GENERATION Practical guide: Sizing a standby power generator · the home or business, it can...
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GENERATION energize - July 2010 - Page 18 Practical guide: Sizing a standby power generator by Philip Hampton, Powermode Standby power generators are becoming an essential component of any emergency power strategy, often complementing the installation of uninterruptible power supply (UPS) systems and power inverters. the identification plate or in the owner's manual). Add the “starting” or “loaded” values to arrive at the total power requirement in terms of watts. Don't be tempted to exclude any item if its use will be even rarely called upon. Remember that appliances and tools with electrical motors, such as circular saws, drills, washing machines, dryers and others will vary greatly in power consumption on start-up or when operating under load. Power consumption can spike 200 to 300% under these circumstances. If the appliance doesn't state a figure for “start-up” or “load”, factor this in to your calculations. It's the safest way to arrive at the required capacity of the generator. In order to convert the total wattage to a VA rating (and arrive at the correct capacity generator), use the following formula: = ( ) Unfortunately, PF values are seldom stated on modern appliances' specification sheets so, as a rule of thumb, use PF = 0,6 Another way to calculate the VA rating is: VA rating = Total amperes x 230 The most important benefits of choosing the correctly sized generator include fewer unexpected system failures, no shutdowns due to capacity overloading and increased service life of the generator and the items it powers. In addition, the generator will have a better chance of meeting its stated performance parameters in terms of its specification and permit scheduled maintenance period to be adhered to without the deed for crisis intervention. Contact Philip Hampton, Powermode, Tel 011 235-7750, [email protected] While a generator can be a convenient source of power around the home or business, it can represent a serious threat to safety if installed incorrectly. So, before buying a generator, consider its application. This will determine its size or “capacity”. Generators with power supply capacities of between 5 and 50 kW are readily available for home and home-office use, while industrial generators from 50 kW to over 1 MW are common. Unfortunately, there is a degree of confusion in the marketplace between Watt and VA measures for electric power, often leading to under-sizing of generators which are usually marketed in terms of their VA ratings. Not only does under-sizing put the generator itself at risk, it can also irreparably damage other expensive equipment connected to it. Because under-sizing can create hazardous situations and even limit overall productivity of the business relying on it, its best to ensure that the correct capacity unit is specified. The first step is to make a list of all the items that need to be powered in the event of a power outage and note the “starting”, “loaded” and “running” wattage of each appliance (found on
Transcript of GENERATION Practical guide: Sizing a standby power generator · the home or business, it can...
GENERATION
energize - July 2010 - Page 18
Practical guide: Sizing a standby power generator
by Philip Hampton, Powermode
Standby power generators are becoming an essential component of any emergency power strategy, often complementing the installation of uninterruptible power supply (UPS) systems and power inverters.
the identif ication plate or in the owner's manual). Add the “starting” or “ loaded” values to arrive at the total power requirement in terms of watts. Don't be tempted to exclude any item if its use wil l be even rarely called upon.
Remember that appliances and tools with electrical motors, such as circular saws, drills, washing machines, dryers and others will vary greatly in power consumption on start-up or when operating under load. Power consumption can spike 200 to 300% under these circumstances. If the appliance doesn't state a figure for “start-up” or “load”, factor this in to your calculations. It's the safest way to arrive at the required capacity of the generator.
In order to convert the total wattage to a VA rating (and arrive at the correct capacity generator), use the following formula:
𝑉𝑉𝑉𝑉𝑉𝑉𝑉𝑉 𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟 = 𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑇𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑇𝑇𝑇𝑇 𝑤𝑤𝑤𝑤𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑟𝑤𝑤𝑤𝑤
𝑃𝑃𝑃𝑃𝑃𝑃𝑃𝑃 (𝑃𝑃𝑃𝑃𝑇𝑇𝑇𝑇𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑤𝑟𝑟𝑟𝑟 𝑃𝑃𝑃𝑃𝑟𝑟𝑟𝑟𝐹𝐹𝐹𝐹𝑟𝑟𝑟𝑟𝑇𝑇𝑇𝑇𝑟𝑟𝑟𝑟)
Unfortunately, PF values are seldom stated on modern appliances' specification sheets so, as a rule of thumb, use PF = 0,6
Another way to calculate the VA rating is:
VA rating = Total amperes x 230
The most important benefits of choosing the correctly sized generator include fewer unexpected system failures, no shutdowns due to capacity overloading and increased service life of the generator and the items it powers.
In addition, the generator will have a better chance of meeting its stated performance parameters in terms of its specification and permit scheduled maintenance period to be adhered to without the deed for crisis intervention.
Contact Philip Hampton, Powermode, Tel 011 235-7750, [email protected]
While a generator can be a convenient source of power around the home or business, it can represent a serious threat to safety if installed incorrectly. So, before buying a generator, consider its application. This will determine its size or “capacity ”. Generators with power supply capacit ies of between 5 and 50 kW are readily available for home and home-office use, while industrial generators from 50 kW to over 1 MW are common.
U n f o r t u n a t e l y, t h e r e i s a d e g r e e o f c o n f u s i o n i n t h e marketp lace between Watt and VA measures for e lect r ic power, often leading to under-sizing of generators which are usually marketed in terms of their VA ratings. Not only does under-sizing put the generator itself at risk, it can also irreparably damage other expensive equipment connected to it. Because under-sizing can create hazardous situations and even limit overall productivity of the business relying on it, its best to ensure that the correct capacity unit is specified.
The first step is to make a list of all the items that need to be powered in the event of a power outage and note the “starting”, “ loaded” and “ running” wattage of each appliance (found on
