Scoping a diesel backup generator can be daunting, and you will often come across references such as ATS, MTS, and more acronyms – which if you are not familiar with can be confusing.

We recently published a guide on what ATS/AMF means in reference to a diesel generator, which you can read here. In this article, we are going to cover off what an MTS is, and an outline of how it works.

Here is a summary of the main acronyms for transfer switches/methods related to starting a generator.

What does MTS mean for a generator?

• ATS – Automatic transfer switch
• AMF – Automatic Mains Failure
• MTS – Manual Transfer Switch
• 2 Wire Start – A way of wiring a simple ‘on/off’ switch to your generator so you can start it up from a distance, or, in some instances this is required if you are using a generator in an installation with batteries and renewable energy sources.

These are the main ways to switch your generator on or off, and the most common setups for installing a system to switch your house, property or the load which you are trying to power from the mains supply to your backup standby generator.

How does a manual transfer switch work?

A Manual Transfer Switch, or MTS as it is shortened to, is a panel which gets installed after the meter on the outside of your property, but before your consumer unit (fuse board).

It is essentially a large switch, which has the mains power cables running into it, and also the cables from your generator.

When the mains power fails, it gives you a way to switch your property so it is running off the power generated by your backup diesel generator. It is a large switch, which normally has 3 settings – mains – isolation – generator. When the power fails, you turn the switch from mains to ‘off’ or isolation to make sure the connection is terminated, and then switch it to the generator setting. This means your home is now connected to the power cables running from your generator.

When the mains power returns, you do this in reverse order – switch the panel from generator to off/isolation, and then over to the mains setting so that your house is back on the mains supply incoming.

Unlike an ATS (automatic transfer switch), which doesn’t need any interaction, with an MTS you must ensure that you turn on your generator and let it come up to speed BEFORE you switch the panel over to feed your house from the generator. There isn’t a link between the MTS panel to ‘tell’ your generator to start or stop, this must be done manually. This is where a 2 Wire Start function comes in very handy…

Here is a illustration showing a typical setup of an ATS and MTS panel.

What is 2 Wire Start?

2 Wire start is a way to turn a generator on or off, using a simple switch, just like a light switch.

Almost all generators that have ‘ATS’ compatibility will also work on a 2 wire start system. All you need to do is run a simple on/off switch to the relevant ATS socket or terminals on your generator. This switch will act like an on/off switch for your generator, turning it on or off by completing a circuit when switched on.

These are really handy, as it allows you to run a small cable from the ATS port on your generator, to a suitable location and wire that cable to the switch.

When used with an MTS, you can install your manual transfer switch outside by your meter, and the on/off switch inside your house by the consumer unit.

As the generator will likely be installed some distance from your property, in the event of a power cut this means you can simply turn on the generator using the switch by your consumer unit (the 2 wire start set up), then wait for the generator to be up to speed, walk to the MTS panel and switch your property from mains to generator power.

Once the mains power comes back online, switch the MTS panel from the generator to mains, then inside your property, you can turn off the generator via the two-wire start switch.

If you are using a diesel generator with ATS compatibility to power your workshop or garage, a 2 wire start set up is great as you can install and position your generator in a suitable location, but run a cable from the ATS port, into your workshop and wire in a simple on/off switch for your lights/tools.

Simply turn on the generator, then use your appliances or tools. When finished, you can turn the generator off using the switch in your workshop.

ATS vs MTS

Sometimes, this setup is preferred in backup situations as with a fully automated installation using an ATS/AMF panel, even in very brief short power cuts the ATS will fire up your backup generator when you may not want it to run, such as a brief power cut in the early hours of the morning when you would be asleep and not notice.

With an MTS you have full control over the start and stop procedure. An MTS set up is usually a more cost-effective solution too when compared to an ATS.

The downside is in the event of a power cut when you are not home, your generator will not start. This is not acceptable if you are using backup power systems due to exotic pets or for medical reasons when power at all times is essential.

To summarise

An MTS is a manual version of a switch, which changes your property from mains supply to generator supply in the event of a power cut. But, this switch must be changed manually.

Usually, if the generator is installed away from your property, a manual changeover switch will be installed alongside a 2 wire start switch to turn the generator on and off.

If you are looking for complete control over the use of your diesel genset, then an MTS is a cost-effective way to do this.

If you would rather not get involved, and have peace of mind that whenever the power fails, night or day whether you are home or not, then an ATS or auto-transfer switch set up would be best.

Every diesel generator we build or supply has ATS, AMF, MTS or 2 Wire Start compatibility. Browse our range of Cummins powered 3 phase generators, or single phase Evopowered sets to find the right generator for your needs.

