Space heating: Efficiency matters
25 January 2017
When optimising the efficiency and performance of heating systems in factories and warehouses it makes sense to take advantage of the latest technologies. Stuart Parris, general sales manager with Powrmatic, explains
The design of heating systems for factories and warehouse needs to take account of several factors, including the nature of the building and the layout of machinery, racking, and so on. It also needs to use the most appropriate heating and control technologies to optimise comfort and energy performance.
In many cases, the system of choice is warm air heating and the relatively recent introduction of condensing warm air heaters provides building operators with an opportunity to improve their energy efficiency significantly with a fast return on investment.
For instance, current models can deliver minimum full and part load efficiencies of up to 107% (net) in condensing mode. This compares to around 91% net efficiency for non-condensing models. To put this into context, a 140kW output gas-fired condensing warm air space heater will deliver a payback in less than two years, compared to a non-condensing heater with the same output (based on 10 hours per day operation, 5.5 days per week during a typical heating season).
In parallel, advances in control technology have resulted in digital controllers capable of controlling multiple heaters in zones, including functions such as optimum start/stop with weather compensation adjustable frost protection, remote burner reset and summer fan-only operation.
Apart from energy and cost saving benefits, another driver for use of condensing warm air heaters is regulation. For example, from the 1st January 2018 warm air heaters will be required to have a seasonal space heating energy efficiency of not less than 72%, rising to 78% from 1st January 2021. And although our relationship with the EU will probably change before 2021 it seems likely we’ll maintain some parity of regulation post-Brexit.
The efficiency of a warm air heating system can be further enhanced by using a destratification system. In a typical pitched roof building with an average height of 5-7m, the temperature difference between the working zone and the roof space will be around 5°C – clearly wasting energy by heating the unoccupied roof space. There will also be increased heat losses through the roof of the building.
A well-designed destratification system ensures effective distribution of heat so there is only a very small temperature gradient between the working zone and the roof space. The Carbon Trust estimates that destratification in an industrial building with a warm air heating system can reduce energy consumption by as much as 20%.
Air rotation heating
Typically, warm air heaters will be sited throughout the building, either suspended from the roof or standing on the floor, and controlled in zones. In some cases though, particularly where there is dense racking and a requirement for an even, relatively low, temperature throughout the space, air rotation heating may offer a better solution.
Pioneered by our sister company in the United States, the principle of air rotation heating is that large volumes of air are moved through the space at relatively low temperatures, from one or more fixed, floor standing heaters using high efficiency axial fans. The air is recycled through the heater every 30 minutes or so, with the low temperatures facilitating condensing for maximum efficiency.
In our experience, temperature variation either side of the set point is typically no more than 1.5°C – even in areas furthest from the heater(s) and irrespective of how the space is configured. This means the layout can be changed without any impact on heat distribution.
In any such project, the key to optimising energy and comfort performance is to tailor the design of the heating system to the exact requirements of the space. It therefore makes sense to work with an experienced team that can advise on – and deliver – an efficient solution.