Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

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Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

November 25, 2017, 12:49:28 pm

Question: If an inverter's passthrough functionality is active, (IE: if the generator is running or plugged into shore power, but the inverter itself is off), do you still need to limit the load being plugged into the outlets powered through the inverter to the load rating of the inverter?

Hypothetical Example: 8KW generator is running, power being passed through a Magnum 2812 (2800 W continuous rating) inverter. If I plug in two 1500 W space heaters and use an 800 W toaster (3800 W total), all through inverter-wired outlets simultaneously, will I pop something in the inverter?

We have a magnum 2812 inverter. When I look at the side of the inverter, it appears there is a built-in 30 Amp fuse/breaker reset button (which I assume would pop somewhere between 2800 W and 4300 W (80-120% of 30A/3600W). Does this get popped through passthrough loads when the inverter is turned off?

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #1 – November 25, 2017, 01:01:35 pm

The second ATS is passing that current around the invertor. If you are wired like mine and have the 2nd transfer switch.

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #2 – November 25, 2017, 01:02:38 pm

First question, How is it wired to shore power. OEM had two transfer switches and did not use pass through mode on inverter, because inverter was 30 amp pass through, with bypass full shore power/generator 50 amp was available If your Magnum was put in with OEM wiring, you are likely bypassing the inverter completely while on shore power Should be two transfer switches under bed. One pulls in when not on shore/generator and supplies power from electric inverter to the smaller 115V inverter subpanel with about four breakers in it.
Second transfer switch allows show powe/generator power to full 115v panel How is your Magnum wired into coach?

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #3 – November 25, 2017, 01:34:58 pm

This is a good question that I may not know the answer to. When we put in the magnum, we did not change/remove/switch any of the wires. Pulled each wire out of the heart freedom, and put them in the corresponding slot in the magnum. So I assume we are bypassing the inverter completely with the generator running?

While the generator is running I can manually switch off power to the inverter via the magnum display and there is no interruption to the power supply at the outlets. Would this be indicative of an inverter bypass?

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #4 – November 25, 2017, 01:57:02 pm

Quote from: Blinded04 – November 25, 2017, 01:34:58 pm

This is a good question that I may not know the answer to. When we put in the magnum, we did not change/remove/switch any of the wires. Pulled each wire out of the heart freedom, and put them in the corresponding slot in the magnum. So I assume we are bypassing the inverter completely with the generator running?

While the generator is running I can manually switch off power to the inverter via the magnum display and there is no interruption to the power supply at the outlets. Would this be indicative of an inverter bypass?

Yes, it has the Foretravel bypass [inverter or gen/sp] ATS. Some SOB's use the transfer switch in the inverter which would limit you to the built in 30 amp breaker.

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #5 – November 25, 2017, 02:29:40 pm

do you have two transfer switches or one in the coach?

Tim Fiedler

Sure Start Soft Start

TCER Direct generator-gas-prod 630 240-9139
Gen-Pro

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #6 – November 25, 2017, 03:51:27 pm

when you go on to the inverter, do you here a transfer switch "clunk" before power comes on? Do you have two sets of 115V breakers in the coach? a main panel and a smaller set of 4 or 5 115V breakers in a separate panel?

Tim Fiedler

Sure Start Soft Start

TCER Direct generator-gas-prod 630 240-9139
Gen-Pro

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #7 – November 25, 2017, 04:02:59 pm

Best thing is to shut off power to inverter at main panel, shut off invert on magnum display. If you still have power at your 110 v inverter outlets when on gen or sp, you have the second sp/gen/inverter ATS.

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #8 – November 25, 2017, 04:53:47 pm

agreed. Also, in the original owners manual in my 2000 is a wiring diagram specific to the shore/power ATS installation - if you have original manuals, check your wiring diagrams in there

My bet is you have two -this was done to get around the 30 amp pass through litigation of the Original Inverter in the coach.

