A load off the estates manager’s mind

Modular boilers with large turndown ratio and wide differential temperatures between the flow and return are rising in popularity. Stuart Turner, national sales manager for Hamworthy Heating, takes a look at the challenges they can help overcome in commercial heating system design, for both refurbishments and new-build projects, with a particular focus on their advantages in healthcare settings.

A commercial heating system is designed to match the peak load to heat a building up to full temperature. This requires a large load from the heat source – the boilers. However, most of the time the boilers will be working at much lower loads, since demand varies throughout the day. So, when designing these systems, it is essential to be able to match both peak loads and low loads effectively – in other words reacting quickly to the changes in demand. How, however, do you match both loads without either oversizing the plant and wasting energy, or undersizing and not being able to meet peak demands for heating? To do this you need a system with a large turndown ratio. This is where a modulating boiler comes into play. 

Turndown ratio refers to the width of the operational range of the boiler, and is defined as the ratio of the maximum capacity to minimum capacity. A typical modulating boiler could have a turndown ratio of 5 to 1, enabling it to modulate between 20 and 100% load. If this was installed in a modular boiler system with, say, a vertical stack of three modules, you would then have a combined 15 to 1 turndown. This means the boilers can provide a substantial range of outputs to match demand and heat the system up quicker.