Single Vs Parallel: 8 Factors to Consider When Choosing Generators

 Historically, synchronized generators have often been viewed as the default option for many smaller installations and using generator load sharing systems has only been considered an option when looking for a solution for larger industrial requirements.

Today, advancements in digital control technologies have now made it more viable to consider the idea of operating paralleling generators, so you should consider a number of  key factors before choosing the right generator for your requirements.

Here is a look at some of the main differences and salient points to consider when trying to decide between single and parallel generators.

Meeting your load requirements now and in the future

A good starting point would be to evaluate what your power load requirements, both now and in the future, are likely to be.

You don’t want to find that your power upgrade options are limited if you find the need to increase capacity at a later date without incurring unnecessary expense. A typical large generator set rating for a single engine unit is unlikely to exceed 4000 kilowatts but if you combine multiple generators in a paralleling system you will not experience the same power upgrade restrictions and your KW capacity will be far more flexible.

Paralleling is the term used to describe the synchronized operation of multiple generator sets which are connected together. If you want to be sure of meeting your load requirements paralleling generators offer you that opportunity.

Reliability is a major factor

It stands to reason that if your business or installation such as a hospital cannot afford to lose power at any point you will need to design a system that gives you that a critical safeguard.

Paralleling is most suitable in that scenario as you have multiple generator sets to fall back on in an emergency rather than relying on one standalone unit, which will bring your power supply down if it fails.

You will often find that critical system are designed with redundant generator sets that can be called upon in an emergency situation.

Cost is always an issue that needs to be addressed

Most installations are planned with a budget in mind and you need to be able to calculate the cost per kilowatt of running your system.

If you are comparing the cost of running a single engine generator to paralleling it is clear that multiple generators are likely to prove the more expensive option. However, larger capacity applications can result in a higher cost per KW figure due to the engine size.

Running a series of smaller engines could potentially work out cheaper so it is always advisable to do your cost per KW calculations in order to see which option is more economical.

Consider generator and room size carefully

Your hand might be forced when it comes to choosing what type of generator system you have as generator and room size are major considerations.

You have to allow sufficient space for access and maintenance of the generators and you also need to think about weight and load-bearing limits.

A single generator set will often be much heavier than a machine used in a paralleling situation, which would be a key issue in some installation scenarios.

Understanding Load shedding

You will need to be aware of the potential risks associated with a paralleling setup that if one generator fails it could put too much strain on the remaining generators, leading to a complete system failure.

This situation is avoidable and can be planned for by incorporating load shedding into your design scheme.

Calculate the reserve capacity needed in the event of an engine failure so that you don’t create an overload situation when one generator fails.

Parallelling is not always possible

It should not be assumed that all generators offer the option of being paralleled together.

Generators produced by different manufacturers may not prove to be compatible. Check with your installer to clarify whether you will be able to parallel generators of different manufacture and size.

Approval from your utility service provider

When choosing between a single or parallel generator option it is highly relevant and important to remember that your generator system will become part of the utility system.

You will normally be required to make provisions for adequate protection of both the generator and the utility service connection.

The relevant utility service provider for your area will be able to provide guidance on this subject and will often require their approval for your generator system.

It is essential that you consult local codes and standards when planning utility parallel operation.

Calculate non-essential loads

Designing your system should include making calculations for non-essential loads that could be shut down in the event that generator capacity is reduced by a generator failure.

You could probably reduce lighting capacity by half in the event of a parallel engine failure. As well as working out what you could do without in a reduced power situation you also need to accurately estimate how much minimum power you need to keep critical systems up and running.

Reserve capacity needs to be sufficient to cater for these needs.

Consider scalability

Very few businesses stand still for long and this means that their power needs are constantly evolving.

While you never want to overspend on trying to meet future power requirements you do ideally want to install a generator system that offers a degree of scalability.

This is where a parallel system will generally offer a clear advantage over a single generator.

When you are comparing one system to another there will invariably be some pros and cons attached to either option and this is the case when it comes to single and parallel generators.

If you consider some of the main factors mentioned and they become part of your planning agenda, you can improve your prospects of getting a generator system that meets your current and future needs in the most cost-effective way possible.

Each installation will be unique but at least you should have a clearer idea of whether you should go down the single or parallel route once you have considered these key factors.

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