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Old 05-23-2015, 08:14 AM   #29
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Wryly, many new 5th wheels are coming with residential fridges and a dedicated inverter. I know at least one brand (Heartland) is using a Magnum 1000W. It does not power anything else. They have had wide-spread issues with them and have had to change them out. It is supposedly a firmware glitch having to do with the inverter's surge capability when the compressor kicks in. That's why I suggested not to go with anything less than 1000W.
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Old 05-23-2015, 10:45 AM   #30
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Quote:
Originally Posted by Scottybdivin View Post
Wryly, many new 5th wheels are coming with residential fridges and a dedicated inverter. I know at least one brand (Heartland) is using a Magnum 1000W. It does not power anything else. They have had wide-spread issues with them and have had to change them out. It is supposedly a firmware glitch having to do with the inverter's surge capability when the compressor kicks in. That's why I suggested not to go with anything less than 1000W.
I have seen this happen. A guy at the campground had a brand new Heartland Bighorn. He had just bought it and this was his first trip. His inverter kicked out and he called the dealer they told him when he got back to bring it in and they would go to a bigger inverter the 1000 would not handle the unit.
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Old 05-23-2015, 02:02 PM   #31
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Well that's disappointing - Magnum's are one of the most trusted brands on this forum. Logically, I have to wonder if a bigger inverter really is the right solution. Plenty of owners on here are running their entire coaches on 2000w inverters - including their residential refrigerators. And that's my dilemma:

If I have to go to a bigger psw inverter just to cover the start-up surge, I might as well go one step further an get one for the whole rig. It doesn't make sense to have a dedicated 2000w psw inverter just to run the fridge when one that size or maybe one step bigger will run the whole coach.

The only way it would make sense is if I could get by with one that was under 1000w (and under a few hundred bucks), but I just can't find the numbers I need to do the math to make sure it'll work.

Guess I'm calling Electrolux on Tuesday... see what they say.

Have a great Memorial Weekend all!
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Old 05-23-2015, 02:46 PM   #32
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Quote:
Originally Posted by Darrel
I am currently replacing my failed Norcold with a residential model (AMANA model ART104tfdb). I just measured the 12V draw with the refigerator running. It measured 18 amps. 18amps X 12Volts is only 216 Watts!

Have a nice day - Darrel
That's correct if it's running on straight 12volts, he's using a household fridge at 120v inverting from 12v.

My norcold draws 2.5amps on 120v shore power but 25 amps inverting from 12.
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Old 05-23-2015, 03:01 PM   #33
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That's correct if it's running on straight 12volts, he's using a household fridge at 120v inverting from 12v.

My norcold draws 2.5amps on 120v shore power but 25 amps inverting from 12.
The refer is still drawing 2.5 amps when running on the inverter. It is the inverter itself that is eating up the remainder. Plan on 10 amps of DC to make 1 amp of AC
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Old 05-23-2015, 03:07 PM   #34
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Amps X volts = watts. Both of your figures = 300 watts.

A 600 watt inverter, with a 1200 watt surge capacity will run your refrigerator.

Of course there is the 90% efficiency rating, so that is a small factor in the
math.

I have a 7.6 c.f., apartment size fridge, drawing 8 amps, 12 volts (96 watts ). On startup my Tri Metric reads 35 amps, for a second. Thats 420 watts.

I have test run it, on a 350 watt msw inverter. At startup, the inverter would beep, but overcome it and run.

I'm sure Magnum will work out the kinks with 1 RV builder.

Amazon takes everything back, order one and try it.
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Old 05-23-2015, 04:03 PM   #35
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Originally Posted by gemini5362 View Post
I have seen this happen. A guy at the campground had a brand new Heartland Bighorn. He had just bought it and this was his first trip. His inverter kicked out and he called the dealer they told him when he got back to bring it in and they would go to a bigger inverter the 1000 would not handle the unit.
The ultimate fix has been a firmware upgrade to handle the surge at startup. They are replacing them with updated 1000W Magnums and they are working fine.
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Old 05-23-2015, 08:07 PM   #36
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What is the difference between the two invertors?
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Old 05-23-2015, 08:45 PM   #37
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Warning! Opinions are free and worth every cent.
I would imagine that all refrigerators run less than 100% duty cycle. Your rating of 102 watts could be appropriate for 30-40% duty cycle.

Have a nice day - Darrel
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Old 05-24-2015, 02:41 AM   #38
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Quote:
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Amazon takes everything back, order one and try it.
Yeah, you're right. What the hell

Done!
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Old 05-24-2015, 10:48 AM   #39
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Quote:
Originally Posted by dons2346

The refer is still drawing 2.5 amps when running on the inverter. It is the inverter itself that is eating up the remainder. Plan on 10 amps of DC to make 1 amp of AC
Yes it takes 10x the power from DC to make AC when inverting, 12vx10=120volts. That's why lots of off grid cabins etc use 48v battery banks and 48v inverters.
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Old 05-24-2015, 11:04 AM   #40
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For 20 bucks, buy a kill A Watt, watt meter and plug it in, to see the draw.

It is a handy tool to check anything you want to run off your inverter. It helps calculate your energy budget.

Agree. Killawatt - One of the handiest items to have around. You can see running draw, surge draw, and consumption over time (great for knowing how much power a refrigerator really uses).
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Old 05-25-2015, 08:41 AM   #41
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Agree. Killawatt - One of the handiest items to have around. You can see running draw, surge draw, and consumption over time (great for knowing how much power a refrigerator really uses).
The Killawatt meters are excellent for measuring plug in devices. However, they are kind of difficult to use on an already installed residential fridge since you have to pull the fridge out to access the plug. Best to get some type of permanent solution like the Trimetric or the Magnum ME-BMK, since you should have one anyway for this type of use.
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Old 07-03-2015, 12:13 PM   #42
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Quote:
Originally Posted by Wryly Blithe

Yeah, you're right. What the hell

Done!
Well how's the fridge/inverter working? What did you purchase? just curious if you're satisfied with it all.

Have a great day
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