Vendor Teardown 05 — Dehumidification
Source: 02_dehum_hvac.jpeg + 07_pricing_offer.pdf
Read (equipment spec)
| Room | Capacity | Units |
|---|---|---|
| Flowering Rooms | 276 L/day | 1 / room |
| Vegetative / Mothers | 90 L/day | 1 / room |
| Dry Room | 90 L/day | 2 |
Pricing offer breakdown
| Room | Capacity | Qty | Unit € | Line € |
|---|---|---|---|---|
| Flowering 1 | 276 L/D | 1 | 1 800 | 1 800 |
| Flowering 2 | 276 L/D | 1 | 1 800 | 1 800 |
| Mothers | 90 L/D | 1 | 890 | 890 |
| Vegetative | 90 L/D | 1 | 890 | 890 |
| Dry room | 90 L/D | 2 | 890 | 1 780 |
| Total | € 7 160 |
Findings
Finding 1 — Transpiration sanity check
Per flowering room, with 11.76 kW lighting over a 12 h photoperiod:
- Lighting energy: 11.76 × 12 = 141 kWh/day
- Canopy interception (~80 %): 113 kWh
- Latent heat of vaporisation: 0.68 kWh per L water evaporated
- → Maximum pure transpiration: ~166 L/day
- Plus irrigation surface evap + runoff evap + drain-catchment evap: +50–110 L/day
- Total moisture load: ~220–280 L/day per flowering room
Vendor spec at 276 L/day has essentially zero headroom. Any of these will push it into saturation:
- Dropping VPD setpoint from 1.2 → 1.0 kPa (tighter bud development)
- Summer ambient humidity bleeding through door seals
- A dehumidifier reboot cycle lasting 15–30 min during defrost
- An over-irrigated day
Recommendation: size at 350 L/day or install a backup 90 L/day unit running in series.
Finding 2 — €1 800 per 276 L/day unit is mid-tier
Commercial 276 L/day dehumidifiers (Quest 225, Anden A210, Trotec DS95) retail €2 200–3 600. At €1 800 the vendor is likely supplying:
- A Chinese equivalent (Yaoshi, Dehumidifier Power, Cuoga OEM)
- Or a slightly undersized unit rated 200–240 L/day
- Or a refurbished/B-stock commercial unit
Ask the vendor for the exact model. If it's not Quest / Anden / Aprilaire / Trotec, budget for 2–3 year lifespan (compressor wear in continuous 24/7 duty) and factor replacement cost into the 5-year TCO.
Finding 3 — 90 L/day at €890 is cheap
Residential-grade 90 L/day units (Inventor, Woods, Meaco, Midea) retail €350–650. At €890 the vendor is presumably supplying something slightly commercial (Kaiser, Chinese OEM commercial). Price is defensible.
Finding 4 — Where does the heat go?
A dehumidifier is a heat pump. For every litre of water it condenses out of the air, it puts ~0.7 kWh of sensible heat back into the room unless the hot side is ducted to outdoors.
For 276 L/day ≈ 11.5 L/h, the sensible heat reject is ~8 kW, continuously, straight into the room. This is the same order of magnitude as the lighting heat load, and dramatically changes the HVAC sizing math — see 06_hvac_cooling.md for the detail.
The pricing offer does not specify whether the dehumidifiers are ducted outdoors. If not (and there's nothing in the mounting-hardware extras that looks like dehu exhaust ducting), the HVAC is dealing with the dehu heat and is badly undersized.
Finding 5 — Dry room at 2 × 90 L/day = 180 L/day total
Dry room moisture removal for ~15–20 kg wet biomass per batch × ~75 % water content = ~12–15 kg water to remove over a 10–14 day slow dry. That's ~1–1.5 L/day per kg of dry flower target, realistic for the proposed yield. 180 L/day is correct for controlled slow-dry at 60 % RH / 18 °C target.
Confirmations still needed from vendor
- Exact model numbers and brand for 276 L/day and 90 L/day units.
- Is the hot side ducted outdoors or into the room?
- Warranty term in the offer.
- What happens when a dehumidifier fails at 3 AM in week 7 of flower?