Problem with Magnum Inverter 4448 and Dishwasher - Low Power Factor - Help?

DrySide · March 2021

Hello,

About 6 months ago we had a new whole-house off grid system installed which has magnum 4448 as the inverter. For the most part this system is working fine.

One strange problem that I'd really like to get resolved is with the dishwasher. The dishwasher will power up and run, but it runs and runs and runs...... it never stops. It seems to be re-setting to the first cycle every so often. It's a brand-new GE Profile model PDT715SYNFS. We even had it replaced with a replacement unit and it does the same thing.

I'm told that this is due to a low power factor of the dishwasher, and that the magnum 4448 is incompatible with certain low-power-factor devices. And that there are two possible solutions: 1) we'd need to get a different dishwasher with higher power factor that is compatible with this inverter, or 2) we could install a run capacitor to help overcome the low power factor. We really don't want to install a run capacitor, mostly because I can't get any reliable info (so far) on how to size it. So our preference it to just get a different model dishwasher that is compatible with this magnum 4448 inverter.

So my question is, are any forum members here running a dishwasher on a magnum 4448 inverter? What model is it? Ideally looking for a recent-model DW that I can still find new.

Thanks!

BB. · March 2021

This is one case where a good quality Oscilloscope (that can measure 120 VAC power lines) would be really helpful... Many timing circuits do not "like" less than perfect sine wave power... A motor run capacitor may help--But it could just as easily make things work if the AC inverter's output is simply not a good sine wave under the dishwasher load.

One thing to check on--Measure the DC input voltage to the AC inverter right on the inverter's input terminals. Too long/too small of DC Wiring could be causing low input voltage to the inverter...

This will not solve your problems... But it gives you a pretty good in depth/readable explination of gensets (and inverters) and their AC loads. And what can go wrong:

http://www.screenlightandgrip.com/html/emailnewsletter_generators.html

-Bill

DrySide · March 2021

Bill,
I don't have an oscilloscope handy but perhaps could borrow one from work in the next couple weeks.

The inverter was installed as "pre-wired" in a Midnite Pre-Wired MS4448PAED 2-CL200. Are the DC wires you refer to directly from the battery bank to the inverter? Or to this pre-wired panel? I want to believe that since this was all professionally done, that the DC wiring is sufficient and won't lead to the low input voltage at the inverter. But I will check this. Not sure how easy it will be as the inverters are inside the panel doors, and I don't actually have a decent DVM handy

so this will also have to wait.

Another forum member suggested that I should run another load (like a high wattage hairdryer) while I run the dishwasher. This is actually working! The DW is running fine. (With the hairdryer on LOW it did nothing, but with the HD on HIGH the DW is running correctly). Does this offer any clue as to what I may be able to do with the inverter to get to be happier running the DW (of course, meaning happy but without a hairdryer running)?

Thanks,
Eric

BB. · March 2021

Eric,

You need to measure the voltage at the AC inverter's DC input--And you do not want too much voltage drop for the entire wiring path from battery bank to AC inverter input... It is not only a waste of power (heating the wiring), it is also not supplying the voltage/instantaneous current needed by the inverter to supply a "clean sine wave" output.

Using the hair dryer on high--That sort of indicates that the dish washer probably has a "power factor" problem... Many electronic devices have a "non-linear" input current profile. For example, they only take current when the AC voltage sine wave is near it's peak... That can be a big problem for AC power supplies to maintain the sine wave (causes lots of distortion). Using a motor run capacitor to "fix a phase issue--Lagging current because of induction motor" will not fix non-linear loads.

This compares power factor correction because of inductive loads (which a capacitor "can fix") vs "active" power factor correction to support non-linear loads. Modern electronic devices/appliances are supposed to have active power factor correction... What yours has, don't know. (could be motor, could be heating element control to increase water temperature/drying).

https://chargedevs.com/features/a-closer-look-at-power-factor-correction/

It is possible that a different brand of TSW/PSW (true/pure sine wave) inverter might behave better.

