Outback FX2524T Maximum Actual AC Grid Current Pull

marsofold

Just bought an old rural house in WV with a 100 amp breaker box. I need to know if I need a new 200 amp breaker box to power the FX2524T under maximum grid current draw, such as charging the batteries with a simultaneous 2 kilowatt 120 volt AC load. My interpretation of the specs say it stays within a 28 amp pull from the grid, but also say to use a 60 amp circuit breaker and 6-AWG wiring. Why the disparity? Will it pull 28 amps max or 60 amps max? The answer to this question will decide if a new breaker box is needed. Thanks...

mcgivor

The breaker is sized according to the size of the conductors, not the load, the manufacturer probably oversizes the gauge to cover worst case scenarios which are beyond their control, extremely long runs for example.

The question regarding capacity of the 100A service would depend on demands of all other loads during charging. Charging could always be done at night when demands are generally low and rates are sometimes lower.

Tecnodave

A 100 amp service panel is 24,000 watts , assuming that it is 120/240 volt split phase,  it will easily handle the Outback charge mode at 100% duty, it uses only 28 amps at 120 volts , 3360 watts..

marsofold

By my math: 3200 watt max 30 minute load per spec: 3200/120 = 26.66 amps. Maximum battery charging amps per spec sheet is 35 amps dc: 29 volts x 35 amps = 1015 watts. At 93% inverter efficiency per spec: 1015 watts/0.93 = 1091 watts. 1091 watts/120v input = 9.09 amps. Adding the two values: 26.66 amps to loads + 9.09 amps to the charger = total 35.75 amps maximum draw. If my math is wrong please show me where...

Tecnodave

I made some assumptions as to the output capability, this unit is not a standard outback but a special version.....

What does inverter effeciency have to do with the battery charging? Inverter/chargers can do one or the other, you cannot run the inverter off the battery to run the charger to charge the battery!!! It's either an inverter or a charger!!!

Inverter effeciency has nothing to do with battery charging!!!  So my math was a bit wrong, your argument is way out in left field!!!

from the spec sheet maximum battery charge current 55 amps not 35 amps, maximum battery charge voltage 34 volts, not 29 volts.....1870 watts, but most outback chargers are 1500 watts max so output max current depends on voltage

battery charger maximum            1500 watts        12.5 amps at 120 volts

Other load.                                     2000 watts       16.66 amps at 120 volts

Total load                                       3500  watts       29.667 amps at 120 volts

So where is the argument? 

Back to the question "Can the outback and a 2000 watt load run off a 100 amp panel?  Well let's assume that it is 120 volts only that load is 30% of that panels capability,

So will it run that load?

Yes it can......

I was assuming that the OP was providing me with the battery charge current draw, not the charge current plus the load current.....my bad

Tecnodave

The reason for the 60 amp breaker requirement is when AC input is applied not only does the battery charger get powered the pass through relay will connect the AC input to the AC output so the AC feed from the breaker panel needs to supply not only the AC power for the battery charger but the AC pass thriogh power as well. The pass through relay on most outback inverters is 30 amps, so the 60 amp breaker and 6ga. wire is appropriate for the AC feed on this inverter.

marsofold

The relay may be rated at 30 amps, but the official spec sheet says that the maximum load rated for a 30 minute interval is 3200 watts. At 120 volts the allowed pass-through function at most is 26.66 amps. The official spec sheet also says that the grid supplied battery charging function supplies 35 amps to the batteries. Since no machine is 100% efficient at converting 120 volts AC to 29 volts DC to do the charging, then the official spec sheet value of 93% efficiency most definitely applies. 29 volts at the 35 amps supplied to the batteries equals 1015 watts. If the gadget were 100% efficient this would only add up to 8.45 amps pulled from the grid to perform this function. Nowhere near another 26.66 amps. Since I have some faith in the official spec of 93% efficiency,then I believe the actual grid pull to do the charging function is at most: 1015watts/0.93 = 1091 watts. 1091 watts pulled from the grid at 120 volts is: 1091watts/120volts = 9.09 amps for charging. NOT 30 amps, NOT 26.66 amps, but a mere 9.09 amps. And 26.66 amps pass-through + 9.09 amps for charging = 35.75 amps. NOT 60 amps. The above specs quoted are the OFFICIAL specs, not my opinion. The above calculations are not rocket science or university level math, it's elementary grade school math. I consider that my question has not been answered with any degree of real world math. A 40 amp breaker loaded to 80% per usual practice can handle a maximum continuous value of 32 amps. More than 35.75 amps, so a 40 amp breaker won't do. A 50 amp breaker maximum and 8-AWG wiring minimum. Breaker box replacement to be decided by total house loads.    

