Hospital hot-water savings come on a plate

Published:  20 September, 2005

DHW plant
Replacing existing DHW plant in a Plymouth with a system based on five Alfa Laval plate heat exchangers has saved £51 000 in the first year of operation.

Derriford Hospital in Plymouth has reduced the cost of generating domestic hot water by £51 000 a year following the installation of a new system based around five Boss plate heat exchangers made by Alfa Laval for BSS.

Opened in 1978, the hospital has capacity for 1100 patients, a new large, cardiac unit and is a tertiary treatment centre for neurology, renal and burns.

The existing hot-water plant was coming to the end of its engineering life, and there had also been significant changes to the hospital’s hot-water demands, so it was decided to replace the existing plant. There were originally seven load levellers serving the wards, the sterile disinfection unit and the laboratories. Two further large calorifiers provided hot water for catering. An HTHW main connected to the main HTHW boilers delivers water to the plant room, which has a total storage capacity for 44 000 litres of hot water.

A switch to cook–chill catering plus changes to patient bathing regimes had drastically reduced the demand for hot water.

Rather than replace like with like, the estates department chose plate heat exchangers served by LTHW, so that large volumes of hot water would no longer have to be stored. Existing over capacity in the non-storage heating calorifiers provides the primary heat source for these heat exchangers. Among the benefits is the release of HTHW capacity for the new 7-storey cardiac block completed this year. The need for insurance inspections has also been eliminated because of the switch from HTHW to LTHW as the primary heat source.

The local branch of BSS, one of Ala Laval’s principal sales channels, designed a system using five plate heat exchangers to make best use of the existing over capacity. The design included buffer vessels to provide for periods of peak demand, reducing initial capital costs.

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