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Old 07-16-2011, 09:15 PM   #15
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Quote:
Originally Posted by CrawfordGene
...My converter is under the bed, too far and complicated to run a telephone line anywhere that far away to the battery disconnect area. Aren't the 120 v. wires connected directly to the unit? ...Gene
For me, there was space behind the converter/breaker box in the galley area and with my floor plan the battery disco switch is adjacent to the entry door so that was the logical location for me and I had to drill one small inconspicuous hole for the display cable. Do you have an accessible area where the 30A power enters the coach? The Surgeguard can go anywhere in the line between the breakers and the point where the 30A line enters. I think the cable for the display panel was about 50' long. I would choose a location for the unit so that it could be accessible for service if needed.

Here's a snapshot of the 50A model, the wiring is the same except the 30A uses one less wire.
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Old 07-16-2011, 09:21 PM   #16
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Originally Posted by davidz71
...Mine is mounted 4 ft. from the junction box where the 30 amp cord enters the trailer. This is underneath my streetside rear corner bed. The box was placed inside a small plastic crate similar to a milk crate but considerably smaller. This was to prevent it from tipping over and to allow ventilation on all sides if needed. The box stays cool so I guess ventilation wasn't an issue. I have never heard the box hum so it isn't an issue either...
Thanks for the additional info. That makes it more interesting.
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Old 07-16-2011, 09:42 PM   #17
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We went to CW this afternoon and purchased a 30 amp Surge Guard (model 34730). This is the plug-in unit not the hardwired unit. Glad we now have some protection from "sketchy" CG power posts. Thanks for all of the quick responses to my question, I feel much better about spending a relatively small amount of money to protect our AS.
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Old 07-16-2011, 11:17 PM   #18
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Yankee, thanks for posting the instructions. Not enough bandwidth to get to see them here, so I'll have to wait until we get home tomorrow.

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Old 07-17-2011, 08:19 PM   #19
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I came home and the box with the surge protector was here. This model is different than the one Yankee' described. It is one piece—no separate monitor. Wires connect at the top and bottom and they are not inside much protection against shocks. You have to strip back the outer insulation on the 120 v. wires to get the 3 wires (4 for 240 v.) into the clamps. I haven't looked on the box to see what organization approved this, but it certainly wouldn't pass most codes.

I could mount it below the bed or maybe on a nearby wall and using a lot of tape, make it safe. I want it somewhere where I can see the lights on it so I can tell what is happening, so it has to be easy to see.

I don't know of any other brand for RV's and don't want to go through the hassle of returning it, so I guess I'll figure out something. If I had known how it is designed, I would have looked harder for alternatives.

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Old 07-17-2011, 08:48 PM   #20
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Quote:
Originally Posted by CrawfordGene View Post
Sailer', I never heard of this device, but the formula for volts, amps and watts is to be respected. You say it only operates when needed, but what is the effect on amps and watts?

If you boost volts by 10%, you will probably have fewer watts and amps—10% less. On a 20 amp circuit that would be instead of 2,400 watts, you have 2,160—and that is if you have 120 v. Or 18 amps. An A/C likes to have all those watts and amps whenever the compressor starts, so I would be careful of just how this thing works. Total load on the system would be similarly affected. Instead of a 30 amp total capacity (again, if you have 120 v.), you would have 27 and a microwave + a toaster + lights + TV might be affected. Or, if the campground only has 90 volts, the most you can get is 99 volts, not enough for appliances and especially for electronics. I think it may be safer to have a shut off system for shore power and just use batteries and propane.

I admit to being skeptical and may be getting the formula wrong. We will probably see posts by those who know more soon enough.

Gene
THe Hughes Autoformer, and competing devices that operate on the same principle, are automatic buck-boost autotransformers. For the 30a units, electrically, they consist of a transformer with a 115 volt primary and a low-voltage secondary (Probably 18 or 24 volts, I've never had one apart) with several taps (probably every 6 volts). If the campground voltage is low the secondary windings are used to boost the voltage. So for example to get 12 more volts the 12 volt tap on the secondary would be used. If the campground voltage is high the phase of the secondary is reversed to lower the voltage. The tap selection is controlled electronically.

50a units are similar but have additional components to be able to work on both 120v legs.

The current draw of the primary winding of the transformer adds to the overall draw from the campground pedestal. So for example if the unit is providing an 18 volt boost at 20 amps to the trailer it will draw 23 amps from the campground ( (1+18/120) * 20).

The autoformers also have MOV (metal oxide varistor) surge protectors which provide some protection against voltage spikes. Spikes in the range they can protect against are rare in modern campgrounds because modern campgrounds use underground wiring that isn't as suspectible to large spikes from lightning as overhead wires used in the past.
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Old 07-17-2011, 08:52 PM   #21
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Originally Posted by YankeeDoodle View Post
How much heat does this transformer produce? Do you think it could be hardwired and mounted inside the trailer? Does it make any appreciable noise, hum? I've only seen them advertised as a portable unit that you sit outside. Never considered if it was just for convenience for the average user, or maybe they get too warm to put in a confined area.
The units do produce a small amount of AC hum though far less than the air conditioner or other noisy appliances.

