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Old 04-08-2016, 06:31 PM   #1
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Inverter for Residential Fridge - Fail

I have just completed my conversion from Norcold to a residential fridge, making considerable alterations to my fridge cabinet to accommodate it... so don't try to talk me out of it! LOL Anyhow, I thought I had done all my homework and knew exactly what I would need electric-wise. My fridge has a variable-speed compressor and variable fans so I knew that I'd need a pure-sine inverter. The fridge draws 170w when running and 150w/h average (i.e. the fan runs almost continuously).

I ordered a Xantrex PROwatt SW 1000 PSW inverter (2000w surge) figuring even if a momentary surge were 10x normal demands (1700w) that this would have sufficient capacity. Hooked it all up and unplugged from shore and it ran like a charm... until the battery bank discharged to about 65%. Then it reported an overload condition and shut down.

When I started the generator the charger kicked on and the inverter again refused to run, reporting an over-temp condition, I assume because of the higher charging voltage, though it is supposed to accept up to 15.5v input. I let the inverter cool off for a while (even though the housing was never warm) and again immediately got an over-temp shutdown. My plan was to run the fridge off of the inverter 24/7, as I've read others do, but cannot run it in either of these two, common, states. The inverter ran fine while the engine of the coach is running (charging the batteries) and while plugged into shore (30a, I suspect it would complain under 50a shore).

The battery bank is essentially new, 4 x 6v 220AH rated Trojan t125plus. The inverter was connected with 1-gauge, 18" cables. I am monitoring the bank using a Trimetric shunt-ammeter. I talked with Xantrex and their only suggestion was thicker cables (pretty sure that wasn't it) or buying a bigger inverter (for double the money). It seems ridiculous to me to buy a 2000w continuous duty inverter to run a 170w fridge! Is this really what's needed or am I missing something?

Even if I get a 2000w, I assume it will complain about being connected while the charger is running, too. It sounds like keeping power running to the fridge is going to be a very manual operation. While we're spending all that money I'm half inclined to replace the Freedom with a Magnum hybrid 3000w inverter/charger, replace the Trimetric with a Magnum BMK, add the advanced remote and auto generator start. Why spend $500 (for no real gain in functionality) when you can spend $2500 (and get a lot more functionality)?! Not that I have $2500 laying around burning a hole in my pocket! The PROwatt is boxed up and heading back to Amazon, but I'm very unsure what my next move is. Any insights appreciated.
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Old 04-08-2016, 07:06 PM   #2
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Your residential fridge probably pulls 1700 WATTS instead of 170 like you mentioned ! That's your problem, so get the proper inverter to run your fridge.
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Old 04-08-2016, 07:21 PM   #3
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Can you tell us what refrigerator you have. It might keep someone else from having the same problem in case that is where the fault lies.
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Old 04-08-2016, 07:33 PM   #4
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Your residential fridge probably pulls 1700 WATTS instead of 170 like you mentioned ! That's your problem, so get the proper inverter to run your fridge.
That's 14.5 amps. Not likely.
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Old 04-08-2016, 07:33 PM   #5
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BTW a modern refrigerator consumes about 180 watts so the 1700 figure above shouldn't be the issue.
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Old 04-08-2016, 07:43 PM   #6
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Is you refrigerator the only thing running of the inverter? Sounds to me like your inverter is trying to run your converter/charger too.
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Old 04-08-2016, 07:43 PM   #7
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I have gone thru 3 xantrex ProWatt PS2000 inverters.

The first lasted a month, the second 8 months and the third going strong for 4 years.

I also use a Xantrex ProWatt PS1000. It has been trouble free for 2 years. We run a 700 watt coffee maker off it along with Sat. TV.

I ran the 1000 with 2 gauge cables about 3 feet long.

Send it back as defective and get a replacement before doing anything else.
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Old 04-08-2016, 10:16 PM   #8
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Quote:
Originally Posted by Santa_Claus View Post
I have just completed my conversion from Norcold to a residential fridge, making considerable alterations to my fridge cabinet to accommodate it... so don't try to talk me out of it! LOL Anyhow, I thought I had done all my homework and knew exactly what I would need electric-wise. My fridge has a variable-speed compressor and variable fans so I knew that I'd need a pure-sine inverter. The fridge draws 170w when running and 150w/h average (i.e. the fan runs almost continuously).

I ordered a Xantrex PROwatt SW 1000 PSW inverter (2000w surge) figuring even if a momentary surge were 10x normal demands (1700w) that this would have sufficient capacity. Hooked it all up and unplugged from shore and it ran like a charm... until the battery bank discharged to about 65%. Then it reported an overload condition and shut down.

When I started the generator the charger kicked on and the inverter again refused to run, reporting an over-temp condition, I assume because of the higher charging voltage, though it is supposed to accept up to 15.5v input. I let the inverter cool off for a while (even though the housing was never warm) and again immediately got an over-temp shutdown. My plan was to run the fridge off of the inverter 24/7, as I've read others do, but cannot run it in either of these two, common, states. The inverter ran fine while the engine of the coach is running (charging the batteries) and while plugged into shore (30a, I suspect it would complain under 50a shore).

The battery bank is essentially new, 4 x 6v 220AH rated Trojan t125plus. The inverter was connected with 1-gauge, 18" cables. I am monitoring the bank using a Trimetric shunt-ammeter. I talked with Xantrex and their only suggestion was thicker cables (pretty sure that wasn't it) or buying a bigger inverter (for double the money). It seems ridiculous to me to buy a 2000w continuous duty inverter to run a 170w fridge! Is this really what's needed or am I missing something?

