Soft start question

ELYNN4

I have an LG gas dryer - not electric… when I start the dryer the in rush current is high enough that the LED lights in the house flicker.  I have an XW 6848+ inverter.

If my generator is running, charging the batteries, it gets kicked off line when the dryer starts.  The generator stays on line with all other loads in the house.  My generator is a 6 kw, the breaker size on the XW+ is 35 amps and the battery charge rate is set at 50%.

My question is - does anyone have experience with any of the after market soft start products?  They all advertise that they are designed for air conditioners.  I’m curious if a soft start device would work in this application or if there is a different approach I should use?

Thanks in advance…

BB.

That is a strange issue...

First, would need the model number of the LG Dryer to look up the parts/repair data for it... Older (decades), you could assume that these were induction motors with starting capacitor... Today, there is a chance that these are motors with some sort of VFD (variable frequency drive) that do not use starting capacitors.

I am not sure why your generator is going off line... A typical problem is that there is a poor electrical connection between the energy source (city power, Genset, inverter) and the circuit breaker panel. Typically, you would open the various access points/j-boxes and look for browned/blackened wire connections, corrosion, loose wire nuts, etc.

It is not uncommon for a poor connection in one of the "hot lead" (black/red wires) circuits--Or in the  Neutral (white wire) some where... An poor neutral connection on a home with 120/240 VAC split phase power (typical North American home), the poor neutral connection could cause the some lights to go dim and others to even brighten when there was a motor starting (the red to neutral and black to neutral should each be around 120 VAC... With a poor or open neutral connection, the motor starting will "collapse" the (for example) red to white voltage to well below 100 VAC, and the other black to white voltage to to 140 VAC or higher (and why some lights dim while others turn white).

Generally, I would not expect a Genset to be knocked off line with a "poor" black/red/white electrical connection...

It does sound like your dryer may be "surging" more current than it should while starting... You can look and see if yours has a "starting capacitor" on the motor... The motor could take more current with a beginning to fail starting capacitor. And replacement capacitors are usually pretty cheap (less than $20???).

My first two guesses.... 

-Bill

ELYNN4

Thanks Bill - the dryer is a 2015, so not real old.  It is a DLG3170 LG.  The XW+ senses the generator struggling - you can hear it as well, right when you start the dryer.  Once the dryer is up to speed every thing is happy and the XW + puts the generator back on line.  The loads from the toaster, microwave, well pump etc. are handled with ease.  I try not to use my table saw, chop saw etc. while charging batteries, since they have bigger motors.

I will try replacing the capacitor - seems like a cheap experiment.

thanks again.

NANOcontrol

I think there is a relatively and cheap way to fix this.  Incidentally, I have one of these soft starts to review and was going to put one on my refrigerator.  As part of this, put in a question to the manufacturer's help line which promised an  answer in 48 houts.  It has been two weeks and have never heard anything back.  I don't really need their help as I could design one.  Just wanted to see the response time as part og the review.

The problem is starting the motor and heater at the same time.  I'm sure the inverter could start the motor without issue.  I would buy a cheap on delay timer rated for that voltage, this should only cost about $15. Doesn't need a lot of current because there is likely a relay for the heater element.  Remove one of the wires from the relay coil and insert the on delay.  Thirty second should be more than enough time for motor current to stabilize.  There are always schematics on the back of the machine or up in the control panel.  This will remove excess motor starting current from the machine's operation.  

NANOcontrol

OOPS, missed it was a gas dryer. Answer may help someone else.  I tried to find a schematic and that only resulted in a website locking up my computer.   Did this ever start well?

ELYNN4

We have only been off the grid with this for five years.  I have finally gotten the generator(s) settings on the XW+ dialed in, with the help,of Dave A.  My 9 kw can usually carry the dryer, but it grunts when the dryer starts.  The 6kw falls to its knees and gets booted off line.  I can’t say that it’s gotten any worse.  Just trying to get things to run as smoothly as possible.

BB.

Some reports of a "bad motor" tripping a breaker (does not always start, buzzing, sounds like "struggling" to run)...

(not sure if I have the right/complete dryer part number--One listed may be for an electric dryer?):
https://www.appliancepartspros.com/repair-help/lg-dryer-dle3170w-repair/dle3170w-tripping-breaker.html

Two "big" current draws typical for dryer... The main motor, and the ignitor (for gas dryer):

https://www.appliancepartspros.com/drum-parts-parts-for-lg-dlg3171w-00.html (may be yoe ur gas dryer?):

https://www.appliancepartspros.com/lg-dryer-ignitor-5318el3001a-ap4439620.html

The ignitor typically draws something like 3.5 to 4 amps @ 120 VAC (rough guess)...

