Do you know how much HP (horsepower) your boiler has? Are you aware that the horsepower of your boiler can make a real difference to its performance and capability? Here we take an in-depth look at horsepower – from what it is to how it’s measured, how horsepower is related to BTU, and how to choose the right boiler capacity for your operation.

Horsepower is defined as a unit of power or the rate at which work is done. It normally relates to the output of engines or motors.

Horsepower is calculated using this formula: HP= Torque x RPM / 5,252.

The term horsepower was invented way back in the 1800s when steam engines began to replace horses in coal mines. Mine managers wanted a way of working out how many horses a steam engine could replace. The inventor of the steam engine, James Watt, came up with a suitable calculation, the result of which was horsepower.

Horsepower is the unit used in the US, however, in the UK a similar unit, Brake Horse Power (BHP), is derived slightly differently and will be slightly lower than the US equivalent. On the continent, PS (Pferdstärke) uses the same calculation for horsepower as here in the US but uses metric units rather than imperial ones.

Boiler HP is the unit used for measuring the power of a steam boiler.

A single HP as it relates to a car is the power needed to move 33,000lbs one foot in one minute. In contrast, a single HP as it relates to a steam boiler is equivalent to 34.5lbs of steam evaporated at or from 212° F / hour.

Boiler HP can be measured in watts, calories/hour, or BTU (British Thermal Units). The most common way that modern Boiler HP is measured is in BTU.

BTUs are British Thermal Units. They are a measurement of heat, which is a form of power. One BTU is defined as the amount of heat required to raise the temperature of 1lb of water by 1°F.

One boiler HP is equivalent to 33,479 BTU.

BTUs are part of the imperial system of measurement, which was common to both the US and the UK until the UK’s adoption of the metric system. BTUs are frequently used as the unit to compare different fuels – rather than attempting to compare using weight or volume, BTUs are a useful, accurate way of comparing output from different sources.

BTUs are frequently used to measure the output of boilers, HVAC, and related systems. If you’re planning on getting a new boiler and/or want to compare different boilers, using and understanding BTUs is important.

In the first instance, you need to work out total steam requirements. Depending on the complexity of your operation, there are several options for doing this accurately.

- In some cases, you will be able to use fairly accurate estimates based on heat transfer equations. In many circumstances, data already exists that can be utilized.
- Use the thermal rating given on an appliance or piece of equipment to calculate the likely amount of steam it accounts for.
- Measure the steam needed for a particular application using a flow meter.

When your steam outputs are totaled, it should provide a fair estimate of the amount of steam you need. This figure can then be used to work out the minimum amount of power you’re going to need for your operation to function smoothly.

Depending on what your final minimum power figure comes out at, it may be that some additional work to optimize energy conservation and energy efficiency in your operation is needed before coming to a final decision on the level of power needed.

Obviously, the right boiler for your needs is going to meet the required operating pressure.

Because of the range of factors that can affect operating pressure, it’s also helpful to have a load profile in pounds/hour of steam. This should include:

- Maximum load – the biggest output that could possibly be required.
- Average load – the most commonly needed output.
- Minimum load – what is the very least amount of consumption that’s going to be needed?

It’s also helpful to consider the number of hours the boiler will be in operation, and how much fuel is going to be needed.

Another factor to take into consideration is whether a backup boiler or some other form of heating (a redundancy) is needed in case a fault develops in the primary boiler, or there is some other need to shut it down.

Measurement is also a key consideration.

- Spend large amounts of time working at maximum capacity, which is frequently inefficient. This may result in higher energy usage.
- Increased wear and tear, as the boiler is performing at maximum capacity.
- Reduced life span.
- Increased risk of malfunction.
- Inability to provide the amount of heat energy needed for your operation to function effectively, ultimately limiting production and having a negative effect on operational efficiency.

- Oversized boilers can lead to overheating.
- They waste fuel and are inefficient, as they’re not working optimally. Usually, boilers are at their most efficient when they work within the mid-range of their capabilities. Both performance and efficiency drop at the top and bottom of the boiler’s range.
- A higher purchase price that doesn’t deliver the value you need.
- Reduced performance.
- Premature wear.

Working out which boiler is going to be the best fit for your premises can be a challenge! There are a lot of factors to take into consideration, some of which require accurate computation to provide an accurate picture of your boiler requirements. For many businesses, it makes sense to use a professional to correctly assess the boiler capacity that’s going to work best for your circumstances.

CTC Air offers a complete boiler assessment service, completing the work needed to accurately determine the boiler specification that’s going to be the best fit for your needs.

Get in touch with the team at CTC Air for further information.