Inverter for Residential Fridge

[SLSettles]

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. It demands 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 to recharge the batteries, 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 realize that an auto-transfer switch can help by switching to AC when the generator is running (or plugged into shore) but the inverter will be shutdown when the power is cut, requiring a manual restart, which I can imagine forgetting to do. 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.

If that IS what's needed I'm wondering if I can take the 120v outputs from my existing MSW inverter (Xantrex Freedom 20 2000w inverter/charger) and power them off of the new PSW inverter so that the microwave and computers will benefit from the PSW? 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 help appreciated.

[dickandlois]

SLSettles,

Welcome to the FMCA Forum!

Reading over your post, with the refrigerator requiring 170 watts of power and the inverter is putting out 1000 watts. You have 10+ times the power requirement available.

That being the case there should be plenty of power to run a microwave for short periods of time with the batteries charged. 

The Item you mentioned regarding the problem when the discharged to 65% and starting the generator you still got an error code is due to limited charging current of the current inverter / charger.

Remember the charger / inverter is rated at 1000 watts, but the charger portion current capabilities are not able to keep up with demand under high loads until the batteries are charged to a level where they can supplement the power needed under a  heavy load.

The 2000 watt inverter would have a higher DC changing current and this fact reduces the chances of reaching the overload point you experience.

A 2000 watt inverter will generate an overload code at the same battery voltage or the 65% point as the 1000 watt unit does.

So investing in a newer unit will help, but will still have the same maximum house battery AH level to work with.

Rich. 

Question. does your inverter have a 120 volt bypass that enables you to run the items you want when the inverter function is turned off allowing the unit to charge the batteries only while running the generator?

 

 

 

[huffypuff]

We need model of fridge and coach.  I have a Norcold with icemaker in my coach and it has 2 120 volts outlets.  One is for the fridge power and not inverted and the other is a inverted (on all the time) outlet.  If you have similar see if you have power to one of the outlet when coach is unplugged from outside power.  That is how my coach is wired.   

[SLSettles]

Rich, thanks for the response, but we seem to be missing each other's point.

Huffypuff, my coach is a 2004 Fleetwood Revolution 40D and my fridge is a GE Profile PDS22SBSRSS. As for the outlets in the fridge compartment, yes, I have both an inverter and a non-inverter outlet... but, for my initial tests with this new inverter I plugged the fridge directly into the inverter's outlet. I would eventually rewire the outlet to use the new inverter, if it worked, which it didn't, so it's in a box heading back to Amazon. 

Ultimately, my frustration is this: this fridge is designed to run on a 15amp 120v household circuit. As near as I can figure that means it cannot draw more than 1800watts or it'd trip a breaker every time it started up. Therefore, I got an inverter that could handle this absolute max and then some, 2000watt surge. But it couldn't. I don't understand why, but it seems the next step up is double the price and double the wattage. Which seems ridiculous, that I should need a 2000watt (4000watt surge) to run an appliance that draws 170watts. If that is the answer then I will have to cough it up and live with it. But I still don't understand why this unit is not enough, and I'm more than a little hesitant that the next one will perform as expected, i.e. supply 170watts continuous/1800watts surge until my batteries are discharged to 50%, not 65%. 

A separate, but equally vexing issue is that my plan was to use the PSW inverter to power the fridge at all times (as I've read others do). However, when the generator is running, providing 50a to my existing built-in MSW inverter/charger, the amperage appears to have been too high for the new PSW inverter which went into shutdown, even though it is supposed to be able to accept up to 15.5v in. Actually, I'm not sure why it reported an over-temp condition, but the charging amperage is my best guess. But it would not work with the charger in full acceptance charge mode. I did not try it in float, it was back in the box by then, but it really wouldn't have mattered. If I had an auto-transfer switch things would have still gone awry because the fridge would have switched over to use the generator, but the PSW inverter would have gone into overload and shut down, and then when I turned off the generator there would be no power from the inverter to switch back to and I wouldn't know until the next morning when I opened the warm fridge. So that leads me to think that the only good solution is to replace my MSW inverter/charger with an equally capable PSW inverter/charger, that can handle the loads and the transfer switching and the charging seamlessly. But why pay $1600 for a 2000w when you can spend $1800 for a 3000w hybrid? Of course, then you've got to get a compatible remote, and at some point you'll want to add the AGS, so you should get the advanced remote. Oh, and that Trimetric ammeter you just installed... wouldn't it be better to get the one that integrates with the new inverter? 

