Converter amp rating - Fiberglass RV


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Old 11-01-2007, 11:06 PM   #1
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Dear RV cruisers; I'm ready for an Intellipower 9200 series converter replacement from an old (maybe original) installed unit. I have a Main on a 30amp breaker with sub-panel breakers of 20a, 15a, 15a & 15a. D/C is on separate bus bar. My A/C draws about 20a and my shoreline plug is for 30a. I can get the new converter in a range of amp output from 30a on up. What amp rating should I get? Is it true that the 30a main will determine the max. converter output amps? Wouldn't drawing any more than 30amps trip the main breaker?
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Old 11-01-2007, 11:31 PM   #2
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Dear RV cruisers; I'm ready for an Intellipower 9200 series converter replacement from an old (maybe original) installed unit. I have a Main on a 30amp breaker with sub-panel breakers of 20a, 15a, 15a & 15a. D/C is on separate bus bar. My A/C draws about 20a and my shoreline plug is for 30a. I can get the new converter in a range of amp output from 30a on up. What amp rating should I get?
I doubt you'll ever need more than a 30 amp converter.
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Is it true that the 30a main will determine the max. converter output amps?
No. The maximum input for a 30 Amp converter is approximately 3 amps.
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Wouldn't drawing any more than 30amps trip the main breaker?
You'd need a 300 amp converter to get to 30 amps input.

Bottom line, my converter is a 20 amp converter and that's plenty, a 30 amp is more than you'll ever need. In this case bigger is not necessarily better, in fact any bigger could be a hazard.
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Old 11-02-2007, 06:21 AM   #3
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Hmmm. Perhaps we're all talking the same thing and I may be confused but I always thought that the amperage rating of the converter referred to DC amps output.

As a sanity check, bear with me.

There being are two separate ratings (AC and DC) that are similar and so can be confusing. A 30A shore power plug spoke to the maximum AC the trailer should draw. Having a 30A plug doesn't mean that 30A is always present, only that in theory everything is sized for 30A maximum.

A 30A converter spoke to the amount of DC current the converter converted from the 30A AC that the plug could let in.

If I have a 30A shore power plug and the appropriate circuit breaker, I assumed that up to 30A AC could come into the trailer. If my AC used 20A of that AC, then it left up to 10A AC for the converter to convert to DC current. Not counting efficiencies, that 10A AC (at 120vAC) is equal to 100A DC (at 12vDC), so a 30A DC converter (for example) would work just fine.
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Old 11-02-2007, 08:58 AM   #4
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We're essentially saying the same thing Steve.
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Old 11-02-2007, 01:46 PM   #5
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We're essentially saying the same thing Steve.
Thanks everyone! Great discussion. I'll get the 30A converter. Is the 'danger' in using a higher amperage rated converter due to excessive heat?
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Old 11-02-2007, 02:46 PM   #6
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Thanks everyone! Great discussion. I'll get the 30A converter. Is the 'danger' in using a higher amperage rated converter due to excessive heat?
The danger is something would draw close to the rated current, but the trailer wiring isn't large enough to handle current. That wire would then get hot, maybe hot enough to start a trailer fire. So you really don't want a converter that will provide more current than the wiring will allow.

I know somebody will point out that the battery can supply large amounts of current. True, but not for very long, the converter will supply up to it's rated current for as long as it's plugged in. Another argument is the fuses will protect you. Response, maybe. Some fuses will take a long time to "blow" even with twice the rated current. CSA and UL will disable any consumer replaceable fuse prior to testing. They don't consider consumer replaceable fuses as a reliable safety device.
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Old 11-03-2007, 03:51 PM   #7
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There are circumstances where you may want a converter bigger than 30 Amps. It depends on the size of the battery you have on your trailer and how quickly you need to charge them. The PD9200 series converters are smart chargers which are capable of delivering their full rated output to the house battery. The most efficient charging rate for your battery is about 20 to 25% of the battery's capacity. So, if you have a 100 to 125 amp battery, a 30 amp charger would be fine. If you have dual 6 volt golf cart batteries with a capacity of 225 amps or more, a 60 amp charger might be a better option for the most efficient charging. If you always camp with AC, you are probably not worried about how efficient your charging time is and the smallest converter is fine as long as it can handle your DC loads and some charging.

I don't think a larger converter should be a hazard. Your 12 volt circuits should be protected by fuses. The circuits won't draw any more power than the load (lights, fans) require and the fuses or breakers allow. Your car or truck has a 50 to 200+ amp alternator which uses a very similar wiring/fuse scheme as your RV.

I have an Intellipower PD9245 which is the 45 amp version of the converter you are looking at. The rated input of my PD9245 is 750 watts (just over 6 amps) AC so if you have a 30 Amp AC system on your Boler you should be fine.
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Old 11-03-2007, 07:26 PM   #8
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I'll get the 30A converter.
That's what I thought, too.