The heat output is proportional to the current draw and the amount of boost. So, if the campground voltage is at the low end of what the autoformer can correct for, and the current draw is close to the maximum rating, you'll get the most heat. For a 30a unit I would guess you'd get around the same amount of heat as a 25w or 50w incandescent light bulb, twice that or more for a 50a unit.
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Old 07-17-2011, 08:54 PM   #22
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Originally Posted by YankeeDoodle View Post
The Surgeguard can go anywhere in the line between the breakers and the point where the 30A line enters.
The surgegard units are just a set of MOVs. I don't believe they provide any benefit, because any sensitive electronics you might have already have MOVs, and because any spike large enough to damage the air conditioners or the fridge is going to be more than the MOVs can handle.
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Old 07-17-2011, 09:00 PM   #23
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Wow!
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Old 09-06-2011, 08:45 PM   #24
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Quote:
Originally Posted by Scott J-24 View Post
We went to CW this afternoon and purchased a 30 amp Surge Guard (model 34730). This is the plug-in unit not the hardwired unit. Glad we now have some protection from "sketchy" CG power posts. Thanks for all of the quick responses to my question, I feel much better about spending a relatively small amount of money to protect our AS.
I found this thread while researching Surge protectors.

I just ordered this one also. I ordered from Amazon because of free shipping and I had a credit sitting there burning a hole in my pocket.

I was attracted by the high and low voltage shut off.

This is investment to protect the Airstream, however it is an investment of its own. To protect that investment, I also ordered the TRC 34590 Surge Guard Lock Hasp. Now to protect that device, I will add a chain through the padlock and around the power pedestal. Now how do I protect the whole shebang from bolt cutters and hack saws?

Ken
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Old 09-06-2011, 09:21 PM   #25
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These are a very good idea, as our experience shows: Last week we had an electrical storm over Angel Fire, and two RVs took direct hits. One of them lost both TVs; the other lost control units for ACs and slides. (We took it in the house through the phone line, the one and only unprotected part of the house, wouldn't you know it. It took out our DSL modem.)


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Old 09-06-2011, 10:39 PM   #26
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According to the patent issued to Mr Hughes:
"[ln ] a voltage booster device for increasing the voltage level of power received by a recreational vehicle... an autotransformer.. is adapted to increase the actual voltage level of the separate 120-volt power source a predetermined amount.

A relay is provided for switching the ...outlet between ...the transformer so that the transformer increases the voltage level by the predetermined amount, and (ii) a second circuit configuration that bypasses the transformer so that the transformer does not increase the voltage level by the predetermined amount.

A control circuit controls the relay so that (i) the relay switches to the first circuit configuration when the actual voltage of the separate 120-volt power source falls below a predetermined first threshold level, and (ii) the relay switches to the second circuit configuration when the actual voltage rises above a predetermined second threshold level."

The fundamental operation of a transformer requires that the volts x amps at the input must equal the volts x amps at the output. The transformer only operates on alternating current.

For example if the output called for 15 amps at 120 volts and the input was 108 volts then: the input current x 108 = 15 x 120

Input current must equal 16.67 amps to get the 15 amps out at the higher voltage.

The patent also shows some devices in the circuit to supress surges coming in on the shore power.


I have a surge protector that I use between the RV cable and the power post because I lost my power converter when there was a lightning strike nearby that put a surge on the incoming power cable. I learned the hard way that my OEM converter had no surge protection and it was easier to replace surge protectors than power converters. Since I was only charging the battery at the time, no other appliances were on and they all survived.
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Old 09-07-2011, 07:17 AM   #27
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Quote:
Originally Posted by eubank View Post
These are a very good idea, as our experience shows: Last week we had an electrical storm over Angel Fire, and two RVs took direct hits. One of them lost both TVs; the other lost control units for ACs and slides. (We took it in the house through the phone line, the one and only unprotected part of the house, wouldn't you know it. It took out our DSL modem.)


Lynn
Here's my issue with surge protectors: The Camping World President's Club magazine had a letter to the editor like this a couple years ago, talking about how several other people in the campground lost various other appliances, while they didn't lose anything but the surge protector that saved them.

Sounds great, except the surge protector CAUGHT ON FIRE inside their camper. I would MUCH rather replace a fridge and microwave or whatever than have a fire in the trailer. They were holding it up like some kind of victory; I was scared at the thought of a fire breaking out in my camper, especially if I wasn't there and my cat was.

I can't believe I found this link... on the very first try! Read for yourself: June 2008 RV View, page 8

My recommendation - if you use one, keep it away from the camper. Make sure they can be exposed to the elements, though. I'm not generally against surge protectors, mind you...I think it's actually a pretty good idea, but if the option is "surge" or "fire" I know which one I'd rather have...
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Old 09-07-2011, 07:24 AM   #28
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Certainly possible, Skater! However, the same could also hold of the device(s) that the surge device is protecting: One giant surge, and the thing overheats and catches fire.

One of the RVs that was hit during the recent storm had a surge device connected outside between the RV and the post. Its undamaged presence -- and the selective nature of the damage to the RV -- was pretty much how we figured out that the lightening hit the RV itself and not somewhere else in the park. (Since utilities are underground, it would have had to be either some other RV or one of the telephone poles out at the highway.)


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