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Magnum Hybrid Inverter wiring

Prior to storage for the winter I had a company install a new Magnum 3012 Hybrid inverter. Since March of this year we have had ongoing problems with the system (Magnum solar charge controller, ARC remote, Magnum BMK). The 350 amp fuse between the battery and inverter keeps blowing. After a lengthy discussion with Magnum tech support they recommended that switching relay #2 be eliminated (relay under the bed). After reviewing the Foretravel Relay System wiring diagram and comparing to the Magnum instructions this makes sense. With the relay in place I do not see how the Hybrid inverter is able to function. I am scheduled to go back to the installer this Tuesday to have them eliminate switching relay 2.

A few questions:
1) Has anyone installed a Hybrid inverter and had to remove switching relay 2?
2) Magnum suggested changing the Battery Charger circuit breaker from 20 amp to 50 or 60 amp. In order to do this a larger wire would need to be run to the inverter in place of the 12 g wire. The inverter output wire should also be changed from 10 g to 6 g. It looks very difficult to pull these larger wires from the inverter to the main and sub panels under the bed. Has anyone done this? What if I ran conduit on the underside of the coach?

Help is appreciated as I am losing confidence in my installer.

Thank you,

Ed W
2003 U320 4010 - SOLD
2014 RAM 1500 Ecodiesel

Re: Magnum Hybrid Inverter wiring

Reply #1 –
Ed, I am looking at the specs for a Magnum MSH3012M 3000 Watt Hybrid Pure Sine Wave Inverter-Charger.

The max battery draw is 400 amps. A 400 amp time delay fuse is required with no less than 4/0 cables from the batteries to the inverter.  Your OEM wiring is most likely 3/0, undersized for this inverter. If the wire length exceeds 5 ft you should be using two 4/0 cables on both the + and - side.

The charger side uses 18 amps AC.  The maximum pass through is 60 amps.  You have a maximum of 50 amps possible on one leg of your 120 volt electric service so the circuit breaker ahould be at max 50 amps.  Wire size should be no less than #6 wire.  Both from the primary panel to the inverter/charger and back to the secondary panel. 

The OEM 120v cables are round twisted cales in a black sheath.  Once they are out there is some room.  You can get flat romex style #6 cable.  These cables run though a floor chase from the the TV cabinet in the corner to the bed box end.  (In my 2001 36'). It is a tight fit but with a fair amount of cable lube it should work. 

If you bypass the secondary transfer switch (landline or generator  on one side or the inverter on the other side) then the secondary panel is powered either by pass through or the inverter using the Magnum's internal transfer switch. 

You do not have to use the Magnum's transfer switch.  If you use it the way its is currently wired then you get up to 50 amps from the land line or whatever the inverter will put out.  Since this inverter is bigger than the OEM then you need to increase wire size from the inverter to the secondary panel (or the transfer switch)

If you are blowing the 350 amp fuse,  your battery voltage may be very low.  It takes a lot to blow a 350 amp fuse. 

Something is not right.

I think Don (Don and Tys) has one of these.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Magnum Hybrid Inverter wiring

Reply #2 –
What kind of load are you putting on the inverter when it blows the fuse?

How good are your house batteries and are the connections hospital clean?

Seems to me that assuming a reasonable load, the transfer switch in good condition and not trying to run the microwave while dropping shore power, aka hot switching, then I don't see the transfer switch having much to do with it.

Taking their advice would eliminate a lot of variables and let you take full advantage of your new gear
2003 U320 PBDS

Re: Magnum Hybrid Inverter wiring

Reply #3 –
Just to elaborate on what Roger posted, which I agree with.
The reason that Foretravel used two separate transfer switches is to allow 50 amps from the inverter power panel, even though the output of the inverter was only 30 amps.
Many other motorhome manufacturers keep the costs down by using one transfer switch for the genset/shore power while using the 30 amp switching built into your chosen inverter/charger. This limits the inverter power panel to 30 amps even if the power is passing through from shore or genset.
Wyatt
96 U320 40 WTFE, build 4943
84 Toyota Supra towd
2015 Jeep Wrangler towd
Victoria, BC, Canada

Re: Magnum Hybrid Inverter wiring

Reply #4 –
Thank you for the comments thus far. Since March 26 I have blown about 6 fuses. Two of them were 400 amp fuses because 350 amp fuses were not available. Although Magnum recommends a slow blow fuse, I have not found any 350 or 400 amp slow blow fuses.