In this article, we are going to explain what is an ‘ATS or AMF’ panel when referred to on a diesel generator, like our Cummins powered genset range. We will also cover a basic outline of how they work. Hopefully, this will help you choose which one is best for your requirements.

You may also see references to MTS or 2 Wire Start on some generators. We have given the meanings below, but due to the complexity of these installations, a full article on MTS’ or 2 Wire systems will be written shortly. Follow our social media pages to keep up to date on Facebook or LinkedIn when we launch new articles.

What does ATS mean for a generator?

• ATS – Automatic transfer switch
• AMF – Automatic Mains Failure
• MTS – Manual Transfer Switch
• 2 Wire Start – A way of wiring a simple ‘on/off’ switch to your generator so you can start it up from a distance, or, in some instances this is required if you are using a generator in an installation with batteries and renewable energy sources.

Now, let’s look deeper into how the automatic transfer panels work.

How does an Auto Transfer Switch Work?

An ATS, or AMF are essentially the same thing. Both of these, an automatic transfer switch, or auto mains failure installation include panels, also known as switchgear which monitor the mains electricity coming into your property and will prevent downtime by turning your generator on and off, and switching your load (the house, property or equipment you are backing up) onto the generator and back to the mains when required.

An ATS panel will be installed after the meter outside your property (so that it does not count the electricity from the generator on your meter usage!), but before the consumer unit (previously known as a fuse board). You would need to install electrical cables from the generator, to the switchgear in the panel, but also another smaller cable, known as communication from the panel to an ATS or AMF port/terminal on the genset.

The ATS/AMF panel will monitor the main supply passing through it. Then, in the event of a power cut, or mains failure, the panel will send a signal to the diesel generator through the communication cable to turn it on. Once the generator has come up to the right speed, the panel will disconnect the load/property from being on ‘the grid’, and power it using the generator.

The panel continues to monitor the main cables, even though you are now being powered by the generator. Once the panel notices the grid is back up, it will work in reverse. It will connect your property or load back onto the mains supply, then send a signal to the generator to start it’s run down/cooling cycle and to stop.

Here is a simple image showing the basic positions of an ATS panel. Obviously these are not electrical schematics and in all instances, we advise you to consult a certified electrician or generator installation company for your install. 

Why use an ATS?

Essentially, as the names imply, an Auto transfer switch, or auto mains failure system monitors for power outages, starts/stops the generator and switches you from mains to generator – and back again – without any interaction needed at all. This means it will work regardless of whether you are near your property and no intervention is required which is appealing.

The downsides of an ATS or AMF panel is that they can be more expensive to purchase, and to install, than a manual changeover switch and if the power outage is very short you may not want your generator starting up. You can set a relay, which basically delays the onset of the switch over and generator start up but this involves some work during the installation. 

What does ATS mean on generators?

When you notice generators being labelled as ATS or AMF compatible, or ATS ready – this usually means that they have a socket installed or a control panel which is ready for the communication cable to be wired up – the cable that ‘tells’ the generator to start or stop. In some instances, additional plugs or sockets may be required for the communication cable, but essentially, the genset itself is ready to work with an ATS/AMF/2 Wire start set up.

What size ATS do you need?

This varies depending upon the size of load or circuit you are looking to back up. The amount of power you need from your generator to power the appliances you want to run. As the power cables run through the ATS panel (for it to be able to switch between the mains power and the generator power it must break and remake the circuit), the ATS or AMF panel should have a slightly higher max rating than the max rating of your generator

We can give you some advice on the pros and cons of using an auto set up vs a manual set up, but consulting a professional company regarding the size of panel and set up is always advisable. If you consult an electrician on the size of generator that you require (usually defined by the max amperage draw you are using), they can also advise on the size of panel.

Generally, a residential property uses a 100 Amp mains breaker. This would mean, if you are using the full capacity of power available in your property you would be using around 23kW of power. Therefore you would need a generator that produces around 28kW to be running at it’s best, and an ATS panel that is 100Amp rated with a slight buffer for overload should you require it.

Automatic Transfer Switches – 3 Pole Vs 4 Pole…

When browsing for an ATS or AMF panel you will often see 3 Pole or 4 Pole noted.

This refers to the number of ‘cores’ in the cable you are using, or the number of connections/terminals within the panel.

3 Pole refers to a single phase, 230 volt set up. Just like on a household plug, you have 3 pins. One is the live, one is neutral and one is earth. So, if you have a 230 volt generator, to power your 230 volt property (which most residential are), you need a 3 Pole panel.

If you are using 400 volt equipment, and are backing up your load or property using a three phase generator, you would need a 4 pole panel.

