AC and Microwave August 27, 2016, 11:27:00 am I don't have our LD manual with us. But we have a quick question. If we have 30 amp shore power, should we be able to run the microwave with AC? Last year on a very hot day in a crowded park, we lost power at the shore connection. Re-set the breaker and all was good. This happened with AC and microwave. Since that incident, we've not run both at the same time.This morning, DW asked for a definitive answer. Thanks for guidance.
Re: AC and Microwave Reply #1 – August 27, 2016, 11:42:22 am I don't hook up that often, but, when I do, I don't run power suckers like the AC and the micro (or micro and the electric space heater) at the same time; the EMS has never shut down the power, but the voltage when using both at the same time drops almost into the "clamp down" range.And, many RV parks, particularly older ones, may have electrical systems that are not capable of handling heavy power demands; a lot of rigs running their AC on a hot day puts a huge stress on a system, and voltage drops are to be expected. YMMV, but I prefer not to run high voltage demand appliances at the same time. 3 Likes
Re: AC and Microwave Reply #2 – August 27, 2016, 11:47:03 am Quote from: Traxless - August 27, 2016, 11:27:00 amI don't have our LD manual with us. But we have a quick question. If we have 30 amp shore power, should we be able to run the microwave with AC? Last year on a very hot day in a crowded park, we lost power at the shore connection. Re-set the breaker and all was good. This happened with AC and microwave. Since that incident, we've not run both at the same time.This morning, DW asked for a definitive answer. Thanks for guidance.I can't remember the exact amps that are drawn but when we tried and I looked at the read out on the EMS it was drawing over 30 amps. We turned one off before the breaker tripped.Jim
Re: AC and Microwave Reply #3 – August 27, 2016, 12:45:22 pm Ed & Margee,A 1500 watt microwave on full power with a 120 vac power source draws 12.5 amps<>. The AC, depending on size and outdoor temperature may draw 14 to 16 amps. The combination, without considering any other loads, exceeds the duty rating of 24 amps for the 30 amp circuit (if only briefly while the microwave is on). With good connections and electrical components from end to end including the breaker at the pedestal, it may hold. I turn off my AC when I want to use my microwave so as not to push the limits. BTW-When I do shut off my AC to use the microwave, I make sure to leave it off for five minutes before turning it back on. JMHO 2 Likes
Re: AC and Microwave Reply #4 – August 27, 2016, 01:30:28 pm According to my power surge read out the microwave pulls about 26 Amps. the air-conditioner pulls anywhere from 22 to 18 that's over the 30 amp limit so I don't do both at the same time whether I'm on shore power or the generator running 1 Likes
Re: AC and Microwave Reply #5 – August 27, 2016, 03:37:11 pm Quote from: Gini Free - August 27, 2016, 01:30:28 pmAccording to my power surge read out the microwave pulls about 26 Amps. the air-conditioner pulls anywhere from 22 to 18 that's over the 30 amp limit so I don't do both at the same time whether I'm on shore power or the generator runningGini, was that readout at peak surge or after? I just installed a new over-the-range microwave and it draws a max of 13 amps. Perhaps those are peak surge at start up amps??? Most microwaves are rated at 13 amps or lower.C
Re: AC and Microwave Reply #6 – August 27, 2016, 03:57:16 pm Chris, my micro is the original 1998 model... Probably ought to switch it out one of these days to a more energy efficient one, but it's low on the priority scale..and yes it does go all the way "down" to 22amps. Same for the much newer AC installed in 2011.... Runs at 16 amps once it's up and running My genset guy told me I ought to be able to run both...HA!
Re: AC and Microwave Reply #7 – August 27, 2016, 06:48:55 pm Quote from: Gini Free - August 27, 2016, 03:57:16 pmChris, my micro is the original 1998 model... Probably ought to switch it out one of these days to a more energy efficient one, but it's low on the priority scale..and yes it does go all the way "down" to 22amps. Same for the much newer AC installed in 2011.... Runs at 16 amps once it's up and running My genset guy told me I ought to be able to run both...HA!Gini, have you measured the amperage with any other device? Do you have a Kill A Watt electricity usage device? https://www.amazon.com/P3-International-P4460-Electricity-Monitor/dp/B000RGF29Q If so, try it with that. It's not that I don't believe what you are seeing. It just seems so unreasonably high for a microwave, even if it is a '98 - probably the same one that's in my '02. BTW, I have a Kill A Watt and have measured all the heavy-duty appliances with it and then Sharpie the amperage on the back or base of the appliance so I don't have to measure it again.Chris 1 Likes As an Amazon Associate Lazy Daze Owners' Group earns from qualifying purchases.
