Heating that works in workshops
Space heating systems for workshops need to address a number of criteria that may not apply to other applications. Brett Smith reviews the most important considerations.
When it comes to keeping a workplace comfortable for its inhabitants, workshops present a number of challenges. The optimum solution depends on factors that include size and layout of the space, the building’s construction and how the building is used. Other factors, such as the potential for buildup of explosive vapours and harmful fumes that mustn’t be recirculated into the space may also need to be considered.
In these applications, the choice of space heating system usually comes down to either radiant heating or warm air heating. Buildings with reasonable insulation typically favour warm air as the installed load is generally significantly lower. Poorly insulated buildings can benefit from radiant heat, especially if doors are opened and closed regularly.
With radiant heating, radiated heat from a hot surface passes through the air and raises the temperature of any solid objects (people, machinery etc.) it encounters. The temperature of the surrounding air is not raised, though as machines and building surfaces warm up they will begin to warm the air slightly.
For effective spot heating of people at their workstations, radiant heating is a great option. Also if there are high levels of air infiltration, radiant heating is likely the best option, as it doesn’t heat the air, helping keep energy costs down.
Warm air heating
Warm air heating is the most common choice for workshops. Warm air heaters draw in air from the space and pass it across a heat exchanger to warm it. The heat source can be a burner in the unit fuelled by natural gas, LPG or oil, an electric element or a hot water emitter supplied from a boiler.
The number of warm air heaters and their positioning are important in ensuring efficient warm air distribution. A well-designed system will ensure hardly any variation in temperature throughout the area. In warm weather the fans of warm air heaters can be used to circulate air without heating it, creating cooling draughts.
In hazardous areas where flammable vapours that are lighter than air are present, BS6230 dictates that warm air heaters can only be used if all incoming air to the heater is outside air (no recirculated air) and the outlets from ducts into the space are at least 1.8m above floor level. They should have full automatic and proven pre-purge and post-purge of the combustion chamber and any associated inlet/outlet ducts.
Where there are flammable vapours that are heavier than air (e.g. petrol), BS6230 dictates warm air heaters may be suspended from the ceiling or mounted on a wall within the space. The bottom of suspended warm air heaters should be at least 1.8m above the floor to comply with BS6230.
If inflammable or explosive gases are likely in the workshop, a warm air heating system with hot water from an external boiler room will be a good choice.
Any electrical apparatus in these situations that is within 1.2m of the floor level in the heated space should be protected in line with BS EN 60079-10-1.
In other areas, warm air heaters may be suspended from the ceiling, mounted on a wall or they may stand directly on the floor. Floor-standing heaters are only suitable for workshops where there are no heavier-than-air flammable gases present (see above).
In such applications, where suspended or high wall mounted heaters are not practical, weatherproof warm air cabinet heaters sited outside the building are an alternative. These can be free-blowing or ducted and configured to just recirculate internal air or introduce a controlled amount of fresh air – including a summer air movement facility.
Externally-sited warm air heaters have the benefit of freeing up floor space in the work area and eliminate the risk of indoor floor mounted heaters being damaged by vehicles (e.g. fork lift trucks) or other activities in the space.
Destratification fans in conjunction with warm air heaters are recommended. This also reduces heat losses through the roof, particularly important with poorly-insulated roof structures.
It’s important that the selected heating system can be controlled to reduce energy waste. Typical control options include optimum start/stop, adjustable frost protection and summer cooling (warm air only). In a large workshop with multiple heaters, independent operation of the heaters is recommended.
There is no single, off-the-shelf heating solution for workshops. Each workshop will have a unique layout and be used for a variety of jobs. Arriving at the best solution requires an understanding of the space and how it is used, as well as how the different heating options work.
Brett Smith is UK heating manager with Powrmatic