Case Study 2

Background - energy costs
As energy prices rise it is necessary to review them much more actively. A manufacturing company noticed that its energy costs for a spring quarter were higher than expected.

Problem - heating bills
The site consisted of three separate buildings of 7,000 sq. ft each heated by gas hot air forced convection. Early suspicions, via invoices, were that perhaps the heating had been coming on during the cool nights in April. The controls on the heating system, originally with a 7 day time clock and wired thermostats, had been upgraded to a wireless type thermostat. The time clock was awkward to adjust, both because the user interface was not intuitive and because it was awkwardly situated. It appeared that it had been switched over to manual - probably during a Saturday overtime period and no one had noticed. It also appeared that the heating had been left on all the time during the previous winter.

Solution - independent monitoring
An upgrade to the factory heating controls was undertaken and an optimum start, seven day programmable thermostat was chosen and placed to be easily accessible. A Planer Assure24seven alarm and monitoring system, measuring temperature in the factory at one point was easily also installed and set to send me a graph of the previous 24 hours of temperature data on a daily basis.

Solution - what was found
It was noticed that one factory took longer to warm-up than previously realised. Because of poor insulation it warmed at approximately two degrees per hour.

Examining the graph, to ensure that the temperature was 21° in the factory at the start time of 07:30, the heating needed to be turned on in the early hours of the morning, but the temperature controller fitted, could only automatically adjust the start time by a maximum of one hour.

Using the figure of 2° per hour it was calculated that if the night temperature was set to be 10° from midnight onwards, the worst case for the morning start would be to warm from 10° to 22°. This was a 12° rise which could be achieved in 6 hours at 2° per hour. The end setting was therefore to bring the heating on at 01:30; 01:30 plus 6 hours equaling 07:30. This could be verified by consulting the e-mailed graphs from Assure24seven - done in the office or from an ordinary browser at home as the system is web based.

Daily graphs also enabled further optimisation of the system by dropping the temperature to seven degrees at 6 o'clock in the evening, when the heating went off, and then increasing it at midnight - up to 10 degrees. From midnight to 01:30 or 1.5 hours at 2° per hour to get from a possible low of 7° up to 10°, ready for the heating to come on full at 01:30. This works out precisely at 3° for the worst case which is the figure needed.

All of this type of fine tuning to optimise the system was feasible because of the availability of a daily graph delivered by e-mail each morning.

To add to the problems a new thermostat was later installed and incorrectly configured so the heating remained on a whole weekend. Previously, there would have been no way of knowing this. Assure24seven showed the flaw up.

Using a feature of this system it sent e-mails and SMS alarms as the temperature was higher than expected during the night.

There are heating controllers available that claim to be “self learning” - however without independent monitoring it is not possible to know what they are doing out of normal hours or whether someone has wrongly adjusted them.

Costs - Example
Say a factory of 5600 sq.. ft. uses £5600 of gas per year. If the heating was left on 24 hours a day in winter, the saving resulting from the heating being off for 7.5 hours per day plus Saturday afternoon and all day Sunday would give a total “off time” per week of 73.5 hours or 44% of this. Expected saving each year would be 44% of £5600 or £2450. In reality, this would probably not be achieved; in the case given, the system has been set to keep 7° as a minimum, and there will be winter nights when the heating will need to come on to maintain this temperature.

Other Possible Benefits
The Assure24seven is not an expensive system and can monitor and alarm most requirements.

Assure24seven
Planer plc, Sunbury, UK

Case Study - Assure24seven to optimise building heating:
Potential savings of £2000 per year were identified