Re: AC and Microwave Reply #8 – August 27, 2016, 06:57:11 pm Yes I do, Chris, but it's so hard to get to the back of the micro where it plugs in, and until now never crossed my mind to try it. Will do. But my surge protector and trimetric do show used amps about the same. Like I said probably need to replace it. 1 Likes
Re: AC and Microwave Reply #9 – August 27, 2016, 10:04:32 pm We popped a breaker running the AC and microwave at the same time. If it's hot and we need to nuke, we turn off the AC temporarily while cooking, then back on when the microwave is finished. We also (experimentally) flipped the breaker on the generator attempting the same thing for some undetermined reason. FWIW, if you cook mostly from scratch, as we do, there are few things you can cook in the microwave that don't come out just as well (and sometimes better) in the Instant Pot (or other electric multi-cooker), without popping breakers while the AC is running. Less power required, and more cooking options as well. It's good for boondocking as well -- runs easily on a 2k inverter, and once it gets up to temperature, it takes very little juice to keep it going, compared to a microwave which is typically on constantly while it's cooking. fu2015 TK 2 Likes
Re: AC and Microwave Reply #10 – August 28, 2016, 08:37:16 pm Things initially seemed to be fine with both the AC and microwave running but I hadn't considered the fridge also kicking in, and that was all she wrote. From that point on, we stop the AC before using the microwave.FWIW - the Instapot automatically cycles on at 1000 watts and off according to its program. Lower peak current than a microwave and it's a resistive load (Kill-a-Watt shows PF at 1.0) so issues with power factor.Steve
Re: AC and Microwave Reply #11 – August 28, 2016, 09:01:01 pm Hi Steve. A power factor of a resistive load is perfect at 1.0. That is a good thing!, Inductive loads usually motors, or less frequently capacitive loads have shifted power factors that commonly cause problems with control circuits, and other loads. my original '99 microwave has only about 600 watts output, and is probably just as efficient as newer models. It just uses less power when running. Have run the A/C, 'fridge and microwave off of the 32 amp generator easily. RonB
Re: AC and Microwave Reply #12 – August 28, 2016, 09:19:43 pm The simple answer is no. You may have 30 amps total from the shore power inlet, but that's split into two 15 A circuits at the Lazy Daze's breaker box.One supplies all the visible AC outlets, plus the fridge's outlet (which is hidden inside its outside compartment).The other supplies both the air conditioner and the microwave (via an outlet hidden in a kitchen closet).In other words, no matter how many amps shore power can supply, those two devices only have 15 A to share. And as others have pointed out, they are too power-hungry to share those 15 amps nicely. 2 Likes
Re: AC and Microwave Reply #13 – September 07, 2016, 04:18:40 am So I thought I'd take some measurements with my Kill-A-Watt to see how my motorhome was behaving. My A/C is a '99 13,500 Btuh Dometic. The Microwave is certainly less powerful than my home 1300 watt MW. While plugged in at home on a 30 A. breaker the converter draws about 2.9 A. pf=.13. A/C on low fan 9.8 amps pf=.85. Hi fan about 2 more amps. With microwave on, it draws 9 amps. Reefer at max takes 1.4 A. With everything on, (A/C at low fan) The KAW showed 19.1 amps and the voltage sagged to 111.3 VAC. One light was on at about 14 watts.(LED) Of course the surge current for starting the compressor on the A/C is quite a bit, but the new rotary compressors spin up quickly. The surge for the microwave isn't that much and doesn't last very long. A 4 KW generator can provide about 32 Amps and a slow 30 A breaker shouldn't trip as long as you stayed under 30 Amps most of the time. My electrical panel is more well behaved I guess. The converter has a 15 A breaker by itself. Being a 'dumb' one, a 6345, it won't draw that much unless i've got lots of 12 v. items are running. The battery charging part is pretty anemic. The A/C is on a separate circuit with a 20 A. breaker. The Microwave has it's own 20A. breaker and doesn't share with anything else except the other half of the duplex outlet inside the upper cabinet, and I don't use it. Both MW, Converter and A/C are not GFCI protected. My 15A. GFCI provides power to all of my 5 outlets. Reefer running on half of the 'inside the reefer vent' outlet #1. I also have an optional 110VAC outlet above the vanity, one I added at floor level next to the heater air inlet, one under the fold up TV shelf, and one underneath the cabinet between the cook top and sink. If you add up all the breakers, 70A. far exceeds the available 30 A. but my stuff seems to share well. A residential style powerful microwave, an electric water heater, coffee maker or other power hoggish appliance would upset the applecart, but I think Lazy Daze did a good job setting up the power distribution panel. I have no qualms running the A/C and microwave at the same time. I hope this made a little sense. RonB 1 Likes
Re: AC and Microwave Reply #14 – September 07, 2016, 11:45:25 am Thanks for posting those measurements, Ron. I'm sure they'll come in handy."Reefer at max takes 1.4 A."I assume you mean when running on propane. The electric heating element in the standard Dometic fridge uses upwards of 3 amps at 120 V when running in AC mode.
