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 > Why won’t my Champion C46540 generator run the microwave?

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2112

Texas

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Joined: 07/16/2011

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Posted: 01/05/22 04:07am Link  |  Quote  |  Print  |  Notify Moderator

Before i got a 240V generator, I connected my 30A 120V generator to my panel by connecting hot to the L1 lug on the panel, neutral to the neutral bus and ground to the ground bus. Then I turned ALL 240V breakers OFF. After that I jumped a 10AWG wire from L1 to L2. This powered everything 120V.

Disclaimer: I did not say do this, I did not recommend doing this, I do not advise doing this. I'm just saying I did it.


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enblethen

Moses Lake, WA

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Posted: 01/05/22 07:02am Link  |  Quote  |  Print  |  Notify Moderator

The OP needs to tell us what he is trying to do.
He is talking a building in posts. This is different and potentially dangerous!


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2112

Texas

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Posted: 01/05/22 07:13am Link  |  Quote  |  Print  |  Notify Moderator

Let's look under the hood to see how this generator works:

Here: a color illustrated schematic of your generator

[image]

Notice MW1 and MW2 in the red square boxes. These are your two windings that output your 120V. Each has a maximum of 14.6A (1750W)

Notice the switches, up is green and down is orange. This is the 120V/240V switch you move to select which outlets have power.

Notice the blue square at the bottom of MW1. This is where the AVR samples a portion of MW1 voltage. This is all the AVR knows, the voltage of MW1.

Now, when your switch is on 240V you are using the green and purple wires on the L14-30R connector. They are common to the black wire. MW1 120V is at the purple and black wires, MW2 120V is at the green and black wires. 240V is at the green and purple wires. 240V at 14.6A is 3500W.

I believe your microwave is being powered from the green and black wires, MW2. This is an unregulated 120V 14.6A (1750W) leg. The AVR is looking at the purple and black wires, MW1, so he's clueless to your microwave's existence. This is one flaw of this design.

Let's look at the 120V side. When you move your selector switch to the 120V position you are now using the orange wires powering the TT30R connector. This places the two windings MW1 and MW2 in parallel. Two 120V 14.6A windings in parallel will provide you 120V 29.2A, or 3500W.

You can get a regulated 120V 3500W using the TT30A connector, but the L14-30R is limited to 1750W regulated on MW1 and unregulated 1750W on MW2. This doesn't matter if you are powering only 240V devices. The AVR sees that. The problem occurs when you split them as you did. You're not the 1st one to stumble onto this issue, and you won't be the last.

I hope this helps

Bobbo

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Posted: 01/05/22 07:22am Link  |  Quote  |  Print  |  Notify Moderator

tonyclifton wrote:

It was mentioned the 3 wire RV outlet could power both 120v legs with an adapter. What is this adapter? Sounds like this will provide more wattage.

My microwave is an inverter style, or at least says so on the front. I’ll lug it out to the 46540 tomorrow and hook up to the RV outlet (i have a pigtail to 2 120v outlets in a box) and see if it has same issues. I suspect it will run better.


30amp to 50 amp RV adapter

[image]


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bgum

South Louisiana

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Posted: 01/05/22 08:19am Link  |  Quote  |  Print  |  Notify Moderator

If there is one thing I have learned in the recent past is that there are a lot of would be electricians running around that don't know squat. After proven wrong some will admit they were wrong and some never will.

Gdetrailer

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Posted: 01/05/22 09:48am Link  |  Quote  |  Print  |  Notify Moderator

2112 wrote:

Let's look under the hood to see how this generator works:

Here: a color illustrated schematic of your generator

[image]

Notice MW1 and MW2 in the red square boxes. These are your two windings that output your 120V. Each has a maximum of 14.6A (1750W)

Notice the switches, up is green and down is orange. This is the 120V/240V switch you move to select which outlets have power.

Notice the blue square at the bottom of MW1. This is where the AVR samples a portion of MW1 voltage. This is all the AVR knows, the voltage of MW1.

Now, when your switch is on 240V you are using the green and purple wires on the L14-30R connector. They are common to the black wire. MW1 120V is at the purple and black wires, MW2 120V is at the green and black wires. 240V is at the green and purple wires. 240V at 14.6A is 3500W.

I believe your microwave is being powered from the green and black wires, MW2. This is an unregulated 120V 14.6A (1750W) leg. The AVR is looking at the purple and black wires, MW1, so he's clueless to your microwave's existence. This is one flaw of this design.

Let's look at the 120V side. When you move your selector switch to the 120V position you are now using the orange wires powering the TT30R connector. This places the two windings MW1 and MW2 in parallel. Two 120V 14.6A windings in parallel will provide you 120V 29.2A, or 3500W.

