Key considerations when hiring a load bank
27 January 2021
Interruptions in power supplies can cause lost productivity, damage equipment, have a huge impact on revenue and, in some cases, even risk life. While backup power systems can mitigate that risk, it is vital that they are properly maintained and tested. Joann Price shares some key things to consider when specifying and renting a load bank
WHERE BUSINESSES rely on power to remain operational, having backup power such as a generator is crucial. Wherever there is standby power, there is also a need for a load bank – a device which is used to create an electrical load which imitates the operational or ‘real’ load that a generator would use in normal operational conditions. In short, the load bank is used to test, support, or protect a critical backup power source and ensure that it is fit for purpose in the event that it is called upon.
Should I hire or buy?
When looking at specifying a load bank, the first decision is whether to hire or buy the equipment. Consider how many generators you have on-site and how regularly you’ll need to test them. In applications such as data centres or hospitals, where power is absolutely critical, buying a load bank might be the best solution. However, for those who need to run testing at set intervals, or smaller businesses that have neither the space or the technical expertise on-site, rental can provide an ideal solution.
Generally speaking, load bank rental companies will have the expertise to help specify, transport, install and remove the machines. You’ll benefit from the experience and knowledge of their technicians and have access to a fleet of equipment which ensures that you have the right equipment for the job, all without the capital expenditure.
What type of load bank do I need?
The type of load bank you need will vary depending on the applications involved. Typically load banks fall into three categories:
Resistive: The most common type, a resistive load bank provides a simulated electrical load for generators and back up power systems. They work by mimicking the operational load that a power source would handle during actual use. When used as a controlled system test, the load simulates real-life resistive loads, such as incandescent lighting and heating loads, as well as the resistive or unity power factor component of magnetic (motors, transformers) loads.
It is important to note that, In many applications, resistive loads make up a small proportion of power consumption. In data centres, for example, it is generally only heating and lighting systems which use a resistive-only load. Alongside this, other aspects of the operation incur reactive loads; these create a lagging power factor (pf), typically around 0.8, which is not accounted for when undertaking a solely resistive test.
Resistive/reactive: Resistive/reactive load banks combine both resistive and reactive elements in one load bank package, which can also be switched to enable resistive only, inductive or lagging power factor testing. This type of system can be used to test the generator set fully at 100% nameplate kVA rating.
Resistive/reactive load banks provide a picture of how well an entire system will withstand changes in load pattern while experiencing the level of power that would typically be encountered under real operational conditions. The inductive loads used in resistive/reactive testing will show how a system will cope with a voltage drop in its regulator. This is particularly important in any application which requires generators to be operated in parallel (e. larger business infrastructures such as major telecoms or data centres) where a problem with one generator could prevent other system generators from working as they should.
In addition to the main categories of loadbank listed above, DC load load banks can be used to provide an accurate load for the discharge of batteries, both following amps and voltage, from 24VDC to 700VDC, with power from 10kW to 664kW. Containerised medium voltage load banks can be used to provide higher voltages up to up to 33kV in both resistive and resistive/reactive configurations.
Where will the load bank test take place?
When hiring a load bank, it is important to let your provider know where the equipment will be used and what the site conditions are like. Suppliers such as Crestchic are used to providing load banks to suit varying applications across different continents, from the extreme heat of the Sahara and the cold of the Antarctic to the corrosive saline environments found in Marine environments. Letting your hire company know where the load bank will eventually be used - including the altitude, humidity and ambient temperature - can help them to specify the right equipment for the job.
Equally important is whether the load bank will be used indoors or outdoors. Load banks work by dissipating energy as heat, making it vital that there is space around the equipment for proper airflow, or that the correct type of equipment, such as a vertical blow machine, is used. When used indoors, it is critical that temperatures are monitored to prevent accidental activation of sprinkler systems, overheating or damage to the load bank.
Finally, it helps your supplier if you let them know if the load bank will need to be installed or delivered above ground level, as well as the distance it will be located from the generator. This will ensure that your supplier provides adequate manpower and cabling to successfully carry out testing.
Have the details from your generator nameplate or data tag at the ready
To specify the right equipment for the job, your chosen supplier is likely to ask you for the capacity rating of the generator you wish to test. This information can be found on the nameplate (or data tag) on the generator itself. The capacity rating will be specified in KVA and kW at a specified power factor and maximum output voltage.
The primary difference between kW (kilowatt) and kVA (kilovolt-ampere) is the power factor. kW is the unit of real power and kVA is a unit of apparent power (or real power plus reactive power). The power factor, unless it is defined and known, is therefore an approximate value (typically 0.8), and the kVA value will always be higher than the value for kW.
The nameplate will also have information on the voltage, operating phases and configuration of your generator, all of which will impact the load bank your supplier will specify. Having a photo of the nameplate on your mobile phone will mean you have all the information to hand when talking to your supplier.
Understand what your rental agreement includes
When dealing with your chosen supplier, ensure that you know how much involvement you need from them and get them to quote accordingly. Choose a supplier that offers flexibility - packages vary from supply-only, short-term rental right through to larger multi-megawatt, high voltage projects which are fully managed by a team of engineers. They can also include site surveys, risk assessments and method statements as well as full project management. Equally, understand what peripherals are included, from step-up/step-down transformers and cabling, extension reels, junction boxes, through to control and data collection equipment and load bank fans.
Check lead-times meet your requirements
When time is critical, ensure your suppliers can meet your needs. The COVID pandemic has seen an increase in companies wanting rental equipment to be supplied with a very fast turnaround. Using a supplier with its own fleet of loadbanks and dedicated delivery vehicles can help to reduce reliance on outside suppliers and ensure adherence to strict lead times.
With the COVID pandemic set to impact the way we live and do business for the foreseeable future, it pays to check that your supplier meets the standards set by your business. At Crestchic, we’re doing all we can to protect our staff and our customers and minimise risks. If more than one technician is needed for a job, they will travel separately to ensure social distancing. All staff are also provided with PPE including goggles, masks and sanitiser and we’ll undertake risk assessments to ensure your site is safe.
Joann Price is hire manager at Crestchic Loadbanks