Tecnodave

@Marsfold,


 Again you are misreading the specs.....3200 watts at 30 minutes is the inverter maximum output specs....NOT THE PASS THROUGH POWER......35 amp battery charging is for the FX2532, the 32 volt version.......... NOT FOR THE 24 volt version.........55 amps battery charging is for the FX2524, the 24 volt version......the 93% effeciency is the inverter maximum operating effeciency operating at 80% loading.......NOT THE BATTERY CHARGER EFFECIENCY!
Your interpretation of the specs?     

 but if you know more than a retired electrical engineer who worked for a major power engineering firm that is so well known internationally known by a two letter moniker that nobody uses their full name, it's a household word......and has done electrical contracting as a private contractor for 20 years then you are way smarter than me. I got my first engineering liscene Dec, 19, 1965.......LOL....I do live 480 volt 100 hp work almost daily, I've done literally thousands of power panel upgrades....but I know nada right.....LOL....don't expect a response from me, I help people who can listen and learn OK.......

Please don't comment on my posts and I will ignore your posts.....

Estragon

FWIW, my Outback manual (which covers a number of models)  says "The battery charger has an efficiency of greater than 80%.  Other factors, such as cable losses, might reduce this efficiency".  My 48v versions may be slightly more efficient than a 24v version, but they're likely both in the 80% ballpark.  As @tecnodave says, this efficiency isn't directly related to the DC to AC (inverting) maximum efficiency, it's the AC to DC (charging) conversion efficiency.

On my OBs, there's a setting for max AC input on AC1 (grid), and AC2 (gen).  If using a smaller AC1 breaker/wire, you should be able to simply lower the AC1 max setting accordingly.  If house pass-through loads + charger load exceeds the limit, the unit will throttle charging current as needed to stay under the limit.

Tecnodave

marsofold said:

Just bought an old rural house in WV with a 100 amp breaker box. I need to know if I need a new 200 amp breaker box to power the FX2524T under maximum grid current draw, such as charging the batteries with a simultaneous 2 kilowatt 120 volt AC load. My interpretation of the specs say it stays within a 28 amp pull from the grid, but also say to use a 60 amp circuit breaker and 6-AWG wiring. Why the disparity? Will it pull 28 amps max or 60 amps max? The answer to this question will decide if a new breaker box is needed. Thanks...

@Estragon,

The OP question was "will the FX2524T under maximum grid current draw, such as charging the batteries with a simultaneous load 2 kilowatt load AC load run off a 100 amp panel?

Well seeing that the 24 volt OB inverter has a maximum output of 1500 watts and even at 80% effeciency that's 1800 watts plus a 2000 watts, my answer is yes it can run off a 100 amp panel.

Almost all of America does have a split phase 120/240 volt service which is 24,000 watts then YES an OB will run at maximum battery charge current with a 2000 watt load.

Even if the OP is referring to a 120 volt panel that's 12,000 watts THEN YES IT CAN handle a 3600 watt load.

The OP does not state wether the other load is drawn from the buss of the main panel or the inverter pass through but the end result is the same, the total load is about 1/3 of a 120 volt panel and 1/6 of a 120/240 volt 24,000 watt panel 

I was given incomplete data, I calculated the result and gave a reasonable answer. The OP comes back obviously not skilled in engineering with skewed data and not understanding a data sheet and not the difference between the inverter and the battery charger of the OB and questions my information.

Quoting the inverters maximum output power has nothing to do with the total current drawn by the battery charger plus some other load.

Quoting the inverters effeciency has nothing to do with the battery charger effeciency.

Quoting that a 2000 watt load is 26.66 amps at 120 volts.....that's funny math.....my calculator says 16.66 amps

Quoting that the maximum pass through power is 26.6 amps, where is that published?   It's not in the data sheet!

Not understanding that a breaker is only capable of 80 % of its rating at >2.0 hours use?