Did I mention I'm a little frustrated?

[hermanmullins]

SL,

 

I just installed a Samsung RF 18 residential unit. It has run on my inverter since installed. I have a Trace 2,000 watt Modified Sane Wave. It has never gone below 80% when dry camping, which we have done several times since installation. I have heard of several people installing a 1000 watt Pure Sine Wave dedicated to the Refrigerator. Maybe you could do the same.

Good Luck,

 

Herman 

[jleamont]

I believe he was trying a separate inverter dedicated to the refrigerator. While is factory installed 2000 watt MSW ran the rest of the coach. The question seems to be why wouldn't a 1000 watt run it? Or better yet why will the stock MSW not work.

Shannon, what did the MSW unit do to the refrigerator when plugged into it? Compressor get loud when it turned on?

 

 

[desertdeals69]

I did some test on residential refrigerators running on different inverters from 300 watt to 3000 watt.  I used 3 refrigerators of different brands and 4 different brand of inverters.  Some of the refrigerators wouldn't even run on some inverters, both msw and psw.  I could never conclude a consensus so I just picked the refrigerator I wanted and then chose the inverter that worked with it. I wound up with a Haier 10.1 cu ft and a Xantrex SW3012.  I did put a switch on the auto defrost because it came on at least once a day and it has a big amp draw.  I have 6 AGM golf cart batteries and 600 watts of solar with a MPPT charge controller.

[SLSettles]

I didn't try running on the MSW, it's just too big of a gamble. I know that variable speed motors do poorly on MSW, so I just accepted off the bat that I'd need a PSW. 

[manholt]

Some Refrigerators, Samsung is one, are quite happy running on MSW.   Re-read Hermans post!

[campcop]

Maybe I am missing something, with the genset running, it's supplying current to both inverters?

we have a 2000 watt pure sine inverter. It runs the refrigerator, micro wave and multiple outlets.

[Cochise49]

4 hours ago, Manholt said:

Some Refrigerators, Samsung is one, are quite happy running on MSW.   Re-read Hermans post!

Kitchen Aid too...

[kaypsmith]

Maybe I'm missing something also, first of all, I have yet to find any residential fridge that will run on 170 watts, that's less than 1.5 amps at 120 volts. The lowest found just last week when looking at the newest models at Home Depot, and Lowes seems to be LG, that one states 3.5 amps, Samsung lowest was still at 4.0 amps, while the lowest GE that was in stock was 7.9, and some other brands were at 11.0 to 12.0, depending on size. 4 amps at 120 volts comes out at 480 watts, while 8.0 comes out at 960. With all this said, why would anyone want to keep their fridge constant on an inverter if it is not a smart inverter that auto reverts to shore power or generator?  The Xantrex Prowatt SW1000 only has one inlet, 12 volts, no 120 voltage, so it can not auto switch to 120 when that voltage is present.

To use in this scenario, one would need to install an " ats", auto transfer switch to switch between shore/generator, and inverter voltage when the first is not present. Also the fridge plug will have be plugged into the ats output.