VIctron 3000 watt Inverter can pass 50 amps - but I could not take advantage of that without upgrading the AC wiring from rear of bus, up to inverter and back to rear of bus. One bay (wet) very difficult to traverse, so opted to save the $$ and stayed with the two ATS installation

Tim Fiedler

Sure Start Soft Start

TCER Direct generator-gas-prod 630 240-9139
Gen-Pro

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #9 – November 25, 2017, 05:08:01 pm

Not all FT have two ATS. The Victron MultiPlus (as Tim said) will do 50 amps pass through but only if wiring is upsized. I have looked at that and it is on my list to do. The only hard part is through the small space under the bedroom floor to the foot of the bed. It is snug in there now but using the old cables to pull new ones with a liberal application of wire pulling lube and they should go through. I think one benefit to using the passthrough on a Multiplus omight be faster switching and more that the Victron Multiplus will back off charging and invert for a while to meet peak loads.

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #10 – November 25, 2017, 09:37:41 pm

Interesting discussion. Our coach has been modified from original factory equipment. First, I removed our generator/shore power ATS and replaced it with a manual switch. Second, when AM Solar installed our Magnum MS2812 inverter, they said the inverter's internal pass-thru relay could replace the coach's inverter ATS, so it was also removed. We have been operating without any ATS box for 2 years now, and everything seems to work fine. The inverter has never shut down for any reason while in pass-thru mode. I have never made any attempt to limit the AC load in this mode, because I was under the impression that the only restriction would be the 50 amp breaker at the power pole (or the breaker on the generator).

But now this discussion has me wondering if we are indeed limited to 30 amps of current draw when the inverter is in pass-thru mode. I looked up the page showing the inverter 30 amp circuit breaker in the Magnum MS Inverter owner's manual. The whole page is linked below in .pdf format. There are two paragraphs pertaining to the 30 amp circuit breaker, which I have copied below:

"AC Input Circuit Breaker (CB3) – this circuit breaker protects the unit's internal charger wiring and pass-thru relay while in Standby mode. The circuit breaker pops out when it opens—press in to reset. The input circuit breaker is not branch-rated, therefore branch-rated circuit breakers must be installed in the inverter's input wiring."

"CAUTION: The inverter's internal AC transfer relay is rated for 30 amps per leg. The pass-thru current must be no greater than 30 amps per leg or damage to the relays may occur."

So does that CAUTION note mean I can only pull a total of 30 amps through the inverter in pass-thru mode, OR can I pull a (theoretical) total of 60 amps (30 amps + 30 amps), in which case the power pole (or generator) 50 amp breaker would control the load? I'm not a electrician, so this stuff gets over my head pretty quickly.

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #11 – November 25, 2017, 09:45:36 pm

My Xantrex sw3012 has the terminals for 2 inputs and 2 outputs. maybe yours has the same. If so, from your literature you would need a 30 amp circuit breaker installed on each input leg.

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #12 – November 25, 2017, 09:50:29 pm

Roger, benefit of Victron pass through changeover from Gore Power is so fast, (per Am solar) electronic equip like my dish receiver would not reboot Since i am not using pass through I solve for this one devices issue by running it though the smallest Battey back up device I could find on Amazon I have old 211VIP dish box in coach. LONG reboot time if power interrupted for any time at all

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #13 – November 25, 2017, 09:52:32 pm

Thanks to Tim, I am doing the same thing.

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #14 – November 25, 2017, 10:00:52 pm

Quote from: Chuck & Jeannie – November 25, 2017, 09:37:41 pm

Interesting discussion. Our coach has been modified from original factory equipment. First, I removed our generator/shore power ATS and replaced it with a manual switch. Second, when AM Solar installed our Magnum MS2812 inverter, they said the inverter's internal pass-thru relay could replace the coach's inverter ATS, so it was also removed. We have been operating without any ATS box for 2 years now, and everything seems to work fine. The inverter has never shut down for any reason while in pass-thru mode. I have never made any attempt to limit the AC load in this mode, because I was under the impression that the only restriction would be the 50 amp breaker at the power pole (or the breaker on the generator).

