Microwave problem with XPOWER 1000 Inverter
 

I just purchased a Tappan 550W microwave that consumes 850W. I
also purchased a Xantrex Xpower 1000W inverter (modified sine wave).
About 20% of the time, when I start the microwave, the light turns on,
the turn table starts to rotate, and just as the magnetron starts up,
the microwave shuts off. The microwave seems to have lost power since
the clock resets. The other 80% of the time, the microwave works fine.
Once it successfully starts up, it will run continuously without a
problem.

The inverter has a continuous rating of 1000W with a peek output of 2000W.
I can't imagine that the microwave ever uses this much power to start.
The fault light on the inverter does NOT come on.

I have 2 large deep cycle batteries connected in parallel. They are
in excellent condition and provide over 260AH. I have connected the
inverter directly to the batteries with 2 AWG battery wire that I
purchased at the auto store. Is there a problem with the microwave
or inverter? Should I buy a more powerful inverter?

Thanks
Brent

We run a 1000W consumption microwave (600W output) on our 1000W
Statpower Inverter (sine wave). Had no trouble with either.
Lyn & Tony
S/V Ambrosia

"Comcast" wrote in message
...
I just purchased a Tappan 550W microwave that consumes 850W. I
also purchased a Xantrex Xpower 1000W inverter (modified sine wave).
About 20% of the time, when I start the microwave, the light turns on,
the turn table starts to rotate, and just as the magnetron starts up,
the microwave shuts off. The microwave seems to have lost power since
the clock resets. The other 80% of the time, the microwave works fine.
Once it successfully starts up, it will run continuously without a
problem.

The inverter has a continuous rating of 1000W with a peek output of 2000W.
I can't imagine that the microwave ever uses this much power to start.

The inrush current of a large transformer can be 5 to 25 times the nominal
current. And that is when fed with a sinewave current. With a modified
sineware (which is just a square wave which stays on 0-V for some time,
every cycle), the inrush current can be much higher.

Meindert

Comcast wrote:

I just purchased a Tappan 550W microwave that consumes 850W. I
also purchased a Xantrex Xpower 1000W inverter (modified sine wave).
snip

snip Is there a problem with the microwave
or inverter? Should I buy a more powerful inverter?

Some types of electrical or electronic equipments do not work or do not
work well on modified sine wave inverters. If you look in your manual
or at the Xantrex web site, it will tell you what those are.

That may be your problem. If it is, a pure sine wave inverter will cure
it. Guess what? It may be time to throw another bucket full of money
into your "hole in the water". :)

Jack

--
Jack Erbes in Ellsworth, Maine, USA - jackerbes at adelphia dot net
(also receiving email at jacker at midmaine.com)

It sounds like the microwave is tripping off on undervoltage. I'd be
looking at my 12 volt connections, as that is the usual source of the
problem. Depending on the length of the run, that #2 wire may be a
bit small.

An easy test is to plug in a low wattage bulb to the inverter and
watch how much it dims as the magnetron comes up to speed. You might
also try running the system with the engine running (assuming a MH) or
a high power charger in place to see if the added voltage will help.

FWIW, I run a 600 watt microwave from a 1000 watt Vector inverter with
no problems at all. I chose a microwave with a mechanical timer so as
to avoid all those glitch problems.

John


On Wed, 23 Feb 2005 01:54:01 -0800, "Comcast"
wrote:

I just purchased a Tappan 550W microwave that consumes 850W. I
also purchased a Xantrex Xpower 1000W inverter (modified sine wave).
About 20% of the time, when I start the microwave, the light turns on,
the turn table starts to rotate, and just as the magnetron starts up,
the microwave shuts off. The microwave seems to have lost power since
the clock resets. The other 80% of the time, the microwave works fine.
Once it successfully starts up, it will run continuously without a
problem.

The inverter has a continuous rating of 1000W with a peek output of 2000W.
I can't imagine that the microwave ever uses this much power to start.
The fault light on the inverter does NOT come on.

I have 2 large deep cycle batteries connected in parallel. They are
in excellent condition and provide over 260AH. I have connected the
inverter directly to the batteries with 2 AWG battery wire that I
purchased at the auto store. Is there a problem with the microwave
or inverter? Should I buy a more powerful inverter?

