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Discussion Starter #1
Hi all,

I have been doing some research, mostly through this forum, and I am wondering if I should modify my electrical system.

I do not profess to be an expert in electrical systems, but I am very good at copying others good practices, and I (among others) have recognized the wealth of talent here on this site.

I have finished my electrical installation but I wonder if I should add a separate/additional circuit breaker between the 30a shore power plug and my inverter. There is some protection at the inverter but I want to be as safe as possible. I have built my system using marine hardware and I have used Blue Sea products to support that ethic. The breaker that I am considering is the Blue Sea AC Main 30a Circuit Breaker Panel; model 335524 Blue Sea 8077. The 8077 also has a reverse polarity indicator light which will be handy as a warning device when plugging in.

I have included my wiring notes—I won’t call it a schematic for obvious reasons.

Any help on this question and my setup will be greatly appreciated.

https://www.bluesea.com/products/8077/AC_Main_30A


Mike
 

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I'm no expert either, but I know the installation guide for my inverter/charger calls for a main panel w/breaker between shore-power and the inverter. It refers to the inverter-powered AC panel as the sub-panel.
 

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'16 2500 159 HT Granite Window - OH(io)
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Adding a breaker is not a bad idea, but remember, the main purpose of a circuit breaker is to prevent fires - it keeps the associated wiring from getting hot and doing crazy things like melting its insulating material and igniting. That being said, the breaker size is determined by the size of the wire that it is protecting.
If the power cord supplying your shore-power (the cord from the side of the van to the campground, dock, etc. supply) is #10 wire, then a 30 amp breaker is what is called for. If the cord is #12 , then a 20 amp breaker should be used. The wiring from the breaker to the inverter should also be sized the same.
Also remember that the longer a wire is, that more resistance it has, and the warmer it will get. You should keep your supply cable as short as possible, under 25 feet.
 

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The Magnum MMP, on which we commented in our two "Electrical" posts [Posts 50 & 60 of our construction thread, http://www.promasterforum.com/forum/showpost.php?p=407650&postcount=60)], uses main breakers both at its input from shore power as well as its inverter output. Maybe overkill, but a shore power input breaker, at the least, provides a quick 'kill' function should you suspect a problem with shore power.
 

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Melmike, if I may ask?

How far are your batteries apart and what size wire are you using there?
 

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Discussion Starter #7
The Magnum MMP, on which we commented in our two "Electrical" posts [Posts 50 & 60 of our construction thread, http://www.promasterforum.com/forum/showpost.php?p=407650&postcount=60)], uses main breakers both at its input from shore power as well as its inverter output. Maybe overkill, but a shore power input breaker, at the least, provides a quick 'kill' function should you suspect a problem with shore power.
Winston,

You have a very impressive setup. Thanks for sharing.

Mike
 

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I have been researching auxiliary battery options for my PM and I am curious about your diagram. You show the isolator placed between the starter battery and the auxiliary battery, with no direct connection to the alternator. Is your isolator a solenoid type? (Stinger sgp32?) From what I have seen, the diode type isolators take power directly from the alternator, then distribute it to the two batteries. (eg: Stinger s2402)
 

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Discussion Starter #11
I have been researching auxiliary battery options for my PM and I am curious about your diagram. You show the isolator placed between the starter battery and the auxiliary battery, with no direct connection to the alternator. Is your isolator a solenoid type? (Stinger sgp32?) From what I have seen, the diode type isolators take power directly from the alternator, then distribute it to the two batteries. (eg: Stinger s2402)
Hi Swoop,

Yes the isolator is a solenoid type, the Stinger SPG32 200 amp is the one that I selected. YouTube has many videos listing pros and cons on these and after close study I decided to stay away from the diode type mostly because it is live all the time and more expensive. The Stinger SPG32 is actuated when the ignition key is on through a pin that I found on the up-fitter plug, so on start I am applying energy from all batteries, and under run I am charging all batteries in the vehicle, and with the vehicle off there is isolation. So far it has worked very well, and if it does not then I can flip a switch to eliminate the house batteries during start--just have to remember to flip it on after start if I want to charge the hose batteries.

