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Old 06-28-2010, 12:18 PM   #1
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200 amp fuse no-go on Inverter? (as per Battery Store?)

I just got off the phoen with the "Battery Experts" store. I told him I wanted to hookup my 1500 watt (300 surge)inverter to my MH. Told him the advice given on hooking up 2 gauge wires from battery bank to inverter with 200 amp fuse on that side and then the 12/3 cable on the other side going to the main power sourse (normally used to plug in to genset or shore power.) Told him all outlets would be available but would only run the tv at the front, tv at theback and possibly a coffeemaker while driving.

He just about lost his marbles, he said I would in all likelyhood burn the MH to the ground on the 200 amp fuse as the rest of the wiring in the MH isnt designed for that?

He suggested dedicated wiring for the plug in I want to use or if I already have the rear part (inverter beyond-which I do)wired, then to add up the total amperages on just the tv's and add a fuse with maybe 5 amps beyond that total amperage (between battery & inverter) and then do the exact amperages needed just after the inverter. he said I might blow a fuse everytime there is too much draw but I wont burn anything?

He said 200 amps was waaaaayy too much?

Any thoughts on this, help on this? I think owning a MH is COOL..I certainly dont want it to be HOT
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Old 06-28-2010, 01:52 PM   #2
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You're not that far off. You should check your inverter's manual to see what therequirements are but normally a 150 amp DC fuse is recommended for most 1500 watt inverters. #2 cable is capable of handling up to 200 amps so you are fine there. You won't burn the RV down because the cable can safely handle 200. The inverter may not like it but a 150 amp fuse easily protexts that as well.

On the AC side of things you will be limited to the inverter's output. Theroretically that would be 12.5 amps (1500 watts divided by 120 volts = 12.5 amps), although you will probably find that the surge is greater but that it is also rated at 1,000 watts on a continuous duty cycle. A 15 amp ort 20 amp breaker will handle the #12 AC wiring well enough. Your biggest concern is that you switch everything off to prevent blowing the inverter fuse or breaker from a possible overload seeing as how you are plugging the entire RV into the inverter's AC outlet.

I don't get why the guy freaked out. You are not running the rest of the RV's wiring on 200 amps. The 200 (or 150) amps is only DC current on the battery cables that you are installing. The most AC current that's evergoing to reach the RV's breaker panel and electrical system is the 12.5 amps that the inverter will produce. I'm thinking he misunderstood you and was thinking you wanted to run 200 amps of AC power to the breaker panel. That would not be good.
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Old 06-28-2010, 02:18 PM   #3
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Okay, thx very much, lotsa minor adjustments on this project but it will pay off with peice of mind for sure!

So I'll run 5 feet of 2 gauge cable with 150 amp dc fuse to the inverter and on the ac side of the inverter I attach a 12.5 amp fuse which attaches to my 12/3 cable?

I'm sure the 2nd fuse is probably just a CYA (cover your a--). I'm happy to replace a fuse or two should we overload it.

So this is normal practice with MH's and inverters? I'll explain it to him for sure..he seemed to think I was on a suicide mission haha

He much preferred running designated plug-ins for tv at front, tv at the back and whatever in between. Hmm, now that I think about it..thats alot of wire and prob a tidy profit lol

I cant for the life of me find what my 19 inch RCA tube tv draws in amps, watts etc?

Thanks once again
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Old 06-28-2010, 02:20 PM   #4
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Well like normal the sales guys at the battery store don't know chit and doesn't know AC from DC. The out put from the inverter is low"(less than your 30 amp plut from shore or gen. Plus the output side of the inverter should have breakers too.


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Old 06-28-2010, 02:32 PM   #5
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You do need to provide overload protection on the inverter's AC output to prevent a fire should a short circuit occur. However, check your inverter. It may already have an AC fuse on it for it's output. If so, you won't need to add another one.
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Old 06-28-2010, 02:49 PM   #6
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The better inverters typically have a circuit breaker on the output side, to prevent you from overloading the inverter. Plus, the control board in the inverter shuts it down if the rated load is exceeded for very very long, or if the surge load is exceeded at all. All that should be covered in the manual for the inverter. I know my Xantrex RV2512 does both of those, plus it monitors the DC input voltage and current.
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Old 06-28-2010, 05:19 PM   #7
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200 amps is way too much? not on the 12 volt side of the inverter,, I think he was thinking of the 120 volt side of life where . Well, 20 amps is about right for that inverter

But 200 amps would be just about the right size FOR THE INVERTER.

now let me check something else/// I thought so.. Here is the URL:

American Wire Gauge table and AWG Electrical Current Load Limits with skin depth frequencies

You will find that for #2 wire you should fuse at no more than 94 (let's round to 100) amps.. For 200 amps you need at the very least 2/0, 2/0 is not the same as 2.

Wire sizes from largest to smallerst, sub set (not covering the full range)

Many zeros
0000
000
00
0
1
2
3
4
5
6


As you can see 2 is a lot smaller than 2/0 (Which means 00) and the chart above says the SAFE capacity of 00 is 190 amps.. 2 is but 94

So... He's right.
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Old 06-28-2010, 06:12 PM   #8
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Quote:
Originally Posted by wa8yxm View Post
200 amps is way too much? not on the 12 volt side of the inverter,, I think he was thinking of the 120 volt side of life where . Well, 20 amps is about right for that inverter

But 200 amps would be just about the right size FOR THE INVERTER.

now let me check something else/// I thought so.. Here is the URL:

American Wire Gauge table and AWG Electrical Current Load Limits with skin depth frequencies

You will find that for #2 wire you should fuse at no more than 94 (let's round to 100) amps.. For 200 amps you need at the very least 2/0, 2/0 is not the same as 2.

