Jump to content
GlennWest

Fuse or breaker for Magnum Inverter

Recommended Posts

My Magnums MS4448PAE call for 2/0 wire with 175 amp protection. I intend to use a fuse and a cut off switch. This will be X2. Is it necessary to have a breaker also?

Share this post


Link to post
Share on other sites

Glenn, in order to provide "Overcurrent Protection" you need only one device and I often prefer fuses versus breakers. An On/Off switch is a separate issue and hey I have no problem with those. Sure, a proper circuit breaker could ??? serve as BOTH if that's YOUR choice and Magnum approves of such ???????????

NO you DO NOT need a Fuse plus a Breaker to provide "Overcurrent Protection" ...………….The time current curves would determine which opens first.

NOTE "Overcurrent Protection" for huge cables FROM a battery TO an Inverter need located at the energy source IE the battery, not far downstream leaving cable unprotected !!!!!!!!!!!

John T

Edited by oldjohnt

Share this post


Link to post
Share on other sites
1 hour ago, GlennWest said:

My Magnums MS4448PAE call for 2/0 wire with 175 amp protection. I intend to use a fuse and a cut off switch. This will be X2. Is it necessary to have a breaker also?

I suggest a 175A breaker instead of a fuse. I used to use fuses too until I had an electrical issue that blew the fuse. Then what? Keep replacing the fuse until you locate the problem? Good luck with that.

Also, you get a fuse & cut off switch in one.

Edited by Zulu

Share this post


Link to post
Share on other sites
1 hour ago, GlennWest said:

The Magnum Panels all come with breakers. That is why I was asking. I agree with yall. one device is enough

Glenn built in breakers are all well and good for their intended purpose and I'm sure your Magnum is properly designed...

 HOWEVER FYI even if you are already aware for those who aren't,  don't forget in order to provide "Overcurrent Protection" for the huge cables FROM the battery TO the Inverter those overcurrent protection devices (fuses or breakers) must be located at the source of energy the BATTERY not later somewhere downstream which would leave that portion of the cable (from battery to a breaker inside the Inverter) UNPROTECTED !!!!!!!!!!!!!!!! Yikes  !!!!!!!!!!! That's a serious potential hazard with 2/0 Cables and a 21 KWH battery !!!! A breaker can only detect current that flows THROUGH IT not elsewhere like from a POS cable shorted to the RV frame BEFORE the Inveter !!!!!

Of course there's no problem in overcurrent  protection at BOTH locations (battery and Inverter) as well as On/Off switches 

NOTE in the area of Electrical Power Distribution there are applications where fuses are favored and others where circuit breakers may be

NOTE for certain applications "Switch Rated" breakers are required that may not be necessary elsewhere

John T  Longgggggggg retired n rusty power distribution engineer and codes change so NO warranty...Consult the manufacturer and local practicing electrical engineers and electricians where fire and life safety is concerned ………...

Share this post


Link to post
Share on other sites

I have #4 running from each battery to a 8 post  buss bar. Leaving buss bar with 2/0 to protection then inverters. 

Edited by GlennWest

Share this post


Link to post
Share on other sites
6 hours ago, jcussen said:

I am also using a 175 amp breaker on the positive lead between my battery and inverter, and normal 20 and 50 amp breakers on the ac outputs.

I had not intended to add breakers on the out side of inverters. It will connect to panel box in RV. It has its own 50amp breaker

Share this post


Link to post
Share on other sites

I do not trust breakers on high ampere dc circuits. I do use Blue Sea battery disconnect switches. I also use these MRBF on the bus bar.   https://shop.marinehowto.com/products/blue-sea-marine-rated-battery-fuse  They save a couple of connections each. A catastrophic fuse could be required at the battery before the bus bar if the cable length is too long.

Share this post


Link to post
Share on other sites
6 hours ago, GlennWest said:

I had not intended to add breakers on the out side of inverters. It will connect to panel box in RV. It has its own 50amp breaker

Glenn, I would expect the AC Output of the Inverter has its own built in limiting protection so no additional DIY after market protection would then be required. Of course, as I explained below, your RV Distribution Panel indeed has "its own 50 Amp Main Breaker" to monitor the current that passes THROUGH and AFTER it, but that doesn't protect the WIRING FROM Inverter output TO the Panels 50 Amp Main, the Magnums output protection and limiting should take care of that.

1 hour ago, Sehc said:

I do not trust breakers on high ampere dc circuits. I do use Blue Sea battery disconnect switches. I also use these MRBF on the bus bar.   https://shop.marinehowto.com/products/blue-sea-marine-rated-battery-fuse  They save a couple of connections each. A catastrophic fuse could be required at the battery before the bus bar if the cable length is too long.

SEHC    DITTO  Indeed there are as I recall numerous applications where fuses are preferred over circuit breakers.   DITTO  Also catastrophic fuse protection can be required "at or near" the battery, I forget the distances and current and voltage etc. requirements.  

