Kelvin

Run a day's operation

Lay the day's deliveries, door openings, defrosts and shifts on a timeline, play it, and watch each room and the rack respond.

Energy and running cost · Updated 27 Oct 2026

  1. 1

    Choose the system in System. The day runs on its Heat Load rooms, the pipe layout that puts an evaporator in each room, and the equipment selection that rates the evaporators, the compressors and the condenser.

  2. 2

    The page seeds a scenario from the records: every door's passages each hour, each evaporator's defrosts, each room's lighting, people, forklift and fan hours, and the heat load's batch arriving at midnight. That baseline reproduces the heat load's own hourly figures.

  3. 3

    Drag events along the timeline to where the day really puts them, drag an event's edges to change how long it lasts, and double-tap an empty track to add one. Choose an event to see its figures beneath the tracks, and Remove to take it away.

  4. 4

    Choose Play to run the day, or drag the time control. The playback band stays pinned under the readings with the moment's figures — each room's air with its door and defrost marks, each compressor's status, the condenser's fans — and a strip of the day's events you can drag, so the cursor moves from anywhere on the page; the arrow keys step it too (Shift for an hour), wherever you are. Step on the playback bar sets how far they move: 1 min runs the day in one-minute steps (five times the work, kept with the scenario); 15 min and 1 h read the five-minute run in bigger jumps. The chart's cursor, the timeline's playhead and everything under Compressors, Condenser, Rooms and The rack read the same moment; on a wide screen those blocks sit beside the chart and stay put while it scrolls. Click a compressor's lane under the chart to open it as a full chart — its capacity and power through the day, each start marked, a VSD unit's speed — and click it again, or Close, to shut it; Compressor detail under the chart opens one without a pointer.

  5. 5

    Click the chart (or press Enter with it focused) to pin a flag at that moment. Hover the flag to read the moment again, click it to let it go. Pinned flags under the chart lists every flag's readings, Go to moves the cursor there, and the flags save with the scenario and print in its report.

  6. 6

    Name the scenario in Name and choose Save as a scenario. Open a saved one from Saved scenario; the run is computed again each time it opens.

Every figure on the page is the engine's. The rooms are the pull-down simulation's, given their air's heat capacity and driven by the events; the rack is the equipment selection's compressors, judged every five minutes on a cycle re-solved at that moment's suction and condensing temperatures; the condenser's fans follow its datasheet.

The settings

  • Ambient: the station's design day for a month (the design dry bulb shaped by the daily range), or the design ambient flat through the day. A project with no location runs flat.
  • Each suction group's Control: Suction pressure is the pack controller's — compressors stage one at a time about the Set point with its Deadband, and the rooms' thermostats hold their set points; Room thermostat is the condensing unit's — each room's coil switches on at the room's set point plus half the Differential and off at minus half, the compressors run while a room on the group calls (or a display case is on) and stop when none does, and the set point is then the low-pressure floor and the VSD target. A VSD unit modulates before anything stages on either.
  • Lead unit on a group with more than one compressor: VSD first (first on, last off), In order, or Rotate by run hours (the fixed-speed unit with the fewest hours comes on first and the one with the most goes off first). Min. run, Min. off and Stage interval are how long a unit must run or rest before it changes again and how close two staging changes may be; the defaults are Kelvin's, not a standard's.
  • Control for the condenser fans: fixed speed, staged off one at a time below the minimum condensing, or EC, slowed to hold it. Min. condensing is the head-pressure floor and EC floor the slowest an EC fan is allowed to run.
  • Heat capacity of the room air: on, a door opening is a rise and a decay; quasi-steady is the pull-down's air, which jumps.
  • Display cases lists every display case on the pipe layout. A case that is on puts the load its layout was sized on onto its suction group all day, as published; a defrost laid on its track takes its coil off for the window. Untick On to run the day without a case — the rack with part of the store out. For a case whose fixture publishes no DEC, enter the hours a day its Fans, Lighting and Anti-sweat heaters run; a load with no hours isn't counted, and the page says so.
  • Seed from the records lays the day out again from the heat load's figures, at new seeded times.
  • Auto defrost keeps each coil's defrosts as the equipment pick has them, evenly spaced, and slides each coil's set to the quietest part of its day — away from door passages, standing-open doors, deliveries and the lighting, people, forklift and fan shifts — never two coils of one room at once, and coils on one suction group staggered where the day allows. It judges no frost: the number of defrosts is the pick's, not a finding.

What the page says, and won't

  • A suction group whose compressors can't be judged for the whole day (a rated-point entry, no pick, a polynomial for another refrigerant) runs uncapped: its suction holds the set point and the page says why.
  • A condenser without a datasheet entry, or a booster's gas cooler, isn't judged: the condensing temperature follows the Energy station's rule and the fans read not judged.
  • A step that didn't settle keeps its last figures and is counted in the margin and under Flags in the report. Nothing is filled in.
  • A defrost puts the heater's energy into the room less the fraction that melts frost, and the coil is off for the window; the frost itself isn't tracked.
  • On a transcritical CO₂ booster the chart's Head lane, the playback band and the Condenser block say which regime the head is in at each step — transcritical, in transition (held above the critical pressure though the gas cooler exit is below the critical temperature, because condensing would cost more work) or subcritical — with the gas cooler pressure and exit, and what the high-pressure valve and the flash gas bypass valve carry with the drop across each. No valve opening is judged: that needs the valve's own published capacity at the drop and its characteristic.
  • A display case's duty is the published figure as it stands: Kelvin has no display-case load model, so it isn't corrected to the suction its group runs at, and a case warming through its defrost isn't tracked.
  • The day's energy counts the compressors, the condenser fans, the evaporator fans at the heat load's fan motor power through their shift, electric defrost heaters through each window, and the display cases' own electricity.
  • A coolroom evaporator placed on the layout but not in a Heat Load room runs in a generic room: the Heat Load's default for its temperature class, with one door, the preset's internal loads and no product. The page counts them under Rooms and the basis says they stand in for a design.

Note

Saving keeps the schedule and the day's summaries, never the run's series. A saved scenario clears its check or approval, like any record.