The heavy loading on your inverter/genset--Does this seem to be from the drive motor (a couple seconds starting, or when running?) or the 5-10 seconds or so for the ignitor heating (on some of my gas appliances, the ignitor turns on, gets hot, then shuts off/turns on gas supply at the same time to light flame).

If you have a Kill-a-Watt type energy meter, you can monitor the AC current and (possibly) figure out the high current flow (during motor cycle, or during ignition cycle)... And figure out what is drawing excessive current (or not?).

Neither the motor or the ignitor should draw enough current (in normal operation) to negatively affect the operation of a 6.8 kWatt (good quality) AC inverter....

Have you experienced any circuit breaker trips on the dryer circuit?

-Bill

ELYNN4

Thanks Bill - the dryer starts easily, with no unusual noises.  The “heavy” load on the system is instant and very short duration - well under a second.  The igniter load is minimal and carried easily.  I started digging for the motor and ran out of time.  The one image does look like an electric dryer set up, but the motors may be the same.  I’m going to try to have a capacitor in hand before digging in all the way.  It takes so long to get parts up here…don’t want to be without a dryer for weeks…

the motor is about what a soft start setup would cost - was hoping someone had had experience with them.

thanks again

BB.

The second link is for model:

LG DLG3171W/00

That appears to be a gas version of the dryer.... Drum Motor is same part number between gas and electric....

https://www.appliancepartspros.com/drum-parts-parts-for-lg-dlg3171w-00.html

The prices for appliance parts appeared to have gone up a lot... If you trust the comments, from $180 in 2016 to $250 in 2024. 

As always, confirm Model numbers and parts before ordering.

The APP company does offer (free?) online chat for questions.

I have not found any starting capacitor for this drum Motor.... Don't know if "custom" or not sold as part... Or it may not have a starting cap.

One commenter 13 years ago ask the parts company for a starting cap, and the response was the "failure" would probably need the motor replaced.. No suggestion for a replacement capacitor.

https://www.appliancepartspros.com/answers-for-lg-drive-motor-assembly-4681el1008a-ap4438218-question-32386.html

-Bill

JRHill

"If my generator is running, charging the batteries, it gets kicked off line when the dryer starts.  The generator stays on line with all other loads in the house."

This doesn't make sense to me EXCEPT the generator disconnects and the inverter kicks in on battery power. But a 6kW genset?!? That's a lot of power but maybe the inverter doesn't like the surge and falls back to battery. The solution is to make sure you are using minimal AC power when you run the drier. Or your dryer has a developing problem. Is this a new issue where it worked before?

BTW you say 6kW then 9kW genset. But the inverter is only going to pass through a set amount. Is there a programmable AC in limitation on your inverter and is your wiring sufficient? One generator is 50% bigger than the other so how can you have AC in amps set to cover both? It would have to be the lessor of the two.

NANOcontrol

Gear type washer motors are high slip design and I assume dryer motors are the same given the high inertial load.  Typical soft start begins with about 60-70% voltage. There are lots of things "I" would try that would be simple for me like putting the igniter on delay. Everything has a tripping point and a couple of amps might help although the igniter may already have a thermal delay. Anything that drops the voltage would help like an extension cord resistance.   I think the easiest and best would be to use an auto transformer.  This not only lowers voltage, but increases current.  I have one I made from an old UPS.  These get thrown away when the batteries die.  I pulled out the innards and left the transformer. This one has two rows of sockets, one for a 12V drop and the other for a 20V drop in voltage.  This allows me to use a chop saw on a small 400W generator. The windings are put in series and can be phased properly with an incandescent lamp in series.   It is a handy little box to have around.   

ELYNN4

Thanks Nano - the igniter already has a 15 second or so delay.  I’ll give the extension cord trick a try…. Don’t have any dead UPS’s laying around, I’ll have to ask around….

thanks!

ELYNN4

Thanks for your response Bill.  I’ll keep researching…

Dave Angelini

35A for an XW AC2 input with a 6kw gen is to high! 

I usually start at 30A and go down if you have a 4 prong 30A plug/receptacle. 

  When you think about the default 60A passthru of XW, you are math wise  at14.4 KW. If you needed 60A you would be using a 20KW genset for reliable loading. Same logic with your 6kw genset.

