G.A.S. Day & Night Dehumidifier Controller — Dial-Based Humidity Control for Grow Rooms
Best for: Growers wanting straightforward day and night humidity control without app complexity or premium pricing
Our thoughts
This is the kind of controller that does one job properly and doesn't overcomplicate it. Day and night humidity management via a light sensor, two simple dials, and a dehumidifier you already own. We bought heavy on this one, so you get proper kit at clearance pricing.
The G.A.S. Day & Night Dehumidifier Controller is a 2.5KW capacity hygrostat designed to automate humidity control across your grow room's light and dark cycles. Plug your existing dehumidifier into the controller, set your day and night humidity targets on two intuitive dials, and let the built-in light sensor handle the switching. It's a simpler, cheaper way to manage humidity than full enviro-controllers, and it does exactly what it should without the fuss.
How it compares
The G.A.S. Day & Night sits in the budget-to-mid-tier humidity control market.
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vs. Inkbird IHC-200: Inkbird offers dual relay control (humidifier + dehumidifier simultaneously) and WiFi options, but costs more and adds complexity. The G.A.S. does dehumidification only, simpler, dial-based, and significantly cheaper.
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vs. AC Infinity Controllers: AC Infinity gives you app control and data logging. If you want app access and smart monitoring, go there. If you want a plug-and-play box with dials, the G.A.S. wins on simplicity and cost.
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vs. G.A.S. Intelligent Humidity Controller: That's the premium line with VPD calculations, four operational modes, and data logging at £200–£300+. This Day & Night version strips back to the essentials and costs a fraction of that.
In short: you're getting reliable day/night switching, no WiFi nonsense, and a price that makes sense for growers who just want humidity sorted without breaking the budget.
Usage guidance
Installation is straightforward:
Setup
Plug your dehumidifier into the controller. Plug the controller into the mains socket (switch off the socket first). Position the humidity sensor in your grow space — on the 4-metre cable — and you're done.
Sensor placement
This is important: the sensor is sensitive, so don't place it directly next to your dehumidifier. Position it where air naturally circulates through your space. This avoids dead zones where humidity pockets build up and confuse the readings.
Dialling in your targets
Left dial = daytime humidity target. Right dial = nighttime humidity target. The controller continuously monitors and switches the dehumidifier on and off to hold those levels.
Why day and night matters
During the dark period, your plants aren't photosynthesising but they're still transpiring — releasing moisture. Lower temperatures at night raise relative humidity naturally. Without active control, humidity can spike and create conditions for mould and mildew. The Day & Night controller prevents that by actively managing humidity when lights are off, keeping conditions stable across both cycles.
Humidity ranges for different growth stages
Seedlings and clones: 70–75% RH. Vegetative and flowering: 40–50% RH. This controller gives you the precision to hit those targets, day and night.
Technical specifications
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Power capacity: 2.5KW (2500W)
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Sensor type: Humidity sensor with 4-metre cable, user-replaceable
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Light detection: Built-in photocell automatically distinguishes day and night periods
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Control interface: Two intuitive dials — left for daytime settings, right for nighttime settings
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Output indicator: Green LED lights when dehumidifier is switched on
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Fault detection: Rapid green LED flashing indicates a sensor problem
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Functionality: Dehumidification only (removes moisture; cannot add humidity)
Who this is for
- Small to medium-scale indoor growers looking to automate humidity control on a budget
- Growers who already own a dehumidifier and want simple, reliable switching
- Anyone seeking straightforward day/night control without app complexity or WiFi
- Hydroponic system operators managing multiple environmental factors
- Growers prioritising mould and mildew prevention at late flowering
- First-time automation buyers who want to keep things simple and affordable
Particularly well suited to spaces where practical humidity management matters more than smart home integration.
Our take
This is a proper controller at a price that makes sense. No app, no WiFi, no over-engineering — just two dials, a light sensor, and a dehumidifier doing what it should. The Day & Night logic is solid: most mould problems happen in the dark cycle when humidity creeps up and temperature drops. This controller stops that happening.
If you're tired of manual dehumidifier switching or you want to step up from nothing without spending £300+ on a full enviro-controller, this is worth picking up while clearance stock lasts. Does exactly what it should, day in, day out.
