Microwave Addition

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Expatriate
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Microwave Addition

Post by Expatriate »

After going through the trials of the convection microwave, we finally installed an ENO propane oven in the space where the convection microwave was installed. I can't say why we had so much trouble with the convection microwave, but two engineers could just not figure it out. The ENO has worked fine over the past year or two. It does not have a thermostat so I use an infrared thermometer to keep track. That is my only complaint except, as with most devices, the users manual is totally useless.

Still, we wanted a microwave and I bought the smallest one I could find. So after some measuring and trial and error, I decided the only place for it was underneath the new ENO oven. There is a storage area there with a shelf. It was clear that the microwave would fit in there if I could get the shelves out.

It turned out to be a piece of cake. The shelves are installed with silicone seal and just popped out. I loosened up the sealer with a filet knife. I drilled a one inch hole in the back of that volume in the center at the top. Then I ran the power cord from the new microwave through the hole and to the 100 AC outlet that was there for the old convection microwave. In this configuration it will only work if plugged into the dock or if the gen-set is running. We anchor out a lot so I wanted it to run on the inverter if possible.

I went into the switch panel and found the wire for the convection microwave breaker with out much effort. The inverter supplies power to the outlets through the breakers labeled port outlets, starboard outlets, head outlet, and flybridge. It was a no-brainer to connect the head outlet wire to the starboard outlets breaker giving me a dedicated breaker for the microwave. My only worry is that the head breaker has a GFI on it. So I just moved the hot wire off the microwave breaker and that was a mistake. I needed to move the hot wire and the neutral wire. If not, all sorts of strange things happen like the microwave coming on when the water heater is turned on. After I got both wires moved there were no problems.

One surprise was that a 700 watt microwave does not use 700 watts. It puts out 700 watts into your food, but uses at least 1000 watts, maybe a little more. Sure enough, I watched the ammeter on the inverter control panel and had my wife turn on the microwave. It drew just about 100 amps or about 1200 watts. So, quite a bit more than 700, nearly twice as much. I looked for a long time trying to find a smaller microwave with no luck except for some from Indonesia that looked really strange. So far this installation works.

I will experiment some more and see how it goes. I will also upload a picture or two. I just installed this thing yesterday.

Tim
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Re: Microwave Addition

Post by thinwater »

The most common problem with running a microwave off an inverter is that the power is too noisy. It needs to be a pure sine wave inverter, not modified sine wave. Short of replacing the inverter, there is no easy solution. Asa result, the microwave probably ran fine on shore power, but not from the inverter. This can also shorten their life. A common problem on PDQs.

The required power supply of any appliance is on the nomenclature plate on the back. The advertising rating has nothing to do with it.
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Re: Microwave Addition

Post by Expatriate »

Right. I have a pure sine inverter. I will double check the rating on the back.

Tim
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Re: Microwave Addition

Post by Expatriate »

So, I installed the microwave without really checking the power it required. On the back of the unit, and online, it claims to use 1050 watts. I have a 1000 watt pure sine inverter. I thought I had really blown it until I looked up the specs on the inverter. The amount of power it puts out varies with time, and probably temperature. So, for 5 seconds (probably the first 5 seconds while still cold) it will put out 1750 watts. For 3 minutes 1600 watts, for 5 minutes 1200 watts, and 1050 watts for 30 minutes or greater. I am highly unlikely to use the microwave for more than a few minutes so probably I have dodged a bullet. I knew that inverters put out less as they warm up, but these numbers surprised me. I know I promised pictures. I will try to get to that done.

Tim
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Re: Microwave Addition

Post by Expatriate »

So, I promised some pictures. Here they are.
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MicrowaveWithShelf.jpg
MicrowaveCloseup.jpg
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Re: Microwave Addition

Post by AMCarter3 »

In case this is helpful to those interested in downsizing your Microwave as Tim did, I did the same thing about a year ago for the similar reasons... The 1200 watt unit we had onboard hammered the batteries and sometimes popped the inverter breaker or the main breaker. And we wanted to make better use of that cabinet space. So we installed a 700 watt Sharp Carosel model and a boating friend, who is a master craftsman, made this cabinet. It created some really useful space.

And I too discovered that a 700 watt unit can consumes about a 1000 watts initially when run at full power. We also learned that a lot of microwaves use a "pulsing" technique to simulate lower power settings... They run full power only but do it in a cycle of on/off pulses to simulate lower power settings. And a few microwaves, harder to find, actually reduce the power setting instead of pulsing at full power. (interesting eh?)
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Re: Microwave Addition

Post by deising »

Yes, Mac, there is a big difference between peak power and average power consumption.
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