Kite Refrigeration

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Archive for July 2011

Efficiency and Comfort

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A commercial heating and cooling installation must fill opposing goals; comfort, energy efficiency, reliability, quiet.

A recently completed project had all these goals.

It was imperative that the temperature be comfortable, there be adequate ventilation. The work performed in the space is very detailed and technical, at the same time repetitive. Uncomfortable staff results in mistakes and low productivity.

There was a working system consisting of an old atmospheric gas burner furnaces with air conditioning condensing units. There was an opening for fresh air. The duct work was adequate.

We installed two high efficiency furnaces, each serving a floor. The furnaces have variable speed ECM motors, and two stage gas burners. We haven’t run the system in the winter months, but in the spring it worked well. The heating would run on low fire and low fan, gently warming the space. The occupants hardly knew the system was running.

We installed indoor coils above the furnaces tied to heat pump outdoor units. This gives the owner economic choices when it comes to heating. Currently natural gas is inexpensive, so the heat pump operation is limited to warmup on cool mornings. The cooling is 15 SEER. When the system is running in cooling it isn’t drafty or noisy.

We installed mixing dampers on both systems, along with a relief air hood. They can be run in 100% fresh air mode, or modulated to maintain discharge temperature, or minimum ventilation air. There was an existing Delta control board which we use to fine tune the control. We implemented a free cooling algorithm, where a call for cooling first tries to satisfy demand with fresh air. At the current loads in the space, we disable dx cooling at 19c. We have found that the occupants don’t notice slightly warmer temperatures if the air is fresh.

We also implemented a building purge and cool down cycle. The building has a south-west facing wall with large windows. It gets the sun until it sets in the evening. Previously, the building would continue warming up in the evening, and when everyone showed up in the morning, the outside walls and furnishings were warm. It would take a number of hours running dx cooling to bring the temperature down. The cool down cycle starts after midnight and runs the fan with full open dampers to cool the space down to a degree above heating setpoint. There are a number of logic checks to prevent cooling things down and needing to run the heat to make it comfortable.

The results have been satisfactory. A July hot day, the system shut down at 5PM and went on setback. The building warmed up to 29C. After midnight the fans came on, and by 6am the building was at 22C. The low outside was 16C. The mechanical cooling didn’t come on until around 11AM when building came out of the shade of it’s neighbor and started warming up. The current draw for the various components makes 1 hour of dx cooling equivalent to 7 hours of fan at full speed. In the hottest conditions we cut the equivalent of 2 hours of dx runtime, or approximately 20%.

We and the client are quite satisfied.

If you would like us to sort out a similar problem, please contact us.

Derek Kite



Written by Kite Refrigeration

July 11, 2011 at 12:14 am

Posted in Uncategorized