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Old 12-02-2011, 06:39 PM   #1
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Why no 50 amp service?

I don't understand why AS put a 7kw generator in my 92 36' LY and only gave it 30 amp service. It's wired to only run one of the air conditioners at a time but the genset has power to spare. Just makes no sense. Any ideas as to how to get full 50amp service?
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Old 12-02-2011, 07:46 PM   #2
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If you ever figure out how to do it, there are a ton of us out here that will worship at your feet. You might find a electrician that would be willing to get you a extra 20 amp cord for the rear roof. My problem was, my electrician said I'd have to dismantle the curbside vanity and closet to get to the wiring, and then figure a way to route the new cable. With my coach, I could understand the 30 amp deal, but, geeez, in '92 50 amp was available and is now standard at most decent parks. It was a stupid mistake on the part of AS from day one with our coaches; we should have had dual plugs so as to run that rear roof air.
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Old 12-02-2011, 08:25 PM   #3
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My '87 MH had the same setup...I'm gussin it a carryover from the days before 50A service
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Old 12-02-2011, 09:54 PM   #4
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I've done several coach conversions and one travel trailer upgrade from 30 amp to 50 amp. None were Airstreams, but the procedure would be identical.

It will involve extensive re-wiring of the coach, new transfer switch, breaker box, breakers and shore cord. Lots of new wires to run and lots of time needed to do the job correctly. Also, all involved replacing both the inverter and converter with a single inverter/charger unit.

I don't have any schematics, as all of the coaches were different in their original wiring approach. Hope you like to pull wire!!! PM me or e-mail for more discussion.

Thanks!
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Old 12-02-2011, 10:52 PM   #5
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My '87 MH had the same setup...I'm gussin it a carryover from the days before 50A service
They kept carrying long after my 2000 unit, but made it a $700 option for 50 amps, even tho they used a 50 amp genset.
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Old 12-03-2011, 10:51 PM   #6
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I have a 1994 LY Diesel pusher with 50 AMP service, I believe you had to order the washer/dryer combo to get 50 AMP service in 1995?, don't know about 1994.
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Old 12-11-2011, 01:06 PM   #7
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Well I'm not an electrician but would it be that hard? I have a 2005 LY 30. The power comes in thru the trunk and under thr bed to the breaker. Why couldn't I add another 30 amp cord coming in the trunk to a breaker there and then run along the road side to the genset just in front of the duals. You could run the wire under the floor. If I disconnect the wires that run from the genset to the rear a/c and connect up the new 30 amp wiring, wouldn't that work. Sure I could not then run rhe rear a/c from the genset but that's ok with us. As far as the genset knows, nobody ever turns on the rear a/c unit so it never has to supply power to it.

Sounds too simple. Maybe an electrician could explain why it wouldn't work.

Why would the 12 volt system need to be involved? I am assuming that the fan in the a/c unit is 110/120.
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Old 12-11-2011, 01:37 PM   #8
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In theory, adding additional circuits seems like it would be an easy job. Just add circuits to the existing box, beef up the transfer switches…
Seems to me like the hardest part is to fish the new wires. From what I can tell, they didn't provide any conduits to fish wires through. Just bundles of wires tie wrapped to frame members. Any additional circuits would require disassembly of the ceiling panles or runs under the floor of the unit. Please correct me if I'm wrong.

Anyone know where the transfer switches are on a 92 36' LY?
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Old 12-11-2011, 04:31 PM   #9
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Originally Posted by 92landyacht View Post
In theory, adding additional circuits seems like it would be an easy job. Just add circuits to the existing box, beef up the transfer switches…
Seems to me like the hardest part is to fish the new wires. From what I can tell, they didn't provide any conduits to fish wires through. Just bundles of wires tie wrapped to frame members. Any additional circuits would require disassembly of the ceiling panles or runs under the floor of the unit. Please correct me if I'm wrong.

