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    0700 JOHN HOLT (0700 5646 4658)
  • 11B Ilabere Avenue,
    Ikoyi, Lagos.
Over 120 years


Below are some frequently asked questions and answers about our products. If you need specific
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Holt Engineering

  • Are your generators air cooled or water cooled?
    All diesel generators sold by John Holt are water cooled.
  • Are your generators one or three phased?
    All diesel generators sold by John Holt are three phase generators.
  • Can a Generator be used during adverse weather conditions?
    Diesel generators sold by John Holt are designed to function in hostile environments and during extreme weather conditions. To extend the life of a generator and to prevent such things as shorting and rusting, if possible they should be protected from the elements.
  • Can enclosures be built around a generator?
    John Holt Engineering offer both open sets and canopied sets - if your generator is being installed outdoors we would recommend that you buy a canopied set. This means that you would not need to build an enclosure around it. Generators require air supply that can circulate to cool such components as the engine. There is need to be a continuous circulation of air when the generator is functioning and this may be unlikely in a home built enclosure. John Holt Engineering canopied sets include proper air cooling.

  • Can I wire a generator into my home electrical system?
    A generator can be wired into your home electrical system with a transfer switch. However, these need to be installed by qualified electricians. It is unsafe for you to attempt to wire such a system independently.

  • How do I determine the size of Generator I need?
    Getting a generator that can handle all your power generation needs is one of the most critical aspects of the purchasing decision. If your new generator cannot meet your specific requirements then it simply would not do you any good, because it can put undue stress on the unit and even damage some of the devices connected to it. To get more detailed information on this subject, please contact John Holt Engineering for expert advice.

  • How does a Generator work with mains electricity supply?
    Constant mains electricity is supplied into premises via electrical cabling. When this mains electricity is disrupted due to power failure, a signal is sent from the transfer switch to the generating set which then starts up and sends generated electricity back into the premises. When the mains supply is restored, the transfer switch blocks the power from the generating set and reverts back to the main supply.

  • How long will a generator run on a tank of fuel?
    The amount of time that a generator will run on a tank of fuel depends on the size of the tank, the amount of time in which the generator is in use and the load that the generator has to carry. 
  • What are the standard components on your Diesel Generator set?
    The standard components on John Holt diesel generators are as follows:

    • Engine
    • Control Panel
    • Base Frame and Fuel Tank
    • Alternator
    • Circuit Breakers
    • Guards
    • Cooling System
  • What do I need to know when installing a Diesel Generator?
    The following are all you need to consider for installing a generator:

    Location - You will need to think of where you want to place the generator. Ideally, it should be located in a place with adequate access and lighting for service and maintenance purposes. Generators can be located inside or outside your premises – John Holt Engineering offers Sound Attenuated Canopies for generators located outside.

    Mounting - Generator should be mounted on a level base and please use anti-vibration mounts when necessary.

    Ventilation and Cooling - It is important to make sure that there is enough ventilation to help keep the generator cool, remove excess fumes and heat produced through engine combustion.

    Fuel System - you will need to consider how you will refuel your generator. Several refuelling options are available, from manual pumps to fully automatic systems. Smaller sets usually have a manually operated mechanical or electrical operated pump, which can refill the set base tank from a fuel drum.
  • What is a Transfer switch?
    A transfer switch is a panel that is wired into the premises electrical distribution system to allow a generator to be used. It prevents the generator from back feeding into the mains power supply which could cause serious injury to line workers trying to restore utility power supplies.

  • What is the difference between standby and prime power?
    Standby power generators are most often used in emergency situations, such as during a power outage.  It is ideal for applications that have another reliable continuous power source like utility power.  Its recommended usage is most often only for the duration of a power outage, regular testing and maintenance.

    Prime power ratings can be defined as having an “unlimited run time”, or essentially a generator that will be used as a primary power source and not just for standby or backup power.  A prime power rated generator can supply power in a situation where there is no utility source, as is often the case in industrial applications like oil & gas operations located in remote areas where the grid is not accessible.   
  • What is the RPM value?
    RPM stands for Revolutions Per Minute and refers to the number of times that an engine rotates each minute. A generator with a RPM of 3000 therefore runs at twice the speed of a generator with a RPM of 1500. When a generator has a four pole alternator and a frequency of 50 Hz, 1500 RPM is the usual speed and when there is a frequency of 60 Hz, 1800 RPM is the usual speed.

  • What is the Warranty Cover on a High Capacity Genrator?
    All diesel generators sold by John Holt Plc for prime power are supplied with a 12 month warranty from the date of start up.
  • When and How do I service and maintain my Generator?
    The frequency and type of service required to maintain a John Holt Diesel generator will depend on a number of things including the usage of the generator, the environment that it operates and the percentage load that it carries. Ensuring that full service is carried out regularly is your responsibility as the owner. You will need to carry out frequent visual inspections every two to three months to check that parts are functioning. Any faults, service or repair issues that you notice should be directed to John Holt Engineering.

    A full service including a change of parts such as filters and lubricating oil should be carried out every 200 hours of running time. We recommend that you check your generator once a week for this.

  • Where can I get parts for my Generator?
     If you buy or own a John Holt Diesel generator set you will be able to purchase any spare parts you require from John Holt Engineering. John Holt Engineering stocks a wide range of original parts for diesel generator.
  • Who provides the service?
    The servicing is provided by John Holt Engineering technicians who have been trained and certified by John Holt's Foreign Technical Partners.
  • Why should I buy a Diesel Generator from John Holt Engineering?
    If you buy a diesel generator from John Holt Engineering, you can be assured of a reliable source of power 24 hours a day, 7 days a week and 365 days a year.

    Our diesel generators are sourced directly from Europe in order to maintain and give you the highest quality products.

    We also have a large stock of original spare parts and our technicians are trained and certified by our foreign technical partners.

  • Will you perform Emergency services for Generators?
    John Holt Engineering service team would be pleased to perform emergency servicing on your generator only if the generator was installed and commissioned by us.