BUT:

When I looked for a 30 amp unit, I found that Camping World only puts the 45 amp and the 60 amp units on their store shelves. They list a 30 amp unit in their catalog, and the boxes have information panels that indicate units rated for 30, 40, 45, 50, 60, and 90 amps. I brought this to the attention of their customer service desk rep, and she saw that their computer inventory system indicated two 30 amp units in their distribution center. She ordered them to be added to that store's stock (so I wouldn't be charged for shipping) and told me to check back after the once-a-week delivery arrived. I went back to the store a week later and found that there were no [b]30 amp units on the shelf, but the number of [b]45 amp units on the shelf had increased by two! I was very busy that day and did not have the extra hour it would take to communicate again with the desk rep. I left the store, dejected.

I was hoping to make the purchase at Camping World due to the "President's Club" discount. The other retailers in my area want full retail price, or a little more...
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Old 11-04-2007, 10:13 AM   #9
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Terry,

I am not sure why you wouldn't buy the 45 amp converter except for price or maybe space limitations. Example: The new 17' Casita's are shipped with a 45 amp converter. I agree with ecasey points on converter size. If I were buying a new converter/charger, I would pay more attention to the quality of the charger. Make sure it is a smart charger / multi stage charger.

Dean
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Old 11-04-2007, 10:36 AM   #10
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Thanks everyone! Great discussion. I'll get the 30A converter. Is the 'danger' in using a higher amperage rated converter due to excessive heat?
Terry,

I also wanted to add an answer to the above question. No. Under the same load the heat produced by both would be the same - physics. I would much rather have a 20 amp load on a 45 amp converter running all day than a 20 amp load on a 30 amp converter.

Dean
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Old 11-04-2007, 11:08 AM   #11
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Terry,

I also wanted to add an answer to the above question. No. Under the same load the heat produced by both would be the same - physics. I would much rather have a 20 amp load on a 45 amp converter running all day than a 20 amp load on a 30 amp converter.

Dean
I wasn't talking about the same load, an overload (wiring overload not converter) on a 20 amp converter of say 40 amps will shut the converter down. The same overload with a 45 amp converter will continue until the wiring burns up. Physics.
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Old 11-04-2007, 03:12 PM   #12
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I wasn't talking about the same load, an overload (wiring overload not converter) on a 20 amp converter of say 40 amps will shut the converter down. The same overload with a 45 amp converter will continue until the wiring burns up. Physics.
Byron,

I didn't think I was responding to your answer, just to Terry's original question. But in response to your comment, it's like having 100 amp or 200 amp service to your house. The 200 amp service to your house does not make it less safe than the 100 amp service. It's all protected by the panel of breakers at the house just like the panel of breakers in the camper. I wouldn't want to rely on a converter going into thermal shutdown or worse to protect wiring. I would want all to be protected by the breakers in the panel, which should be the case. So, a 100 amp converter would be safe if installed properly, just not necessary.

The main reason for me personally to choose a 45 amp converter over a 30 amp converter running a continous 20 amp load would be for a better MTBF (Mean Time Between Failure) rating.

Respectfully submitted, Dean
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Old 11-04-2007, 03:37 PM   #13
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Byron,

I didn't think I was responding to your answer, just to Terry's original question. But in response to your comment, it's like having 100 amp or 200 amp service to your house. The 200 amp service to your house does not make it less safe than the 100 amp service. It's all protected by the panel of breakers at the house just like the panel of breakers in the camper. I wouldn't want to rely on a converter going into thermal shutdown or worse to protect wiring. I would want all to be protected by the breakers in the panel, which should be the case. So, a 100 amp converter would be safe if installed properly, just not necessary.

The main reason for me personally to choose a 45 amp converter over a 30 amp converter running a continous 20 amp load would be for a better MTBF (Mean Time Between Failure) rating.

Respectfully submitted, Dean
I believe you've used the house argument before, it's not quite the same thing. It used to be close to that when houses had fuses instead of circuit breakers. Most trailers use fuses. Most people have at some time replaced a fuse with a larger one. That's why UL and CSA don't recognize fuses as a safety item. Therefore why defeat the thermal shut down safety feature by using an over sized converter?
I don't know about your trailer, but if I doubt I'll ever get close to drawing 20 amps. Therefore the MTTF (Mean Time To Failure) would not be improved by using a 45 amp converter. I also think the biggest cause of converter failure is vibration not over heating.

I've run a lot of power supplies (the DC output part of a converter is power supply) at their limits. I can't remember when or if I've had a power supply failure because of running it at the limits. I'm using one right now I run to limits several times during the day. More than once it's been in an overload condition for the week-end and no failures.

In your house example, buying a 45 amp converter is like paying extra to have a 1,000 amp service brought into your house.

One more piece of information, thermal overload isn't used very much anymore. The most likely protection is fold back. I haven't looked at individual converter specs, so I can't say for sure.
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Old 11-06-2007, 09:58 AM   #14
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I believe you've used the house argument before,
You must be mistaken me for someone else. I am new to the forum and only have about 5 posts.

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In your house example, buying a 45 amp converter is like paying extra to have a 1,000 amp service brought into your house.
So, A 30 amp converter is to a 45 amp converter as a 100 amp house service is to a 1,000 amp house service?

Interesting ...
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