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Benefits of Renewing Large Heating Systems
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Benefits of Renewing Large Heating Systems

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CIBSE Technical Symposium, DeMontfort University, Leicester UK
6th and 7th September 2011


During the summer of 2009 the sixteen 22-year old Hamworthy modular boilers in IBSA House plant room were removed and six new 350 kW Buderus forced draught gas boilers installed.
A new circulation system to the nine building zones was installed using Grundfos Magna energy efficient pumps. Four of the zones were provided with weather compensation circuits, and a high level of insulation was applied
to the pipe work to improve the thermal efficiency of the system.
A full year’s gas meter readings for 2010 are now available, making it possible to analyse the consumption data and compare this to Degree Day data. The colder the weather is the higher the number of Degree Days – and therefore
more heating is required. The predicted gas use for this period was 3,162,387 kWh. The actual use with the new boilers was 2,079,641 kWh. By subtraction the actual savings were 1,082,746 kWh. At the current contract price of gas at 2.0634p per kWh, the saving is £22,342 - representing a 34% saving in fuel.
Noteworthy, in addition, are the savings in electrical consumption by replacing the old circulator pumps with new energy efficient Grundfos Magna pumps which not only have permanent magnets instead of an electric coil, but are also speed controlled according to demand.
The annual electrical consumption dropped from 127,766 kWh to 69,976 kWh – an annual saving of 57,790 kWh which at the present electrical actual cost of 7.4243p per kWh equals £4,291.

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