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Old 06-18-2021, 07:29 AM   #1
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Put Microwave on Inverter Circuit

Does anyone know how to add an existing receptacle to the inverter circuit? I want to put the microwave on the inverter so we can use it Boondocking. I upgraded the WFCO 1000 watt inverter to the 2000 watt model, and also changed the batteries to four 100 ah Battleborns, so power is not an issue for me to run the microwave on the inverter. Thanks for any help in doing this on my 2020 Classic 33 FBT.
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Old 06-18-2021, 08:28 AM   #2
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You will need to pull 12 awg wire to the desired outlet from either the inverter itself or another inverter outlet.

I am not familiar with the 33 to offer any details on how feasible that will be.

If electrical work is not something you are familiar or comfortable with then you should consult with an electrician. However, this would definitely fall under the realm of DYI.
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Old 06-18-2021, 11:24 AM   #3
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Originally Posted by OutdoorIdaho View Post
You will need to pull 12 awg wire to the desired outlet from either the inverter itself or another inverter outlet.

I am not familiar with the 33 to offer any details on how feasible that will be.

If electrical work is not something you are familiar or comfortable with then you should consult with an electrician. However, this would definitely fall under the realm of DYI.


Hey thanks for the reply. That’s what I was originally thinking, but since my original post, I got my hands on the airstream wiring diagram for the 2019/20 33 Classic. Circuit 6 has only the microwave on it, and fortuitously, circuit 7 is the inverter circuit with all the inverter outlets… so, I should be able to just jump the load side of the circuit 6 breaker to the load side of circuit 7, and remove the breaker on circuit 6. The only risk is that I would overload the inverter circuit, which would pop the breaker if it happened. However, the inverter it out is very lightly loaded, and I’ll never have every rv, stereo, blue ray on all at the same time when I run the microwave, so I don’t see any issues. I think I got lucky here, but if anyone see’s an issue with this plan, let me know. Thanks!
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Old 06-18-2021, 12:02 PM   #4
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Hi

The inverter only puts out a bit over 16A. Having it feed a 15A breaker is not going to loose you much.

Bob
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Old 06-18-2021, 01:40 PM   #5
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I suspect that will not accomplish what you desire.

Somebody correct me if I am wrong.

My understanding of how that works is that the inverter is plugged into receptacle L to provide "pass through" power to the inverter outlets N, P, R, S, T, and U while you are connected to shore power. That would mean that the inverter only receives power from L and does not provide power to it.
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Old 06-18-2021, 03:00 PM   #6
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Originally Posted by OutdoorIdaho View Post
I suspect that will not accomplish what you desire.

Somebody correct me if I am wrong.

My understanding of how that works is that the inverter is plugged into receptacle L to provide "pass through" power to the inverter outlets N, P, R, S, T, and U while you are connected to shore power. That would mean that the inverter only receives power from L and does not provide power to it.


The inverter does provide pass through when on shore power, correct, but is not the primary function of the inverter to provide power “inverted” from 12 volt? Where else would the inverter outlets get power from when not on shore power if not from the inverter? I do not see any other connections from the inverter to those outlets.
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Old 06-18-2021, 03:44 PM   #7
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Yes, the inverter powers those downstream outlets when shore power is not available. However, I do not believe the inverter will provide power back upstream to the breaker to allow you to get power to the microwave as you described above.
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Old 06-18-2021, 04:06 PM   #8
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Yes, the inverter powers those downstream outlets when shore power is not available. However, I do not believe the inverter will provide power back upstream to the breaker to allow you to get power to the microwave as you described above.
Hi

Right.

To "move over" the circuit, you need to take it to the output side of the inverter.

Bob
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Old 06-18-2021, 04:31 PM   #9
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Don't forget that you will always have to turn on the inverter to run the microwave, even when you have shore power.
If you are a brave explorer, you may find that the microwave is plugged into an outlet in the back of a cupboard, or behind a drawer. The cord might be long enough to reach an inverter plug above the kitchen counter....