You can get a regulated 120V 3500W using the TT30A connector, but the L14-30R is limited to 1750W regulated on MW1 and unregulated 1750W on MW2. This doesn't matter if you are powering only 240V devices. The AVR sees that. The problem occurs when you split them as you did. You're not the 1st one to stumble onto this issue, and you won't be the last.

I hope this helps


Your close, but not quite correct.

When the switch is set to 120V only, both 120V windings are connected in parallel. This means that not only all of the 3500W is available on the 30A RV outlet but the voltage of both windings are fully regulated by the AVR.

You only need one sample point for the AVR to work and since both windings are in parallel voltage and current will be close enough to be pretty much equal across both windings (remember, both windings are in parallel in this case).

When the switch is set to 120/240 then you now have basically semi-unregulated voltage on one winding and regulated voltage on the other because those windings are now wired in series. AVR will still respond, but not as accurate unless you happen to load the half which has the AVR sample tap.

Gdetrailer

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Posted: 01/05/22 09:57am Link  |  Quote  |  Print  |  Notify Moderator

enblethen wrote:

The OP needs to tell us what he is trying to do.
He is talking a building in posts. This is different and potentially dangerous!


[image]

OP may just be trying to power a "off grid" cabin in the woods also..

There ARE millions (Billions perhaps) of acres of land available which do not have any commercial grid power access in the good ole US of A..

Folks love to assume that commercial power is available everywhere, it isn't and in most of the cases will never be due to extreme costs to build maintain infrastructure for one single home in the middle of nowhere..

enblethen

Moses Lake, WA

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Posted: 01/05/22 10:23am Link  |  Quote  |  Print  |  Notify Moderator

When powering an off-grid system there is many things to consider.
Need to get calculations on what is going to be connected. That would give basics for size of genset.
Some cabins are powered with only a 120 volt source and others install a 120/240 volt source.
We don't know what he is doing!

Gdetrailer

PA

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Posted: 01/05/22 10:57am Link  |  Quote  |  Print  |  Notify Moderator

enblethen wrote:

When powering an off-grid system there is many things to consider.
Need to get calculations on what is going to be connected. That would give basics for size of genset.
Some cabins are powered with only a 120 volt source and others install a 120/240 volt source.
We don't know what he is doing!


OP posted this..

tonyclifton wrote:



My goal; is to power both legs of the building circuit, although selectively powering certain breakers to manage load. I turn off high draw circuits like heat pump, water heater, sewage pump, range. What type of generator output / receptacle will do this as I shop for a replacement generator? I know this unit is getting old although has been a rock solid runner ever since I bought it based upon extensive reviews here.



Seems pretty clear to me what the OPs objectives are.

"My goal; is to power both legs of the building circuit, although selectively powering certain breakers to manage load. I turn off high draw circuits like heat pump, water heater, sewage pump, range."

So, assuming that OP is attempting to setup an emergency backup power system on a on grid home they are planning to selectively enable only the circuits they need and disable the circuits they do not need to power via gen.

The OP does not say exactly how they are feeding the gen into the panel, hopefully it is through an breaker interlock assuming it is on grid home but once again, not really mine or anyone elses business.

The reality however is #1, the OPs current gen cannot supply 120/240V of sufficient current level to run their microwave.

The OPs gen IF switched to 120V only operation and the RV 30A outlet is used could/should power the microwave but will not power both L1 and L2 of the breaker panel due to the possible 240V only devices that may be connected to the breaker panel.

OP could however since they indicated they have an inverter microwave try running the microwave at a reduced power level. Inverter MWs do not PWM modulate the magnetron , instead it reduces the voltage level to control the output to the magnetron. OP could try 50% power level and then work up to 100% until the gen stops..

2112

Texas

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Posted: 01/05/22 11:01am Link  |  Quote  |  Print  |  Notify Moderator

I decided to connect my generator to the house and simulate what OP is describing. Mine is a model 64514, similar to his. What I found really doesn't surprise me, but good to know, and not good.

With typical loads: fridge, TV, satellite receiver, satellite internet modem and router, charging 1 phone and 1 laptop.

All measurements using Kill A Watt P3

L1-123.4V
L2-120.6V
60.6Hz

1200W Microwave on L1, 600W coffee pot on L2.
NOTE: MW is specified as 1200 working watts. The P3 flashes 1700 during operation, indicating the actual load is greater than the P3 1500W rating. However, 8oz of water was placed in the MW. MW was operated for 30sec during each test and operated as expected. The water warmed up each time.

Coffee pot ON, L1-123.4V, L2-117.8V 60.3Hz
MW & pot ON, L1-120.6V, L2-126.5V 59.8Hz

Now here's the kicker
Just MW ON, L1-120.6V, L2-133.2V 60.4Hz

With a heavy load on L1 and little load on L2, L2 goes over 130V

End of Test



Yea, I'm bored

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