A helping hand for demand-controlled heating systems


Demand-controlled heating systems offer a number of benefits but can lead to an increase in boiler dry cycling. In such cases, additional levels of control are required to prevent this

It is becoming common for a building’s heating system to be controlled through a demand-led control strategy, which may be determined by temperature, occupancy or a combination of the two. However buildings are dynamic and typically accommodate multiple uses and, in most cases, will use their boiler plant for both space heating and hot water.

Where boilers are only providing space heating the likelihood of all heating zones being satisfied at the same time is highly unlikely. Therefore one or more of the boilers will be on standby and dry cycling.

If the boilers are providing constant temperature hot water then a demand-led control strategy will not be appropriate. This is because the hot water will need to be maintained at the required temperatures and its use may be sporadic throughout the day.

Installing Sabien’s M2G boiler load optimisation alongside a demand led control strategy will ensure that boiler dry cycling is prevented during periods of the day when the boiler(s) are on standby to meet those transient, short burst heating requirements.

When installed alongside a building energy management system (BEMS) demand control strategy the M2G will ensure the boiler(s) are only ever firing in response to a genuine heating requirement from the building. In fact, M2G will work effectively alongside any BEMS control strategy, be it sequencing, weather compensation or demand-led control.

Another important point to bear in mind is that boiler dry cycling occurs in each individual boiler - not within the system of combined boilers. As BEMS are not typically configured to monitor individual boilers (typically they are designed to monitor the blended temperature from all of the boilers), preventing dry cycling using a BEMS would require sensors to be attached to the flow and return pipework of each boiler and a control strategy written for each boiler. Without that, boiler dry cycling will not be detected or prevented.

The M2G is the first boiler control to use flow and return temperature sensors to monitor, analyse and control the flow and return temperatures of the boiler in real time. As such, it is the only retrofitted control which is able to determine the actual heating demand on the boiler and prevent it from dry cycling without lowering the system temperature or using a fixed time delay.

It is also able to self-learn, continually adapting to the changes in heating load on the boiler.

Furthermore, all of the verified savings delivered by the M2G are actual kWh savings in gas consumption – not the reduction in firing time that some manufacturers promote. The latter has no relation to the money spent when high/low or modulating burners are used.

M2G will typically deliver a payback in less than 18 months and requires no servicing, maintenance or continued commissioning.

Since its introduction in 2004, the patented M2G has established itself as the market leading advanced boiler load controller. Sabien has delivered million pound contracts to install M2G into the estates of BT, Lincolnshire County Council, the MOD and many others – and M2G is now available worldwide.

For more information on this story, click here: February 2015, 13
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