Anyone know where the transfer switches are on a 92 36' LY?
Unfortunately, you don't just 'add a few circuits' and 'beef up the transfer switch'. To do it right (which is the ONLY WAY), you need to replace the 30 amp transfer switch with a 50 amp version, replace your 30 amp 10/3AWG shore cord with a 50 amp 6/4 AWG unit, replace your 30 amp single line circuit breaker box with a 50 amp dual line breaker box and then add the extra circuits (like your #2 roof A/C) and split and balance the circuits so the load is even across both incoming legs in the breaker box.

Sounds simple, doesn't it?

Then you need to be sure that your generator has the capability to be re-wired for dual 120VAC circuits and run the 6/4 AWG wire from the genny to the new transfer switch.

Still with me?

If you're not completely familiar with 120VAC and 240VAC wiring, this is NOT a DIY job.
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Old 12-11-2011, 05:34 PM   #10
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Not being an owner of a MH (bus). My first question would be. Do you have a 50 amp shore power cable? Or is it 30 amp as well? The next question is: What size are the air conditioners? A 7KW generator is good for about 48 amps of continuous load. Is the bus wired for 120 volt or 240 volt? Again not familiar with a bus. An experienced electrician can determine which it is. The electrician can also determine what the load (current draw) of the bus is when you are plugged into shore power and both air conditioners are running along with other items that are in regular use in the bus.
If you are able to run both air conditioners on shore power and you wanted to put up with not having an auto transfer setup. It may be possible to wire the generator to a receptacle that you would plug the shore power cable into. There would be no auto transfer, chances are this function would be removed in the rewire process.
But again you would need to have an experienced (RV savvy) electrician to determine if the generator has the capacity and is wired for the same voltage as the bus.
I don't know where the shore power cable location is relative to the generator, it may not be practical. If the locations work out, there would be a requirement of a properly sized circuit breaker in order to allow the generator to get up to speed and warm up prior to putting power to the bus.
Is the fuel source for the generator the same as for the bus engine? 'cuz that baby is going to consume some fuel with 2 air conditioners running.
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Old 12-11-2011, 06:49 PM   #11
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I'm thinking there is some way (since my gen set will run both roof airs) that there might be a way (without ripping half the coach apart) to install a transfer switch that would enable me to run the the rear air on a seperate 20 amp circuit that would be plugged in to shore power along with our normal 30 amps. That would entail another cable, but, geez, what's the option?
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Old 12-11-2011, 09:11 PM   #12
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I had had a '94 LY diesel pusher that came with 30 amp shore power. I had a friend redesign the schematic using the 2 existing ATS switches to work on 50 amp. Prior to finalizing the design, he checked with CSA to make sure that the changes would comply. The interesting thing is that you don't need the massive cable used for 50-amp, because you are still using 30-amps, but at 240 volts. The wire gauge is unchanged. While I sold this motorhome, I still have a copy of the revised schematic and will email it. Just message me through this forum with your email address.

