In a nutshell
Step 3 recommends you evaluate each equipment category, and gives some general recommendations on the things that you might look at. The checklist suggests specific things you should look at in each category.
Although lighting is often taken for granted, it accounts for 20% of national electricity use, and can account for up to 40% of electricity use in offices. The electricity it consumes becomes a source of heat gain, which can result in overheating or increase cooling load.
Identify the different lamps that are in use, and their wattage. If you can’t see the rating by inspecting the lamps, then ask whoever is responsible for maintaining them.
Key questions to consider:
- Is the lighting performing its task?
- Are the luminaries clean and lamps in working order?
- Are the luminaries effective at casting light into the occupied space, or do they waste light?
- Has light output deteriorated with age, suggesting lamps need to be replaced?
- How are the lights controlled/switched?
- Do operating hours match occupancy hours?
- Are they on when daylight levels would be adequate for requirements?
- Are lighting levels adequate or excessive for requirements? Recommended LUX levels
- What do you hear most often regarding lighting in this building from the occupants?
- Do fluorescent lamps have electro-magnetic or high frequency control gear? If they flicker when they are switched on, then they have electro-magnetic gear.
Consider the suitability of the following energy saving technologies:
- Occupancy based controls
- Daylight linking (auto switch off or dimming when daylight is sufficient)
- Replace traditional bulbs/candle lamps with look-a-like CFLs
- Replace low voltage halogen lamps with Infra Red Coating halogen lamps or, where appropriate, mains voltage mini-CFL fittings.
- Replace high bay fittings in warehouses with automated “Patina” fittings
- Replace outside lights with SON or CFLs
- If replacing fittings use electronic gear, consider dimmable (with associated controls), fittings with reflectors that cast the light into the occupied space, and try to achieve a lower installed watts/sqm.
Evaluate Office Equipment
Office equipment typically accounts for more than 20% of total energy consumption in offices. The electricity they consume becomes a source of heat gain, which can result in overheating or increase cooling load. Despite having built-in powersave features, a recent UK survey found that these are only activated in 25% of cases.
- How many computers are there?
- What proportion of PCs and monitors automatically switch into standby if left idle, and what is the time delay? Note that “screensave” generally doesn’t save energy.
- What proportion of computers are switched off by the users at night?
- What other office equipment is used, and does it switch into standby?
The table below illustrates the impact of using standby on electricity use, and provide an indication of energy savings achievable:
Item Average power [Watts] Standby power [Watts] Target recovery times [seconds]
PCs 40 20-30 Almost immediate
Monitors 80 10-15 Almost immediate
Laser printers 90-130 20-30 30
Photocopiers 120-1000 30-150 30
Fax machines 30-40 10 Almost immediate
Vending machines 350-700 300 Can be almost immediate
Consider the following energy saving measures:
- Enable powersave features:
- Blank screensave after 3 minutes
- Standby after 10 minutes
- Hibernate after 65 minutes
- If powersave features not available, consider use of timeswitches to switch off at night and weekends
- Procurement and installation practices should purchase Energy Star computers with flatscreens, and ensure powersave features are enabled as above.
Evaluate IT & Comms Rooms
Although not much can be done about direct electricity use by this equipment, there is often opportunity to reduce electricity use associated with cooling plant. A recent study we undertook found that 40% of the electricity consumed by a high performance server room was by the cooling plant and associated circulation fans.
Key questions to ask yourself
- Is the temperature in this room maintained below the prevailing temperature in the building (21degC)? Often IT rooms are maintained at 18degC, which results in heat flow from surrounding rooms through the walls into the IT room; this increases both your heating and cooling load. Each 1degC increase in cooling temperature setpoint will reduce energy use by 2-4%.
- If room temperature falls below setpoint, will the cooling plant operate in heating mode to warm the room? If a split a/c unit is being used “Auto” mode will enable heating!
- Are there unnecessary sources of heat gain (solar, warm air supply duct, unlagged radiator pipes)?
- Is the cooling plant efficient and in good condition? Assessing efficiency is dealt with below in the section on A/C units. Because a/c units in IT applications/comms rooms run continuously, energy efficiency is critical.
Evaluate Boiler Plant
- What is the age and condition of the plant?
- Are boilers regularly maintained and air/fuel ratios tuned?
- What is the combustion efficiency? This should be available from the maintenance record.
- Are there separate heating and hot water boilers?
- Is the boiler and pipework insulation present and in good condition?
- If there is more than one boiler, are sequence controls fitted?
- Are extra boilers turned off in mild weather and the summer?
Heating, Cooling and Ventilation
- Do heating, cooling and ventilation hours match occupancy in the different zones/areas?
