With a growing range of commercial condensing boilers to choose from, James Porter, Sales Director at Euro Gas, identifies key factors that will help achieve good design for long-term high heating performance

As environmental legislation tightens, a continued focus on improving building energy performance is essential to meet the more stringent targets. One practical opportunity for improved efficiency lies with the boilers.

Commercial boilers are the heartbeat of many non-domestic buildings. Whether the sole provider of heat or operating in a hybrid system with renewable or low carbon heating equipment, ensuring that they operate efficiently should be a priority.

Replacing any ageing or inefficient non-condensing boiler plant with high efficiency condensing boilers and adding the appropriate controls is widely acknowledged to be one of the most cost-effective means of achieving significant energy and emission savings. At the same time, this relatively simple solution can dramatically increase comfort levels within the home or workplace, improving occupant wellbeing.

But a boiler replacement cannot be regarded as a mere quick fix if the plant is to continue to operate efficiently throughout its lifecycle. Good design is essential, with boiler reliability, future ease of maintenance and part replacement all factors that should be considered from the outset. One flexible and energy-efficient solution to high performance heating, especially in buildings with fluctuating heat demand, is to opt for a modular boiler design.

Modular boiler design

What do we mean by modular? Essentially, a modular boiler arrangement enables a whole design to be broken down into smaller parts or sections for easier integration and improved efficiency.

Historically, larger output boilers would be specified to meet a high heat demand. This was due in part to a limited range of boilers but also to combat poor insulation, infiltration losses and general inefficiencies in the system.

Today, manufacturers offer a wide selection of heat outputs in both wall-hanging and floor-standing models to help avoid oversizing. The advantages of spreading the heat load across multiple fully modulating condensing boilers are many.

Firstly, it increases the turndown ratio, enabling the boilers to match the heat demand more accurately. This in turn prevents on/off cycling, ensuring more efficient energy use. A multi-boiler design will alsoprovide improved reliability and more straightforward, non-disruptive maintenance, as even if one of the boilers is offline, the service will continue uninterrupted.

Good boiler selection

While each building will have its own unique requirements, space and capital costs are two frequent challenges when it comes to refurbishment. So how does a modular boiler design help overcome these particular issues?

The compact design of modern condensing boilers and their ability to be installed in modular configuration enables large outputs to be installed in a tiny footprint as well as in hard-to-reach areas.

A further benefit is that the smaller, more lightweight units can be manoeuvred into position more easily and more safely, reducing installation time and costs. Boilers like the Remeha floor standing range, for example, are designed to fit through standard doorways and lifts, with integral wheels for easier manoeuvrability. With some higher output boilers able to be disassembled into parts, this feature again smooths access constraints and can help avoid associated costs such as the need for cranes. These same design aspects enable the plant to be removed safely from the building at the end of its lifecycle.

But maintenance areas, access space and walkways also need to be calculated when determining boiler selection. With that in mind, let’s consider the options.

Weighing up the options

Modular boiler arrangements can normally be separated into two categories: stacking and floor standing.

Stacking units are designed to be positioned vertically. Typically, a stack of around six to nine modules, usually combined using a vertical header at the rear, will achieve the required output.

A key advantage of vertical-stacking style arrangements is their ability to offer a larger heat output in a smaller physical footprint. However, as these arrangements require access on all sides of the plant and pipework arrangement, this generally results in the units being ‘islanded’ in the plant room. The vertical headers will also need careful attention to ensure that the boiler pumps, system pumps and overall hydronics are set up to perform as intended.

Floor-standing modular configurations occupy a similar footprint in terms of plant, but access is usually only required at the front. As a result, they can achieve an equally, if not more, compact configuration overall (see image below).

The shaded area indicates the required access space for a typical vertical-stacking modular arrangement, on the left, and a floor-standing modular configuration, on the right.

This comparison of the two design configurations assumes an approximate load of 900kW (+/- 10%) across three modules.

A typical three-module vertical stacking arrangement would give the following dimensions: 900kW: 2400mm H x 1540mm W x 4300mm L. This design would therefore require a total of 6.5m2of plant space once clearance is added.

A typical floor-standing arrangement would give us the following: 900kW: 2300mm H x 1900mm W x 2600mm L. Factor in the clearance, and this design would require a total of 4.9m2of plant space.

Whole life costing

Let’s now consider the implications of the two arrangements from a whole-life costing perspective. Multi-boiler floor-standing configurations will typically require fewer modules to match the heat load, so maintenance and servicing costs will be correspondingly lower across the lifecycle of the boilers. And while interconnecting pipework tends to be placed above the units, at a similar height to a vertical-stacking arrangement, the modules are all at the same height. This means that maintenance can be carried out safely at a lower level (see below).

Quality construction

Regardless of the design, with all modern condensing boilers, quality construction and longevity are critical. At the heart of the boiler is the heat exchanger. Many floor-standing boiler arrangements and most vertical-stacking systems use aluminium heat exchangers to keep weight down and efficiency up.

When selecting a modular system, check if the heat exchanger is sectional (made from multiple castings which are bolted together) or monobloc (made from a single casting). The benefit of a monobloc design is that it allows constant thermal expansion across the whole heat exchanger, reducing the need for large joins and improving performance, reliability and lifespan.

Understanding how the connecting pipe kit holds up to the overall job specification, with quality parts, pumps and valves, is also advisable. How flexible and how readily available are the products and accessories? And how easy are the boilers to control? Advanced condensing boilers like Remeha’s Gas 120 and 220 Ace range, for example, combine reliable high operational performance with enhanced control capability to maximise lifetime boiler efficiency.

Efficiency starts with the boilers

When it comes to heating, efficiency arguably starts with the boilers. It follows, therefore, that quality and performance should be the top criteria when it comes to boiler selection.

At the same time, factoring in ease of maintenance, servicing and boiler disassembly as well as installation at the design stage will help ensure high efficiencies throughout the boiler’s lifetime.

Modular boiler designs provide a time saving, energy-efficient solution to meeting heating requirements in restricted plant rooms. And with suppliers like Euro Gas helping consultants and contractors evaluate the various options, we can work towards achieving the best, most appropriate and energy-efficient commercial heating solution in every building, every time.

Get in touch to get more information, or to discuss your specific requirements with one of our team.