Energy comparison scenarios, below the monthly breakdown on the Energy station, sets a measure against the same plant without it. A scenario appears only when the system has what it needs.
EC condenser fans
Kelvin works out what faster condenser fans save from the condenser's own datasheet: its capacity at a higher fan speed against its main rating. Without that rating it doesn't estimate a saving.
- 1
On the Equipment station, open the condenser: choose Enter from datasheet, or its model name if it's already entered.
- 2
Under Rating at a higher fan speed, enter the speed the main rating is at, a higher speed the same datasheet table rates it at, the capacity there and the whole unit's fan input.
- 3
Choose Update this model (or Use this model for a new one), then save the equipment selection with Save selection or Update selection.
- 4
Open Energy and read the EC cooling fans row under Energy comparison scenarios.
At the same heat rejection, the condensing TD falls in the ratio of the two capacities. Kelvin never takes the TD below 2 K, or the condensing temperature below Min condensing temp. It solves the cycle again month by month at the lower condensing temperature, and charges the fans by the fan affinity law at the speed each month needs.
The row gives the Compressor saving, the Condenser fan energy at the higher speed, and the Extra fan energy over the annual readings' condenser fans. The difference between the saving and the extra fan energy can come out as more energy, not less, and the row says so when it does. The datasheet's own fan input at the higher speed is printed beside them as a check.
The row reads not estimated, with the reason, when:
- the condenser has no rating at a higher fan speed;
- its heat rejection is published at one TD only, so the datasheet doesn't say what TD it holds at the higher speed;
- it is rated for another refrigerant and the datasheet gives no factor for this one;
- the system is transcritical CO₂, where a gas cooler holds its approach whatever the fans do, or a cascade, whose condenser belongs to the high stage this comparison doesn't solve again.
Adiabatic pads
- 1
Under Adiabatic pre-cooling, set Pads to On. They start on for a transcritical CO₂ system and off for any other.
- 2
Set Min ambient: the pads run only when the ambient is above it.
- 3
Enter the pad maker's saturation efficiency in Pad efficiency. Until you do, the figure is an assumption, and the sheet says so.
When the pads run, they cool the air entering the condenser or gas cooler by the pad efficiency × (dry bulb − wet bulb). The wet bulb comes from the humidity at sea-level pressure; site altitude isn't modelled. There is no cooling when the wet bulb is below 0 °C.
The humidity comes with the climate: each month's design day at the project location, a preset city's mean 3 pm relative humidity, or the one Relative humidity entered with a custom profile. On the expected basis, the pads hold each month's design-day moisture through every hour they run, so a cooler hour is a damper one.
With the pads on, the annual readings already include them. The Adiabatic cooling row sets them against the same plant solved again at the raw ambient, and gives the hours or months they ran and the cooling they gave.
A compressor on a VSD
When the equipment selection has a compressor set to run on a variable speed drive at a set speed, the Compressor VSD row estimates a saving from fewer starts and from modulation. The page labels it as an estimate from an uncited rule of thumb, and it is a different basis from the one the Equipment station rates a VSD compressor's capacity on.
Note
None of these scenarios changes the annual readings except the pads, which you switch on yourself. The EC fan and VSD figures sit beside the readings, not in them.