As an addenda, with the 6.5kW genset, the house main panel did not need replacing or modifying. The sole modification was to rewire the 2 ATS switches to function as a single one. The original circuit had the neutral being switched - this was not necessary (as per CSA) so the existing relays were sufficient. The shore cable needed to be replaced from 3-wire to 4-wire, but the same gauge.
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Old 12-11-2011, 09:23 PM   #13
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I still think the major issue is in doing the cable runs. Replacing breaker boxes and transfer switches are easy. It's simply a matter of disconnecting and reconnecting the connections to new components and maybe modifying the openings for the additional components. Replacing the main shore cable is a given. Adding the new wires, IMHO, is still the biggest issue. This is coming from 20+ years experience in doing industrial wiring as a controls engineer. I figure, if I can do a new production plant with 480V 3-phase, I can do a simple 120/240 single-phase design. The genset that comes in a 92 LY is a 7KW unit. For AS to install a 30amp system simply makes no sense since the genset can easily pull 48amps continuous. I just wish AS had made it easier to add additional wires without having to resort to running them under the unit or disassembling the ceiling.
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Old 12-11-2011, 09:44 PM   #14
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Search through the Classic Motorhome section. Someone has a detailed write-up of how to run the 2nd A/C unit while still having only a 30amp hook-up. Basically, it involves disconnecting the 2nd A/C (usually the rear) from the existing wiring, and running a separate power cord just for the 2nd A/C. It's fairly simple, by the way I read it, just have never needed 2 A/C's just yet to know if I'll make the attempt. If I can find the thread, I'll post the link here next.
Thanks, Derek
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Old 12-11-2011, 09:57 PM   #15
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It is not uncommon that the AirStream factory had an overstock of 30 AMP wiring harnesses. You know, the more you buy can help to keep overall costs down. They just got caught in an flip of the switch to 50 AMP service, and could not absorb losing what was already in stock.
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Old 12-12-2011, 09:46 AM   #16
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I still think the major issue is in doing the cable runs. Replacing breaker boxes and transfer switches are easy. It's simply a matter of disconnecting and reconnecting the connections to new components and maybe modifying the openings for the additional components. Replacing the main shore cable is a given. Adding the new wires, IMHO, is still the biggest issue. This is coming from 20+ years experience in doing industrial wiring as a controls engineer. I figure, if I can do a new production plant with 480V 3-phase, I can do a simple 120/240 single-phase design. The genset that comes in a 92 LY is a 7KW unit. For AS to install a 30amp system simply makes no sense since the genset can easily pull 48amps continuous. I just wish AS had made it easier to add additional wires without having to resort to running them under the unit or disassembling the ceiling.
As I mentioned before, *if* your main breaker box is wired for 240-volts (i.e., the 2 x 120-volts output from the genset), then the only modification is to redo the ATS switches. I have offered to email the schematic which we used to anyone who PM's me.

In my case, the only cost was the new shore cable and plug (I did have a faulty time-delay relay which I was able to source and replace for $10).

Granted, not all AS motor homes are wired alike, but the schematic, which really is a redesign of the ATS switches from 2 30-amp ones into a single 50-amp one using all the existing components without the need for any additional ones, can be used as a starting point. For someone who has either an electrical engineering background or certified electrician, it should provide a starting point.

If, on the other hand, the shore power, main breaker box and genset are all 30-amp 120-volt, then running additional wiring would be required, and that can be a major undertaking.
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Old 12-12-2011, 11:12 AM   #17
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just have never needed 2 A/C's just yet to know if I'll make the attempt. If I can find the thread, I'll post the link here next.
Thanks, Derek
Would be appreciated, down here in the deep desert, come April, we could use THREE roof airs!
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Old 12-12-2011, 05:47 PM   #18
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Well crazeevw that is what I was thinking in my previous post. The second 30 amp cable is fairly inexpensive and could be hooked up to the 50 amp connection on the post with a 30 to 50 amp pigtail. (you could use one of your extra 30 amp extension cords.) You wouldn't need to have both a/c running unless it was 95 in the shade. And how often are you really hooked up to the genny anyway.

In my previous post, I questioned the 12v requirement but now know that the fan runs on 12v. If my approach to this is valid (still in doubt) then you wouldn't need to fish new wires thru the ceiling to the a/c.

So why won't it work?
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Old 12-12-2011, 09:32 PM   #19
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This may be the link crazeevw was looking for. It is a fairly simple procedure to wire in a separate plug for the second air.
RV.Net Open Roads Forum: How to run two AC's with 30 Amp Service UPDATE UPDATE
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Old 12-13-2011, 07:27 AM   #20
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When we purchased our LY we knew nothing about 30 amp/50 amp service & running the ACs. Our first night in the LY was in hot, humid Florida. When the bedroom air wouldn't start we called the dealership & asked what the trick to turning it on was. We were asked if the front air was running..."yes, it's the bedroom AC that won't start." (We had been shown during the 10 minute walk-thru that it worked.) We were then given this sequence to running both ACs. 1) start the front AC, run on high, get things cooled down. 2) Turn front AC down to low setting. 3) Turn back AC on low. 4) Chill.
This seemed to work. Both Acs were running. Then at some point the front AC turned off. By this time we were sleeping & cooled off... Sometimes ignorance is bliss...just hope this wasn't potentially harmful to the electrical system. We have very few times when 2 AC's are needed. But, I always thought we could use this start-up sequence if needed. Maybe not such a good idea.
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