We got away with passive ventilation for our electrical cabinet (thanks to the MOLLE doors). However, we decided our fridge cabinet would benefit from active ventilation. You see, a fridge is a heat pump that transfers heat from the inside of the fridge to the inside of the cabinet. The cabinet must be vented to maintain an acceptable ambient temperature. Otherwise, the refrigerator works much harder, and power consumption increases. In the case of an electrical cabinet, a high ambient temperature could reduce efficiency and/or damage components.
Below is how we added a temperature-controlled cooling fan to the cabinet using DIY parts. Maybe it gives you some ideas too!
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1. Ventilation Options
Ventilation is a two-part process: intake and exhaust. Warm air rises, so it is typically blown out through the exhaust at the top of the cabinet. Cool air enters through the intake at the bottom of the cabinet. The air exchange can be passive or active.
1.1. Passive
Passive ventilation is achieved without any mechanical systems; air is exchanged naturally. That means no fans or devices that require power, maintenance, or generate noise. Neat, that’s the goal! The Electrical Cabinet for our EcoFlow Power Kit utilizes passive ventilation via the MOLLE doors; the pattern is the same as the Rear Door MOLLE Panels we designed and made, so the accessories are interchangeable:
1.2. Active: Fan Synced WIth Fridge
Active ventilation occurs when air exchange is forced through a mechanical device, such as a fan. The fan is typically located at the exhaust, and creates a negative pressure that forces air to enter through the intake(s). A fan can also be added at the intake.
Our NovaKool R5810 12V Fridge features a fan to cool down the compressor—the fan cycles simultaneously with the fridge, which typically runs 30-50% of the time. To expel the hot air, we could connect the cabinet’s exhaust fan in parallel with the compressor’s fan so that both fans would cycle together. That’s a great solution! It minimizes the components and cost. And since the exhaust fan runs simultaneously with the fridge, the noise is effectively masked.
1.3. Active: Temperature-Controlled
Another approach is to activate or deactivate the exhaust fan based on the ambient temperature in the cabinet. In other words, the exhaust fan is connected to its own thermostat and operates whenever the ambient temperature in the cabinet exceeds a set point. It doesn’t “know” when the fridge runs or not.
Why even bother? Well, the exhaust fan could continue to expel residual heat after the fridge has turned off. Also, when the sun hits our dark-colored van, it heats up quite a lot, and some of that heat is transferred inside the cabinet. A temperature-controlled fan would therefore operate when heat is generated by a source other than the fridge. At the other end of the spectrum, the exhaust fan might not have to run in winter.
A temperature-controlled cooling fan is what we’re going for! Below is how we implemented it.
2. Temperature & Speed Controller
2.1. Parts and Wiring
The main components are:
- Inkbird ITC-1000F 12V Temperature Controller.
- Noctua NA-FC1 Speed Controller. (optional*)
- Noctua NF-A9x14 (92mm x 14mm) PWM Cooling Fan.
- Wago 221 Lever Nuts Connectors.
* Speed Controller: The speed controller allows for reducing the fan’s RPM, to mitigate noise. After the cabinet and fridge are installed, we will determine the lowest speed at which the exhaust remains efficient.
We connected the components according to the Inkbird ITC-1000F (12V) Wiring Diagram:
2.2. 3D Printed Case
Now it was time to design a Case for the Inkbird ITC-1000 Temperature Controller and Noctua NA-FC1 Speed Controller. The requirements:
- Compact.
- Surface mounted (wall).
- Built-in cable retainers, to prevent the connectors from disconnecting due to vibration.
- Resist to high temperatures.
The 3D printed case holds the Inkbird ITC-1000 and the Noctua NA-FC1 controllers:
The cable retainer at the back prevents the connector from disconnecting from the speed controller (vibration):
The wiring as shown in the “diagram” above, but cleaner:
The connector (going to the fan) can’t disconnect thanks to the retention feature inside:
3. Installation in Cabinet
3.1. Fan
We chose the Noctua NF-A9x14 Fan specifically because of its thickness of 14mm, which is just a bit more than the cabinet’s panel thickness of 12mm (1/2″ Baltic Birch). We designed and 3D printed a Wall Mount for Noctua NF-A9x14 Fan:
The grill is based on Noctua’s High-Efficiency Grill Design:
The fan snaps into the mount from the back:
The fridge cabinet only exists in CAD at the moment…
The passive intakes are positioned so that air is sucked towards the coils and the compressor, the exhaust is located at the top. It’s hard to tell in the picture, but there is a gap at the back and top of the fridge:
3.2. Controller
The temperature and speed controller will be mounted inside the cabinet, allowing us to check the cabinet’s ambient temperature on the Inkbird’s display. We’ll add photos when we get there!
4. On Second Thought
So, does this even work? We’ll report back when it enters service!
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