You can read more about 230v and 400v and the differences in our blog here.

To summarise…

An ATS or AMF panel is a way to minimise the disruption of a power cut by automatically monitoring the grid and connecting you to the generator when needed, but they can add some additional cost to a project. However, as they are fully automatic they will work anytime of day or night, even if you are not at the property which does give you invaluable peace of mind.

All of our generators, including the Cummins powered generators we stock are ATS or AMF compatible, which also means they are MTS and 2 Wire start ready. This applies to our entire generator range, whether they are our Evopower EVO range which uses a ComAp control panel, or our Cummins powered UKC ECO range which uses Deep Sea Electronics control panels.

The National grid, over the last month alone have warned on three separate occasions of potential strain or power outages due to a mix of old power plants being offline, their reserve generators being offline for routine work and instances when their renewable sources cannot make up the shortfall vs the expected demand. You can see one of their Tweets here highlighting this warning from November 3rd 2020.

In their winter report, they are also saying there will likely be less reserve this winter compared to last year, and many people suffered last year from unplanned power outages.

As Infrastructure gets older and the demand continues to get higher, planned maintenance and planned power outages will also increase in frequency and duration. It may, as we mention later in this article, increase the appeal or value of your home.

Why buy a backup or emergency generator?

Lots of points are obvious when you think of power cuts, we wrote a blog highlighting what you may miss out on during a power cut, which you can read here, but we have summarised why you should backup your home with a diesel generator below;

• Keep the lights on – which can be dangerous if you do not have lighting, especially in the long dark winter nights
• Keep your central heating on – and stay warm
• Prevent your food from spoiling or going off within your fridge or freezer – which saves you money having to re-purchase perishable items
• Stay entertained – by keeping your TV on, and by keeping gadgets charged up and ready to use
• Stay connected – Wifi is almost essential these days, with so many devices relying on it, being without internet is surprisingly inconvenient
• Continue working – with many people working from home on a part time or full time remote basis, especially at present with the current COVID implications, no power = no work! This could put even more financial and emotional burden on people should there be planned or unplanned outages.

Overall, the main benefit for you is peace of mind that should there be a power cut, you can effectively continue to work, eat and live as you ‘normally’ do.

If you rely on electricity for health reasons, such as keeping medication cool, keeping equipment running or even if you have tropical fish or exotic animals which need a stable temperature then a backup generator is a must have.

Does a standby generator increase the value of your home?

In short, yes it can increase the value and also the appeal.

Many people ask us if a standby or home backup generator can increase the value of their property. This is hard to define exactly, as a home generator can be more important to some than others. It really can be used as a selling point – and as mentioned above – if someone relies on electricity as a must have then this would set your property apart from others.

Some studies say that backup generators, when properly installed with a transfer switch can increase the sales value of your property by 5% or more. Depending on the value of your property, this can make installing a standby generator a realistic option for a return on investment if that is the main driver for you considering one.

Which standby generator do you need?

In all cases, we strongly recommend you consult a qualified electrician before finding a suitable generator for your home. Backup diesel generators can suffer from something called underloading, so bigger isn’t always better when it comes to fixed speed diesel generators.

You will need an electrician to come out and test the power that you are using within your property.

Once you know the backup power you require, try to find a generator which, based on it’s ‘standby’ rating is 70% of that. For example, if you need 70 Amps of power to run everything in your home, try to find a backup power solution which produces around 100 Amps so you are using around 70% of the generator’s max load. This will prevent underloading, but also give you a cushion should you ever need a little more.

So which standby generator is best for your home?

Bare in mind, before getting an electrician, decide what you would want to keep running in the event of a power cut. Most residential homes have a main breaker of 100Amps, meaning that the absolute most you will ever be drawing off the national grid is 100 Amps. This equates to a generator that can produce around 23kW – so, based on specifying a genset, which, when you are using everything you want, you are using around 70% of the generators maximum output, a 28kW diesel generator like our EVO28KSEm should give you ample power to run everything in your house should the power fail, if you are needing 100Amps of power. In most cases, a 230v single phase generator will be sufficient for your home/residential needs. Our 400v Cummins powered generators are usually used for more commercial or industrial applications.

However, the likelihood of you having all of your lights on, all of your TV’s, having an electric shower…etc all during a power cut is low. So, deciding what you would like to keep running as an essential, then getting an electrician over to measure the amount you are using would be beneficial. 
Then, simply give us a call or contact us with those figures and we can help recommend the right generator for your needs.

How To Report A Power Cut:

By calling 105 to get straight through to your network operator.