ELYNN4

Thanks Dave,

I’ll drop it to 30 amps.  At my current setting the load on the generator is between 4 and 5 kw, but as the battery voltage increases during the charging cycle the load does creep up.

Should I increase the battery charge rate to keep it in the 70 amp range or keep it at 50%?  Still trying to understand how the breaker size setting and the battery charge rate affect the behavior of the XW+.

Thanks again.

BB.

Be a bit careful here... I am no expert, but you have to watch what current of 50% of X is... Is this the current at 120/240 VAC, or the current at 48 VDC.

Typically 10% to 20% of battery AH capacity is a good charging current for Lead Acid type batteries... A 300 AH battery bank at 48 volts, would be say 15%*300AH=45amps...

45 Amps * 58 VDC charging current = 2,655 Watts
2,655 Watts battery charging / 0.90 battery charger (example) efficiency = 2,950 Watts AC power (example)
2,950 Watts AC / 240 VAC = 12.3 Amps @ 240 VAC charging side

Note: Highly suggest to "derate" battery charging current by 0.80 (or 1/0.80 = 1.25x) for NEC derating of breakers/wiring etc. for "continuous current loads" such as battery charging (I.e., the battery can take a few hours at "max current" to prevent overheating of wiring/terminals/breakers/etc... I.e. a 12.3 Amp at 240 VAC branch circuit should be rated for a minimum of:

12.3 Amps battery charging circuit (AC side) / 0.80 NEC derate = 15.4 Amps or ~20 amp branch circuit wire/breaker rating.

I am not sure about the XW product line, but I have seen the 0.8 derating implemented in software... For example, a "30 Amp" AC input rating actually limits the inverter/charger AC draw to:

30 amps * 0.80 NEC auto-software derating = 24 VAC actual AC draw by inverter-charger system

Keep track of what circuit you are talking about (120/240 VAC or 48 VDC DC bus) and any "deratings" that may be present. (plus conversation losses of 48 VDC to 120/240 VAC for inverter, and 120/240 VAC to 48 VDC for battery charging).

There can also be "other derating such as 6,000 Watts for 240 VAC circuits, but only (again just an example) a 0.707 Wattage derating (this is example is a common 1/sqrt 2 engineering derating or a 6 kWatt inverter @ 240 VAC is limited to:

6,000 Watts * 0.707 = 4,242 maximum wattage for a pure 120 VAC load

I hope this makes sense... Speaking "generically" can make things a bit more confusing. Using your actual battery bank AH (and voltage) ratings, battery type (10-20% typical for Lead Acid, 50% max rate of charge typical for many Lithium Ion batteries, etc.). vs 50% of "charger DC Amp capacity, etc.)... Just want to be clear and "exact" and avoid mistakes/misunderstandings.

-Bill

ELYNN4

Thanks Bill,

My battery bank is 2,200 AH, the XW+ battery charging is rated at 140 AH.  Neither my 6 or 9 KW generator can come close to taxing the system.  At 70 amps it’s barely more than a trickle charge.  I try not to discharge the battery bank by more than 20% (400 AH).  It’s a real time experiment to see how long the batteries will last (starting the 7th year next month).  I only have to water the batteries two times a year.  I burn less than 1/2 gph charging batteries, and run the generator around 250 hours per year.  I try to keep the generator load between 70 - 80%.  The size of the generators and the load seem to be the sweet spot fuel economy wise.

My challenge is more on the other end - finding a setting that charges the battery bank in a reasonable length of time while handling the household loads.  My household loads are typically in the 300 watt range, they can bump up toward 600 watts if the fridge and freezer kick on.

The microwave, dishwasher, well pump (VFD) blow dryer, toaster etc. loads apply slowly enough that the XW+ can shed the charging load quickly enough to keep the generator on line.  

It’s the surge current from the dryer or garbage disposal that gives the generator fits.  There’s no need to use the garbage disposal while charging the batteries, but it is a good time to do laundry.  I’m going to try the light extension cord trick to see if that might throttle the surge current down to an acceptable level…

Dave Angelini

When in doubt read the manual or watch the video!

 I am in business and only go so far here. Why? because I am busy with clients and it is unfair to them if I do this gratis. You have a ridiculously small generator. Last advice is to get a spare XW. You are damaging transfer relays and this is not the first time for you.  You are not hurting the generator compared to the XW relays!

 I do not like being the bad cop but someone has to.  Good Luck!

ELYNN4

Thanks Dave, I appreciate your guidance and candor.