 1 609.34 | = m | m2 x 1.196 0 | = y2 |
| mile x 5 280 | = ft | ft2 x 144 | = in2 |
| mm x 25.4 | = in | acre x 4 046.825 | = m2 |
| mm x 304.8 | = ft | hectare x 10 000 | = m2 |
| mm x 914.4 | = yard | Density | |
| m x 1 609.344 | = mile | 1 kg/m3 x 0.062 4 | =1 lb/ft3 |
| m x 201.168 | = furlong | ||
| Abbreviations: | |||
| atm = atmosphere BTU = British Thermal Unit cal = calories cc = cubic centimetre º C = degrees Celsius cfm = cubic feet per minute º F = degrees Fahrenheit ft = foot f = force gal = gallon gpm = gallons per minute Hg = mercury hp = horse power hr = hour in = inch J = joule k = kilo (1000) pre-fix) K = Kelvin kg = kilogram kgf = kilogram-force |
km = kilometre kW = kilowatt l = litre lb = pounds (mass) lbf = pounds - force m = metre m = minute m = milli (0.001) pre-fix mach = speed of sound mbar = millibar = bar / 1 000 N = Newton oz = ounce PSI = pounds per square inch R = Rankin (absolute temperature) s = second US = United States W = Watt WG = water gauge y = yard µ = micron ? = delta (difference) |
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Information taken from
African Heating & Cooling - HVAC & R Handbook 2002/3
and
Refrigeration &
Airconditioning Directory 2002
|
The use of the SI System is compulsory in South Africa and there is little doubt that it will become the only measuring system in the world. In view of the international character of the SI System, it is imperative that it be applied correctly. If not, wastage of time and unnecessary expenses may result. The three classes of SI Units Base Units Supplementary Units Derived Units Some derived units have special names and these can again be used to form further derived units. In basic formulae only SI units are used. The seven SI Base Units
Notes
Method of writing SI units and symbols Symbols Symbols are typed or printed in Roman (upright) letters and are always lower case letters except if the name of the corresponding unit is derived from the name of a person, in which case the symbol, or the first letter thereof if it consists of more than one letter, is a capital letter. Examples: metre (M), second (s), watt (W), hertz (Hz), etc. These rules apply always, even if the rest of the subject matter is printed in upper case or other letter types as in headings of tables, paragraphs, etc.
Symbols have no plural, e.g. 1m, 2m, etc. Note that it is incorrect to refer to the symbols as abbreviations. Symbols are therefore not followed by a fullstop unless they occur at the end of sentence, in which case it is recommended that a space be left between the symbol and the fullstop to stress that the fullstop is not part of the symbol, e.g. the length of an object is 2,5m . The product of two or more symbols is preferably indicated by means of a point. This point is preferably raised above the line as in N×M but also may be printed on the line as in N.M if the former position is not easily reproduced, for example in typed work. If there is no risk of confusion with other symbols then the point may be replaced by a space (N m). A
solidus, horizontal line, or negative powers may be used to indicate division of
symbols, e.g. m/s, Example: m.kg.s-3, A -1 or m.kg/(s3.A) When written out in full, the name of a unit is written in lower case letters irrespective of whether it is derived from the name of a person or not. Exceptions are if the unit appears at the beginning of a sentence, in which case the first letter is a capital letter, and if the whole of the subject matter is printed in capital letters e.g. LENGTH IN METRES. The plural form is used in English but not Afrikaans, e.g. 1 metre, 2 metres in English, but 1 meter, 2 meter in Afrikaans. In English, multiplication of units is indicated by means of a space (Newton metre), but in Afrikaans it is indicated by means of a hyphen (Newton-meter). Division is indicated by the word per in both English and Afrikaans, e.g. joule per mole Kelvin (English) and joule per mol-kelvin (Afrikaans). One “per” is used. Where this leads to complications such as with acceleration (metre per second ”per” second), expressions such as metre per second squared are recommended. SI Prefixes The use of only SI units would sometimes lead to inconveniantly large or small values. To avoid this cumbersome notation a series of international prefixes are used to form decimal multiples and sub-multiples of SI units.