Yall be safe and take care now

John T

Share this post


Link to post
Share on other sites
1 hour ago, Sehc said:

I do not trust breakers on high ampere dc circuits. I do use Blue Sea battery disconnect switches. I also use these MRBF on the bus bar.   https://shop.marinehowto.com/products/blue-sea-marine-rated-battery-fuse  They save a couple of connections each. A catastrophic fuse could be required at the battery before the bus bar if the cable length is too long.

My positive cables are 18" from batteries to bussbar. Negatives are 24". Negatives at bottom so they had to be longer.

Share this post


Link to post
Share on other sites
8 hours ago, GlennWest said:

I had not intended to add breakers on the out side of inverters. It will connect to panel box in RV. It has its own 50amp breaker

Mine is in the S&B, so the 50 and 20 breakers are in a breaker box with receptacles, nothing else between inverter and breaker box.

Share this post


Link to post
Share on other sites
4 hours ago, GlennWest said:

My positive cables are 18" from batteries to bussbar. Negatives are 24". Negatives at bottom so they had to be longer.

George, that may well qualify for having "Overcurrent Protection" "At or Near" the energy source. Its been too long and I would have to look up the specs concerning amperage and wire size and voltage etc.  Again, the Magnum likely has its own built in limiting and overcurrent protection ON ITS OUTPUT and if so you're good FROM it TO the AC Distribution Panel

John T

Share this post


Link to post
Share on other sites

Based on above suggestions I believe I'll go with fuse directly leaving bussbar. They will be virtually no way for my cables to short out. Short runs and plywood, not steel around it. I will also enclose this area so nothing going in there.

Share this post


Link to post
Share on other sites
3 hours ago, GlennWest said:

Based on above suggestions I believe I'll go with fuse directly leaving bussbar.

Good plan Glenn, works for me and likely ???? complies with any applicable codes.

John T

Share this post


Link to post
Share on other sites

Good plan. I only know the marine rule,  no more than 7 inches from battery positive. But with no metal, where could it short?

Share this post


Link to post
Share on other sites

I like marine breakers they make a handy disconnect when the fire starts because those DC batteries are bizzy trying to discharge themselves to earth. 

Share this post


Link to post
Share on other sites
On 12/6/2019 at 8:35 AM, Sehc said:

I do not trust breakers on high ampere dc circuits. I do use Blue Sea battery disconnect switches. I also use these MRBF on the bus bar.   https://shop.marinehowto.com/products/blue-sea-marine-rated-battery-fuse  They save a couple of connections each. A catastrophic fuse could be required at the battery before the bus bar if the cable length is too long.

I do believe I will get those MRBF fuses. Like less cables and space savings. also any reason why not on battery post? These little fuses would fit well there.The 3/8" ring would be a little large. Battery is just under 1/4" but metric, M6. Surface area is good though. Washer on top should cause good contact. Would need 3 instead of 2 but all my cables will be protection.

Edited by GlennWest

Share this post


Link to post
Share on other sites

I used these on my battery terminals. I have had no problem after 3 years. I use a voltmeter to check for voltage drop when servicing my battery. The main problem is clearance above. These are higher than the posts.  The ring fits a  5/16 stud.

Edited by Sehc
add correct size number

Share this post


Link to post
Share on other sites

Glenn, wow talk about any code requirements (NEC or Marine or RV)  to provide Overcurrent Protection for the feeders  "AT OR NEAR THE SOURCE" I think that pretty well has you covered...…...Id use those in a heartbeat provided they are the sufficiently rated for your current requirements ???? Also anytime you can reduce the number of cables and extra connections that's good.

Now that you have "Overcurrent Protection" well covered for the feeders FROM the battery TO Load Inputs, you can install a Disconnect at loads such as Inverters or others for safety and convenience and/or as required (Unit may already have that covered??) If you want a pure disconnect only or say a breaker suitable for switching that's between you and what the manufacturers suggest (don't want to void any warranty) and if its needed ???  but I prefer and have at least a disconnect method especially for loads far removed from my batteries. As you already know having the Inverter close to the battery saves on line voltage drop and wasted heat energy concerns...….

Although Marine Grade is great and typically high quality and corrosion resistant and has excellent vibration resistance, using it in strictly RV applications may or may not be absolutely required BUT ITS SO GOOD AND SUCH HIGH QUALITY I've used it and prefer it. I often (right now as a matter of fact) am dry camped right on a beach so Marine grade is a good thing required or not.   

I still want to camp right next to you and plug into your energy source as you have enough to power an entire zip code lol

John T

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

RVers Online University

campgroundviews.com

Our program provides accurate individual wheel weights for your RV, toad, and tow vehicle, and will help you trim the pounds if you need to.

Rv Share

Rv Insurance Benefits.com Logo

Dish For My RV.

Find out more or sign up for Escapees RV'ers Bootcamp.

Advertise your product or service here.

The Rvers- Now Streaming

AGS Now Hiring

RV Pet Safety

RVTravel.com Logo



×
×
  • Create New...