A power cut, or power outage can cause major disruption even when it is for planned maintenance but more so when it is unexpected. Most people, in the event of an unplanned power outage try to find details of their electricity supplier to report it.

Whilst this is sometimes the best approach, providing your supplier and the company that maintains the overhead lines, known as the network operator, are the same firm, but in some UK locations this is not the case.

To make it easy for everyone, no matter where you live to report a power cut – all electricity companies in the UK are now in a scheme to make it much easier to get straight through to your network operator. This is the company responsible for the electricity distribution – which is not always the company you pay your bills to.

Simply call 105, a free of charge number, and you will be directed to the local network operator for your area. Don’t forget, if you spot immediate danger you should also call the relevant emergency services. 

The 105 number is not just for power cuts, you can also use it to report damaged lines (with no immediate risk), or damaged substations and so on.

As soon as you see something which needs to be reported, or you are suffering from an unplanned power cut, call 105.

How Can A Power Cut Affect You?

• No lights – internally, this can be quite dangerous. Especially at night and in winter months. We rely on lighting for everything inside our homes, from safety on the stairs, cooking, reading almost everything relies on having lighting. Returning home to a dark house, when living in a remote area can also be difficult and dangerous in cold dark winter nights without any outside lights to guide you to your door. Try to keep a torch and some candles in your house at all times for safety.
• No cooking – If you suffer from a long unplanned power cut, which can be the case during storms or winter times in particular, you will be unable to use any electric ovens, microwaves or even boiling your kettle. We wrote an article on how to prepare for a power cut, which suggests boiling some water and keeping it in a flask for hot drinks, but when the power cut is unexpected you are unlikely to have this. Some gas appliances may still work however you would not have any mains powered smoke alarms or safety equipment so using any form of large cooking equipment (if you can) in a power cut is not advised. 
• No charge – we all heavily rely on our mobile phones, laptops, tablets or gadgets to keep us connected or entertained. Without power you would be unable to charge any devices. You may be ‘lucky’ and have a high amount of battery life in your devices as the power trips out, but if not these could run down. It may be worth investing in some rechargeable battery banks to keep devices topped up – but you will have to remember to keep these charged up!
• No wifi – having no broadband or wifi due to a power cut is often overlooked. Many people realise ‘we won’t have the internet’ but they do not realise just how much they rely on it. Even if you do have charged up gadgets, you will not be able to stream anything, listen to music or even use most of the apps on that device unless it has mobile data connection. This can also affect your digital TV if you use some of the popular streaming services, or have an internet based TV box. On top of this many smart speakers within the home now connected through Wifi to play music in multiple rooms at the same time. These may not work without an internet connection. 
• No heating – unless you have a traditional log burner, or fire in your home it is highly likely that you will be relying on central heating. Even though these use oil or gas as the main source of fuel – the boiler normally requires electricity to work. Without this, you may not have any heating in your home. This can cause concern, especially for the elderly, young or vulnerable during winter. Keep some blankets and wear extra layers of clothes for safety.
• No hot water – many people not only use their boiler for heating, but also for hot water. You may not be able to pass the time with a bath or shower during a power cut. Well, not a warm one anyway!
• No fridge or freezer – many people think about this one. Without power your fridge and freezer will not work. By keeping the doors closed many appliances will, however, stay cold for many hours.
• No security – this is a concern for anyone with high value items or especially businesses. CCTV, security lighting or alarm systems may not work during a power outage. This could leave you exposed. If you have electric gates you may also need to consider an alternative way to exit your property should you need to in an emergency.

The list above shows how unsettling and disruptive a power cut can be and how a power cut can affect you. It really can take away many of the comforts we take for granted.

One solution to overcome the disruption is to invest in a backup power solution – whether it is a diesel generator or battery solution. Having a backup generator provides peace of mind that in the event of a power cut you can keep your lights on, stay warm and also stay entertained.

We have a large range of home and business backup power solutions. Our 8kW to 28kW 230v range caters for households and businesses that require a single phase supply, then our 55kVA to 550kVA 400v generators cover most industrial applications. If you need any advice on the purchase or specification of a diesel standby power solution that suits your needs feel free to give us a call or contact us using our online enquiry form.

Power cuts, or power outages can be unsettling when at home and potentially disruptive for a business. In our last blog article, we covered the potential cost of a power cut to a business which you can read here.

In this article we are going to discuss how you can prepare for a power cut at home.

What should you do before a power outage?

Firstly, light is very important and power cuts can happen at any time of day. Make sure you have candles, battery lights/torches or fully charged battery powered lighting equipment at all times. Before winter sets in, it is worth making sure you have a torch on hand to use in the event of a power cut. Small things like waking up or down your stairs could be dangerous in the middle of the night.