Wire sizes from largest to smallerst, sub set (not covering the full range)

Many zeros
0000
000
00
0
1
2
3
4
5
6


As you can see 2 is a lot smaller than 2/0 (Which means 00) and the chart above says the SAFE capacity of 00 is 190 amps.. 2 is but 94

So... He's right.
I second that!

My 1500 watt Heart Interface inverter specifically calls out the use of 2/0(say two ought) cables. In addition the 200 amp fuse must be installed in the positive cable no more then 18 inches fom the battery terminal.

The fuse is not just to limit current used by the inverter, but also to protect the battery and input cables in the event the inverter it self shorts out!!

I am wired that way. I have used this inverter for more then 14 years now. Often at max dc inputs of more then 150 amps sourced from the 3 banks of 12 v configured golf cart G2s.

Marty
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Old 06-28-2010, 07:22 PM   #9
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With a 1500 watt inverter the DC current draw will be 125 amps. To specify a fuse size without specifying a fuse class is meaningless so in this case you will need a 125 amp class T fuse which can be found here. The purpose of this fuse is not only to protect the inverter but to protect the conductor. You will also need to buy a fuse block to mount the fuse and I recommend putting it in the battery compartment if possible.

According to the American Wire Gauge chart supplied by wa8yxm, #2 copper AWG is rated to carry 181 amps, which is well above the capacity of the inverter. I recommend that you buy this cable with 19 strands if available. The number of strands will make bending and training the cable easier than the standard 7 strand cable. The cable can be purchased at any welding supply store. When you purchase the cable buy two pieces, one to reach from the positive side of the batteries to where the fuse block will be mounted and the other from the fuse block to where ever the inverter is located. You will also have to decided the type of terminals you want to be swedged onto the cable ends for attachment. Since you said the cable length is small the voltage drop associated with its length is negligible for this application at about 0.5 volts at full load.

On the 120 volt side of the inverter I'm not clear about how you expect to feed your loads or do I know anything about the inverter you have. But if it was me and to avoid problems with back feeding 120 to you power cable if you forget to turn off your inverter, or somebody puts it on when your connected to shore power, I would mount a 30 amp receptacle where your power cord can reach it and run #10/3 AWG copper stranded wire from the 120 volt side of the inverter to the receptacle and plug your power cord into it. To prevent overloading the inverter you can designate certain breakers at the power panel to be shut off when running the inverter.

I'm concerned about what you have for batteries. What could be 100 amps DC being continuously supplied by the batteries can produce a lot of heat if the battery bank is not large enough. As an example, two Trojan T-105 6 volt deep cycle batteries would only last about 1 hour if discharged to 50% at full load.
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Old 06-28-2010, 08:41 PM   #10
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Thx very much, so I will endeavour to get the 125 amp t-fuse between battery and inverter (its a 1500, 3000 surge motomaster eliminator/xantrex). What will I need for fuse on the ac side of the inverter?

I did mount a 30 amp female receptical at the rear where I would plug the house into the genset or to shore power-figured when driving can just connect to teh inverter. I like your idea of the backup plan of shutting off certain braekers such as house air cond etc and I guess the 2 fuses (one on either side of the inverter) are other phases of protection.

The battery guy wanted me to add up all the amperages of everything I wanted to use and then add 5 amps for fudge factor?

Heres extactly what I need to run at any given time while driving:
Microwave- 900 watts, 12.8 amps
15" tube tv- 120 volt, 54 watts, 15 amps
coffeemaker- 900 watts- 41.7 amps
19" tube tv- 80-100 watts (u/k amps)
dvd/vhs player- unknown watts/amps

The inverter will ONLY be used while driving- I am powering it with a 12volt Interstate deep cycle battery which will be paired with a slightly larger CAT battery (still 12 volt) but for transport trucks if that can be pulled off.
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Old 06-28-2010, 09:20 PM   #11
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BadBoy,
Your a little off on your load calculations, this is what your have:

Microwave 900 watts = 7.5 amps
15 tube TV 54 watts = 0.45 amps
Coffeemaker 900 watts = 7.5 amps
19 tube TV 100 watts = 0.8 amps
DVD/VHS player 100 watts = 0.8 amps (just a guess)

Your total load is 17 amps or 2040 watts. You can not run your Microwave and coffeemaker at the same time. There is no need to add a fudge factor. When you parrallel your batteries connect the #2 cables to the POS and NEG posts of the larger battery. I don't know what size your batteries are so when you first use this setup monitor the temperature of the batteries to make sure they don't get too hot. Remember you only have about an hour of use before you get to the 50% load level, just watch your usage.
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Old 06-28-2010, 09:41 PM   #12
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Great thanks very much RJay..that makes it much easier to figure out. In all reality we would only have the front tv and dvd player and the coffeemaker going at any given time. So just to confirm..get the 12.5 amp fuse for the AC side of the inverter? I dont believe my inverter has a built in fuse in it
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Old 06-28-2010, 10:41 PM   #13
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It would be much easier if the front(120 volt) side of the inverter was already fused, if not your going to have to be creative, I don't know what your physical restrictions are where the equipment is being mounted. You will need one 120 volt 15 amp circuit breaker and housing/panel/box. Mount it as close to the inverter as possible. Go to an electrical supply house and tell the clerk what you want to do, he may have just what you need.
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Old 06-28-2010, 11:52 PM   #14
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Gotcha, I have plenty of room as I designated a full side box to the inverter. That box is 5 feet from the battery bank so the heavier cable (2ought) is prob best. I'll do the 125 amp t-fuse on the dc side (as close to batteries as possible and go for the 15 amp fuse on the AC side mounted as close to the inverter as possible.
Hope that will do the trick!
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