The short answer would be yes. Over-current protection (OCP) is very important and should not be overlooked. Remember that your OCP (fuse or circuit breaker) is there primarily to protect the wiring (not the device). The long answer is it also depends on a few variables as to where the OCP should be installed.
What is the difference between a fuse and a circuit breaker?
Fuses and circuit breakers (both OCP) are electrical switches that interrupt current flow when a fault is detected. The main difference between fuses and circuit breakers is that fuses cannot be reused while circuit breakers can be reused over and over again. So fuses must be replaced after each use, which depending on their location may be difficult.
Fuses cannot be reused, but a circuit breaker can be reset and used over and over again
Also it may not be so easy to determine that a fuse has blown without taking things apart. Whereas with circuit breakers it's easy to see if it has tripped and can be reset manually by flipping a switch or triggering the switch (yellow handle on the Bussman marine circuit breakers).
In-line MC4 fuse Circuit breaker (<48V) DIN rail breaker (<150V)
Find out why your fuse/circuit breaker tripped
If more current (amps) flows in a wire than the wire is rated to handle, the wire can heat up, its protective insulation can melt, and the heated wire can start a fire. This overcurrent condition can occur, for example, when a short circuit occurs. Fuses and circuit breakers are used to limit the amount of current that flows through circuit wires and activate if needed.
It's a good thing that a fuse blows, or a circuit breaker trips, because it means they have done their job but you should spend some time investigating why it happened. Find the source of the over-current and prevent it from occurring again and again.
Voltage rating is important
It is also very important to take note of the maximum voltage that could pass through a circuit breaker as they are also designed to operate within certain voltage parameters. The majority of circuit breakers that we sell are the Bussman (or Mechanical Products) marine rated circuit breakers that have a max 48V. This means they are suitable for 12V and 24V battery banks but not 48V as your charge voltage is higher than 48V (often up to around 56V)
If the voltage is too high for the breaker then arcing can occur, and in affect jump (or bridge the gap) in the circuit breaker making it redundant - not a good thing! It is also important to note the difference between AC breakers (used in your house) and DC breakers (suitable for marine applications) and make sure you are only using appropriately sized DC breakers.
We do have higher voltage DIN rail breakers, good for up to 150VDC, that can be housed in the baby-box by Midnite Solar. These are good for customers with 48V battery banks
Where do I need to place a fuse/circuit breaker?
A circuit breaker should be installed after each MPPT controller and before the battery bank (on the positive wire).
You may also consider adding a fuse/circuit breaker after the solar panels and before the MPPT controller, although it is not an ABYC standard. Solar panels are 'self limiting devices' and as such do not require OCP. That said, you should check the potential maximum voltage from the panels and for multiple solar panels wired together in parallel you should verify if in-line MC4 fuses are required.
Tell me more about in-line MC4 fuses
Good question, we have a much more detailed answer on that in a separate news post, click here to learn more. In-line MC4 fuses are easy to install by clicking the MC4 connectors together on the positive wire from your solar panels. It is not needed on every install and typically only required for 3 or more solar panels wired in parallel. In summary don't be in a rush to add in-line MC4 fuses to your install unnecessarily. Read our news post and ask us if you have any questions.
But wait, what's the fuse for inside the Victron MPPT controller?
All Victron MPPT controllers have onboard fuses. The larger MPPT controllers have an internal fuse that is not user replaceable whereas the smaller size MPPT controllers have an external fuse that is user replaceable.
75|10 - 20A 75|15 - 20A 100|15 - 20A 100|20 - 25A
(User replaceable fuses)
The smaller solar chargers are equipped with an accessible fuse, which typically blows when the battery is mistakenly connected in reverse polarity.
Primarily the onboard fuse on Victron MPPT solar controllers provide reverse polarity protection, in that it will blow if you hook the battery up backwards. If you are lucky only the fuse blows, but if you are unlucky the controller itself may be permanently damaged. So always double/triple check the polarity of your wires is correct from the battery to the MPPT controller before connecting them as reverse polarity is not covered under warranty (and yes the Victron tech guys can diagnose that's what happened!)
The onboard fuse does not offer any protection relative to the solar panels.
In summary onboard fuses in Victron MPPT controllers should not be relied on for circuit protection, they are a last line of defense for the protection of the device (ie. stop it from melting!) and you will need to install external and appropriately sized OCP for a safe installation.
OCP size between MPPT controller and battery?
This chart is compiled from information in each Victron MPPT charge controller user manual and refers to the minimum and maximum OCP (fuse or breaker) to go after your MPPT controller and before the battery.
Victron MPPT controller | Minimum battery fuse rating | Maximum battery fuse rating |
75|10 | 15A | 20A |
75|15 | 20A | 25A |
100|15 | 20A | 25A |
100|20 | 25A | 30A |
100|30 | 35A | 40A |
100|50 | 55A | 70A |
150|35 | 40A | 45A |
150|45 | 50A | 63A |
150|60 | 70A | 80A |
150|70 | 80A | 100A |
150|85 | 100A | 120A |
What if I have multiple MPPT controllers going to a busbar?
We would highly recommend having a breaker after each MPPT controller and before the busbar. If you do plan to add OCP after the busbar and before the battery bank then be aware that you are in effect paralleling the MPPT controllers and increasing the current (amps) and would need a larger size fuse/circuit breaker (and likely a heavier gauge wires too)
For example if you had 2x 100|30 MPPT controllers you would need to install 2x 30A breakers (one after each MPPT controller and before the busbar) OR install 1x 60A breaker after the busbar and before the battery.
Summary
in summary OCP is very important, needs to be appropriately sized and installed in the correct place in your solar install aboard. Should you have any questions don't hesitate to contact us
Comentários