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Old 03-04-2006, 12:12 PM   #1
4 Rivet Member
Chuckles's Avatar
1983 31' Airstream310
Iwerne Minster , Dorset. UK
Join Date: Aug 2005
Posts: 274
115 volts on a 1982/3 310 MH

Hi All,
I wonder if any body can shed some light on the 115VAC wiring.

There is the box in the underneath compartment where the shore cable is attached - I take it that this box is an automatic switch that allows power from the site supply when connected, and cuts off the generator supply allowing the generator to power up the rear AC - or not!

I have traced the cables from the generator through a junction box under the wardrobe (very difficult to get at) to one heavier duty cable disappearing into the wall of the coach and another, shall we say the same weight as the remainder of the cables coming to a box under the bed. This box has what looks like a selection switch between Generator and shore power, which then sends power through a breaker and back through a normal cable weight into the wall of the coach.

I am assuming, correctly or otherwise, that the heavier cable is to the rear roof AC only.

There is a "plug" in the generator bay, that would by definition receive 115volts, that also went into the box under the bed. I was told by the PO that this is for an additional external power supply for the rear roof AC only. Is that correct?

In the rear RS corner of the bedroom, behind a small tambour door and directly above the shore cable input/selector box is another box with a ground test switch and two breakers. Do these breakers split the 115volts between front and back of the coach as there is no power from the bathroom back on any sockets, despite both breakers seemingly OK.

What I am trying to do is to substitute the generator supply (Generator died and removed) with power via a 3kw Inverter, but need to know what is going where. The wiring diagrams that I have is for an end bathroom and not the end island bed as we have.

Any light shed on this would be very much appreciated
Dorset UK
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Old 03-04-2006, 01:01 PM   #2
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1984 31' Airstream310
Dunsmuir , California
Join Date: May 2004
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Everything I say is based on my 1984 310 Limited with mid bath and rear twins.

Also I don't know how similar American and British house wiring is so forgive me if the stuff I am telling you is super basic There is a box in the compartment holding the shore power cable which is a transfer switch. It allows power from either the shore line or the generator to energize the circuit breakers found behind a tambour at the foot of the driver side door. The switch in that box with a red button in addition to a switch is a GFI breaker. It should have an on/off position as well as the button. I don't know which circuits are attached to which breakers and my manuals are in the MH which is 50 miles away at the moment.

On my rig, the only way power get to the rear AC is via the plug and outlet in the generator compartment. It is not possible to plug into shore power and run the rear AC. I have a switch in the gallery which will allow you to run the front AC or the Microwave. When the generator runs, it energizes the socket into which the rear AC is plugged and you can run the rear ac. Under the passenger side bed on the back sid of the generator compartment is a circuit breaker which serves only the rear AC.

I hope this information is useful. Good luck.
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1984 310 Limited Motorhome
Courtesy Parking (W/S/E/Wi-Fi) on I-5 in Northern California, 70 miles from Oregon border
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Old 03-04-2006, 02:01 PM   #3
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1983 31' Airstream310
Iwerne Minster , Dorset. UK
Join Date: Aug 2005
Posts: 274
Thanks Guy, for your speedy response.

It would appear from what you say, that I have something missing in the generator compartment that connects to the "plug"; that now makes more sense of that one.

So it would seem that ...yes; the cable from this "plug" does go to the selector switch under the bed, therefore the standard weight cable going into the coach wall must be going to the rear roof AC. I can do a continuity test with the AC shroud off and double check that, and also I will check tomorrow what size the cable is going to the twin breakers the other side. It would make sense if the thicker cable goes here to power the rest of the coach.

The energised switch on the shore power cord must have a purpose? On the other hand, maybe it closes a ring type circuit when not energised and power is from the generator. At this point in time, I cannot see a logical reason for it. (But then who am I to question such control…what do I know!)

I have the same selection switch in the galley so that's OK, and has worked well under generator power.

Once I have this all sussed, then the next stage is to install a transformer to reduce the 230 volt UK/European supply to 115volt to match the coach power requirements. I will get there, after the Solar panels go in, etc. etc. Will there be no end?

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Old 03-05-2006, 01:16 AM   #4
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1983 31' Airstream310
Iwerne Minster , Dorset. UK
Join Date: Aug 2005
Posts: 274
After several conversations, gathering information from the Forums and Guy99, and contemplating some “logical” thoughts on the wiring am I correct in assuming that…

The rear AC can be run on its own direct from shore power by setting the selector switch to “SHORE” as the 115VAC feed is returned back to the House breakers via the “Energise” relay where the shore cable is connected.

When the front, AC is required or other higher loads (Microwave etc.), then the Generator is run, and the rear Aircon is then powered by this, with the selector switch at “Generator”, therefore the power from the generator by-passes the coach 115VAC and only powers the AC via the "plug" in the generator bay, leaving the shore power to do the rest

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Old 03-08-2006, 05:36 AM   #5
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1983 31' Airstream310
Iwerne Minster , Dorset. UK
Join Date: Aug 2005
Posts: 274
Sussed it at last – silly thing really, its quite simple (when you know how!) I describe below what I found if it helps others, although to all of you it may be common knowledge.

The shore power goes into the energise/relay box in the compartment where the compressor and dump hoses are housed. (Shore power cable hard-wired directly into the box). That then sends power out to the main distribution box in the corner of the bedroom behind the little tambours, into the coach.

The power from the generator is split, with one heavy weight cable going back through the coach wall to the energise/relay box. The power from the generator energises the coil that disconnects the shore power side and sends power from the generator to the distribution box, then to the coach. (This includes the front AC/Microwave selector switch as with normal power)

The other part of the split (lighter weight cable) went to the change over switch for the rear roof AC under the bed. This incorporates a breaker and the change over switch between the “plug” in the generator bay and the generator itself.

So no way can the rear roof AC run off shore power, only generator OR the plug in power.

For your information in the UK Shore power refers to only boats. Caravans, motor homes and others have Electric Hook-up or EHU – Just a bit of silly something or other…

I know to most of you this has been teaching “grandmother–to-suck-eggs” time but for me the brain had to convert to the American idea that “every things cool-man”! or, should I say, to be cooled? Here we are lucky to have the windows open, not alone cool down what little heat we have…. Brrrrr! Still only 3-4 degrees out there!

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