Mike
 

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2014, 138WB, High Roof, Gas, SW MT
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Hi all,

I have been doing some research, mostly through this forum, and I am wondering if I should modify my electrical system.

I do not profess to be an expert in electrical systems, but I am very good at copying others good practices, and I (among others) have recognized the wealth of talent here on this site. And, you get that reverse polarity protection as well.

I have finished my electrical installation but I wonder if I should add a separate/additional circuit breaker between the 30a shore power plug and my inverter. There is some protection at the inverter but I want to be as safe as possible. I have built my system using marine hardware and I have used Blue Sea products to support that ethic. The breaker that I am considering is the Blue Sea AC Main 30a Circuit Breaker Panel; model 335524 Blue Sea 8077. The 8077 also has a reverse polarity indicator light which will be handy as a warning device when plugging in.

I have included my wiring notes—I won’t call it a schematic for obvious reasons.

Any help on this question and my setup will be greatly appreciated.

https://www.bluesea.com/products/8077/AC_Main_30A


Mike
Hi,
The 30 amp shore power will have its own protection breakers, and as long as you use wire that can handle the full 30 amps (#10), the shore power breakers will protect your shore power cable. But, there is no harm in adding a breaker so that if the shore power breaker is done incorrectly or fails, you will still have protection.

On your diagram, the 200 amp breakers in the line from van battery to house battery seems large. I guess its OK as long as the hot and negative wires are large enough to support the 200 amps, but if you actually end up charging your house batteries at anything like 200 amps, it will destroy the house battery quickly and is not a safe charge rate for the size of your house battery. I'd try to find out what the maximum rate that your battery manufacturer recommends for charging your house battery, and have some way to check that you are not routinely exceeding that rate by a significant margin -- this could be an amp meter or a smaller breaker instead of the 200 amp breaker?

Good that you have breakers at both ends of this line (near each battery).

Gary
 

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Discussion Starter #13
Hi,
The 30 amp shore power will have its own protection breakers, and as long as you use wire that can handle the full 30 amps (#10 ), the shore power breakers will protect your shore power cable. But, there is no harm in adding a breaker so that if the shore power breaker is done incorrectly or fails, you will still have protection.

On your diagram, the 200 amp breakers in the line from van battery to house battery seems large. I guess its OK as long as the hot and negative wires are large enough to support the 200 amps, but if you actually end up charging your house batteries at anything like 200 amps, it will destroy the house battery quickly and is not a safe charge rate for the size of your house battery. I'd try to find out what the maximum rate that your battery manufacturer recommends for charging your house battery, and have some way to check that you are not routinely exceeding that rate by a significant margin -- this could be an amp meter or a smaller breaker instead of the 200 amp breaker?

Good that you have breakers at both ends of this line (near each battery).

Gary
Hi Gary,

Thanks for your post and I’ll try to answer your questions.

Yes, the wire that I installed for shore power service is #10 and I will be adding the breaker as added safety. I also like the Blue Sea breaker because it will detect reverse polarity right at the source. This will save me from testing the campsite plug prior plug-in.

The 200 amp fuses were sized to the wire and suggestions from tech support from Stinger—the manufacturer of the isolation switch. The wire from the vehicle battery and interconnection is 1/0 and the wire size to the inverter is 2 gauge as stipulated by the inverter manufacturer. I should put a meter on the input side of the batteries to see what the actual current is—any suggestions?

The house batteries (2) are Universal UB121000-45978 12V 100AH deep cycle AGM batteries. The max input current to these is shown as 30A on the tech sheet.
 

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2014, 138WB, High Roof, Gas, SW MT
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Hi Gary,

Thanks for your post and I’ll try to answer your questions.

Yes, the wire that I installed for shore power service is #10 and I will be adding the breaker as added safety. I also like the Blue Sea breaker because it will detect reverse polarity right at the source. This will save me from testing the campsite plug prior plug-in.

