Dual AC Switch broken

[dgapilot]

I have a 1987 Itasca Windcruiser (same as Elandan) and the shaft of the dual AC switch is broken off. The Winnebago part number is 073937-01-000. It's looks like a 4 pole double throw rotary switch that can support the 20 amp draw of the airconditioners. Has anyone found an inexpensive alternative to this switch? I'm thinking it may be less expensive to put an automatic 50 amp tranfer switch than replace the original switch.

[DaveVA78Chieftain]

Listed in Winnebago Accessories Catalog (page 91) as
A/C Selector Rotary: 073937-03-000
Knob:  073937-01-700

Have you tried to find out how much they are?  30A/50A transfer switches are not cheap either.  GIven that it is selecting between 2 power sources with 2 seperate outputs, it may not be the most straight forward situation

Forward selection:  Shore power to front AC, Gen Power to Rear AC

Rear Selection: Shore Power to rear AC, nothing to front AC.

Dave

[dgapilot]

The switch is a 4 pole double throw rotary switch capable of handling 20+ amps. I've seen them in electronics catelogs for about $250.00 so I'm guessing Winnebago pricing will be at least that. I can get a 50 amp auto transfer switch from ebay for about $100. I would also need a new 50 amp shore power chord, about another $100. From the shore power chord I would aslso need a braker box with a 30 amp breake for the leg going to the house power panel, and a 20 amp breaker going to the rear AC. (breakers are to protect the wiring) I don't have pricing for this yet. The down side is if I'm in a campground with only 30 amp service, I don't have the rear AC, and I need an adapter to go from the 50 amp plug to a 30 amp plug. I have seen adapters that go from the 50 to a 30 on one leg, and a 20 on the other leg, but I've also seen discussions on them not working with GFI boxes..

[DaveVA78Chieftain]

If you are going to go to that much trouble then go ahead and upgrade your AC/DC distribution panel.  The PD-5000 I used (http://www.classicwinnebagos.com/forum/index.php?topic=5326.0) could be used in either 30 amp or 50 amp configuration.  Many other brands work the same way.   That way would save you a whole lot of hassels.  A normal 50amp service provides two 120VAC legs; each leg is rated at 50amps.  Like a house, measuring L1 or L2 to nuetral is 120VAC and L1 to L2 is 240VAC so make sure it is wired correctly.  A 30 amp service only provides 3600 watts of power (120 x 30 = 3600).  Each leg of a 50 amp service provides 6000 watts of power (120 x 50 = 6000).  Both legs of a 50 amp service combined together provide a total of 12000 watts (120 x (50 x 2) = 12000).

Many compsites now install a 30 amp GFI breaker at the post.  There are 2 seperate ciruits in a GFI breaker:
1)  Circuit 1 compares the current flow in the nuetral leg to the high leg.  Current flow through L1 must = the current flow through nuetral or the GFI breaker at the campsite post will trip.  When you place a 50/30 amp adaptor on 1 leg (ie. L1) and then connect a seperate 20 amp patch cord supply to the L2 leg, the common nuetral leg sees the sum of the 2 legs.  Because that sum on the nuetral leg is greater than what the campsite 30 amp breaker see's on the L1 leg, it trips the GFI breaker.  Only way you could adapt it would be to completly isolate the L1/nuetral and L2/nuetral pairs completly from each other.
2) Then you also have to consider the ground path (most people do not know about this circuit).  A GFI breaker also produces a small 120Hz signal onto the high (ie L1)  and nuetral leads.  If the power switch is OFF and there is a short between nuetral to ground in the load then current will flow in the nuetral path resulting in the GFI breaker tripping (http://www.rhtubs.com/GFCI/GFCI.htm).  That is why you do not connect nuetral and ground legs together inside the RV (not even in the distribution panel).  Nuetral and ground can only be connected on input side of the campsite shorepower post CFI breaker or at the generator in the RV.  In wet conditions (raining outside) this nuetral to ground path current flow is most likely the culprit tripping a GFI breaker (does not require a load power switch to be in the ON position in order for the GFI breaker to trip). 

Dave

[dgapilot]

So Dave, did you set it up as a 50 amp system (L1 and L2) or did you leave it as 30 amps?

[DaveVA78Chieftain]

I stayed with the original 30 amp system.  I only have 1 AC so 30 amps is enough for me.  Also, trying to run new cabling past the shower enclosure would not have been fun.  My primary goal was the conversion to a 3 stage converter.  My next trick is to add a B.I.R.D isolator relay controller.

Dave

[dgapilot]

Looks like a good piece of equipment. Something to keep in mind for the future.