But now this discussion has me wondering if we are indeed limited to 30 amps of current draw when the inverter is in pass-thru mode. I looked up the page showing the inverter 30 amp circuit breaker in the Magnum MS Inverter owner's manual. The whole page is linked below in .pdf format. There are two paragraphs pertaining to the 30 amp circuit breaker, which I have copied below:

"AC Input Circuit Breaker (CB3) – this circuit breaker protects the unit's internal charger wiring and pass-thru relay while in Standby mode. The circuit breaker pops out when it opens—press in to reset. The input circuit breaker is not branch-rated, therefore branch-rated circuit breakers must be installed in the inverter's input wiring."

"CAUTION: The inverter's internal AC transfer relay is rated for 30 amps per leg. The pass-thru current must be no greater than 30 amps per leg or damage to the relays may occur."

So does that CAUTION note mean I can only pull a total of 30 amps through the inverter in pass-thru mode, OR can I pull a (theoretical) total of 60 amps (30 amps + 30 amps), in which case the power pole (or generator) 50 amp breaker would control the load? I'm not a electrician, so this stuff gets over my head pretty quickly.

Believe the 30 amps per leg refers to two 30 amp circuits. Does not mean they can supply 60 amps. My inverter panel has a 50 amp input breaker and three 20 amp output breakers, so I can only supply 50 amps total before that breaker trips.
Check the wiring to the inverter/charger, doubt it is 50 amps. Pass through power is limited to whatever is supplied to the inverter from the main breaker panel. Power to my inverter from main panel is on a 30 amp breaker, so my max pass through can only be 30 amps. Yours may have been rewired, but the reason Foretravel installed the bypass ATS was because of the 30 amp limitation on the inverter relay.

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #15 – November 25, 2017, 10:08:46 pm

Quote from: jcus – November 25, 2017, 10:00:52 pm

Check the wiring to the inverter/charger, doubt it is 50 amps. Pass through power is limited to whatever is supplied to the inverter from the main breaker panel.

I just pulled up photos of my two AC panels installed by AM Solar. The main panel has a 50 amp breaker labeled "inverter". The inverter sub panel has a 50 amp breaker labeled "inverter".

Looking back over my notes from the installation session at AM Solar, I am sure they told me that the inverter was wired to pass through the full 50 amps that could be utilized by our coach. Nothing has happened since then to make me doubt this, at least until this discussion popped up on the Forum...

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #16 – November 25, 2017, 10:16:15 pm

Quote from: Chuck & Jeannie – November 25, 2017, 10:08:46 pm

I just pulled up photos of my two AC panels installed by AM Solar. The main panel has a 50 amp breaker labeled "inverter". The inverter sub panel has a 50 amp breaker labeled "inverter".

Looking back over my notes from the installation session at AM Solar, I am sure they told me that the inverter was wired to pass through the full 50 amps that could be utilized by our coach. Nothing has happened since then to make me doubt this, at least until this discussion popped up on the Forum...

Looks like they did run 50 amps to the inverter, could not have been a cheap install because new wiring had to been run from the main breaker box to the inverter. This is the proper way to do it. Most people use the original wiring which limits it to 20 or 30 amps through inverter bypass relay. Do not know if the Magnum will actually bypass a 60 amp load, I would call and ask them.

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #17 – November 25, 2017, 10:33:37 pm

Quote from: jcus – November 25, 2017, 10:16:15 pm

...could not have been a cheap install because new wiring had to been run from the main breaker box to the inverter.

It wasn't cheap. They relocated the inverter from under the entry stairs to the big center cargo bay, so it would be as close as possible to the batteries. They also ran all new cables between the inverter and the batteries and the breaker boxes.

I found another page in the owner's manual that shows wiring configurations (pdf file linked below) It shows a "60A Single In/Single Out" setup. I believe this is what was used on my coach. It allows 60A maximum inverter pass-thru.

