Busbar Ampacity Confusion

[BAD ORCA]

So, i want to link two busbars. In the process i started looking at the BEP Marinco link bars.

BEP Marinco Pro Installer Link Bars

SKU: BEP-LB Marinco Pro Installer Link Bars ModelsLB-1: 779-LB-1-BLB-2: 779-LB-2-BLBJ-2: 779-LBJ-2-BLBJ-3: 779-LBJ-3-B

baymarinesupply.com

I found data on another supplier that says each bar can handle 650 amps of current. I then started thinking about my busbars. I normally order them from suppliers according to the amperage description they sell them at and just order them according to what i need.

Now that i need to link a couple i started to get into the details a little bit more and discovered busbar calculators. I started playing around with them and punching in numbers that match busbars that i already own. For example, i have a BlueSeas 250 amp busbar, but if you enter the size of the bar into one of the calculators, the ampacity capability according to the calculators is quite a bit lower (193 Amps) than what BlueSeas specifies what they can carry. Likewise, i entered in the size specifications for a similar sized BEP busbar that claims 500 Amp carrying capacity and its nowhere near that.

I then discovered the copper development associations website.

Electrical: Busbar - DC Copper Busbar Ampacities

The following tables have been provided by the Alliance for Telecommunications Industry Solutions (ATIS), T1 Committee, and represent ampacities for busbar sizes and arrangements typically found in the telecommunications industry.

www.copper.org

which has a table that shows a 1" x 1/4" busbar in a horizontal plane can carry 400 amps. Im assuming this table is more accurate, but i still am just starting to learn about this in detail. My question is why the discrepancy between the table and the calculators?

Reason i'd like to know is, i'd like to order a copper bar from McMaster Carr to join a 500 and 650 Amp busbars that can safely carry 400+ amps of current. Right now i have 1.375" wide X .25" thick silver plated copper bar selected. According to the table on the copper dev. assc. website its more than enough if i'm reading the table data correctly, but according to the calculators, its only capable of 250 amps. So, still a bit confused trying to figure this out, but want to make sure i dont undersize the link bar. Also, i wonder how the tiny BEP link bar can safely carry 650 amps? Its maybe .75" wide x .125" thick. Very confusing...

 

[jssailem]

Rather than connecting 2 dissimilar buss bars, why not make your own copper buss bar using the info from the above site?

 

[rgranger]

This might be an ignorant question (not my first ) but isn't 400 amps a LOT

The typical house only has 100 to 200 amp service.

 

[dlochner]

The Marinco/BEP Proseries is a great system. I especially like the surface mounted switches, a much better design than Blue Sea. BTW, both Blue Sea and Marinco are now part of the Navico Group which is owned by the Brunswick Corp.

To get higher amperages the link bars can be doubled up.

There are several parts to the answer to your question. One part of the answer is the specific loads on the bar and where they are physically located and the kind feeds and loads attached to the busbar. If this is typcial DC+ Distribution bus from the battery, the battery lead would go in the middle with the 2 highest draws immediately adjacent to the feed and the lowest draws at the end of the feed. This will keep the current draw across the whole 2 part bus bar lower than the ratings. Also, the studs can accept both a link bar(s) and terminal so long as the highest draw is on the bottom, which will most likely be the link bar(s).

If the max draw is in the 400-500a range, then 2 500 amp buses with double link bars should be fine if you watch the load locations, i.e, don't put the highest supply at one end and the highest draw at the other, keep the high supplies and loads on the same section.

More information can be found in the BEP Catalog. And of course, if any information conflicts with I just said, go with the catalog.

BEP Catalog 2024

This interactive flipbook is created with FlippingBook, a service for streaming PDFs online. No download, no waiting. Open and start reading right away!

online.flippingbook.com

I noticed you went to Bay Marine Supply, I've purchased from them and they have good service and good prices. If you enter their website through the MarineHowTo.com affiliate link it benefits MaineSail.

 

[dlochner]

This might be an ignorant question (not my first ) but isn't 400 amps a LOT

The typical house only has 100 to 200 amp service.

A little, however, if the house bank is going to double as a back up starting battery, then the instantaneous load could easily approach 400a. Or if there is a large inverter attached to a good sized LFP bank the draw could be that high.