Everyone likes to keep entertained, and many devices like phones and tablets have battery power which can be used for certain things during a power cut, however you have to make sure whatever applications you are planning to use can work without the internet.

Keeping warm is important, so having blankets and jumpers available is a good idea. Most heating devices require electrical power – even oil or gas central heating needs electricity for the boiler to function. This will leave you out of hot water and out of heating. If you have a solid fuel, dual fuel, gas/electric fire or a log burner, try to make sure you have logs or gas…etc at home to keep your house warm during the cold winter nights if you are unlucky enough to suffer from a power cut.

Try to turn off the switches on all affected appliances either before a pre-warned outage, or just after the power cuts out – but leave one light or lamp switched on so you know when the power is restored.

If you are notified in advance, boil up some water and keep it in a flask to make hot drinks during the outage. If the temperature drops dramatically, for example overnight, you could use this hot water to fill a hot water bottle for extra comfort.

Remember to keep fridges and freezers closed to keep them cold. Most modern appliances can last for hours if the doors are kept shut. This prevents your food from getting spoilt.

If you rely heavily on ‘gadgets’ to keep you occupied, purchasing some battery banks/power stations is a good idea. Some of these have fairly good capacity and keep your phones or tablets topped up should you need them. Power stations can however be expensive, and you need to remember to keep them charged up!

To summarise, there are some easy steps you can take to relieve the pain from a power cut, but, without power it will be surprising what you miss – from WiFi, to lighting, Netflix and more – power cuts are never easy unless you have invested in a backup power solution.

Our range of 230v single phase diesel generators range from 8kW up to 28kW which is more than adequate for almost all residential properties. Having a diesel generator as a backup gives you the ultimate ‘safety blanket’ and means you can continue as normal during a blackout. Give us a call if you would like to find out more about our home backup generators and help recommend a suitable solution for your home.

In this article we are going to cover, the different types of power cuts, the areas in the UK that are most affected, the aftermath and downsides to a business as a result of power cuts and finally some tips on how to produce an adequate continuity plan.

What are the different types of power cuts or power outages?

Generally, these can be classified as:

1. Brownout – these are quite uncommon in the UK, but these are when the voltage drops in an area due to excessive demand, but it does not cause a power outage. The lower voltage leads to some more sensitive equipment shutting off and these can cause damage to electrical equipment. The name is derived as the lights will generally run dim during a brownout.
2. Blackout – A complete loss of electricity, a power cut in an area for an unspecified amount of time.
3. Permanent Fault – A loss of power and electricity in an area, sometimes large due to failure of equipment within the grid.

Whilst power cuts can be planned or unplanned, long or short term they can all be described by one of these terms.

What causes a power cut?

The obvious and most common answer is the weather. Wind, snow, storms or rain can all contribute or cause power cuts. You would expect trees and branches blowing into lines overhead to cause some issues, but there can also be problems with rain or flood water making its way into underground cable routes.

All electricity providers work hard to ensure their grid and infrastructure is maintained to prevent downtime, however, failure of equipment can happen and cause longer term power outages.

Unexpected power cuts can be caused by animals or accidental damage to lines or cables by construction or wildlife.

Finally, most planned power outages or power cuts are for providers to maintain or replace equipment.

With the strain on the national grid and the power requirements ever increasing, power cuts are likely to become more frequent as time goes on.

How can a power cut affect your business?

1. Loss of instant/current revenue – the most obvious downside of power interruption for your business is a loss of revenue. The vast majority of businesses rely on some form of electronic presence of communication. Whether this is email, selling on channels such as eBy or Amazon and being unable to process orders or potentially your website or online presence suffering if you have a server in-house.
2. Loss of future revenue – if your business has a sales team, a loss of power means a potential loss of prospecting time. In turn, this affects your sales funnel and pipeline meaning the revenue is not only lost during the outage, but also a potential loss of future sales which can be very hard to quantify.
3. A loss of margin/profit – any business with staff or premises costs has to cover these whether the business has had a good or poor day of trading. Even a fairly short loss in power could directly impact the profitability of your business for that period. If your business is within peak season for products, even a few hours downtime could impact the bottom line dramatically.
4. Health & safety – other less considered impacts are health and safety issues. Does your business use electrically powered fire systems? CCTV? The safety of your staff (or customers in a public environment) could be compromised and leave you liable should anything happen.
5. Security – If your business has a stock holding, valuable equipment or even data storage on-site, with CCTV and alarm systems off you could be exposed to theft and it may make your insurance invalid if it states within your terms you are protected by CCTV.