Outback states that the inverter charger should have a 60 amp breaker and 6ga. wire is done by an engineer who does have the necessary tools to do load calculations and does understand "continuous duty" as well as wiring drop, etc.

If he feels that he needs to upgrade to a 48,000 watt panel to run a 3600 watt load,  then that's his problem, it's his money and his toilet! 

Ive done electricity a long time,  I can do a whole house load calculation in my head without writing anything down with only the total square foot floor plan, and listing of the major appliances. I have all the necessary information in need. I do not need a computer or calculator to do that. And I won't argue about it.  I'm into my  70's and done this too long, since I was a teen......I have never had a building inspector fail to pass my work.

I did not take into account the battery charger effeciency....my bad.....

I said that a 100 amp panel will provide enough power for the charger at full load plus another 2kw load at the same time. from a 100 amp panel , it does not matter if that panel is 120 volt or 120/240 volt panel.......That statement is true!

Rant over........my bad......I tried to help a newbie......my bad

mcgivor

Quiet frankly I'm confused by this discussion, the size of the breaker has nothing to do with loads, it's purpose is to protect the conductors in the event of a short circuit condition, the manufacturer’s recommendations is to use 6 AWG, so the appropriate over current protection is 60A.

The actual AC draw may be significantly less than the rating of the conductors and the OCP for reasons the manufacturer could answer, but in reality if all the breakers ratings within a service  were combined for a 100A service they would more than likely exceed the main OCP rated current. There is rationale behind this is, that not all loads would be used simultaneously. If dishwasher, air conditioning, a jacuzzi, a hot water heater, a microwave, a toaster oven, an iron, a hair dryer, a curling iron and a water pump were all used simultaneously, perhaps a larger service may be required,  but who does that?

Estragon

@Tecnodave - I was agreeing with you. 

If OP wants or needs to use smaller wire and breaker for charging and loads wired to the inverter, he can limit the total AC load.  The default setting is 28aac, maximum is 60aac (combined charger and connected loads).  As the recommended AC supply breaker is 60a, I assume the load isn't considered continuous duty.  My installation manual doesn't list OP's model, but all the dozen or so models listed appear to have the same 60a max ACIN.

I don't know what code is on this, but my understanding is OP's issue was if he has to put a 60a branch circuit breaker in a 100a panel, does that require a panel upgrade?  I don't know the answer to that, so was just pointing out that a smaller breaker might be used by setting the ACIN limit lower. 

If there are few loads connected to the inverter (eg only what the inverter can reasonably support on battery), then a smaller breaker and lower ACIN setting may work?

I have my AC2 IN limited to avoid overloading my smallish (4kw) diesel, and it works reasonably well throttling charging if the fridge comes on or whatever.

Tecnodave

@Estragon ,

Sorry, I did realize that, but the OP wanted to dought my expertise on the issue, I do not have an OB unit but with 55 years in electrical/electronics I generally can get real close to an issue with equipment that I have never seen before. I do have a much larger MagnaSine Inverter/Charger which has twice to triple the battery charging capability and I run it off a smaller panel than he has with no issues at all. 

This OB unit is 120 volt and needs only a single breaker, which is specified to account for the 80% duty cycle. It will not require a panel upgrade with what he has specified, but then again , I do not have all the data to do a load calculation for the whole house.

Im really not on this forum or any of the others to put down anybody or dought their skills. I do gather much information here and the other forums that I read and post on, some good, some way out in left field. I have been wrong on issues, but I'm willing to learn new stuff all the time. 

The OP has a rare variant that is not in the specs sheet for UL1741 accepted models for use in a dwelling, but I will let him do what he wants with it, he might be only using it for a standby power with no solar, he hasn't stated his use.

Yesterday was a tough day, I'm recovering from a nasty bike crash and needed to do a long range consultation and failure analysis technical trouble shooting on a complex system for a true friend . A freind in need is a freind indeed!

didnt mean any anger at you at all, your posts are to the point and very accurate, 

If you have any really tough questions on power engineering, please do poke me with that, I retired from industry as a failure analyst in electrical engineering and can't stand the boredom so I still do electrical for a living, only not for major corporations now.

the problem with retiring.....every TV I have ever seen has a "brightness" control and anywhere you turn it it's still really dumb shit!   LOL
David...