I have always recommended that the inverter be a minimum of twice the wattage of all appliances that will be used after the inverter, that means the so called run wattage, not the surge wattage, surge wattage on most inverters are no more than a used auto salesman pitch, if you read the fine print, 500 to 1500 ms, that's 1/2 to 1 1/2 seconds, no fridge startup is that fast. But, I would like to know the model GE fridge in the application so that if it is truly 170 watts I can install one at my home, as I really need to reduce my electric bill. Oh yes, those compact fridges , 1.5 cf to 4.0 cf models, will not even state their true max amps, I have measured several of those and found them pull as much or more than many of the full size refrigerators. But good luck with your installation, I hope this tidbit proves to be helpful in making it become a smoother transition. Kay

(PS)

After rereading the op, I did miss out on that has a variable speed compressor and variable speed fans, this means that it is an inverter technology fridge, I have covered this on another post nearly 5 months ago. While this is a wonderful new innovation for reducing power consumption, I'm not so sure about inverting an already inverted signal. To run with reduced input wattage, the fridge built in inverter, now has to take 60 hertz "cycles" and then re invert that to sometimes 600 cycles, depending on demand. The slowest speed of the compressor and fans use 60 hertz and then the inverter takes over to change to the number of cycles to run at higher speeds. I would strongly recommend that you contact a GE technical engineer to find if they have even tested your model with any inverter to know the results of their findings. 

[SLSettles]

Actually, I've been looking at residentials in the 22ft range for a year and find most run in the 70-100 w/h range. Now that may mean they run at 300 watts for 20 minutes an hour. So my older, 150 w/h model is pretty average. Forget the amps, what you need is the yellow tag with the annual kw usage figure. Divide it by 365, divide that by 24 and you'll get what the fridge should average in normal usage. Both my Trimetric shunt ammeter and my Kill-a-watt confirm the wattage I reported. So, the inverter I bought was 6 times the run wattage of the one appliance it was intended for  

As for a transfer switch, yeah, I'd probably install one if the inverter worked as expected, but for my test I saw no point in complicating things: inverter hooked to batteries, fridge plugged directly into inverter. Glad I didn't invest more time effort and money just to find it didn't work... especially if I end up upgrading my main inverter/charger. 

I've contacted GE multiple times and let's just say they were not encouraging, strongly making the point that their appliances are made for homes and power grids and that they have no info about other uses. 

Thanks for the considered response. 

[hermanmullins]

There is a point to installing a smaller Pure Sine Wave inverter: Cost. If everything in your coach works on your MSW inverter but you want a Residential Refrigerator that doesn't run on MSW, why spend the big bucks on a new PSW inverter. Just purchase a 1,000 PSW for far less money and just run the refrigerator on it. Both inverters will draw from the house batteries and the MSW inverter will still charge the batteries.

I hope this makes sense, it does to me.  

Herman

[kaypsmith]

I'm sorry that you do not understand the difference in kw average and actual watt usage for this purpose, yes the yellow tag does give the watt average but there is also a specification tag inside the door of most refrigerators that give the maximum amperage draw of the unit, this tag is the only one that matters in the land of physics, which is the only one that ANY inverter understands, it does not average out over time, which is what that yellow energy tag does.

"AMPS DO MATTER", this is what current is actually expended at any given time to make it happen. The little cartoon that appeared the other day showing voltage pushing current through (OHMS) resistance is actually very accurate.

Herman, that is what he has done, he has purchased a "psw inverter" for the fridge only, and allowing the already installed msw inverter to run what was already there.

[dickandlois]

1 hour ago, kaypsmith said:

I'm sorry that you do not understand the difference in kw average and actual watt usage for this purpose, yes the yellow tag does give the watt average

but there is also a specification tag inside the door of most refrigerators that give the maximum amperage draw of the unit, this tag is the only one that matters

in the land of physics, which is the only one that ANY inverter understands, it does not average out over time, which is what that yellow energy tag does.

"AMPS DO MATTER", this is what current is actually expended at any given time to make it happen. The little cartoon that appeared the other day showing voltage

pushing current through (OHMS) resistance is actually very accurate.

Herman, that is what he has done, he has purchased a "psw inverter" for the fridge only, and allowing the already installed msw inverter to run what was already

there.

Kay, The inverter will run with an input voltage of 15.5 to 10.5 volts DC. The house batteries when charged and no input charge, set at 12.5 for all intensive purposes.

The SW 1000 inverter shuts down in overload when the Battery voltage drops to 10.5 and will not rest until the input voltage reaches 11.5 DC.

I have to believe that the start current for the refrigerator is 12.5 amps and the run current is around 5 amps. 

