Installation of main boiler digital burner controls
The main boiler house at The Royal Sussex County hospital houses four large boilers which supply MTHW @ 125°C to large areas of the site.
The boilers are old and were outdated featuring mechanical controls with cable and bar linkages to valves and flaps. In addition, system temperature was controlled from a sensor positioned to monitor system supply temperature. As a result control was sluggish and unreliable. System control sensors were repositioned to monitor return temperatures which now control the boilers.
Prior to funding approval for the burner replacements, as a first initiative the York BMS was thoroughly interrogated and control changed to look at return temperatures rather than flow. This had an immediate saving in gas usages.
The outdated burner controls were replaced with digital boiler controls supplied by the burner manufacturer at a cost of £8,000 per boiler. Total cost for the project was £32,000 and paid for itself within six months.
Savings have been from both gas and electricity and were installed and commissioned in April/May 2011, this is shown in the electrical savings picture, bottom left.
Key electrical savings were from:-
- the variable speed drives on fans
- reduced boiler running times through better firing management
- Removal of the electrical heating from the old heavy oil system.
The change in gas usages could have been a lot better as they have been masked by operational constraints that have needed the boilers to be kept at 125°C due to hot water concerns. This situation is being addressed with a view to reducing the MTHW to 110°C in the near future.
An Obsys data collection system was added to measure the required data that the York BMS could not provide.
This is an on-going project that has a lot of scope on the huge quantity of gas burned each year in the main boiler plant.
Since the installation completed in April/May 2011, allowing for the milder weather conditions through degree days, the following savings were made:
6 month gas savings of 1,018,800 kWh compared to the previous year, £40,752
or 187 tonnes of CO2
6 month electrical savings of 88,800 kWh compared to the previous year, £8,000
or 46.5 tonnes of CO2
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