The 200 amp fuses were sized to the wire and suggestions from tech support from Stinger—the manufacturer of the isolation switch. The wire from the vehicle battery and interconnection is 1/0 and the wire size to the inverter is 2 gauge as stipulated by the inverter manufacturer. I should put a meter on the input side of the batteries to see what the actual current is—any suggestions?

The house batteries (2) are Universal UB121000-45978 12V 100AH deep cycle AGM batteries. The max input current to these is shown as 30A on the tech sheet.
Hi,
I'm a bit surprised that they recommended such large wires. I don't see the value in putting in wires that support charge rates that would destroy your house battery :) But, they won't do any harm.

To check that the charging current is not to high -- a couple methods:

You could just use a clamp on meter on the wire coming into your house battery from your van battery. I use this Klein Tools cl2000: http://www.kleintools.com/catalog/discontinued-products/400a-acdc-true-rms-clamp-meter
Its kind of pricey, but very nice and can used for all electrical measuring chores. I'm sure there are some less expensive ones, but be sure that the clamp on part does DC and AC amps as a lot of the camp ons only do AC. Best way would be to discharge the house battery down to a fairly low level, then start the van and clamp the meter over the wire from the van to the house batteries to measure the charging current. You would only have to do this a couple times to make sure the charge current when the house battery is low is within the manufacturers maximum charge recommendation.

If you want a permanent way to check the charging current, something line this one would likely be OK: https://www.amazon.com/dp/B01JOUZELG?psc=1
I think you will want one with a shunt as you are not going to want to have to wire those heavy conductors over to the meter itself. The shunt would go in the negative line and the meter just measures the voltage drop across the shunt and converts it to amps.

Another option would be to put in a battery monitoring system like the TriMetric or Victron.
https://www.amazon.com/Victron-BMV-...=1-1-catcorr&keywords=victron+battery+monitor

This measures the total current flow into and out of the battery at all times and will sum this over time to give you the actual state of charge of your battery (ie percentage of juice left). To check the charging current with this one, you would turn off the electrical loads and solar charging in your RV, start the engine -- then the current reading on the battery monitor would be the charging amps from the van generator.
This is more expensive than the meter, but its nice to be able to tell at a glance how much juice is left in the battery.

Gary
 

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Discussion Starter #15
Hi,
I'm a bit surprised that they recommended such large wires. I don't see the value in putting in wires that support charge rates that would destroy your house battery :) But, they won't do any harm.

To check that the charging current is not to high -- a couple methods:

You could just use a clamp on meter on the wire coming into your house battery from your van battery. I use this Klein Tools cl2000: http://www.kleintools.com/catalog/discontinued-products/400a-acdc-true-rms-clamp-meter
Its kind of pricey, but very nice and can used for all electrical measuring chores. I'm sure there are some less expensive ones, but be sure that the clamp on part does DC and AC amps as a lot of the camp ons only do AC. Best way would be to discharge the house battery down to a fairly low level, then start the van and clamp the meter over the wire from the van to the house batteries to measure the charging current. You would only have to do this a couple times to make sure the charge current when the house battery is low is within the manufacturers maximum charge recommendation.

If you want a permanent way to check the charging current, something line this one would likely be OK: https://www.amazon.com/dp/B01JOUZELG?psc=1
I think you will want one with a shunt as you are not going to want to have to wire those heavy conductors over to the meter itself. The shunt would go in the negative line and the meter just measures the voltage drop across the shunt and converts it to amps.

Another option would be to put in a battery monitoring system like the TriMetric or Victron.
https://www.amazon.com/Victron-BMV-...=1-1-catcorr&keywords=victron+battery+monitor

This measures the total current flow into and out of the battery at all times and will sum this over time to give you the actual state of charge of your battery (ie percentage of juice left). To check the charging current with this one, you would turn off the electrical loads and solar charging in your RV, start the engine -- then the current reading on the battery monitor would be the charging amps from the van generator.
This is more expensive than the meter, but its nice to be able to tell at a glance how much juice is left in the battery.

Gary
Gary,

Great info--many thanks!!

Mike
 
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