Welcome To PenPower Diesel Generators

Establishing what your power requirements are is the first step in deciding if you need to a generator or alternative and if you do need a generator which generator you would need.

There are a few different methods that can be used and before I get into them you must know the golden rule of generator sizing which is too big is better than too small.

Single phase vs three phase

You will need to establish if your load is single phase or three phase. Typically smaller loads residential / office loads are single phase and larger insdustrial loads are three phase. If you have single phase load there is a lot of choice and you may find value in checking out the alternative power solution section under Benefits of diesel generators.

Standby vs Prime duty

In standby applications where your generator will be back up to utility supply the sizing requirement will be to start the load, if the generator is big enough to start the load it will be big enough to run the load.

In prime applications where the generator is the primary source of power, the focus moves to efficiency. This is specialized and if you have this type of application it is best to get in touch with us as there is a lot to consider.

Sizing off main breaker

All loads will have a main breaker with an Amp rating and this rating can give you a very loose idea of kVA or kW generator you may need. On a three phase you can divide the main breaker Amp rating by 1.4 to give you an indication of kVA and on a single-phase system divide by 4 to give you an indication of kW.

There are still a number of factors that need to be considered to precisely size your machine but working off main breakers is very effective in quickly giving you an idea of what range you are in and hence an idea of costs. This is method is most effective in feasibility stage of the process.

Sizing off amp readings

This method is very low cost and is quick. It is not accurate but effective in the range 30-150kVA where cost per kVA decreases steeply as you increase in output. It is done with the use of a clip-on meter that reads Amps. These meters are readily accessible, and any good or even not so good electrician will have one. When using this method, the load is turned off, the clip meter is clipped onto the load cable, turned to read Amps and then the load is turned on. While the load is starting Amps will peak and then as the load starts running this Amp reading will come down to the running load. The peaks on start up are very quick and clip on
meter may not register them but it will give you an idea.

As this system is not accurate and also a single point in time you need to allow some buffer in the sizing. Generally we would like to match kVA to running amps provided the start up amps are not too high. So a typical scenario would be running amps of 40 and starting Amps of 55 we would recommend a 40kVA unit. Running amps of 40A and starting Amps of 75A we would most likely recommend more in the region of 55kVA.

Sizing off data logging

This method is precise but has a cost and takes time. Data logging costs about R5 000.00 depending on a few factors and you would need to log for a typical load cycle, so most likely 1 week. Logger also needs to be available for the logging to happen so it can take a bit of time.

The data logger records all parameters of power usage and with this info we will be able tosize the generator spot on. The only think that this method does not account for is future expansion. It is a vital method for larger loads where relatively small changes in output relate to substantial costs.

Sizing off installed capacity

You can list all the items that make up the load with their capacities, sum this and decide on a utilization factor. Once you have this you can add a safety buffer, remember too big is better than too small and you can arrive at the generator size. This method is less accurate than even the Amp reading method and is also arduous as you have to list every item with their capacities. Typically this method is only used for future loads, not existing loads where readings can be conducted.

Motor starting or simple loads

All of the above info applies to complex loads with many different components. Some loads are however simple and the generator needs to be sized to start and run a single item or piece of equipment. A typical scenario would be an electric motor driving a pump. Electric motors have different starting requirements compared to running. You can apply and mass of electrical formulas and combined this with specific alternator and engine characteristics to size the right set for the application or you can simply us sizing software like the MeccAlte sales assistant https://support.meccalte.com/sales-assistant-21 . it is worth while noting that
very often the best solution in this application maybe a special built machine with oversized alternator and auxiliary excitation windings are very useful.

Fuel consumption figures can be found on the engine specification sheet or sometimes on the generating set specification sheet, all available on this website on the specific generator pages.

Fuel consumption is directly proportional to level of load drawn, specifically your kW load drawn. So as load goes down you use less fuel and as it goes up you use more fuel. This relationship is not exactly linear as engines have different efficiencies across there output range. Generally engines are most efficient when 70% loaded and least and below 25% or above 100% (standby rating is 110% of prime rating).

To give you a good indication of the fuel consumption you can expect for a well sized set you would expect to run some where inbetween 50-75% average load.

Penpower Diesel Generators, manufacture, import, distribute and support a range of 1500rpm diesel generators, 3-phase, 30-1000kVA. We focus on doing this well so that customers purchasing this type of capital equipment can have peace of mind when doing so. There is no substitute for this type of product in certain applications but applications are many as well as alternatives. Here are some notes on some typical alternatives

Solar, batteries and inverters

Solar panels allow you to generate power from a source that is readily available and free to use, the sun. The time and quantity of power you can produce is dictated to you by things like weather and season and because of this is not really an alternative to a generator. In fact solar and generators very often work together, solar producing power basically for free while the generator is able to supply power at the time and in the quantity that you need it. In this space and on standby applications the real alternative to generators is a battery and invertor system. Power can be stored in batteries and made available when you need it and invertors can be sized to give you the quantity of power you need. Here are some points to consider on kW for kW basis:

• Diesel generator will take up less space
• Diesel generator will have a lower capital cost
• Invertors have less cooling and exhaust requirements
• Batteries need to charge which takes time and a alternative power source,
  generators with fuel can run and can be refueled quickly
• Good quality, well maintained, well supported generators can last you a life time, battery life spans are volatile.
• Generators are much more recyclable
• Generators have much higher running costs.
• Generator installations are generally less complicated and quicker.
•  

Petrol, 3000rpm, invertor generators, portable generators

A PenPower diesel generator is not really an alternative to this type of product as these products are generally single phase below 20kVA. There are 1500rpm diesel generators that do go this small and can be single phase here are some points to consider:

• 1500rpm diesel capital is much higher, by a factor of x4 or more
• Power quality of the 1500rpm machine is superior (excluding invertor generators)
• 1500rpm is designed to run and be serviced so running costs are lower and longevity
  better
• 1500rpm machines are bigger and heavier, more often a fixed installation.

Generally a diesel generator needs to be inspected, checked and tested once a fortnight or monthly if it has not been in service in that time. Then it will need an oil service annually or 250 run hours, which ever occurs first. These are general figures, they may vary depending on product or application.

A running open generator with silencer only, runs at about 95dBA at 7m. This would be considered loud and only suitable for heavy industrial, mining or remote agricultural sites. There is a lot that can be done by adding housings, attenuators and resonators to specific installations that can bring the noise level down to acceptable levels for office environments.

1500rpm multi cylinder diesel engines driving high quality alternators with auxiliary excitation windings in correctly sized installations deliver a high quality of power suitable for most equipment. Very sensitive equipment which can not take any power fluctuation will be fitted with their own power supply or filter to the machines requirements

Correctly rated sets can run indefinitely provided they are fueled and service.