This is not an exhaustive list of the potential effects to your business from power cuts or outages, but it should give you some thoughts to consider.

Now you may be thinking…

‘How can I protect my business from power cuts?’

The answer is quite simple. You need a contingency plan in place to cover who has responsibility for certain emergency tasks and procedures in line to prevent downtime.

For example, who is responsible for contacting the power supplier, who will ‘lock up’ and arrange security if appropriate. Furthermore, having backup mobile phones for internet/data usage and for outbound calls would be beneficial. All things considered, by the time you invest in equipment to prevent downtime, it is quite often easier to invest in a diesel generator to backup your business in the event of a power cut. Diesel is safer and can be stored for longer periods of time vs. a petrol generator.

The lifespan of a diesel genset, and especially the diesel engine is vast, with some diesel generators happily providing over 10,000 hours of usage providing they are maintained and serviced as required.

There are other options, such as backing up your business with solar, wind or battery banks which each have their positives and negatives, but a diesel generator is a very ‘stable’ option which, providing you are checking your fuel and battery level should always be there to help.

You can view our range of backup generators here. We offer single phase 230v and three phase 400v options so regardless of your business type we are likely to be able to cover your standby power needs.

When trying to specify which diesel generator is suitable for your power or backup requirements, you may be tempted to purchase a 3-phase or 400 volt generator. On the face of it, these 400v / 230v generators provide more power output compared to single phase 230v stand alone sets in a cost to power comparison.

Given the fact that from most 400v three phase generators, you see them listed with 230v output too, it looks appealing to purchase one of those – even if you do not have 400v equipment to power. If you do have any 400v equipment then a three phase diesel generator would be essential. All of our Cummins powered diesel gensets are three phase 230v / 400v outputs. View our range of gensets here.

Before we explain exactly what a phase imbalance is, it is helpful to know the difference between single phase 230 volt power and three phase 400 volt power.

What is single phase and three phase power?

It is quite a technical answer to explain the difference between single phase and three phase generators, however the very simple answer is that 230v / 240v is one phase of alternating current or voltage within an electrical system or alternator. It is one ‘pulse’ of electricity switching between negative and positive polarity, and this can be seen using an oscilloscope – a device which maps out the sine wave against time.

AC or alternating current describes the way in which the sine wave, or power output alternates over time, as shown below.

The above would be representative of a typical 230 volt, single phase power output sine wave. As you can see, there is one ‘pulse’ of electricity alternating over time.

In three phase, or 3 phase power systems of diesel generators, there are 3 pulses of electricity produced as the motor turns components within the alternator. The alternator is usually made up of copper wires and magnets in different arrangements.

In single phase alternators, there is usually one copper winding, which is what produces the single pulse of electricity as the magnetic field oscillates.

In three phase alternators / 3 phase generators, there are three separate copper winding sections, so, as the internal components spin three pulses of electrically are created as an output.

If using an oscilloscope, a 3 phase generator output would be shown as below;

(Image By User:J JMesserly modification of original svg by User:SiriusA – File:3-fas-spänningar.svg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=5607023)

As you can see, there are three pulses of current/voltage created over time from the alternators three sets of windings, referenced to the neutral.

So now you may be asking, why is three phase 400v (Not 690v)?

Without going into extreme technical detail, this is due to the fact none of the phases ‘peak’ at the same time. As shown in the representative image, each phase is offset slightly, so when Phase 1 is at peak output, Phase 2 and 3 are in negative voltage/current.

How do you get 230v out of a three phase generator?

This is by connecting to one phase, and the neutral/earth terminals. This gives you a reference of 230 volts between that individual phase, and the reference neutral point.

How do you get 400v out of a three phase generator?

This would be by connecting to all three ‘live’ phases, and also the neutral and earth. In some systems the neutral and earth are linked, which means your plug or socket would have 4 pins, Live 1, 2 & 3 and Neutral/Earth. In other systems, the neutral and Earth are not linked, meaning you would have a 5 pin set up. For further clarification on any of this, please ensure you consult a qualified expert.

What is a phase imbalance on a diesel generator?

At the start of this article, we stated it is possible to run 230v equipment from a 3 phase diesel genset. Now that we have covered the basic principles of single phase vs three phase, we need to explain why it can be difficult to run 230v / 240v equipment from a 400v three phase generator.

Whilst this is possible, you need to be careful not to run the generator in a way which can cause phase imbalance. Trying to draw too much 230v power from a three phase generator can lead to the breakers tripping and you losing power to your equipment or for prolonged periods of time it can cause major damage to the alternator windings which can be a costly repair.

There are two main reasons for damage – Magnetic / Electrical & Temperature.

