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Author Topic: MC5B upgrade to 50A service advice needed  (Read 368 times)
Astro
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« on: November 08, 2017, 01:55:56 PM »

I have a MC5B conversion (c. 1995) with shore power fed by twin 30A inputs.  One main and one aux. The main feeds from shore through inverter (25 yo Heart Interface 2800 12v with a bad charger) then to the circuit panel with eight branch ciruits. Aux input, when used feeds directly to service panel. There is a switch on the service panel that switches between all branches fed from main through inverter or when switched to aux, four feed directly from aux input. It works to give me a bit more power options when two 30A feeds area available, but requires two cords and two outlets. Kind of a pain, but does allow for a bit more power on occasion.

I have a new Magnum MS4024 I plan to install sometime later and switch over to 24V, but first I want to sort out my power input options.  I plan to use the bus this winter in the Pacific northwest and need more power for heat and such.  Where I am parked I have a 30A/50A outlet 50 feet away fed by 6 awg wire. I could move it 25 feet closer, but would need to change wire feed to 4 awg (~$1000 option).  If I keep it where it is, I would have to use a 50 foot extension cord plugged into the current outlet whether it is 30A or 50A.

My questions so far are:

1.   Is it worth it or safer to rewire and move outlet closer or should I stick with a extension cord for 50A and save the $1000?
2.   What AC feed wiring changes should I consider on bus now to increase my power and be ready to work when I swap the Inverters?
a.   Note: I know I need to reconfigure house batteries to 24V and install a vanner to pull 12v.
3.   What other issues should I be considering? I currently do not have an onboard generator. I have a small portable one that I have never used. I would like to add one later though.
Your advise is appreaciated.
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Ken
Arlington, WA
1971 MC-5B, U7017, S9226 (On the road)
1945 Flxible Clipper (Stripped and in the shop for conversion)
1945 Flxible Clipper town buggy
richard5933
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« Reply #1 on: November 08, 2017, 02:32:08 PM »

When I switched my 4106 to 50-amp service, I changed out the input receptacle as well as the wiring between the receptacle and the load center. If you are currently fed by two 30-amp feeds, than I'd work under the assumption that the wiring in your bus is rated for only 30 amps until it was verified to be rated for more.

Once you do get the bus set up for 50- service, I'd vote for just running an extension cord to the pedestal.

Can you post a few photos of your current panel set up to help us better understand what you're working with?
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Richard
1974 GMC P8M4108a-125 (Current Bus)
1964 GM PD4106-2412
Located in beautiful Wisconsin
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brmax
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« Reply #2 on: November 08, 2017, 03:14:49 PM »

Are you saying the post is fed by 6 something and your extension cords are ? X2 sometimes

Its late, or the days done anyway
Floyd
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Allison
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« Reply #3 on: November 08, 2017, 05:52:26 PM »

50 anp power cord should be fine and if you are concerned about the long run you can change the beaker at the panel to a 40 amp beaker ( 80 amps total ) but yes make sure your coach is set up for 50 amps before you go any further . 80 amps should be lots of power

dave
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dave , karen
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Astro
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« Reply #4 on: November 08, 2017, 09:28:46 PM »

Yea, bottom line is I need more amps. If I have to use an extension cord, I want only one and it should be 50A. Its probably not worth ~$1000 to get 25 feet closer with 4awg, although if I take Dave’s suggestion and reduce supply to 40A (or even 30A to begin with as my Heart is rated for 30A), I could probably still extend the current 6 awg at pedestal another 25 feet for much, much cheaper and then only need a short 25 ft 50 amp extension cord.

As for the bus, it looks like the PO wired the input to inverter and circuit panel with standard 30A rv extension cord.  My Magnum AC input takes a max 6 awg wire so I can replace the current input wires with new 6 awg easy enough.

I am not sure my current power supply routing is sufficient to keep same. It seems like I should bring new 50A through a new inlet receptacle to a switch first. Then, can I rewire as it is now with one leg direct to panel and one leg direct to Inverter then to panel or change it more like my Magnum manual shows with input to a main panel, then to magnum then to sub panel?

I included pics of my shore power inputs and the circuit panel.

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Ken
Arlington, WA
1971 MC-5B, U7017, S9226 (On the road)
1945 Flxible Clipper (Stripped and in the shop for conversion)
1945 Flxible Clipper town buggy
bevans6
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« Reply #5 on: November 09, 2017, 04:31:05 AM »

The Magnum is a 120 volt unit while the full use of the 50 amp service is 240 volt split phase down to two 120 volts.  What I would do is have two panels.  I would have one panel with 240 volt service and balance the high current loads that you wouldn't run from an inverter anyway, like AC units, electric heaters, electric hot water.  Without knowing your load profile it's hard to get specific, but that will allow you to use both legs of the 50 amp to best benefit.  I would power the Magnum from one leg of the 50 amp 240 volt panel through a normal 120 volt breaker, and run the output of the Magnum to a small 120 volt breaker panel.  I would run loads specific to the inverter from that panel (if any are high current add them to the overall load balance in the first 240 volt panel).  I built my system essentially the same way - main panel direct from post with high current, non-inverter loads, inverter fed from that panel, second small panel for inverter loads.  Since I do have a generator I front-end that system with an automatic transfer switch that switches between pole power and generator power, and the inverter (Magnum 4024) has a built in transfer switch that switches between external power (in my case either pole or generator) and battery power.  All quite automatic and seamless, I don't need to think about it.

In terms of extending your pole vs extension cord, I guess I would probably extend the pole wiring if this was going to be a long term solution (say 4 - 5 years) and use an extension cord if this was going to be a one-winter deal.  Draping a cord over 50 feet of ground permanently and just hoping that no one drives a lawnmower over it, or otherwise disturbs or damages it isn't really the way I roll.  But there are lots of ways to protect a cord on a semi-permanent basis that can be somewhat easy and make sense.  As far as the bus wiring is concerned I would upgrade to a 50 amp 240 volt Marinco and change the internal wiring to 6 gauge to the first panel.  Remember to float neutral in the panels.

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
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