And be careful with the O'scope... You know that typical leads are ground referenced to the the AC plug (the ground pin). If you try to clip the lead ground to one of the AC wires (i.e., "hot" vs "neutral" wiring for 120 VAC)--You will be seeing sparks/blowing equipment and breakers.

Good luck,

-Bill

DrySide · March 2021

Thanks Bill for your heads up on using a scope. Ideally I won't have to go down that path but if I do I'll get smart about it before I start.

And yes I agree that this problem is almost certainly due to the DW low power factor or lack of active power factor correction.
Given how much $$ I just recently invested in this inverter setup, I'm not inclined to swap out inverters. I'm really looking for a suggestion on which DW would work on this inverter setup.

I believe there must be other users of this inverter who have a DW with adequate power factor. Can any Magnum 4448 users chime in with what DW has worked for them?

Thanks,
Eric

mcgivor · March 2021

The power factor of the DW is unlikely the sole problem because the major draw would be the heating element which is resistive, the most likely cause is imbalance on the output of the inverter compounded with the pump start inrush and subsequent surge, especially when there are other potential loads on the given leg of the inverter.

The best solution would be to utilize a 240V machine which would allow the full potential of the inverter rather than half of it's rated capacity, something like this https://adaappliances.com/product/ge-gdt2256-built-in-dishwasher-copy/

BB. · March 2021

I was thinking the electric heating element may use the equivalent of a lamp dimmer (thyristors) that "chop" the current to the element to control the temperature.

No clue if they are really doing that--Just an idea of why the dishwasher could be having problems.

-Bill

DrySide · March 2021

This 240V DW is an interesting option; I will consider that.

I do have another observation about my system. If I leave my DW circuit energized at the circuit breaker, the DW will "wake up" every couple minutes even if it's not running. That is, it will be off but will emit a chime/sound as if it just turned on or woke up. It shows some digits on the countdown timer but that's it. Then a couple minutes later, same thing, it emits a chime like it just woke up. One of the forum members had suggested that my inverter may be "searching" using it's power-saving search function. Does this sound like something related to a search pulse? I did check my inverter controller and it says search is "OFF". As noted in my signature, this system actually has TWO magnum 4448s running.... I wonder if the inverter controller is only controlling one of them and the other is still sending a search signal?

Thanks for the continued ideas, always looking to learn something :-)

Dave Angelini · March 2021

A master and a slave inverter work by having the slave in search mode to save power when not needed. I do not use your inverter but if you can force the slave out of search, it may shine more light. I only use the XWP and in over 350 offgrid homes andnever have appliance issues, or any for that matter. XWP is a single 6.8kw split phase inverter.

You might try the Bosch DW!

DrySide · March 2021

Dave Angelini said:

You might try the Bosch DW!

If I knew the Bosch would work, I would get it in a heartbeat. I asked my appliance guy to get the power factor specs from Bosch and he said he they were not available. Do you know these for Bosch or where they are available? or know some other way I could know it would work before buying it?

Dave Angelini · March 2021

I tell my clients to buy everything they can from Costco. 90 days minimum return and longer for most things.
I think you should talk to the person who installed your power system as this is not an appliance issue. Good Luck !

SolarMusher · March 2021

DrySide said:

Dave Angelini said:

You might try the Bosch DW!

If I knew the Bosch would work, I would get it in a heartbeat. I asked my appliance guy to get the power factor specs from Bosch and he said he they were not available. Do you know these for Bosch or where they are available? or know some other way I could know it would work before buying it?

I have a customer that is using this Bosch DW and never had any issue with the same dual PAE setup.
He used this DW for a few years on a single 4448PAE and upgraded his system 5 five years ago.
Search watt is 5 watts per defaut, so you'll have to disable this setting by manually selecting Off=>Enter in the RTR or ARC-50 menus.
A+,
Erik

Wheelman55 · March 2021

DrySide said:

I do have another observation about my system. If I leave my DW circuit energized at the circuit breaker, the DW will "wake up" every couple minutes even if it's not running. That is, it will be off but will emit a chime/sound as if it just turned on or woke up. It shows some digits on the countdown timer but that's it. Then a couple minutes later, same thing, it emits a chime like it just woke up.