Almost all three phase diesel generators have an alternator with three copper windings, and a rotating section attached to the drive from the engine.

While this component spins within the alternator, it creates a magnetic field / flux in the copper windings. It is this magnetic field of flux, alternating in polarity that creates a current or voltage between the winding and neutral.

If you are drawing heavily from one of the phases, this will create a stronger magnetic field between the internal component and one set of windings. As the rotor inside the alternator spins, it will be drawn to one winding more than the others. This can cause the rotor to spin off center, which strains the crankshaft from the engine and can cause damage to the rotor or the engine.

Secondly, as you are drawing heavily from one phase, the winding can become extremely hot which can cause it to perish, which breaks the circuit and means you may need to get your alternator ‘rewound’.

How can I prevent phase imbalance or damage to my generator?

In order to prevent this happening, all of our Cummins powered ECO range of gensets have Deep Sea Electronics control panels, which have built in safety features – one of which being to protect your generator against phase imbalance.

If the control panel senses a dangerous amount of power being drawn from one phase, it will automatically trip the breakers, meaning the power output ceases – but this prevents damage to your engine or alternator.

Most three phase gensets have a tolerance of around 50% use from one phase against the load being applied to the others. In simple terms, if you had a three phase generator which produced 30 amps, 10 amps per phase, running from one phase on 230v you could draw 5 amps without the control panel kicking in for safety.

As this is a % based tolerance, using the same theoretical 30 amp generator, if you are drawing 5 amps from 2 phases, on the third phase you could draw between 2.5 amps and 7.5 amps – the third phase would be within 50% to the other two.

As you can see, this can quite easily become very complicated so we always advise you to get advice and help from qualified experts for the purchase of your generator to make sure you specify the correct one for your needs.

Feel free to contact us if you would like to know more about any of this article. Alternatively, you can browse our quality range of UK designed Cummins powered generators here.

These are defined by regulations stated out in ISO 8528 standard.

Large diesel generators are usually used for two main purposes – To maintain power supply during a power cut, to keep your electrical items and appliances running, or for continuous or long term power in areas without any mains power supply or to buildings which are not connected to the grid, such as workshops or businesses.

When generators are used infrequently in the event of a power failure, this is defined as standby or backup power. When they are used for long periods of time or as the sole source of power to a facility this is deemed as prime power.

When gensets are tested and rated, they are classified into their standby or prime ratings. Part of this classification style is to make it easy for consumers or purchasers to be able to compare generators on a like-for-like basis from different manufacturers or retailers. It gives an even basis for comparison as all sets are rated within pre-defined terms.

The two most common definitions you see, when named in full are ESP (emergency standby power), and PRP (prime rated power). There are also definitions for LTP (limited time power) and COP (continuous operating power) stated within ISO8528, but these are less common when comparing sets.

What does Standby Power mean?

ESP or emergency standby power, which is the ‘Standby Power’ rating you see stated is based on a genset being used in power outage or power cut situations, with an anticipated annual usage no more than 200 hours, and the average load factor in any 24hour period not exceeding 70% of the ESP rating.

If you plan to use your generator for short periods, in the event of mains failure, a power cut or running equipment only in the event of an emergency, it is acceptable to base your decision on the power you require vs. the standby power rating of the sets you are comparing.

In short –

Power is available for the duration of the emergency outage. The average power output = 70% of standby rating with a variable load during the period. Typically this is below 200 hours a year and no more than 500 hours a year.

What does Prime Power mean?

PRP or prime rated power, which is the ‘Prime Rating’ that you see online, is based on a genset being used for longer periods of time, usually as a sole source of power on worksites or areas where mains grid power is not available.

According to the definitions within the ISO8528 directive, prime power rating is ‘the maximum power which a generator set is capable of providing a variable electrical load sequence for an unlimited number of hours per year’.

Further to this the average load factor cannot exceed 70% of the PRP in any 24 hour period.

In short, the definition of PRP is unlimited hours use per year (8,760 excl. service), 70% load factor in any 24 hour period, a variable load being applied and a small amount (10%) of overload, in accordance to AS 2789, ISO 3046, BS 5514 and DIN 6271.

If you are looking for a genset to use as the sole source of power, always look at the prime power rating.

In short –

Average power output is 70% of the prime power rating over 24 hours with a varying load. Unlimited hours per year with a peak demand of 100% of prime rating and potentially an overload period of 10% but for no more than 1 in every 12 hours.

LTP & COP

Earlier in this article we mentioned lifetime power and continuous operating power. THese are more uncommon ratings and are not usually applicable to our customers. If you do require further information on these, please let us know.