There does not seem to be a good correlation of what causes the fuse to blow, it is definitely not circuit overload. The best commonality seems to be a few hours after I plug the shoreline in. I think something is internally wrong with the inverter, but Magnum said no. The inverter was removed from the coach and bench tested. Two weeks ago I disconnected the inverter output wires and Friday the fuse blew again. The fuse has also blown with output wires connected and the inverter off.  Magnum initially told me there must be a DC short or loose connection.

The 3 8D AGM batteries were new one year ago. All connections are clean and tight.
2003 U320 4010 - SOLD
2014 RAM 1500 Ecodiesel

Re: Magnum Hybrid Inverter wiring

Reply #5 –
A 400 amp fuse takes 5000 watts or so to overload.  If the inverter is off and the fuse blows then the only thing the Magnum could be doing is charging and its max output is 125 amps. Not going to blow a 400 amp fuse.  So that leaves lots of current going through the fuse to somewhere. No mater what something is seriously wrong.  The idea of a short circuit somewhere is very plausible.  Figure it out, this is a safety issue.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: Magnum Hybrid Inverter wiring

Reply #6 –
A couple of random thoughts... first, is it possible that the installer bonded the neutral to the ground at the inverter (a big no no!)? The inverter internally bonds the neutral and ground when it is not hooked up to shore power because the neutral and ground should only be bonded at the source, and when on shore power, that is at the pedestal... not at the inverter. Second, have you checked the diagnostics in the ARC-50 remote (it is under the technical menu item, if memory serves)? That may register the source of the fault, particularly if there is an internal problem in the inverter.
Don
The selected media item is not currently available.
Don & Tys
1999 U270 3602 WTFE #5402
Xtreme Stage 1 w/Headlight, Step Conversion, etc.
2009 Honda Fit Sport with Navi
Freedom is NOT "just another word for nothing left to lose"... with apologies to Kris Kristofferson

Re: Magnum Hybrid Inverter wiring

Reply #7 –
Don, I will check or have the installer check the ground. We have looked at the stored fault codes. They range from unknown to FET overload to dead battery (indicating to me the fuse has blown). The installer replaced the ARC in May, system seemed good for about 10 days and then went crazy again.

Have you eliminated switching relay 2?

Right now the system is shut down . I have the Battery Charger breaker in the main panel turned off and the inverter output wires are disconnected. I am using a car charger set at 2 amp to keep the house batteries up a bit. My voltage is running about 12.5.

I do hope to get this figured out tomorrow as we are planning to move from Michigan/Indiana to Colorado at the end of the week.

I will show these comments to the installer tomorrow. I also will send another email to Magnum.

Thank you all for your continued input.
2003 U320 4010 - SOLD
2014 RAM 1500 Ecodiesel

Re: Magnum Hybrid Inverter wiring

Reply #8 –
Problem is hopefully fixed. Installer found a bad FET board on the inverter. The 3 diodes on the back we're visibly destroyed. New board installed.

I did not change the wiring. Leave that after we have confirmation the rest of the system is working.

Thank you for your help.
2003 U320 4010 - SOLD
2014 RAM 1500 Ecodiesel

Re: Magnum Hybrid Inverter wiring

Reply #9 –
Ed, I hope that does the trick. I have to wonder made the FET board fry.  It is not something you are going to be able to fix on the fly.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN
 

Re: Magnum Hybrid Inverter wiring

Reply #10 –
The picture below shows what happened to my first Magnum MSH-3012M. Here is a thread on that event;
Up in smoke! (not the Cheech and Chong movie)
I found  some stored error messages on the ARC remote when I was setting up the replacement MSH-3012M that said FET temperatures were high, I think it was registering around 190ยบ and the time shown indicated it was the last gasp of that inverter. In case you don't want to read through that thread, that first MSH-3012M was extremely noisy when charging, no matter the rate. I was very disappointed to say the least! But since I had bought it almost a year before I got around to installing it, returning was not an option and the inverter was otherwise functioning. The replacement Magnum sent me, a remanufactured unit, has been as I had hoped the first one would be... dead quiet and so far has proven flawless after about a year of use. I hope yours behaves now.
Don
Quote from: Ed W –
Problem is hopefully fixed. Installer found a bad FET board on the inverter. The 3 diodes on the back we're visibly destroyed. New board installed.

I did not change the wiring. Leave that after we have confirmation the rest of the system is working.

Thank you for your help.
The selected media item is not currently available.
Don & Tys
1999 U270 3602 WTFE #5402
Xtreme Stage 1 w/Headlight, Step Conversion, etc.
2009 Honda Fit Sport with Navi
Freedom is NOT "just another word for nothing left to lose"... with apologies to Kris Kristofferson