Depending on the make and model MSW inverter installed(OEM) and the load it is carrying and the 12 volt Charge current from the unit limits the load the system setup can handle. 

The specifications for the 1000 list a continues load of 900 watts @ 7.5 amps. As the battery voltage drops the current is increasing to meet load and it will hit the overload point quickly.

The only way one could have the needed power would be to have a high current charger running off the generator or by running the engine alternator to maintain a good 12 to 13 volts for the inverter. This would keep the current lower and minimize the overheat issue.

Like you mentioned the laws of physics get into the equation.

Rich.

NOTE! We have no information on where the second unit was installed and if there is enough space and ventilation to keep the unit cooled ! 

[kaypsmith]

Yes Rich, the voltage of the batteries is the deciding factor, along with the ability to produce enough amperage to maintain that voltage.

But to the OP, what would be the best investment would be to go to a smart psw inverter rated at least 1500 watts for this type application. One that has both 12 volt and 120 volt input and the ability to sense when 120 volts are present and pass that voltage through to the fridge and automatically start the recharging process back to the batteries. His current battery bank when fully charged should carry a 5 amp draw, if continuous would be about (60 amps, allowing for overhead just to run the inverter function) about 6.5hours. Of course nothing is absolute, since as you described a startup of 12.5 amps must  be factored into the equation along with idle times when only the fans are running inside the fridge. Those energy stickers are designed to let one know how large a purse one will need to pay the power bill when it comes due, but will not describe actual running amounts necessary to make it go. If you set the computer on your car to read mpg, when you step on the accelerator the mpg will drop to an unreasonable amount, then while descending down a grade it will likely look the other way sometimes showing 60 or better mpg, electricity works the same way.

When the battery bank reaches its low (10.5) volts, it is at its low and does not have the ability in amperage to restart the inverter.

[SLSettles]

3 hours ago, kaypsmith said:

I'm sorry that you do not understand the difference in kw average and actual watt usage for this purpose, yes the yellow tag does give the watt average but there is also a specification tag inside the door of most refrigerators that give the maximum amperage draw of the unit, this tag is the only one that matters in the land of physics, which is the only one that ANY inverter understands, it does not average out over time, which is what that yellow energy tag does.

Nothing like waking up to a little condescension. That little tag tells me exactly what I need to know about HOW LONG I can run the fridge off of my battery bank, and as I've stated before, my Trimetric and Kill-a-watt bear out these numbers. MY FRIDGE USES 150 W/H AS INDICATED BY THE TAG, THE MFG SPECS, AND MY OWN MEASUREMENTS! When running, my fridge ACTUALLY draws 170w. The only unknown for me is what the surge draw is, and the amp rating you give so much credence to does not seem to help. My ratings tag in the fridge states 3.5 amps at 115v, or 402 watts, which makes zero sense as I have never seen my Trimetric register more than 200w with just the inverter and the fridge running. Perhaps that rating is if it goes into defrost mode with both doors open and the factory halogen bulbs burning (180w worth of halogen, which I've replaced with LED, BTW). It certainly doesn't represent normal hourly draws... not even in the 36 hours right after I installed it and it cooled from room temp, which average 190w/h. But who cares!? 402 is way less that the 1000w peak (5 min), and the 900w continuous duty rating of the inverter, so the inverter is more than double the demands of the fridge under the worst case scenario. The one thing I don't know is what the surge demands are, other than they were obviously too great for this PSW inverter. Finally, yes, amps matter... just as much as watts and volts, they are inextricably linked. Labels matter too, so long as you know what they are trying to relate, which apparently we don't since they don't agree with the thing we do understand, METER READINGS, which are very clear, easily interpreted and do not have a sales motive skewing them. 

FWIW, I've been a member of FMCA for exactly a year and have lurked on these boards many time and never participated until now because I got a generally nasty tone in many of the responses. I was told by a Facebook "friend" that I should post this question here because he thought there was at least one very sharp, helpful person. I'm sorry I took his advice and I do not think I will be renewing my membership after this experience.

