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Old 04-30-2014, 10:28 AM   #1
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Autoformer / Surge Protection Order

Hey All,

I know there is a old thread on the Class 'A' forum, but I wanted to start one here for the visibility of us 30 AMP folks.

I have a 30 Amp Hughes Autoformer. I do *not* have a automatic transfer switch. I used the install kit that you can buy separately so that I have this:

Coach -> 5' Autoformer Cord from install kit -> Autoformer -> Original Coach power cord (with plug from the Autoformer install kit attached to the formerly naked end) -> pedestal. Just as Hughes recommends.

What I WANT to do is assure that a surge doesn't fry the Autoformer and the Coach. The Autoformer has some nice voltage regulation but its surge rating is not particularly good. Plus for the cost of it, I don't want the Autoformer performing surge duty anyway.

My thoughts were to put a SurgeGuard 34730 30 Amp in between the Pedestal and Autoformer. So essentially I'd have this:

Coach -> 5' Autoformer Cord from install kit -> Autoformer -> SurgeGuard 34730 -> Original Coach power cord (with plug from the Autoformer install kit attached to the formerly naked end) -> pedestal.

This gives me a few things:
A. Both Autoformer and Surgeguard can sit in the electrical compartment away from the elements and hopefully thieves
B. I protect everything I care about in the Coach including the Autoformer
C. The SurgeGuard cuts power between 102v and 132v. Why would I want the power cut if I have a Autoformer? The Hughes Autoformer is only going to bump my volts by 10% max. If my park volt levels are that low to begin with, at 103 volts my Hughes is only going to get me up to a little over 113 volts anyway. Super low voltage is not going to be addressed by my Autoformer, so I might as well have the system cut off until it can be managed again.

So - am I missing something here?

2015 Jayco Greyhawk 29MV
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Old 05-01-2014, 11:55 AM   #2
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IF your concern is surges (SUSTAIN HIGH VOLTAGES)

Park--Surge Guard--Autoformer---RV

However the more common problem is LOW voltages.

Park---Autoformer----Surge Guard---RV...

LOGIC: First, the auto former can take some LMITED over voltage, (Though I think pulging into 240 volt welder outlet may fry it). But it will correct low voltage so your low voltage protection with the surge guard will be 100A% operative and will not shut you down when the autoformer is working properly and effetively.

On the other hand... IF you plug into a welder outlet.... Well, meter before you connect and that way you can avoid that problem.

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Old 05-01-2014, 12:24 PM   #3
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Is it safe to run the coach on 113 CORRECTED volts? I thought anything under 115 was generally considered bad. That's why I though the SurgeGuard first would be okay. ???
2015 Jayco Greyhawk 29MV
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Old 05-02-2014, 02:26 PM   #4
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No... it sounds like you've thought it through pretty well. I currently have my RV setup the way wa8yxm does (Park---Autoformer---Surge Guard---RV) based on the same logic: that the Autoformer will provide some over voltage protection, while ensuring that it gets to boost the low voltage before the Surge Guard would cut me off. I'm pretty sure the Autoformer will also cut out it's operation at some low voltage level... which would then pass through the low voltage for the Surge Guard to cut it off. But I don't know the numbers where that happens off hand.

As an aside, I just saw today that there's a giveaway for a Hughes Autoformer... so anyone in the market for one may want to enter! You can check it out here:

Protect Your RV From Low Voltage with a Hughes Autoformer
2005 Newmar MADP
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