|
| Prefixes (Preferred) | |||
| Factor | Factor in words | SI Prefix | SI Symbol |
| 1 000 000 000 000 or 1012 | billion | tera- | T |
| 1 000 000 000 or 109 | milliard | giga- | G |
| 1 000 000 or 106 | million | mega- | M |
| 1 000 or 103 | thousand | kilo- | k |
| 0.001 or 10-3 | thousandth | milli- | m |
| 0.000 001 or 10-6 | millionth | micro- | u |
| 0.000 000 001 or 10-9 | milliardth | nano- | n |
| 0.000 000 000 001 or 10-12 | billionth | pico- | p |
| 0.000 000 000 000 001 or 10-15 | billiardth | femto- | f |
| 0.000 000 000 000 000 001 or 10-18 | trillionth | atto- | a |
|
Prefixes (other) |
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| Factor | Factor in words | SI Prefix | SI Symbol |
| 100 or 102 | hundred | hecto- | h |
| 10 or 101 | ten | deca- | da |
| 0.1 or 10-1 | tenth | deci- | d |
| 0.01 or 10-2 | hundreth | cent- | c |
|
Units used together with the SI The units in the table below have attained such a wide general use that there is little hope of eliminating them. Because they play such an important part, they have been recognised and must be retained for general use together with the SI.
Note 1 Note 2
Additional rules, notations and hints
Notation for numbers Standard Values
Values of the accelerations due to gravity at various places in Southern Africa
A good average value for Southern Africa is 9.79m/s2 Standard Temperature and Pressure (S.T.P) Density of Dry Air
Note: References
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SI Electrial Symbols
Comparative table of the most commonly used symbols
| Nature of Symbols |
European Standards |
US Standards |
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| (Old Version) Power |
(Old Version) Control |
(New Version) Power |
(New Version) Control |
Power |
Control | |
| Normally open contact N/O |  |
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| Normally closed contact N/C | ||||||
| Contact delayed on energisation "on delay" timers | ||||||
| Contact delayed on energisation "off delay" timers | ||||||
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Fuses |
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| Rolays | ||||||
| Operating coils | ||||||
| Motors | ||||||
| Disconnect switches, isolators | ||||||
| Circuit breakers | ||||||
Information supplied by the
Refrigeration & Airconditioning Directory 2002
www.plumbingafrica.co.za
and African Heating & Cooling - HVAC & R Handbook 2002/3
Air conditioning Design Check Figures
| Description | Sea Level | Altitude |
| Cooling load offices - standard design | 110 W/m2 | 100 W/m2 |
| Heating load office - standard design | 45 W/m2 | 50 W/m2 |
| Cooling load offices - energy efficient design | 90 W/m2 | 80 W/m2 |
| Heating load offices - energy efficient design | 40 W/m2 | 40 W/m2 |
| Cooling Loads of Commercial Office Building Elements: | ||
| Load Element | Average | High |
| Lights | 18 W/m2 | 25 W/m2 |
| Equipment | 15 W/m2 | 35 W/m2 |
| Fresh Air l/s/m2 and (Resulting W/m2) | 0.75 l/s/m2 @ 11W/m2 | 1 l/s/m2 @ 16W/m2 |
| m2 per person and (Resulting W/m2) | 10m2 @ 13W/m2 | 7m2 @ 18W/m2 |
| Facade load per floor area | 45 W/m2 | 55 W/m2 |
| Cooling Loads of Retail Building Elements: | ||
| Load Element | Average | High |
| Lights | 30 W/m2 | 60 W/m2 |
| Fresh Air l/s/m2 and (Resulting W/m2) | 0.75 l/s/m2 @ 11W/m2 | 1.61 l/s/m2 @ 24W/m2 |
| m2 per person and (Resulting W/m2) | 10m2 @ 12W/m2 | 6m2 @ 20W/m2 |
| Facade load per floor area | 10 W/m2 | 30 W/m2 |
| Energy Consumption - Commercial Offices (Total electrical consumption): | |
| Description | Check Figure |
| Energy efficient design electrical demand - Average per m2 | 65 W/m2 |
| Energy efficient design electrical consumption - MJ/m2.annum | 500 |
| Standard design electrical demand - Average VA/m2 per month | 90 |
| Standard design electrical consumption - MJ/m2.annum | 1100 |
| Design Weather Data: | ||
| City | Winter (°C db) | Summer (db/°C wb) |
| Bloemfontein | 1.7 | 35/21 |
| Cape Town | 7.0 | 35/21.1 |
| Durban | 10 | 30/25.5 |
| Johannesburg | 2 | 30/20 |
| Port Elizabeth | 7 | 30/22 |
| Pretoria | 5 | 33.3/21 |
- Source: Based on CSIR Research Report 300: Van Deventer, E.N. 1971. Climatic and other design data for evaluating heating and cooling requirements of buildings. CSIR. Updated by RIchard Pearce & Partners, February 2002.