 

[BAD ORCA]

The Marinco/BEP Proseries is a great system. I especially like the surface mounted switches, a much better design than Blue Sea. BTW, both Blue Sea and Marinco are now part of the Navico Group which is owned by the Brunswick Corp.

To get higher amperages the link bars can be doubled up.

There are several parts to the answer to your question. One part of the answer is the specific loads on the bar and where they are physically located and the kind feeds and loads attached to the busbar. If this is typcial DC+ Distribution bus from the battery, the battery lead would go in the middle with the 2 highest draws immediately adjacent to the feed and the lowest draws at the end of the feed. This will keep the current draw across the whole 2 part bus bar lower than the ratings. Also, the studs can accept both a link bar(s) and terminal so long as the highest draw is on the bottom, which will most likely be the link bar(s).

If the max draw is in the 400-500a range, then 2 500 amp buses with double link bars should be fine if you watch the load locations, i.e, don't put the highest supply at one end and the highest draw at the other, keep the high supplies and loads on the same section.

More information can be found in the BEP Catalog. And of course, if any information conflicts with I just said, go with the catalog.

BEP Catalog 2024

This interactive flipbook is created with FlippingBook, a service for streaming PDFs online. No download, no waiting. Open and start reading right away!

online.flippingbook.com

I noticed you went to Bay Marine Supply, I've purchased from them and they have good service and good prices. If you enter their website through the MarineHowTo.com affiliate link it benefits MaineSail.

Thanks again for the informative reply. Its actually for my main DC- bus. My DC+ is one single BlueSeas 650A bus bar. It has enough studs that i can connect everything to it. My original DC- bus (500 A) only had four studs which i have outgrown since adding a lithium battery bank and a 3000Watt inverter. The inverter requires two 4/0 connections so had/have to add a new bar and link them. Currently i only have a single BEP link between them. but was questioning if that single link was enough.

Good to know on the BEP links. I'll add another and double it up. It will be cheaper than buying copper bars.

I will have to do a little wire re-arranging though. I have my lithium batteries connected to the end of the pos+ busbar and my neg- busbar is similar arrangement with the main engine ground connected to the end.

Agreed on BayMarine. I have been ordering from them first if they have what i need. Customer service and price have been excellent. My only gripe with them is half the time they dont have what i need.

 

[BAD ORCA]

This might be an ignorant question (not my first ) but isn't 400 amps a LOT

The typical house only has 100 to 200 amp service.

Agreed. The most i will ever draw is maybe 150 amps. The 400 Amps is potentially what the lithiium bank and inverter could short through the wiring and busbars before a fuse blew.

 

[BAD ORCA]

Rather than connecting 2 dissimilar buss bars, why not make your own copper buss bar using the info from the above site?

I would if i had a very specific need but i already own all the busbars i need. To me its just easier to use pre-made bars and add a link or two. If i was starting from scratch again i would probably use the Victron Lynx bus. Everything all in one place.

 

[dlochner]

By the way, the Link bars only work with BEP bus bars and the bus bars are shorter than Blue Seas bus bars of the same amperage. The height of the bars is also different. Been down this road.

 

[BAD ORCA]

By the way, the Link bars only work with BEP bus bars and the bus bars are shorter than Blue Seas bus bars of the same amperage. The height of the bars is also different. Been down this road.

Yeah what a pain. I noticed that as well. The two busbars i linked are both BEP busbars and seem to be the same height, or very close. It seemed like the smaller busbar might have been 1/32" lower but it was really hard to tell. The link looks like its fairly flat. I'll double check when i add the next link and shim them if i have to.

The studs are also quite a bit longer also on the BEP bars. I need to cut out a part of my companionway steps now to clear the top of the studs on the larger busbar.

 

[heritage]

This might be an ignorant question (not my first ) but isn't 400 amps a LOT

The typical house only has 100 to 200 amp service.

100 amp service panel for a house runs at 110 volts, that's 11,000 watts of potential power.
A boat drawing 400 amps at 12v is only using 4800 watts of power.

 

[dlochner]

The studs are also quite a bit longer also on the BEP bars. I need to cut out a part of my companionway steps now to clear the top of the studs on the larger busbar.

Yes the outer 2 studs are longer because the cover fits on the top of those studs. This provides much easier access to the studs. Overall the busbar takes up less room than a comparable one from Blue Sea with a cover. Always a compromise.