HomeSPONSORED FEATUREHeating depots old and new

Heating depots old and new

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High Speed 2 (HS2) is one of the largest infrastructure projects that this country has ever seen – six times the budget of the 2012 Olympics. It will provide a new high-speed railway link between London, Birmingham, Manchester and Leeds, speeding up journeys, releasing space on crowded lines and bringing Britain closer together.

HS2 will create thousands of jobs during its construction process, as well as 2,000 apprenticeships. Approximately 25,000 people are needed to build the project and, to support this, Network Rail is providing two state of the art colleges to train the next generation of rail engineers, located in Birmingham and Doncaster.

Network Rail’s high-speed rail colleges will be elite institutions, defined by their focus on progression to a higher level of study – delivering truly innovative training and offering the very best in teaching and specialist equipment.

The college occupies a 5.1 acre site at Doncaster’s Lakeside. As an elite institution, the college will be a flagship facility for advanced and higher-level apprentices as well as providing opportunities for the existing workforce to learn new skills in the latest technology. Thus it meets the wider economic need for an increased supply in engineers and will therefore have a purpose beyond the timeframes of HS2.

The new pool of talent will need to understand the challenges involved in high-speed electric railways of the future rather than the steam and diesels of the past. Doncaster is one of two High Speed rail colleges we’re building.

Heating a rail shed

Increasingly, almost as much attention is being paid to topics such as energy efficiency, sustainability and the environment as the traditional topics of railway engineering and operations. This is as true of train depots as of any other part of the rail network.

The ways in which train care depots are utilised, often intermittently and at irregular time intervals, make the efficient use of energy extremely difficult. Therefore, consideration must be given to selecting a heating system that offers flexibility of operation at optimum efficiency.

Train maintenance sheds are invariably very long and narrow, with large doors opening constantly at each end, and are thus notoriously difficult to heat and even more difficult to keep warm. The doors often occupy the full width of the building and may be left open for many hours a day, creating a wind tunnel effect as cold air at high velocity is drawn through the shed. This means that air infiltration can severely disrupt worker comfort within the interior.

A heating system needs to be able to sustain a comfortable environment in these conditions and, especially, provide rapid recovery once the doors are closed. Air curtains over or to the side of the doors, either ambient or heated, can mitigate the issue of air infiltration.

Maintenance is frequently carried out at night, thus compounding the inhospitable climatic conditions and, with partial occupation, it is therefore important, for efficient use of energy, that the heating system can be easily and effectively zone controlled.

But air ingress is not the only problem. The mass of a train is considerable and when a cold and wet train enters the shed it creates a cold sink, so the heating system needs to be able to provide rapid response to changed conditions.

Radiant heating

The primary source of radiant energy in the natural environment is the sun. By standing in the sun’s rays, a feeling of warmth is experienced, whilst in the shade it feels considerably cooler. Radiant heat warms all solid objects and surfaces in its path.

Reznor has exploited this concept in its energy efficient radiant heating systems. Radiant-tube heaters, mounted overhead, produce infrared radiant heat that is directed downward by a reflector. The infra-red heat passes through the air without heating it and falls on people, floors and equipment below, creating comfortable, all-round radiant warmth at low level, without wastefully heating the whole volume of the building or the roof space. Because radiant heat can be controlled directionally, only the occupied areas of the building need to be heated, which enables considerable energy savings to be realised.

The objective of a radiant heating system is to ensure that the people in the building are comfortably warm. By the correct application of a radiant heating system, comfort levels can be optimised. Radiant heat warms objects and surfaces, increasing the mean radiant temperature and reducing the body’s loss of heat to its surroundings. In addition, by eliminating air movement, convective loss of heat from the body will also be reduced.

Differing specifications

Steam Loco Sheds

While no longer built, many sheds today were constructed in the age of steam. Due to the nature of the locomotive, vast amounts of steam were released, captured by massive hoods and released to the atmosphere.

These sheds due to the age were notoriously poorly insulated structures with open doors at each end creating a massive wind tunnel. Radiant heat was the only realistic option as a heat source and, when designing a heating system, account of these hoods in the roof space was critical.

The majority of work undertaken on these locos was at low level, so ensuring heat between the tracks on the platform and in the pits was vital.

Nor-Ray-Vac, due to its unique long lengths of radiant emitter is an ideal solution for heating the long distances between trains.

Some rail sheds are over 300 metres long. Due to the physical size of the sheds, the design of the heating system is paramount to ensure optimum zoning capabilities, both for client operational flexibility to minimise running costs and to ensure the capability of being able to rapidly respond to changed conditions.

Diesel sheds

Many of these sheds derive from the steam era and consequently some still lack good insulation values for the fabric. Diesel locos also have hoods, this time to collect the diesel fumes from the engines, but, due to the general atmosphere within these sheds, the radiant heating system has to be designed to have a ducted fresh air supply from outside to the gas burners. This ensures the filters within the burners are kept clean and not clogged from the diesel fumes.

Again, the above points 1 to 3 are relevant to heating these sheds.

Third-rail electric sheds

These sheds tend to be cleaner, due to the lack of diesel fumes, and do not require ducted air to the gas burners of a radiant heating system. The work on these trains is primarily at low level, so the above points 1 to 3 are also relevant to heating these sheds.

Overhead electric sheds

These sheds are primarily new facilities, in which case they are well insulated. Again, due to the cleanliness within the sheds compared to diesels, there is no requirement for ducted air to the gas burners of the radiant heating system.

However, unlike the previous types of locos, work has to be undertaken on top of the loco to maintain the pantograph and power systems. As a result, these sheds have personnel staging for access to the top of the trains.

When designing a radiant heating system for such facilities, due regard of the staging has to be taken into account. The radiant emitter cannot be too close to the working area above the trains. The staging is normally in a defined location within the facility. This can result in a challenge for designers, but it is achievable given sufficient roof height within the facility. The ability to be able to zone the radiant heating is paramount in such instances.

Evidence of success

Amongst other successful traincare applications, Reznor was able to provide the ideal heating solution for the National College for High Speed Rail at Doncaster. Radiant heat (Nor-Ray-Vac – NRV) was specified as the heating system for the Large Scale Workshop, comprising an area of 1,906m2 within the facility.

The selected NRV system was made up of nine 38LR burners arranged in three branches, suspended at 12 metres above the finished floor level, with one discharge fan flue. Due to the type of operation within the facility – the training of students throughout the floor area – the system is controlled as one zone and produces blanket, uniform heat coverage for the complete workshop.

Operating costs are minimised by concentrating the heat at low level, where it is most needed, without heating the volume of air in the building. Rapid response times reduce running costs further and mean that warmth is felt by people in the building within minutes of start-up and no fuel is wasted bringing the whole volume of air to a comfortable temperature.

Since the Nor-Ray-Vac radiant system burns fuel at point of use, there are no distribution losses to take into account.

Nick Winton is divisional manager for Reznor, a subsidiary of Nortek Global HVAC.

Read more: Depot control for the 21st century


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  1. I appreciate this article and the detailed look at depot heating systems. However, due to the climate change emergency I think fossil fuel heating for such large facilities will be banned quite soon.

    It would be interesting to hear about the electric heating alternatives.


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