Are customers being misled?

Sometimes, designers take the easy option, leaving end users with features they don’t actually need and long-term running costs that could have been avoided with a bit more care at the outset. People like to make a big song and dance about CoP, but the reference point is often based on the compressor working at full-load conditions, whereas for the majority of the year, the compressor running cost is probably only a tiny fraction of the overall system cost. The big element is moving the air (ie the cost of driving the fans) and if that isn’t properly examined, you will design the wrong system for the application.

For example, at Lennox we often have customers asking for heat recovery on all their rooftop air conditioners – why? If you have less than 50% fresh air, then don’t even think about heat recovery, because the saving will never pay back. It would be much better to look at reducing the build cost, improving the efficiency of the fan and concentrating on the reliability and overall efficiency of the system. In a number of cases, we will offer a line-up of, say, 10 rooftop units and engineer heat recovery only into the one mainly responsible for delivering fresh air, as that will give the customer the best solution for their needs.

Also, how about looking at reducing humidity rather than constantly concentrating on temperature? You could reduce the system’s energy burden by increasing the temperature slightly, but occupants will still feel comfortable because you have reduced the relative humidity.

For years, end users have been crying out for usable data about lifecycle running costs – and that clamour will only get louder in the current climate of rising fuel costs. It is no longer good enough for the industry to say we can’t produce that information – we can.

The software, like the L3C system developed by Lennox (Life Cycle Cost Calculator), can quite easily establish the running costs of most buildings, which allows us to customise the equipment to suit the application – and prove that the full-load CoP of the compressor is rarely a major factor. Free cooling should be available in the UK climate for large parts of the day and night, so the compressor is hardly running at all.

We have to be more open with clients and educate them away from “headline” energy saving measures in favour of more meaningful long-term decisions. It is time that the industry looked behind the grand gestures and started working that bit harder for its customers.