[SLSettles]

2 hours ago, DickandLois said:

The specifications for the 1000 list a continues load of 900 watts @ 7.5 amps. As the battery voltage drops the current is increasing to meet load and it will hit the overload point quickly.

...

NOTE! We have no information on where the second unit was installed and if there is enough space and ventilation to keep the unit cooled ! 

Battery voltage was about 12.4 (under load) when the inverter went into shutdown, so it never approached the specified low voltage rating.

The second inverter was not "installed" it temporarily hooked up and was sitting loose in a cool compartment (chilly day) with the door open and airflow all around. It never got even warm to the touch and I never even heard the fan kick on. 

[SLSettles]

10 minutes ago, SLSettles said:

Double-post

 

[wolfe10]

SLSettles, et al;

Actually both your perspective and that of several other is looking at the same problem, rationally, BUT from different perspectives.

BOTH/ALL perspectives are important: 

Peak amps on start up, running amps, MSW vs PSW, one large inverter vs separate small one for residential refrigerator, inverter with build in ATS vs separate ATS vs having to move plug manually from shore power outlet to inverter powered outlet, on and on.

Said another way you have brought good perspective to the discussion, and so have others.

I hope the dialogue has been of benefit in making our decisions.

NOTE:  One thing we all need to keep in mind (PLEASE): It is fine to challenge someones ideas.  It is NEVER OK to challenge/attack another person.  Let's keep the FMCA forum a friendly, as well as helpful site.

 

[SLSettles]

I'm not trying to defend, challenge or attack anything or anyone. I am asking if anyone knows why, given these facts, this inverter didn't work. If someone has an idea about why a 1000/2000w inverter could not handle the actual load of 170w, I am very open to hear it. 

[manholt]

After reading all off this, there seems to be one only one question left in my mind, and since unit has been sent back, no way of knowing for sure.  Did you do any tests to verify that the unit was good to begin with?  Also, have you tested the Fridge prior to installation, to determine that it also operated within specs?

Mr. Settles, what you and Kay and Rich are saying is correct, but only as long as the other variables have been established.

Carl

[dickandlois]

SLSellles, Thanks for your up dated and relevant feedback. We all try to fill in gaps in how I or anyone posting a thought or question are interpreting the original post.

Not always easy. The one item I had to dig out was the fact (I think) that you where installing the SW 1000  in parallel with an OEM Modified Sine Wave unit.

Good to know that ventilation was never an issue regarding shutdown. Also the fact that the battery bank voltage never dropped below 12.4 volts while the PSM unit was trying to power the refrigerator. 

Like you have asked - why will the 1000 watt inverter not power a refrigerator and all the information we have on hand it should. I have to keep asking myself what am I missing.

Power is power and a load is a load. When the numbers do not make sense what is going on!

So if you would or if you can - What was the current load of the inverter and was there any chance of an AC ripple being present on the 12 volt input.

I do not disagree - the inverter should power the refrigerator - given the fact that the battery level never dropped  to the cutout point. 

A defective inverter? 

Rich.

[SLSettles]

37 minutes ago, Manholt said:

After reading all off this, there seems to be one only one question left in my mind, and since unit has been sent back, no way of knowing for sure.  Did you do any tests to verify that the unit was good to begin with?  Also, have you tested the Fridge prior to installation, to determine that it also operated within specs?

First, thanks for the perseverance to read through all this! I did not do any other tests on the inverter, other than to see if it worked on batteries, on shore with the MSW off, on shore with the MSW on, and with the coach running. Once I found that it would not work in two key conditions I called Xantrex and talked with a tech. The result of that call was the suggestion that I try larger cables (which I dismissed out of hand, #1 18" cables do not have significant drop at these loads) or upgrade to a 2000w version. 

As for the fridge, yes, it has had an extended burn-in period... we have used it at home for years. And yes, I have run it with a Kill-A-Watt many times to evaluate it's consumption, including a couple of days right before moving it to the motorhome to confirm that the numbers were in line with what my batteries can provide. 

Thanks again