help extend the life of the engine, a good and considered CHP service plan will also include some engine overhauls. With such a hard working engine, running 6,000 to 8,000 hours a year at an average of 1,500RPM, the concept of an engine overhaul should not be alarming, and is in fact just part of the lifecycle of the system. For example, the Bosch service schedules see a cylinder head change after 22,000 run hours and then a complete engine rebuild at 44,000 run hours. This approach injects new life into the unit and can keep it running as a long term investment.

While Combined Heat and Power (CHP) systems continue to grow in popularity, aftercare all too often remains an afterthought. Here Carl Main, business development manager – commercial and industrial after sales at Bosch Commercial and Industrial, explains the importance of servicing and maintenance in order to protect what often is a sizable investment


HP systems are becoming increasingly popular due to their cost

and fuel efficiency, as well as their ability to help heat networks meet legislation such as, the Building Regulation’s Part L and exceed CRC Energy Efficiency Scheme (CRCEES) targets. However, as a relatively new technology, there remains a knowledge gap among many users regarding its proper maintenance and servicing requirements. CHP straddles two disciplines, bridging the gap between traditional space and water heating and electrical generation. As such, its implementation is often left in the hands of the manufacturers, which can lead to many users feeling daunted by the concept of maintaining it. Correct design and sizing during the

planning stage is vital if a CHP system is to hit peak performance, however, facilities managers should not underestimate the importance of aftercare and regular maintenance too. CHP systems operate at their most efficient when they are kept running, due in part to the payback period often outlined at installation. It may sound simple enough, but as with any engine a

CHP system needs to be regularly maintained to guard against breakdown. In much the same way as the engine of a car is serviced year after year, it is crucial for any size CHP system to be regularly inspected. Oil should be monitored in order to prevent contamination or low oil levels causing long-term damage. Over time the oil will congeal and thicken as it picks up metal and dirt and embed into the unit, labouring the engine. A simple service involving a drain and refill can avoid both the unit’s performance being affected and expensive repairs. It is not only the oil quality that needs observation, service schedules should also include repeated spark plug changes and gas and air filter checks. With use, gas filter and air filters get clogged up and dirty resulting in the engine not pulling in enough air. Similarly, the Lambda probe, which measures CO2, needs to be replaced occasionally in order ensure that the correct levels are being met for the engine to fire. Without these relatively straightforward checks the CHP system may operate inefficiently, unsafely or not at all.


Figure 1: CHP systems operate at their most efficient when they are kept running, due in part to the payback period often outlined at installation

PLANTROOM PRACTICES As well as protecting the technology from breakdown, maintenance and servicing is also necessary in order to maximise the efficiency of the system. Although the larger servicing operations are often best carried out by the manufacturer or servicing provider, there are plenty of ways facilities managers can ensure a system is running at its most efficient – many of which can be worked into general building maintenance. Like any heating system, water quality

will go a long way towards determining the efficiency of a CHP system. Contamination of system water causes restrictions through the plate heat exchanger, which will subsequently cause reduced heat transfer and increase internal temperatures, eventually preventing the CHP from staying on for long periods. On- site water quality management help to promote a long lasting system and where necessary daily checks should be made to avoid damage caused by dirty water entry. It is also important to consider whether the return temperatures are too high. This can sometimes be rectified by ensuring other heat sources, such as boilers, are allowing the CHP to take the lead in the controls strategy. A CHP prioritised control system will

Figure 1:

Carl Main, Business Development Manager – Commercial and

Industrial After Sales at Bosch Commercial and Industrial

keep gas costs down, and will help keep CHP systems running for as long as possible allowing the returns that co- generation is designed for. To that end, facilities staff should have a good general knowledge of the basic controls and functions of the CHP installed. Most service provider technicians will be happy to give training on the fundamentals of CHP so service and maintenance can be at the forefront of any CHP planning.

Bosch Commercial and Industrial T: 0330 123 3004


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