The buyer's question: why can two apparently similar greenhouses need different machine quantities?
Area describes the project, not the answer. The recorded geometry is about 49,920 m² (20 × 12.8 m × 195 m), approximately 5 ha. A defensible quantity still requires a time-matched moisture load and a verified removal rate for the selected equipment at the project inlet state.
Project background
This walk-through is based on a pre-engineering evaluation carried out for a tomato greenhouse project in Armenia. The client is not named.
| Parameter | Value | Source |
| Greenhouse area | 5 ha (20 spans × 12.8 m × 195 m) | Client-provided |
| Crop | Tomato | Client-provided |
| Eaves / ridge height | ≈ 6 m / ≈ 10 m | Client-provided |
| Climate control | Automated glasshouse climate computer | Client-provided |
| Nighttime RH peak | up to 98% RH, vents fully closed | Client-provided |
| Target setpoint | 16 °C / 75% RH | Client-provided |
| Heating | 8 loops of 51 mm rail pipe, crop pipes at 1.5 m, upper pipes, eaves snow-melt | Client-provided |
Scope note: this is a pre-engineering record. Client inputs are recorded inputs, not validated field measurements, and no delivered installation result is claimed.
The Source column separates client-reported inputs from engineering questions. The case records a target and a building, but it does not establish the operating load or equipment capacity needed to close the selection.
What must be calculated before quantity
Build the design load for the same operating period used for selection. Irrigation and evapotranspiration data are not automatically equal to pure crop transpiration. Include sources and sinks that occur in that period, and resolve condensation or storage terms before treating them as removal duty.
For infiltration, use the signed humidity-ratio difference between inside and outside together with the measured or justified air exchange. Outdoor relative humidity or cold weather by itself does not establish a positive moisture load. A humidity peak trace alone also cannot identify crop flux or leakage.
Transient events require a state and time balance with an allowable excursion. An average value plus a universal buffer cannot substitute for that balance. Representative climate, screen, irrigation and control records, together with measured or justified engineering inputs, are needed before the design load is closed.
Capacity must match the design condition
The recorded 480 L/day divided by 24 hours gives 20 L/h as an arithmetic average of the stated daily figure. It does not prove a removal capacity at 16 °C and 75% RH, and the applicable test condition for this case is not established. No equipment model, rating curve or field result should be inferred from that arithmetic.
For a stable operating period, use N_duty = ceil(D_design / C_effective), where both terms are positive kg water/h and ceil means round up to the next whole unit. C_effective must be verified at the project inlet state and the agreed control and runtime basis. If capacity is unknown, the quantity remains open.
For variable capacity, compare available aggregate removal with the load in each relevant period. Account for defrost or duty fractions once in that time basis; do not add a generic derating a second time. The design explanation should be read with the capacity basis and greenhouse design data references.
Decision status
| Question | Status before engineering close |
| Design load for each relevant period | Open until representative inputs and a time balance are confirmed |
| Effective capacity at 16 °C / 75% RH | Open until an applicable rating or test basis is supplied |
| Quantity | Open; do not infer it from floor area or the daily arithmetic |
| Zoning, drain and power availability | Open until layout and interfaces are defined |
| Agricultural commissioning targets | Open until operating acceptance criteria are agreed |
A purely hypothetical calculation
To show the arithmetic without turning the case into a proposal, assume an unrelated design load of 8.5 kg/h and an assumed applicable single-unit capacity of 2 kg/h. The result is ceil(8.5 ÷ 2) = 5 operating units. Neither 8.5 kg/h nor 2 kg/h belongs to the Armenia case, and neither is an equipment performance claim.
Availability and layout are separate decisions
Redundancy is not an automatic extra unit. Define the failure state, critical duty and zonal coverage, then verify that the remaining available aggregate capacity meets the stated duty. Distribution, drainage, electrical supply and control interfaces can leave quantity open even after a load and capacity are known. See the humidity distribution and commissioning checklist references.
What a review package should contain
Before a selection can be reviewed, assemble the target temperature and RH with tolerance, representative indoor and outdoor records, irrigation and crop-state information, infiltration evidence, the selected capacity curve at the project state, runtime and defrost basis, and the layout and interface constraints. Mark each item as measured, justified, or still open.
This case should therefore be read as a method boundary and an input register. It records the project geometry and client-provided conditions while keeping the machine quantity unresolved. The next defensible step is to close the design load and capacity basis together, then test the result against zoning, availability and commissioning requirements.
About Yakeclimate
Yakeclimate specialises in selection, design and supply of industrial and greenhouse dehumidification equipment. On greenhouse projects our sequence is: evaluate the operating conditions, then discuss unit counts and pricing — because greenhouse dehumidification behaves differently from standard industrial applications, and only duty-matched sizing puts each machine where and when it is needed.
Related reading: dehumidifier capacity basis · greenhouse design data · humidity distribution · commissioning checklist · agriculture
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