Please note, this article is only a brief summary of the ratings, and does not include all elements to ensure compliance. We are providing this article to try and help you understand the ratings we use to compare our sets.

To maintain 1500rpm, the fuel being pumped into the engine is varied depending upon the load which is being applied – the more load being applied, the more fuel it takes to maintain the engine at 1500rpm speed and vice versa.

If you run a diesel generator on very light loads, the engine is unlikely to reach an adequate temperature as it is burning or combustion less fuel and generally working too light.

The optimum temperature for a diesel generator is when it is being used to power between 30% to 80% of its rated power output. This can prevent underloading a diesel generator.

How does it happen and what does it cause?

If you consistently run a diesel generator for less than 30% of it’s rated output, you are likely to cause wet-stacking, or underloading as the engine is not being worked hard enough to reach the right temperature and combust all of the fuel being pumped into the engine.

When the engine is not reaching an adequate temperature, some of the fuel which is being supplied into the combustion chamber is not burned/spent. This unburned fuel then glazes the cylinder bores, reduces the efficiency and compression within the chambers and the unburned fuel causes carbon build up on the injectors.

This unspent fuel also causes a large build up of soot, and in extreme cases some of the unburnt fuel can mix with this soot and travel through the engine into the silencer and exhaust.

This unburnt fuel leads to a potential fire risk – if the generator is suddenly or subsequently placed under a large/full load, the temperature of the exhaust fumes will heat the silencer up to an extreme level and the unburnt fuel mixture could ignite.

How can I tell if my generator is being underloaded?

Ideally you should know the load that you are applying and you would have worked is this out when deciding what generator to purchase. However, if not, the first signs are usually very heavy smoke coming from the exhaust while the generator is on, or the soot and fuel mixture which has made its way to the exhaust silencer will seep out. This mixture appears to be an oil leak as the unburnt diesel and soot forms a thick oil like substance which is very dark and heavy.

How can I prevent wet stacking?

In the first instance, before purchasing a generator, make sure you always spec the generator to the correct load. It is usually easiest to work out the max amperage draw of your load and then spec a generator so the amps you are expecting to use, equate to around 80% of the output of the generator. A suitably qualified technician or electrician should be consulted on your project.

How can I ‘fix’ underloading or wet stacking?

If your generator has already suffered from underloading, you should look at implementing a load bank programme. You can usually prevent underloading by making sure you run the generator on three quarters or 75% of its prime rated capacity, for around 2 hours in every 100 hours use. 

If you implement a programme to ensure the generator is brought up to 75% to 100% of its prime load capacity in a controlled manner, this can gradually burn off the carbon deposits and the unburnt soot/fuel mix and prolong the life of your genset. 

Failure to fix underloading can cause permanent damage to your engine and generator and will void any warranty terms in place.
If you would like to discuss this in more detail, please contact our generator specialists on sales@evopower.co.uk or call +44(0)1646 687880 and speak to one of our diesel generator technical experts.

If you open the industrial grade canopy to expose the engine, on the top of the engine block, there is a data (or specification) plate, which will display the date of manufacture, the serial number and importantly (when ordering replacement parts or filters) the engine model number.

Cummins engine model numbers follow a logical pattern, which allows you to figure out certain aspects of the engine and its components by breaking down the model number.

The full specification can be found within the manual which you will receive with the delivery of your diesel genset, but for quick reference the model numbers for Cummins engines are broken down as follows.

Below is an example of a model name for engines in automotive and 96 industrial applications.

Here is an example of a model name for pre-96 industrial and non-automotive application use;

For example our UKC110ECO 110 kVA 3 phase generator uses a Cummins 6BT5.9-G2 engine, which is a 6 cylinder, B series, Turbo charged, 5.9L engine.

Should you require any replacement parts, the engine model number will help ensure the correct parts are supplied to you.

Our Cummins powered generator range utilises BYC or Bosch injector systems and governor.

On the side of the injection pump, there is a data plate showing some information for calibration purposes, and a further specification or data plate can be found on the governor. Noted on the governor dataplate is the Cummins part number for the injection pump and the governor.

The Cummins engines are renowned worldwide and have after sales and parts back up to match the high standards and quality of the engines.

Should you ever need to order replacement filters or more, you will now know how to quickly ensure you get sent the right part first time.

We, Evopower, have been building power equipment since 2006. Our vast experience in power generation and diesel generators in particular is one of the reasons we decided to use Cummins engines in our 50kVA to 550kVA ECO range of gensets.

The ECO Cummins powered generator range by Evopower are designed by, and held in stock in the UK at our 120,000 sq. ft. distribution centre, offices and workshop.

You can view our range of generators here.