On a site in central London we have replaced 7 water chillers rated at c400Kw each using R.22 with new ones operating on R410A to comply with regulations.

Save the Pounds and the Planet

Our client occupies a 300,000 ² ft building in London, served by a VAV system incorporating 4 roof mounted A.H.U. to supply enough fresh air at 12 ° C to accommodate 2000 persons. The fresh air is distributed to 22 air handling units on the office floors, each in an air mixing plant room.

Due to the nature of our client's business there can be as few as 200 occupants in some parts of the building, some of the time. Vast quantities of heated/cooled fresh air (up to 20000 L/S) are pumped into the building 24/7 most of it not necessary.

The Problem:

How can we reduce the volume of fresh air and provide adequate fresh air and extract to a small occupied area anywhere at any time. To make vast energy and cost savings on heating/cooling fresh air??

The Solution:

The fresh air inlets and extract air outlets were fitted with motorised volume control dampers in all 22 plant rooms. Via the B.M.S. the dampers are controlled by a CO 2 sensor in the return air from that zone. Hence the lower the occupancy, the lower the fresh air quantity supplied. Opening and closing the dampers, varies the supply and extract duct static pressure. This is measured and used to control the inverter driven supply and extract fans on the roof. The inverters and suitable fan motors were fitted to achieve this.

The Results:

Now only occupied areas of the building are supplied with the correct fresh air quantity. The 4 supply air units run at between 10% and 30% capacity most of the time.

Our client's independent air quality monitoring shows more than adequate air quality at all times in all areas.

Energy use and costs have reduced by 25% - 60% to treat the fresh air.

It is inherent in our ethos to advise all clients on reducing energy costs and use.