Fuse sizing for inverter

I just go by the regular TF mantra...never believe some guy posting in the Forum...go to an expert source.....that's why I post links and not just reply with my experience as some here shoot it down every chance they get.

And believe me...I do my homework and while I can see both sides of a simplistic definition ...more than one source had the "same" simplistic definition about "basic resistance"...so take it all for what it's worth.

rwidman said:

An appliance such as an inverter needs a positive means of being disconnected for the safety of anyone working on it (and possibly for convenience). While removing the fuse is a positive means of disconnecting the appliance, it's often not the most convenient or fast way of doing so.

In my case, removing the fuse means getting out the tool box, removing four screws to swing out the electrical panel, removing the plastic cover over the fuse, then finding the correct socket and handle to loosen the nuts holding the fuse in place. The option is to reach down and turn a knob on a switch.

BTW: An inverter, even one with a remote power switch will still draw a small standby current when connected to the battery. A switch in the DC circuit will eliminate this standby current when turned off.

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I agree Ron for the safety factor of making sure the high current DC can be removed quickly an in-line high current battery switch should always be used on marine inverter installations. This still doesn't negate having the proper sized wiring and a fuse to protect the inverter.
Bill

I know I said I was done, but here's one more note. This discussion started with a drawing of an inverter wired to a battery bank with a fuse and no switch. I gave several reasons to install a switch, as has Ron, but was still ask "why add a switch if the inverter manufacturer doesn't recommend it". If those reasons aren't good enough, this one should be. Truth is, all marine rated inverter manufacturers do require one. Here's why.
ABYC E-11.6.1.2.1 States " A battery switch shall be installed in the positive conductor(s) from each battery or battery bank with a CCA rating greater than 800 amps or 100Ah if CCA is unavailable".
Every marine rated inverter I've installed somewhere in the installation instructions says the inverter must be installed in such a way as to meet ABYC recommendations and I've never installed a marine rated inverter with a battery bank smaller than 100AH.
So, if ABYC says it MUST be done, and the inv manufacturer says you have to follow ABYC guidelines, then the IM is requiring a battery switch. Yes, it could be the same switch that is used for the house loads, but I'd rather not have to work on the inverter in the dark while the beer and ice cream get warm.............

And by the way, this also pretty much locks you into having to install a switch in every starting circuit, unless you have a starting battery smaller than most group 27 batteries. They (ABYC) do not require a fuse in a dedicated starter circuit, nor have I seen anyone say you should.

BillyIII Wrote: I am not sure who's high current inverter's battery switch costs $25.00? I like the BlueSea gray high current battery switch to shut down the inverter's DC feed as well as installing the properly sized Class T fuse in the 12VDC feed to the inverter. (endsnip)

Billy, the smallest Blue Sea battery switch, (I think the model is a 6006 but don't have a book in front of me) has a continuous rating of 300 amps and much higher rating for short periods of time. I believe the gray switch you are referring to is rated at something like 600 amps continuous. The small one can be bought for around $25 and will handle the inverter loads. (if it does have a 300 amp fuse) Obviously the gray switch would be better, overkill maybe, (and I do like overkill) but my thinking when I said that was if someone really didn't want to install a switch, they were more likely to pony up $25 than $100. And I've used that 6006 switch in MANY inverter installation and have not seen a failure yet. On the other hand, I've seen several Perko switches (Not installed by me) fail under inverter loads. I wouldn't install a Perko battery switch on a dingy.

Brent Hodges said:

I know I said I was done, but here's one more note. This discussion started with a drawing of an inverter wired to a battery bank with a fuse and no switch. I gave several reasons to install a switch, as has Ron, but was still ask "why add a switch if the inverter manufacturer doesn't recommend it". If those reasons aren't good enough, this one should be. Truth is, all marine rated inverter manufacturers do require one. Here's why.
ABYC E-11.6.1.2.1 States " A battery switch shall be installed in the positive conductor(s) from each battery or battery bank with a CCA rating greater than 800 amps or 100Ah if CCA is unavailable".
Every marine rated inverter I've installed somewhere in the installation instructions says the inverter must be installed in such a way as to meet ABYC recommendations and I've never installed a marine rated inverter with a battery bank smaller than 100AH.
So, if ABYC says it MUST be done, and the inv manufacturer says you have to follow ABYC guidelines, then the IM is requiring a battery switch. Yes, it could be the same switch that is used for the house loads, but I'd rather not have to work on the inverter in the dark while the beer and ice cream get warm.............

And by the way, this also pretty much locks you into having to install a switch in every starting circuit, unless you have a starting battery smaller than most group 27 batteries. They (ABYC) do not require a fuse in a dedicated starter circuit, nor have I seen anyone say you should.

Click to expand...

Thank you...that's what I was looking for...though a review of Xantrex install diagrams and instructions did not see mention of a switch...but as you said there are higher suggested standards

It is a good idea though and even better if recommended by ABYC in this case.

Great info, Brent. Thanks for posting. Here's the Blue Sea 6006 switch for $25.

Al, thanks for the link to the BlueSea 375AH intermittent rated switch.
Brent thanks for posting the ABYC rules as they apply to inverters DC feed. I like to oversize everything when it comes to a boats house battery system.
However the fuse must be rated to match the manufactures suggested value there should be no over sizing for the DC source fuse.
Bill

Looking at Blue Sea Systems site, that 6006 switch is rated at 300 amps continuous, 500 amps for 5 minutes, 775 for 1 minute, and 1500 amps for 10 seconds. Quite a stout little switch for it's size and price. Blue Sea Systems 2014 Catalog

And, Billy, there is certainly nothing wrong with going bigger on everything except, like you said, the fuse.

I use a lot of Blue Sea products and have had very few disappointments. The disclaimer here is that I do work for a marine service company that is a dealer for Blue Sea products as well as about everything else marine related.

Thanks Brent, I am partial to BlueSeas products as well why? Because they perform as advertised and I have had few if any returns. They are a full line electrical marine specific manufacture that stands behind their products.
Bill