- Are the space temperature setpoints for comfort heating at or below 21degC?
- Are the space temperature setpoints for comfort cooling at or above 23degC?
- Is there potential for simultaneous heating and cooling? Consider split air conditioning units operating in conflict with heated supply air; consider fan coil units operating in conflict with fresh supply air.
- Are portable electric space heaters in use? These are very energy intensive, but their use suggests a broader heating system issue.
- Are toilet and other extract fans switched off during unoccupied hours?
- Are there large fans/motors in use (air handling units)? If so, check operating hours, conditions and controls.
- Do the radiators have thermostatic radiator valves, and are they operated correctly?
- Are frost protection thermostats/controls set correctly?
- If radiant heating is used, does a black-bulb thermostat control it?
- Are building controls such as weather compensation and optimum start present?
Consider following energy saving measures:
- Variable speed drives on ventilation motors above 5kW in size. A 20% reduction in speed can deliver a 50% reduction in power.
- Consider the following boiler controls:
- Lead/lag or sequence control
- Inhibit operation in mild weather (outside air temperature > 16degC)
- Inhibit short cycling of boilers when there is not a genuine heat demand
- Boiler flow temperature weather compensation
- If heavyweight boilers are used, identify options to minimise standing losses, e.g. back-end isolation valves, burner or flue dampers.
Split air-conditioning units
Small packaged air-conditioning units are proliferating. They are often referred to as DX (direct exchange) units, or split a/c units. Each unit has an indoor unit (evaporator) and outdoor unit (condenser). They are generally installed to provide cooling, but are generally capable of heating too.
- Where are they used and is their function comfort cooling or IT equipment cooling?
- Are they required to maintain comfort? Frequently they are installed to offset heat gains associated with poor housekeeping of lights and office equipment.
- Are they switched off when not required?
- Are the temperature settings appropriate? Cooling temperature setpoint should not be below 21degC in either a comfort or IT application. Each 1degC increase in cooling temperature setpoint will reduce energy use by 2-4%.
- Is the condenser coil clean, and situated in a well-ventilated (preferably shaded) location?
- Is the pipe insulation in good condition?
- What is the Coefficient of Performance (COP) in cooling mode?
- Are they equipped with variable speed inverters, which improve part load operating efficiency?
- Is energy efficiency a factor considered in the procurement process?
- Procure A-rated appliances
- Procure appliances with variable speed inverters
- Procure appliances with a high COP (2.0 is poor, 4.0 is good).
- Due to the continual operation of a/c units in IT applications, if the unit has a low COP (2.5 or lower) consider replacing the unit with a high efficiency model.
Coefficient of Performance (COP) is a measure of the effectiveness of an air conditioning unit (or chiller) in converting electricity into cooling or heat. Once you buy a unit, the COP cannot be changed. For a given appliance, the COP in cooling mode will differ from the COP in heating mode. Usually the COP will be supplied with an appliance’s technical literature. If it is not given it may be calculated simply:
COPcooling = rated cooling output [kW] / rated electricity input [kW].
Domestic Hot Water (DHW)
Instantaneous undersink heaters are effective where there are limited hot water requirements (e.g. hand washing only). Check the temperature setting for these units is 60degC.
For a boiler heated system, key questions to consider
- Do operating times for the circulating pump (on the secondary side) match occupancy?
- If the boilers are off at night, are the electric immersions inhibited?
- Is the water maintained between 55 and 60degC? Lower runs the risk of legionella, higher increases standing losses.
- Is the water pressure appropriate? High water pressure increases use.
- Is there adequate lagging on the calorifier and pipes?
If the space heating boilers are also used for DHW, consider switching off the boilers in mild weather and using the electric immersion on night-rate electricity to heat water.
Key questions to consider:
- Is equipment switched off when not in use? This is a significant source of waste in kitchens.
- Is there speed control of the extract fan, and is speed reduced when full speed not required?
- If there is a supply air handling unit, what is the supply air temperature? 14degC often used for kitchens.
- Are supply and extract fans switched off when not required?
- Is the dishwasher plumbed with hot water from the central system?
- Are energy efficient appliances purchased?
- Are gas appliances favoured over electric appliances? Gas is cheaper as a source of heat.
For refrigeration equipment, specific issues are:
- In cold stores the evaporator should not be obstructed, the door should be left closed and the light should be switched off.
- The condenser should be mounted in a shaded, well ventilated area, and be in good condition.
- Check the refrigerant sight glass to ensure adequate charge.
- Check the pipe insulation is in good condition.
- Are the temperature settings appropriate?
- For display fridges, are the blinds pulled down at night?
Return to Step 7