Junction Box

From Official Barotrauma Wiki
Revision as of 15:52, 7 December 2021 by 31percent (talk | contribs) (rephrased a few things)
Jump to: navigation, search
This article is a stub. Help the Official Barotrauma Wiki by expanding it.
NOTE: Images appreciated
Version Checkmark False.png
Data is Potentially Outdated

Last updated for version v0.14.6.0
The current game version is v0.17.15.0

Junction Box
Junction Box.png

Category Electrical Installation
Repair Requirements
Electrical Repairs
Electrical Engineering 55
Items Needed Screwdriver

The Junction Box is an installation which serves as a hub for power distribution and relaying signals between devices. For this reason, it is usually a crucial part of the submarine's wiring.


The Junction Box distributes Electricity and Signals through its connected wires. Like all other wireable installations, every pin can have up to five connected wires.

Junction boxes deteriorate over time while powered, when overloaded with power beyond their overload threshold, when powered and in water, and when on fire. The overload threshold for damage on most vanilla Submarine's junction boxes is 1.7.

Overvoltage / Undervoltage

Junction Boxes require as much power as the current sum of the ship's powered electrical devices. If that value changes rapidly, the submarine's junction boxes will either light up with Overvoltage or Undervoltage.

  • Example Undervoltage: The submarine is not moving, engine is off, and the reactor is not emitting a lot of heat. The captain suddenly accelerates (by clicking far away from the submarine in the nav terminal, stretching the directional arrow to the maximum, meaning more engine and/or pumps activity). A reactor on automatic control will crank up heat emission as quickly as it can to meet the new power demand. While the reactor struggles to meet the required amount of power, undervoltage happens. This will result in brownouts, where submarine systems will cease to function as there is not enough power to go around. The Junction Box Undervoltage light will turn on. It has no other effects, and the brownouts will cease when reactor reaches the total power demand.
  • Example Overvoltage: The submarine is moving at full speed. The captain suddenly decelerates (by clicking on the submarine or close to it in the nav terminal, resulting in a short or non-existent directional arrow, meaning very little or no engine and/or pumps activity). A reactor on automatic control will lower heat emission as quickly as it can to meet the new power demand, but it takes some time to adjust and while it does, it will still be producing more power than needed. That excess power will cause a Junction Boxes Overvoltage, and the Overvoltage lights will turn on. The Junction Box will deteriorate and eventually fail and catch fire, unless the reactor is able to reduce its heat output to match the level required by the engine activity. Aside from rewiring, a few things can be done to mitigate overvoltage:
  1. The crew can buy submarine upgrades to lower the junction box damage from overvoltage.
  2. The captain can (and should) try to decelerate progressively, by slowly dragging the directional arrow towards the desired position. This will give the reactor time to adjust its power generation.
  3. When manned by a (player-controlled) character, typically an engineer, automatic control can be turned off, and fission rate and turbine output can be set manually, which allows for a faster adjustment. Communication between the captain and the engineer is important as they will need to synchronize properly.


In order to edit the connections on a junction box, a screwdriver must be equipped in one of the two hand slots, and then the Junction Box Left left-clicked when highlighted. To add a wire to a connection, a wire must be equipped in the other hand, either before or after the Junction Box has been left-clicked.

Damage Values

Unsuccessfully attempting to repair a Junction Box damages the user.

Attack Damage
Kinetic Force
Unsuccessful Repair
Affliction Burn.png Burn : 5

Affliction Stun.png Stun : 5


Junction Boxes take damage while in water, and if they are overvolted beyond their overvolt protection limit:

Cause Damage rate
Submerged in water 0.25/second
Overvolted beyond limit 10.0/second

Connection Panel

Connection panel for Junction Box
Hover over pins to see their descriptions.
Connection Port.png
Connection Port.png
Connection Port.png
Connection Port.png
Connection Port.png
Connection Port.png
Any devices that are wired to this output will draw their power from the reactor or batteries through the junction box.
Devices wired between this will send signal from one to each other.
Devices wired between this will send signal from one to each other.
Devices wired between this will send signal from one to each other.
Devices wired between this will send signal from one to each other.
Outputs the Junction Box's current condition. (0-100)


Submarine Weapons