DrySide...I've been getting a chime sound in my system too. The chime sound lasts for a long second, and repeats at irregular intervals, often hours apart from occurrence to occurrence.. The only thing that we've got installed is a Mitsubishi mini split so far. I'll try turning that breaker off to see if the chime stops.

Good to know that we aren't alone with the chime sound:)

PS. Our system is Schneider.

NANOcontrol · March 2021

I have a GE profile dishwasher and I run it on a little 400W MSW inverter. It is interesting to note that it only draws 100W maximum and a little over 100WH for a whole cycle. You are probably wondering how. The heater runs off DC of the panels. Those wires that went to the element now control a relay. Heater is fully on in cycles that have water moving around and in the dry cycle it is on for a couple of seconds and then off for about 50% duty cycle. I have an off delay relay of about 15 seconds that keeps the element on for higher power. Added insulation greatly reduces heat loss so the system works. This motor is brushed and control module has a transformer supply so it has nothing to do with power factor or waveform. Power drops to nothing between cycles so I suspect this low load is shutting inverter off. Your best option would be to operate on a switched outlet with a 40W lamp to place a minimum load.

DrySide · April 2021

Dave Angelini said:

I tell my clients to buy everything they can from Costco. 90 days minimum return and longer for most things.
I think you should talk to the person who installed your power system as this is not an appliance issue. Good Luck !

Thanks everyone for all your replies so far. It's a lot to sort through and taking it slowly now as I learn more.

I don't yet have a decent DVM but I do have a Kill-a-Watt. Dave your comment got me thinking to take this issue to my installer. I'd like to have some data available to help them understand what's wrong. (They already made an off-hand comment about power factor and motor run capacitor so they're not biting on this being a system issue). What can I measure with my Killawatt that would help demonstrate that there is a system issue? Things like power stability? Frequency stability? What kind of data would support that this is a system issue?

Thank you.

Dave Angelini · April 2021

Did you do or verify what was said in post #12 ? You can't be in search mode! It should be disabled for most all offgrid!

DrySide · April 2021

Voltage Stability question: I have tested some circuits in the house using the KillaWatt. I found the voltage varies a lot but not sure if this is normal/expected. Is this too much voltage variation?

No-Load Voltage at a random outlet in the house is roughly 123 V. No-load voltage fluctuates between 122.3 and 124.1 while watching over 60 seconds or so.
Turn on 1800W hairdryer and voltage drops as low as 104V.
With hairdryer on, voltage stabilizes at ~ 112V

To me this seems like too much voltage drop. I suspect what BB said initially may be true, that the voltage input to the inverter may be too low and/or the cables from battery to inverter are too long and/or too small. They are 4/0 and are roughly 9 feet long. Is this reasonable? (When I get my hands on a DVM I'll measure this voltage.....)

I haven't done this with the dishwasher yet as I need to rewire it (it's hardwired so need to install a power cord kit to plug into wall outlet)

Thanks,
Eric

DrySide · April 2021

Dave Angelini said:

Did you do or verify what was said in post #12 ? You can't be in search mode! It should be disabled for most all offgrid!

Yes, search mode is off. It was installed that way by the installer, I didn't have to change it.

DrySide · April 2021

Actual DW power factor:

I've wired the DW through a wall outlet (the disposal outlet on same circuit as DW) and can monitor power factor on the killawatt.
Power factor with DW plugged in = 0.33
Power factor with DW filling with water = 0.6
Power factor when cycle starts = 0.22.
Bounces between 0.3 to 0.5 when running with occasional low of 0.22 and high of 0.63.

So clearly the power factor is low. Is this strictly due to the dishwasher itself? or is PF a combination of the DW load and how the inverter power responds? (in other words, if I plugged this DW into grid power would it have a high power factor?)

-Eric

Problem with Magnum Inverter 4448 and Dishwasher - Low Power Factor - Help?

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