Re: AC and Microwave Reply #15 – September 07, 2016, 12:42:36 pm Hi Andy, you're right. My driveway isn't level so I didn't want to run it very long. I made sure it was in auto, and the Kill-A-Watt was plugged in outside to my incoming power line. The reading did jump up 1.4 A, but maybe it takes awhile to actually turn on the main heater. The refrigerator was at ambient, about 95 degrees that day inside and the doors were propped open except when I started it. I'll recheck that when I'm parked level. Thanks. RonB
Re: AC and Microwave Reply #16 – September 07, 2016, 01:45:26 pm I'm all too familiar with the standard fridge's power consumption when running on 120 VAC, because of the few times I've accidentally left it in that mode while running on inverter power. (I have a whole-house inverter.) In that scenario, it draws upwards of 30 amps worth of 12 VDC when running, which will drain batteries pretty quickly.This is one of many reasons I plan to switch to a 12 VDC Isotherm compressor refrigerator this winter. It will draw only about 5-6 amps of 12 VDC when running--enough that my solar power system should easily handle it. Running the fridge on sun power will cut my propane consumption significantly, extending my boondocking time. Not to mention that a compressor fridge is insensitive to level, and uses no flammable chemicals or flames.
Re: AC and Microwave Reply #17 – September 07, 2016, 07:18:58 pm Quote from: Andy Baird - September 07, 2016, 01:45:26 pmI'm all too familiar with the standard fridge's power consumption when running on 120 VAC, because of the few times I've accidentally left it in that mode while running on inverter power. (I have a whole-house inverter.) In that scenario, it draws upwards of 30 amps worth of 12 VDC when running, which will drain batteries pretty quickly.This is one of many reasons I plan to switch to a 12 VDC Isotherm compressor refrigerator this winter. It will draw only about 5-6 amps of 12 VDC when running--enough that my solar power system should easily handle it. Running the fridge on sun power will cut my propane consumption significantly, extending my boondocking time. Not to mention that a compressor fridge is insensitive to level, and uses no flammable chemicals or flames.How close/tight is the fit in existing MB fridge space?Chris
Re: AC and Microwave Reply #18 – September 07, 2016, 07:33:01 pm "How close/tight is the fit in existing MB fridge space?"I don't have the exact numbers at my fingertips, but as I recall, the Isotherm "Cruise 195 Classic" model I have my eye on has slightly more interior space (6.9 cubic feet) than either my old Dometic or my new Norcold, but is slightly smaller outside, because the compressor fridge's guts are a lot less bulky than an absorption fridge's collection of boilers and tubes. The smaller outside dimensions allow room for more surrounding insulation, which should help save power).This particular model has separate compressors for the fridge and freezer, so the two sections have completely independent temperature controls--no more sliding the thermistor up or down to try to get the right balance of fridge/freezer temperatures.
Re: AC and Microwave Reply #19 – September 07, 2016, 07:55:47 pm Quote from: Andy Baird - September 07, 2016, 07:33:01 pmThis particular model has separate compressors for the fridge and freezer, so the two sections have completely independent temperature controls--no more sliding the thermistor up or down to try to get the right balance of fridge/freezer temperatures.Lucky dog, lucky dog, lucky dog!!!!
Re: AC and Microwave Reply #20 – September 07, 2016, 08:34:30 pm RonB: Thanks for posting your test results. For reference, our TK was delivered with an Advent MW912b 900W model. Haven't checked wattage or VA with the Kill-a-Watt but the specs say it draws 1350W. So microwave + fridge on electric + AC concurrently is definitely a no-no for us.Andy: That fridge is exactly what I'd want should this unit fail. Let us all know how it goes!Steve
Re: AC and Microwave Reply #21 – September 07, 2016, 10:41:23 pm Quote from: Andy Baird - September 07, 2016, 07:33:01 pm"How close/tight is the fit in existing MB fridge space?"I don't have the exact numbers at my fingertips, but as I recall, the Isotherm "Cruise 195 Classic" model I have my eye on has slightly more interior space (6.9 cubic feet) than either my old Dometic or my new Norcold, but is slightly smaller outside, because the compressor fridge's guts are a lot less bulky than an absorption fridge's collection of boilers and tubes. The smaller outside dimensions allow room for more surrounding insulation, which should help save power).This particular model has separate compressors for the fridge and freezer, so the two sections have completely independent temperature controls--no more sliding the thermistor up or down to try to get the right balance of fridge/freezer temperatures.Thanks, Andy. We'll look forward to a full report once you have it installed.Chris
Re: AC and Microwave Reply #22 – September 07, 2016, 10:41:49 pm "That fridge is exactly what I'd want should this unit fail. Let us all know how it goes!"I will!
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