- Data quoted are for 2.5% probability levels.
Check Figures for Cold and Freezer Room Loads
|
Cold Room 1°C Capacity based on 100mm polystyrene panels with an outside box temperature of 32°C, compressor suction -5°C and a 6K difference on blower coil. Holding only: Zero product load Average usage: Based on 35kg/m3/day coming in at 20°C Heavy usage: Based on 70kg/cm3/day coming in at 20°C |
|
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Freezer Room -20°C
Capacity based on 150mm polystyrene panels with an outside box temperature of 32°C, compressor suction -26°C and a 6K difference on blower coil. Holding only: Zero product load Average usage: Based on 35kg/m3/day coming in at -5°C |
Freezer Room -20°C
Capacity based on 150mm polystyrene panels with an outside box temperature of 32°C, compressor suction -26°C and a 6K difference on blower coil. Heavy usage: Based on 35kg/m3/day coming in at +10°C
|
Average Power Factor Efficiencies and Full Load Currents
Details are given for 3000 rpm motors. Details for other speeds vary slightly.
| Three-phase motors: | ||||
| Output power | ||||
| kW | hp | Power factor | Efficiency % | Amps @ 380 V |
| 0.37 | 0.5 | 0.81 | 66.0 | 1.05 |
| 0.55 | 0.75 | 0.81 | 71.0 | 1.45 |
| 0.75 | 1 | 0.85 | 72.0 | 1.85 |
| 1.1 | 1.5 | 0.82 | 75.0 | 2.7 |
| 1.5 | 2 | 0.86 | 78.0 | 3.4 |
| 2.2 | 3 | 0.82 | 80.0 | 5.1 |
| 3 | 4 | 0.88 | 84.0 | 6.2 |
| 4 | 5.5 | 0.85 | 84.0 | 8.5 |
| 5.5 | 7.5 | 0.89 | 84.0 | 11 |
| 7.5 | 10 | 0.87 | 88.0 | 15 |
| 9.2 | 12 | 0.88 | 87.0 | 19 |
| 11 | 15 | 0.90 | 88.0 | 21 |
| 15 | 20 | 0.90 | 89.0 | 28 |
| 18.5 | 25 | 0.89 | 89.4 | 35 |
| 22 | 30 | 0.87 | 90.0 | 43 |
| 30 | 40 | 0.88 | 90.6 | 57 |
| 37 | 50 | 0.87 | 91.0 | 71 |
| 45 | 60 | 0.87 | 92.0 | 85 |
| 55 | 75 | 0.87 | 92.7 | 104 |
| 75 | 100 | 0.89 | 92.5 | 139 |
| 100 | 136 | 0.88 | 92.8 | 187 |
| 110 | 150 | 0.89 | 93.5 | 200 |
Source: Nustart Electric Motors
| Single-phase motors: | ||
| Output power | ||
| kW | hp | Amps @ 220 Volts |
| 0.37 | 0.5 | 3.9 |
| 0.55 | 0.75 | 5.2 |
| 0.75 | 1.0 | 6.6 |
| 1.1 | 1.5 | 9.6 |
| 1.5 | 2 | 12.7 |
| 2.2 | 3 | 18.6 |
| 3 | 4 | 24.3 |
| 4 | 5 | 29.6 |
Source: Telemecanique
Download the PDF document of the chart by clicking here