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Top 4 Issues with Standby Generators

& How to Prevent Them

Below are the top 4 issues standby generators commonly face. This helpful guide could help save you time and money and ensure your generator is always ready.


1 .  Batteries

When we receive a service call out for a generator not starting undercharged batteries are the primary cause of failure. A 12V battery if fully charged will usually show a voltage of 13.5 – 14.8V with a battery charger fitted and working. A battery that is showing 12V does not have a working battery charger connected  or is not holding its charge. Much below 12V and the battery will not have sufficient output to crank the engine through the starter motor at sufficient speed to start the engine. Note the engine may still crank, but slower than usual, deceasing in speed on each crank as the battery is drained.

What are the most common causes of low voltage batteries?

1. The battery charger has been switched off !! Yes, it is sad but true. Engineer call outs costing hundreds of pounds are solved by flicking a switch and advising on operation protocols. Generally the auxiliary supply to a generator which powers the battery charger is external to the generator itself and is switched via an MCB or a rotary isolator. Often there are on / off switches within the generator itself. Employees / contractors not understanding what these are for have been known to turn them off resulting in battery drainage causing an inability to start the generator within a couple of days.

2. The battery charger MCB has tripped. The battery charger circuit is connected to the mains at one end and the battery at the other and as such it is susceptible to spikes in the circuit. Consider your home system where occasionally a MCB trips within your main fuse board this is what can happen with the battery charger and turn it off. When this happens it is always good practice to understand if it is a one off or to investigate for a potential issue.

3. The battery charger is faulty – this is quite rare but can happen on older chargers as the copper windings within the charger break down after repeated on / off cycles.

4. Faulty batteries. Batteries do not have an infinite life, they have a certain number of charge cycles within them. Depending upon your application it is recommended to change them every 2-5 years. We have been called out on numerous occasions to generators not maintained by us in critical installation that have 10 years old plus batteries on them. Battery maintenance is part of a good service visit.

Remember – the batteries are the heart of the system, without them nothing else works so treat them well. Regularly check that the batteries are charging and that the electrolyte levels are good.


2. Fuel:

Standby generators do not run very often and the fuel can run back from the fuel pump / fuel supply pipes into the tank. When it comes to start the generator then there is only air in the system and a little fuel in the fuel filter. The engine cranks but will not start. We are often called out to faults of this type and either need to bleed the air out of the fuel system or after another couple of cranks it self bleeds and starts.

This fault can be prevented in a couple of ways. Firstly, start the generator for a few minutes every week. This is good practice to ensure there are no faults within the generator and will prevent the fuel from running back as long as there is not major air ingress due to a faulty hose / fuel connector. Secondly, fit a non return valve within the fuel lines which will prevent the fuel from running back – it is still good practice to run the generator weekly.


3. Damp:

We often are called out to standby generators that have not run for many weeks / months and have had water ingress within the canopy. This can cause many problems from damaged electrical connections (particularly on PCB boards) to causing a straight short within the alternator leading to upwards of £2,000 of remedial costs.

Again prevention is better than the cure. By regularly starting your generator you will notice any signs of serious damp early and be able to identify the cause preventing further water ingress.

Jacket water heaters and alternator heaters will help to remove some of the  dampness that is inevitable on metallic surfaces caused by condensation but they will not remove water ingress from a heavy downpour. Regular checking is the key.


4. Hoses:

Fuel hoses and coolant hoses will eventually perish. They can crack on the outside due to general deterioration and can also begin to erode away from the inside. Oils and coolants are there to protect the engine but their very nature means that they will chemically erode silicon and rubber hoses over time. The jacket water which keeps the engine at a good consistent temperature over time can also produce a dry, warm environment within the generator housing causing the hoses to crack externally over time. If left untreated the hose will eventually fail usually when it is under load i.e. when you require it the most. A good service visit will check the condition of all hoses and advise remedial actions. If your service provider is not checking the condition of your hoses during a service visit then they are not doing their job correctly – please insists upon it.


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