I have a 2012 and a wimpy inverter, which I LOVE to use to watch TV weather and charge my cell phone whenever a storm, etc. causes a.power outage. I do have the convection/microwave which would be a PITA to try to use without any power hookup. I simply use either the stovetop.or an outdoor grill to cook in those cases. I could use my induction burner, but ANY high usage electrical equipment can overburden the inverter, so propane or charcoal are my "boondock/power outage" choices.
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Old 06-18-2021, 05:27 PM   #10
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Hi

There are a lot of inverters out there. Some do and some do not have transfer switches. At this point we really don't know which one the OP has ...

Bob
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Old 06-18-2021, 08:07 PM   #11
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As long as you changed the wiring to the inverter and upgraded the fuse to run the extra load you should have enough to power the MW. As far as jumpering the output circuits my only worry would be if you left it like that and then plugged into shore power. You would be back feeding the inverter. I'm not sure it can handle that. It may not have protection built into it for this and that may damage the inverter.
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Old 06-18-2021, 08:43 PM   #12
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What size microwave are you going to try running from the inverter? Unless it's quite small, you may find that you can only go a few minutes, even with 400 Ah of lithium.
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Old 06-18-2021, 09:02 PM   #13
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What size microwave are you going to try running from the inverter? Unless it's quite small, you may find that you can only go a few minutes, even with 400 Ah of lithium.
Microwaves do use much more power than their "Cooking" rating. For example, our 750W microwave actually pulls about 1200W when running. I don't know what is taking the additional power or if it is just inefficiency.

However, we run our microwave on only 2-Renogy 100AH lithium batteries and a 3000W inverter/charger *. It doesn't drain the batteries more that what I expected so his 400AH batteries will do just fine since a microwave only runs a few minutes at a time. If he has a larger microwave, he may be closer to his inverter limit, but should handle the load fine.

(* - yes, I understand my batteries won't power 3000 watts, but I bought it instead of a 2000W for possible future battery expansion).
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Old 06-19-2021, 06:33 AM   #14
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Microwaves do use much more power than their "Cooking" rating. For example, our 750W microwave actually pulls about 1200W when running. I don't know what is taking the additional power or if it is just inefficiency.

However, we run our microwave on only 2-Renogy 100AH lithium batteries and a 3000W inverter/charger *. It doesn't drain the batteries more that what I expected so his 400AH batteries will do just fine since a microwave only runs a few minutes at a time. If he has a larger microwave, he may be closer to his inverter limit, but should handle the load fine.

(* - yes, I understand my batteries won't power 3000 watts, but I bought it instead of a 2000W for possible future battery expansion).


So the inverter is 2000 watts. It has a transfer switch and pass through. As for the microwave, it’s 850 watts and we only run it for 2 min or so at a time. It’s just a convenience thing to be able to have it available on batteries when boondocking. So my only confusion at this point is passing electricity “upstream” if I join the circuits, which was mentioned in one of the replies. (and to think I was once an avionics tech in the Navy many years ago and I can’t figure this out!) I think I need to diagram this to understand the electrical flow. If combining the circuits does not work, yep, plan B will be to plug it into the next closest outlet on the inverter circuit.
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Old 06-19-2021, 06:56 AM   #15
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Originally Posted by OutdoorIdaho View Post
I suspect that will not accomplish what you desire.

Somebody correct me if I am wrong.

My understanding of how that works is that the inverter is plugged into receptacle L to provide "pass through" power to the inverter outlets N, P, R, S, T, and U while you are connected to shore power. That would mean that the inverter only receives power from L and does not provide power to it.


The lightbulb in my head has illuminated. Thanks OutdoorIdaho for rattling my brain before I potentially broke something. Jumping the circuits will not work because that would require the inverter to pass current in the opposite direction to feed the microwave outlet. On to plan B, find the closest outlet on the inverter and run and hide an extension cord thru the cabinets.
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Old 06-19-2021, 08:43 AM   #16
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You need a switch like this. We have solar installed, when we want zero power to plugs then the switch it off. When we are on shore power, it’s on charge only (or pass through). When boondocking or want power to plugs and no hook ups then we switch to on. We are usually in the on position as we mostly boondock
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Old 06-19-2021, 09:11 AM   #17
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...... As for the microwave, it’s 850 watts and we only run it for 2 min or so at a time. ....
Hi

The microwave "power rating" is the amount of microwave energy delivered to the food inside the microwave. The input power to generate this energy will always be higher than the delivered power. Check the back plate on the microwave to see what the input power rating is. Don't be surprised if it's 10A or more off of 120V ....

