Chance to gain without pain

Modern condensing boilers can be introduced to upgrade existing industrial heating systems with the minimum amount of upheaval and maximum savings, according to Pete Mills, commercial technical operations manager at Bosch Commercial & Industrial Heating

For those thinking of embarking on a boiler replacement project, the good news is that carrying out work to upgrade a system needn't be as intrusive as you might expect. While one solution definitely doesn't fit all, there are ways and means of integrating new condensing boilers into existing systems and pipework, without the risk of any contamination of the primary boiler circuit or loss of performance.

Today, most high performance condensing boilers need to be installed as part of a sealed system, and those that don't still benefit greatly from being separated from an old system where the water quality may be difficult to control. In the industrial and commercial sector, conversion from an open vented to a sealed system can be tough to achieve with potential leaks from old pipework and fittings to consider, as well as the possibility of corrosion problems if water from an old system is allowed to circulate freely around a new condensing boiler.

In situations like these, the most practical way of overcoming this kind of problem is to leave the existing system open vented while separating the boiler primary circuit using a stainless steel plate heat exchanger.

Introducing a plate heat exchanger to the system ensures a safe and protected primary circuit for the new condensing boiler, while ensuring there is no risk of an increase in corrosion to the existing system.

The most usual position for the plate heat exchanger is to replace the low loss header usually associated with modular boiler cascade systems. In industrial and commercial heating systems, fitting a low loss header allows the creation of a primary circuit, within which water velocity can be maintained at the required constant, regardless of changes or requirements in the secondary circuits. In cases where plate heat exchangers have been introduced there is no longer a need for the low loss header as there is now no chance of the system pumps having influence over boiler shunt pumps.

From the point of view of control, the plate heat exchanger functions in much the same way as a low loss header. The system strategy sensor is placed on the secondary flow, which compensates for any flow temperature loss across the plate heat exchanger (typically at 5°C). However, it is vital that the heat exchanger is correctly sized to ensure both the correct heat transfer and hydraulic resistance can be handled by the boiler and the system pumps.

Over the years, condensing boiler heat exchangers have become significantly more sophisticated, as manufacturers have optimised designs to deliver greater outputs from highly efficient, compact exchanger units. As a result of being smaller by design, some heat exchangers can have small water ways that are in danger of becoming blocked if large debris finds its way in.

Depending on the system condition, the addition of a strainer, a filter, or even a dirt separator, on the common return to the plate heat exchanger is recommended to protect the unit from debris that has not been successfully flushed from the old system.

Where plate heat exchangers have been installed, the expansion vessel required to accompany the installation can be sized to accommodate the expansion of water of the small primary circuit.

This is another plus for investors, as it saves on both the cost and space of buying a much larger vessel than may otherwise be required if a plate heat exchanger is not incorporated into the system design. It is however, important to note that the filling arrangement will still need to comply with the requirements of the Water Regulations relating to the size of the boiler and the property - typically fluid category 4.

Finally, on the secondary side of the heating system, the position of the existing open vent and cold feed will need to be considered carefully, as the changes made to the system may mean further alterations are required. Within the new system, the plate heat exchanger effectively becomes the heat source and therefore careful consideration needs to be given to the positioning of the open vent and cold feed in relation to the existing heating pumps.

Although clearly there is a lot to consider where any installation work is undertaken to improve the efficiency of a current heating system, above all it is reassuring for investors to know there are ways and means of managing the process within existing parameters to make it as smooth and effective as possible.