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Old 07-14-2015, 08:56 PM   #1
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Electrical (surge) protection before or after gen transfer

After everything that I've read about the possibility of electrical problems due to power issues, I just bought a Progressive EMS-hw30 for my Forester. I have an Onan on board generator wired into an automatic transfer switch.

I'm trying to decide where to install the HW30 - before or after the transfer switch.

I know that if I install it before the switch then I'm not protected from surges coming out of the generator. Is that really an issue, do generators throw surges and high or low voltage?

If I install it after the transfer switch I've read some posts that have indicated the transfer switch can get fried. But, I've also read that if the generator controls the transfer switch then it's not a problem.

At this point I'm totally confused.

Does the factory installed Onan generator control the transfer switch so that installing the surge protector after the switch won't be a problem?
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Old 07-14-2015, 09:05 PM   #2
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Transfer switch has to sense from gen.......otherwise gen wouldn't power anything.
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Old 07-14-2015, 09:10 PM   #3
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Originally Posted by bob caldwell View Post
Transfer switch has to sense from gen.......otherwise gen wouldn't power anything.
OK, so does that mean that any surge coming through the line from the street will go right through the transfer switch without damage? I don't fully understand the transfer switch operation. My sense is that when the generator fires up and sends power up the line there's a relay of sorts that senses it and switches the "track" for the power to follow from the street side to the generator side of the switch.
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Old 07-14-2015, 09:28 PM   #4
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Been trying to remember how the race car transporter is set up and works.....but, to be safe, call you brand of surge pro.and ask....don't want to lead anyone astray. Fonzie seems to be the elec. library on the forum.
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Old 07-14-2015, 09:34 PM   #5
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Wired ours on the 36 CKTS after the transfer switch, when it sees a good voltage from generator it kicks in.
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Old 07-14-2015, 09:40 PM   #6
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To me, that would just protect against gen. power surge....I'm leaning toward shore power and transfer switch. I, HAVEN'T seen a power surge from generator as long as it's been maintained.
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Old 07-15-2015, 07:52 AM   #7
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OK, I don't know if this helps or stirs the pot more.... I found this on Surge Protector - Only for Shore Power, or on everything?? - iRV2 Forums What he's saying seems to make sense to me.

"It seems most people put it before the transfer switch. That's what Progressive recommends. They say it's to protect the transfer switch, and it's not necessary to put it after, because the generator is a cleaner source of power with its own protection.

But I don't buy that logic. A transfer switch is basically a set of relay contacts. There's nothing there that is easily damaged by the kinds of things the EMS protects against: high/low voltage, surges, or wiring problems. The odds of the incoming shore power damaging the transfer switch are VERY low, and if the worst should happen, a transfer switch is one or two hundred dollars, tops.

On the other hand, generators can fail, and when they do they can cause all sorts of nasty problems, including very high voltages if the voltage regulator fails. If that happens, the potential cost to equipment in the coach could be in the thousands.

While I've heard of transfer switch failures caused by loose connections or switching while under heavy load, I've not heard of a single transfer switch failure that was caused by bad shore power. However, I've heard several stories of massive coach equipment damage caused by a failed generator.

So, would you rather risk an inexpensive piece of equipment that is robust and not prone to failure, or would you rather risk many expensive pieces of equipment that are more likely to be damaged? In my mind, the decision is easy: don't worry about the transfer switch, but protect everything else from shore power AND the generator -- I put the EMS after the transfer switch."
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Old 07-15-2015, 08:51 AM   #8
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I absolutely agree to put it after the transfer switch. Make it the guard dog of all power entering your trailer whether shore power or generator through the transfer swirch. What people miss when thinking about the type of surge protection provided with this type of unit is that it will protect devices upstream of the protector as well as downstream. If this was a huge surge protector like you would find in a big industrial complex, factory, then there is some validity to having better protection after the surge protector than before it. That is not the case with this unit
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Old 07-15-2015, 11:36 AM   #9
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Definitely after transfer switch. If gen voltage regulator has problems you are protected
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Old 07-15-2015, 11:54 AM   #10
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OK, I don't know if this helps or stirs the pot more.... I found this on Surge Protector - Only for Shore Power, or on everything?? - iRV2 Forums What he's saying seems to make sense to me.
Any conclusion must include hard numbers with each statement. For example, what is voltage of that rumored surge? Let's define a surge. One is a low voltage. Another is a high current. Another is a noise spike of maybe ten volts. Another is a floating neutral. Another is a high voltage. Another is a low current. Another is a microsecod spike - done long before your protector even saw it. All are completely different. Which surge does your protector address?

A typical Progressive protector is for surges that are low voltage, reverse polarity, or other anomalies that do not harm the transfer switch and most electronics. A most common reason for that completely different device (called a surge protector) is so that low voltage does not damage motorized appliances. Same amonaly would do no harm to electronics.

Are you concerned with something completely different and also (subjectively) called a surge? Your protector is not for another and completely different surge. Protection from that type of surge must be located as close as possible to the pole and to what actually does that protction - an earth ground electrode. Another example of the word surge and what your protector will completely ignore. And an example of what you must know long before making any conclusions.

If your generator is making surges that damage appliances, then you are the reason for that damage. You bought a crap generator. Generators must include circuits that make such damage impossible. But some 'save money'. Then you must spend tens or 100 times more to protect from that 'money saving' decision.

They said where that completely different device, called a surge protector, best does what it claims to protect from. If you need protection from that generator, then fix the problem by spending less money - trash that defective generator.

How often does your generator create a revserse polarity? Exactly which anomalies does that Progressive actually protect from?
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Old 07-15-2015, 12:04 PM   #11
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I had my dealer install my HW50 after the transfer switch. My thinking was it would protect everything from the input be it shore power or generator.

Low and behold my first time at an Air Force Base in Colorado and we get a couple of power surges (on/off/on/off) during a storm. Fried the transfer switch and the HW50. Nothing wrong with anything in the camper.

Purchased a new transfer switch and a new HW50 This time I installed it before the transfer switch. I don't use the generator but a few times a year. We don't dry camp, but I use it during shore power outages. Generator has built in protection (Onan 5500).

You can protect everything, but at what cost...

Just MHO

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Old 07-15-2015, 12:08 PM   #12
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All of them I've seen specifically tell you the install must be on the shore power side of the transfer switch and will not work otherwise. The generator should have its own protection hard wired into the controller on the generator.
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Old 07-15-2015, 12:49 PM   #13
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Originally Posted by John Hagen View Post
You can protect everything, but at what cost...
Each anomaly must be discussed separately - and with specification numbers. For example, those plug-in protectors are some of the most expensive. And do not claim to protect from typically destructive anomalies. Those are recommended when advertising, hearsay, and wild speculation replaces concepts taught in junior high school science.

A Progresssive is for anomalies often found in campgrounds. Word protector can describe 35 completely different and unrelated devices. That becomes obvious when every discussion includes plenty of numbers - no subjective conclusion. Often a best solution is also a least expensive one.
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