Even if I get a 2000w, I assume it will complain about being connected while the charger is running, too. It sounds like keeping power running to the fridge is going to be a very manual operation. While we're spending all that money I'm half inclined to replace the Freedom with a Magnum hybrid 3000w inverter/charger, replace the Trimetric with a Magnum BMK, add the advanced remote and auto generator start. Why spend $500 (for no real gain in functionality) when you can spend $2500 (and get a lot more functionality)?! Not that I have $2500 laying around burning a hole in my pocket! The PROwatt is boxed up and heading back to Amazon, but I'm very unsure what my next move is. Any insights appreciated.
Hi Santa,

Your description sounds like what I experienced during my residential install. I sort of glossed over it in my project thread located here.

Like you, I bought a 1000watt PROwatt inverter. Figured with the 2000 watt surge capacity that surely would handle the start up of a fridge. Right? Not!

I had the same symptoms that you mention. It ran OK once or twice. Then I'd get an overload and have to reset it. When I had the charger going I'd get the over temp alarm.

Hmmmm. That's not good.

I read over the PROwatt documentation and looked deeper at the power draw on the fridge. This is where I learned about a thing called LRA. LRA stands for Locked Rotor Amps. This is the max current the compressor will draw when it starts up. Yes, it's momentary but an important number to know. The LRA will be listed on the compressor data plate.

In my case my LRA was 9.5 amp-ish (if I remember correctly). The PROwatt 1000 has a max current of 9.6 A. This rating is buried on page 21 of the owners manual.

So, I called Xantrex support and explained my problem. They asked some questions about cable size from the battery, distance, and any other loads. All was according to their specs for cable and the fridge is the only thing on the inverter.

After some discussion, I was told that the 9.6 max is truly the max and it can only put that out for a few milliseconds. Any longer than a few milliseconds and it will alarm.

Basically, the temporary current demand from the fridge was right on the edge of what the inverter could supply. So this is why it might work or it might not.

I bit the bullet and bought the 2000 watt PROwatt model. Cabled it up, plugged in the fridge, held my breath, and turned on the fridge. It started and has run well!

I've had the fridge installed with the 2000 watt PROwatt inverter since early December 2015. We've spend 4 weeks traveling covering 5,000 miles. About 1 week of the travels we were boon-docking. All has worked without issue.

In addition to the above travel, we also had the fridge running off the inverter for about 10 days or so as I was doing other stuff to the MH. Just wanted to make sure it would work. It did.

If you get the larger PROwatt, I'm sure it will work.

In my case, I had found a really good price on both inverters. Problem was no returns.

So, anyone want to purchase a really new 1000 watt PROwatt inverter? Hardly used....

Anyway, Santa, hope this helps you.
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Old 04-08-2016, 10:32 PM   #9
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Did I understand you are running the refrigerator full time on the inverter, even on shore or generator power and the charger us running? If yes, I suggest to get a inline transfer switch so as to operate the refrig on the genny or shore when available.

As the the locked rotor amp draw, yes it's large and short term. I also suggest a larger inverter is needed.

2000w or larger inverter with a transfer switch is my recommendation.
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Old 04-08-2016, 10:44 PM   #10
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Quote:
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Did I understand you are running the refrigerator full time on the inverter, even on shore or generator power and the charger us running? If yes, I suggest to get a inline transfer switch so as to operate the refrig on the genny or shore when available.

As the the locked rotor amp draw, yes it's large and short term. I also suggest a larger inverter is needed.

2000w or larger inverter with a transfer switch is my recommendation.

Hi vsheetz,

Let me clarify. I failed to include that bit of info.

I did install the PROwatt automatic transfer switch. It's sold as an accessory.

I leave the inverter on all the the time. So when not on shore or genny power, the inverter takes over.

Thank you for asking the question.
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Old 04-08-2016, 10:59 PM   #11
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Did I understand you are running the refrigerator full time on the inverter, even on shore or generator power and the charger us running? If yes, I suggest to get a inline transfer switch so as to operate the refrig on the genny or shore when available.

As the the locked rotor amp draw, yes it's large and short term. I also suggest a larger inverter is needed.

2000w or larger inverter with a transfer switch is my recommendation.
Just curious why someone would need to transfer the fridge off the inverter.

My boats residential fridge is 8 years old and been running on the inverter it's whole life. We average 7 months a year full timing with it.

During the rare times we have shore power, my shore power cord runs my chargers and air conditioning. The inverter covers eveything else.

My charger has the capacity to charge the battery bank and cover the inverter load.
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Old 04-08-2016, 11:17 PM   #12
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My charger has the capacity to charge the battery bank and cover the inverter load.
This is not usually the case. My factory Inverter/converter/charger only outputs 85 amps. It's designed to charge the batteries and output some extra for lights, etc. It would need to output almost 300 amps to also fully power the inverter in addition to those loads.
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Old 04-09-2016, 05:15 AM   #13
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This is not usually the case. My factory Inverter/converter/charger only outputs 85 amps. It's designed to charge the batteries and output some extra for lights, etc. It would need to output almost 300 amps to also fully power the inverter in addition to those loads.
In this conversation we were discussing the inverter load of the fridge.

The OP was using it as a dedicated power supply.

My fridge draws about 10 amps @ 12 volts DC, while running.
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Old 04-09-2016, 05:47 AM   #14
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Santa,

There was a thread a couple of years ago where another member had similar problems with a 1000 watt Xantrex ProWatt inverter. Others who had the same fridge were using the more expensive 1000 watt Xantrex ProSine with no problems even though the rated peak for the ProSine is lower.

We had a 1000 watt Tripp-Lite inverter powering a residential fridge in the motorhome we used to have, and we have a 1000 watt Magnum for our residential fridge in our current 5th wheel. We never had problems with either one.

I can only conclude the problem has something to do with the ProWatt only being able to handle the peak for a few milliseconds as Mr. Dave reports in Post #8.
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