Thanks
Brent




---
John De Armond

http://www.johngsbbq.com
http://neonjohn.blogspot.com -- NEW!
Cleveland, Occupied TN

"Comcast" wrote in news:W5idnZlIFrFdz4HfRVn-
:

Is there a problem with the microwave
or inverter? Should I buy a more powerful inverter?

Thanks
Brent


No, you should buy a cheaper microwave! We paid $15 for the Samsung with
the windup timer on the front and NO ELECTRONICS to screw it up!

Microwaves with cheap, mechanical windup electric timers work just fine off
inverters....even the cheap 1KW Radio Shack screwed to Lionheart's bulkhead
with the custom miniature power switch at the nav table...

On Wed, 23 Feb 2005 19:37:56 GMT, Larry W4CSC wrote:

"Comcast" wrote in news:W5idnZlIFrFdz4HfRVn-
:

Is there a problem with the microwave
or inverter? Should I buy a more powerful inverter?

Thanks
Brent


No, you should buy a cheaper microwave! We paid $15 for the Samsung with
the windup timer on the front and NO ELECTRONICS to screw it up!

Microwaves with cheap, mechanical windup electric timers work just fine off
inverters....even the cheap 1KW Radio Shack screwed to Lionheart's bulkhead
with the custom miniature power switch at the nav table...


Our Samsung works off a single marine battery, but... it takes about
twice as long to heat stuff up and it chomps on the battery pretty
hard. When practical we use propane to heat food and beverages
instead.

On Wed, 23 Feb 2005 11:45:14 -0500, Neon John
wrote:

It sounds like the microwave is tripping off on undervoltage. I'd be
looking at my 12 volt connections, as that is the usual source of the
problem. Depending on the length of the run, that #2 wire may be a
bit small.

=============================

I agree that #2 wire is marginal at best. You are pulling well over
100 peak amps and voltage loss in the cable increases as the square of
current flow. I'd sugggest something like 2/0 cable both to the
inverter and for your battery parallel straps.

It is true however that some devices just refuse to run on modified
sine wave power. We had to try several different brands of electric
blankets before we found one that worked.

Wayne.B wrote in
:

It is true however that some devices just refuse to run on modified
sine wave power. We had to try several different brands of electric
blankets before we found one that worked.


Oh, Wayne. I just gotta hear all about your house battery banks and
charging system.

How many amp-hours are aboard to run electric blankets and the other loads
all night?

Thanks.....



(Nothing is funnier than a boater with a new 4KW inverter carrying his
electric heater down the dock with that knowing smile on his face....)

On Thu, 24 Feb 2005 11:46:01 GMT, Larry W4CSC wrote:

Wayne.B wrote in
:

It is true however that some devices just refuse to run on modified
sine wave power. We had to try several different brands of electric
blankets before we found one that worked.


Oh, Wayne. I just gotta hear all about your house battery banks and
charging system.

How many amp-hours are aboard to run electric blankets and the other loads
all night?

I just looked at the tag on my king-size electric blanket. It draws
200 watts. That'd be about 16.67 amps at full load from the battery.

Not many people would use a king size bed in an RV. More like a twin
or regular. I'd guesstimate the draw to be more in the 60 watt range
or 5 amps. This corresponds well to my 12 volt electric throw that I
use that draws 3.5 amps. Remember that these things are
thermostatically controlled so they don't run all the time. That
makes the actual situation better than it looks.

I have a couple of Group 29 batteries in my rig and have no problem
running the blanket, the furnace and other loads for a day at a time.
According to the E-meter, I'll typically use 80 ah per 24 hour period
in the winter.


(Nothing is funnier than a boater with a new 4KW inverter carrying his
electric heater down the dock with that knowing smile on his face....)

Yup. Old rule of thumb, a gallon of gas is about the energy
equivalent of about 1000 lbs of lead-acid batteries.

John
---
John De Armond

http://www.johngsbbq.com
http://neonjohn.blogspot.com -- NEW!
Cleveland, Occupied TN

Neon John wrote in
:

(Nothing is funnier than a boater with a new 4KW inverter carrying his
electric heater down the dock with that knowing smile on his face....)

Yup. Old rule of thumb, a gallon of gas is about the energy
equivalent of about 1000 lbs of lead-acid batteries.

John


Thanks. Good rule of thumb.

http://www.fleetsubmarine.com/battery.html

On Thu, 24 Feb 2005 11:46:01 GMT, Larry W4CSC wrote:

How many amp-hours are aboard to run electric blankets and the other loads
all night?

