Worked cases · Seattle
An edge data centre's 18 °C cooling return, lifted to 54 °C for the offices next door by a water-source heat pump: seasonal COP 5.6 against 2.9 on outside air, the chiller makes 13 % less, and the site runs on 12 % less electricity.
Open the building in the Simulate tabCascade is a 200 m² edge data hall — 42 kW of IT held in ASHRAE A1's 18–26 °C band by a CRAH on a 13 °C chilled-water loop — with two 250 m² office floors next door on radiators, one glazed to the south and one facing north with the bigger envelope. The arrangement is the one Danfoss's Impact paper describes at the Westin Building Exchange in Seattle, where two pipes carry the colocation centre's 18 °C return across the street and a heat pump lifts it to 54 °C for Amazon's headquarters: here the CRAH's return water goes to a water-source heat pump's evaporator first, the chiller finishes what the heat pump did not take, and the heat pump's condenser feeds the two floors on a 54 → 35 °C heating curve. Three blocks on one water ring, and the ring conserves: what the chiller makes plus what the heat pump takes is what the CRAH moved, every week of the year.
The A/B is the same heat pump on outside air. The machine is the catalog's Copeland ZP91KCE scroll run as an inverter, a 25 kW class unit, and on Seattle's year it puts 55.3 MWh into the offices' radiators either way. On the loop it sees 18 °C water every hour of the year and does it for 9.9 MWh of electricity — a seasonal COP of 5.6; on air it sees Seattle's winter, loses capacity on the cold mornings, and does it for 19.2 MWh at 2.9, leaving the north floor 27 hours short where the loop-source plant leaves it 6. The saving is counted twice, which is the whole economy of the arrangement: the heat pump's own 9.3 MWh, and the 4.0 MWh the chiller no longer spends making the 47.9 MWh of cooling the heat pump took off the loop for it. The site — CRAH fans, chiller and heat pump — reads 93.4 against 106.7 MWh, twelve per cent, on a hall that rejects 373 MWh a year and hands the offices 13 % of it. Westin's loop was designed to heat almost half a million square metres; the arithmetic per kilowatt is this one.
What it cost to learn. The first draft put the radiators on a trickle — 0.25 kg/s for a 30 kW bank, a 29 K drop at the rating — and two things went wrong at once: the north floor read nine kilowatts short on a 46 °C shoulder-season flow, because a radiator's output is its mean water temperature and a slow flow leaves cool; and the heat pump, handed the sum of two nearly shut valves, spent thirteen hours a week with no converged state to run at — the recorded weakness of the flats' plant. Doubling the flow to a bank's 0.5 kg/s held the floor to one unmet hour and the plant to none. On the loop the offices ride the summer on their windows, 3 air changes an hour when it helps, peaking at 27.9 °C; there is no cooling machine on that side, and the case does not pretend one.
| Heat delivered | 55.3 MWh at the offices' radiators — 22.8 south, 32.5 north — on a 54 → 35 °C curve |
| Heat pump | 9.9 MWh on the data-hall loop, seasonal COP 5.6; 19.2 MWh on outside air, COP 2.9 — the same ZP91KCE-class inverter |
| Chiller | 324.7 MWh of cooling on 41.9 MWh with the heat pump taking 47.9 MWh off the loop; 372.6 on 45.8 without |
| Site | 93.4 MWh against 106.7 — 13.2 MWh (12 %) a year, half of it the chiller's |
| Data hall | 26.0 °C held on 42 kW of IT, no unmet hour past the cold start; 373 MWh rejected, 13 % of it recovered |
| Offices | 20.0–27.9 °C south, 19.9–27.5 north; unmet heating 0 / 6 hours on the loop, 5 / 27 on air; summer on the windows |
Readings of the shipped model on the building's own PVGIS typical meteorological year; engineering estimates from catalog data and published correlations. The building runs on every plan, including Free, a few times a day.