No, this doesn't matter in terms of maxing out the inverter with just the microwave running. However, folks do tend to operate multiple devices at once. Understanding what each one pulls is important. Equally important is understand just what the "2000W" rating on the inverter applies to. On some that's a 3 second rating. On others it might be continuous at 30C (with another rating once the insides get to 40C ( maybe a minute later .....).

Bob
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Old 06-19-2021, 12:45 PM   #18
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I had the same thought and my local tech talked me into putting all outlets on the inverter (when turned on) and all outlets on (even previously inverter only) when on shore power/generator. Upgraded 1500 W renogy inverter. Just have to remember power management while using Microwave in inverter mode. Auto switch recognizes power source and defaults to shore power when connected. I keep inverter turned off unless boondocking.
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Old 06-19-2021, 01:34 PM   #19
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So from what I understand:

1. you have one circuit #6 which is connected to shore/gen power dedicated to the microwave.
2. you have one circuit #7 which is dedicated to all inverter circuits. I assume that this circuit is also connected to an automatic transfer switch such that it will also be powered by shore/gen power. Hence, this would be the 120v outlet circuit regardless of power source.

Basically both of these are connected to shore/gen power but the manufacturer never thought that people would use battery to power microwave ovens because it is not in the cards for lead acid battery systems. Lithium is a new ball game.

It seems to me the simplest solution would be to install an ATS - automatic transfer switch. you would install it on the power supply side of breaker #6. There are two incoming power sources, one would be from the existing line (shore/gen) and a second line would need to be run from the inverter. The default would be the shore/gen power and when the inverter is powered up, it will override.

Progressive Dynamics produces a good ATS which is rated 120V / 30A.
here is a possible source: https://www.etrailer.com/RV-Transfer...hoC3NMQAvD_BwE

I would not worry about energy usage. 400Ah of lithium provide over 5 kilowatts of usable power which will power most microwaves for 4 hours. (that is at 1200 watts per hour). The inverter will draw 10x the 12v amps to convert to 120V - 1200w = 10A @ 120v = 100A @ 12V. I have installed the BattleBorn batteries and they are good. The only drawback is that they have 100A BMS. In a 400Ah parallel bank that shares the load, there should be little issues unless the banks SOC gets too low. Lithium batteries discharge rate is limited by the BMS and each battery acts independently. In other words, they will individually shut down if stressed. I have seen BMS circuit board connections melted because too many amps were pushed through. I generally prefer the 200Ah battery with 150A or 200A BMS, 300Ah with 150A to 300BMS or 400Ah with 250A to 300A BMS. In my opinion, this provides better system protection. There are a lot of suppliers that offer the larger batteries with larger BMS. The more amps a BMS is designed to handle, the less chance it will fail under normal use.
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Old 06-19-2021, 01:35 PM   #20
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So I recently got rid of a 3000 watt inverter and I have 4 lithium ion batteries and 4 solar panels. Second owner so I know what was spent and it was a fortune ($30K) for little reward. I took the microwave off the inverter circuit it is a terrible energy hog. The lithium ions shut down to protect the batteries just above 10 volts. So you will be stranded if they shut down, I was. I had to jump them in the morning after running furnace all night it was very cold. and running the microwave first thing in the morning to defrost a bagel.

I really think it is a callosal waste of money for little return on investment. I converted the inverter circuit to shore power also.

If I ever want an inverter again I would go smaller and use the original circuit. I really can live without a microwave on demand. The solution offered to plug in the inverter circuit is a good one you could even fish some romex wire to create one underneath.

Really glad I got rid off the inverter, it was a victronix 3000 watt 16 amp and took up a lot of space in the interior, I was able to reclaim valuable space.

Hope this helps

Cheers.
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