When it comes to storing hot water and ensuring the correct circulation temperatures are being achieved at the extremities of any size of circulation system, we know the measures that need to be put in place to achieve compliance with Approved Code of Practice L8. Including pump selection and positioning of both Thermal Balancing Valves and Thermal Regulating Valves.
The issue of maintaining the correct cold-water temperature is becoming more common particularly as newer buildings are more air-tight and better insulated. Buildings that are occupied 24/7 and 365 days a year are more problematic in this regard. Keeping cold water at 20 degrees or less in a pipework system that is not being used a great deal is almost impossible without some form of intervention.
Our studies into this have revealed the following:
• If cold water sits stagnant in pipework inside a warm ceiling void or IPS panel then, over time, it will become the same temperature as its surroundings.
• The amount of insulation applied to the pipe and it's thickness ultimately has little effect in preventing the water temperature in the pipe matching its surroundings if the water is not drawn off over a period.
• Pipework insulation becomes the same temperature as the void around it. The only thing that changes is the temperature of the cold water in the pipe, after it has been drawn off and replaced.
• Ceiling voids and IPS panels are typically a couple of degrees warmer than the space temperature of a room.
What this means is, even in buildings that are constantly occupied, cold water that sits in a warm void over a period will eventually rise to above 20 degrees. The periods of time it takes will vary although we have seen evidence of this happening in 2 to 3 hours.
Preventing cold water from remaining static is good practice to help stop Legionella from settling in pipework and without some form of cold-water cooling system or cold-water re-circulation system then regular flushing of cold water is essential.
The ultimate backstop is an automated system that releases cold water to drain when its temperature reaches 20 degrees, however these systems are wasteful of water and not ideally suited from a sustainability perspective.
Flushing of water outlets either manually or by automated devices, along with monitoring of the cold-water temperatures in tanks and pipes, are necessities without any other form of technology.
The ability to adjust the amount of water within cold water storage tanks is also good practice to make sure that stored water in a tank is replenished at least once in a 24-hour period. This helps to avoid a scenario where too much water is being stored when demand is low.
If you are experiencing problems with warm cold water then, hopefully, you will find some of the above helpful.
More about Neil...
Neil joined the practise in 1999 having served a five year apprenticeship with a national contracting company, qualifying as a Building Services Engineer in 1998. He is experienced in the design of mechanical services and in the development of the detail, producing working drawings, specifications, and liaising with other members of the professional team has been extensive over the years.
Neil has been the lead mechanical engineer across most of our biggest schemes, in terms of construction cost, covering a wide range of different sectors. Also performing the role of Senior Project Engineer overseeing both mechanical & electrical design work and installations on site.
Speak to Neil about your next project: neil@stevenhunt.com