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #18 – November 25, 2017, 10:38:04 pm

Quote from: Chuck & Jeannie – November 25, 2017, 10:33:37 pm

It wasn't cheap. They relocated the inverter from under the entry stairs to the big center cargo bay, so it would be as close as possible to the batteries. They also ran all new cables between the inverter and the batteries.

I found another page in the owner's manual that shows wiring configurations (pdf file linked below) It shows a "60A Single In/Single Out" setup. I believe this is what was used on my coach. It allows 60A maximum inverter pass-thru.

I have "inverter envy". Will try to copy your system when I redo mine.

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #19 – November 25, 2017, 11:17:53 pm

Tim, it is not usually an issue going from landline to inverter. That seems to be quick enough for my stuff. Generator to inverter is too slow. Not sure if the Victron can sense the generator slowing down in time. I used to have all of my sensitive stuff on an uninterruptible power supply, worked well. Now it is all on a subcircuit that is always on an inverter. No transfer switch issues anymore.

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #20 – November 25, 2017, 11:37:00 pm

This discussion has progressed to far more interesting areas than my original question - but to put the rest my personal scenario: Tonight because of forces beyond our control we'll have the generator running all night, 15-20 degrees outside on only generator-generated electric heat, and needed to know what I could use while it was still warm outside. So, I just decided to just load down the genny until either she or the inverter popped. The breaker on one leg of the generator popped, the 30 amp passthrough breaker on the inverter did not. Guess my 2nd ATS is functioning as expected!

And Tim better late to answer than never, sorry I didn't get to earlier: at the foot of the bed I have a 12V fuse box, the main breaker box with the A/C units etc, with one of those breakers dedicated to the second sub-panel with the inverter breakers.

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #21 – November 26, 2017, 12:38:36 am

Jim, FYI, Foretravel originally ran 120v/50-amp Romex (3-wire # 6) from main breaker to bay for Freedom 25 inverter/charger installation on our coach. With only one transfer switch, the inverter panel was switched by Freedom 25 with its internal relay. I figured it was 30 amps passed from main panel through Freedom (on #10 Romex) to inverter breaker panel, with the other 20 amps being available for battery charging.

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #22 – November 26, 2017, 10:04:11 am

Quote from: Barry & Cindy – November 26, 2017, 12:38:36 am

Jim, FYI, Foretravel originally ran 120v/50-amp Romex (3-wire # 6) from main breaker to bay for Freedom 25 inverter/charger installation on our coach. With only one transfer switch, the inverter panel was switched by Freedom 25 with its internal relay. I figured it was 30 amps passed from main panel through Freedom (on #10 Romex) to inverter breaker panel, with the other 20 amps being available for battery charging.

Thats a good setup. All my Foretravels have had #6 wire from main breaker box to inverter ats, and then 6 to the inverter sub panel. Unfortunately they ran 12 from main panel to inverter and 10 from inverter to inverter ats. This of course really limits your inverter pass through in you decide to get rid of the inverter ats. Your system and Chucks are what should be in all Foretravels.

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #23 – November 26, 2017, 03:51:46 pm

Quote from: Chuck & Jeannie – November 25, 2017, 10:08:46 pm

I just pulled up photos of my two AC panels installed by AM Solar. The main panel has a 50 amp breaker labeled "inverter". The inverter sub panel has a 50 amp breaker labeled "inverter".

Looking back over my notes from the installation session at AM Solar, I am sure they told me that the inverter was wired to pass through the full 50 amps that could be utilized by our coach. Nothing has happened since then to make me doubt this, at least until this discussion popped up on the Forum...

Chuck, noticed you put front ac on inverter panel, have you ever used the ac on inverter only?

Re: Question for Inverter Gurus: Passthrough vs. Direct Inverter Load

Reply #24 – November 26, 2017, 07:47:45 pm

If you have enough inverter capacity to run an AC for any length of time you also need battery capacity and alternator capacity to make it work in a balanced sort of way. And really big battery cables.

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