======================================

It's not really a problem believe it or not. On our old boat the
house bank was 4 golf cart batts in series-parallel, total capacity of
440 A-H, usable capacity about 150 A-H. We had a 7.5 KW genset so
recharge was never a problem.

The electric blanket has a peak load of 300 watts translating to about
30 amps at 12 v. Duty cycle is about 50% on a chilly 50 degree night
in the north east. So for 8 hours of sleep we were pulling down about
120 A-H for the blanket (15 x 8), and maybe another 30 A-H for the
fridge. Never had a problem. The batts were 3+ years old when I sold
the boat and still going strong.

For the new boat (GB49 trawler), I plan a house bank made up of
individual 2 volt cells bolted together. It will weigh close to 1,000
lbs but that's not really an issue on a boat that weighs 60,000 fully
loaded. Total capacity will be over 1,000 A-H with usable capacity
greater than 350. Those 2 volt cells are guaranteed for 10 years so
they may turn out to be the last battery I ever buy. Recharge will be
via a high power inverter/charger, 20KW generator, and/or high
capacity alternators.

Might be a dumb question, but did you have anything else drawing off the
inverter the 20% of the time it didn't work? I'd say you are close to the
capacity with just the microwave.

Cheers

"Comcast" wrote in message
...
I just purchased a Tappan 550W microwave that consumes 850W. I
also purchased a Xantrex Xpower 1000W inverter (modified sine wave).
About 20% of the time, when I start the microwave, the light turns on,
the turn table starts to rotate, and just as the magnetron starts up,
the microwave shuts off. The microwave seems to have lost power since
the clock resets. The other 80% of the time, the microwave works fine.
Once it successfully starts up, it will run continuously without a
problem.

The inverter has a continuous rating of 1000W with a peek output of 2000W.
I can't imagine that the microwave ever uses this much power to start.
The fault light on the inverter does NOT come on.

I have 2 large deep cycle batteries connected in parallel. They are
in excellent condition and provide over 260AH. I have connected the
inverter directly to the batteries with 2 AWG battery wire that I
purchased at the auto store. Is there a problem with the microwave
or inverter? Should I buy a more powerful inverter?

Thanks
Brent

Wayne.B wrote in
:

For the new boat (GB49 trawler), I plan a house bank made up of
individual 2 volt cells bolted together. It will weigh close to 1,000
lbs but that's not really an issue on a boat that weighs 60,000 fully
loaded. Total capacity will be over 1,000 A-H with usable capacity
greater than 350. Those 2 volt cells are guaranteed for 10 years so
they may turn out to be the last battery I ever buy. Recharge will be
via a high power inverter/charger, 20KW generator, and/or high
capacity alternators.



I like this guy!.....(c;

I've mentioned it before, but have you seen these guys in Colorado that
make all their own power?
http://www.otherpower.com/

Talk about energy independents!

Neon John wrote:

Depending on the length of the run, that #2 wire may be a
bit small.

According to the chart in the West Marine catalog, it has a resistance
of 0.157 ohms per 1000'. At roughly 100 amps draw (1000 watts or so
output) that means about a tenth of a volt drop for every three feet
of cable run (two conductors) between inverter and battery. Under
peak current that would get larger. Depending on the length of the
run, it could have a significant effect.

To find out, check your battery voltage at the inverter terminals
while turning on the microwave. This will also check the resistance
of the connections. If you made the cables up using untinned auto
cable rather than tinned marine cable, it might be more prone to
corrosion and resistance in the lugs.

If the voltage at the inverter is OK, then it's probably the
difference between modified and pure sine wave.

Does that model microwave lower its power levels by running less than
100% duty cycle, so if you're running at less than full power you keep
hearing it cycle on and off? I ask because this chart
http://www.sailorsams.com/mall/tm5030_power_levels.asp seems to imply
that it actually lowers the peak power consumption. If so, try
running at 90% power. (It could also be that the chart shows average
rather than instantaneous consumption, or that the guy who made it was
using assumptions rather than knowledge.)

- Walt Bilofsky

"Comcast" wrote:

I just purchased a Tappan 550W microwave that consumes 850W. I
also purchased a Xantrex Xpower 1000W inverter (modified sine wave).
About 20% of the time, when I start the microwave, the light turns on,
the turn table starts to rotate, and just as the magnetron starts up,
the microwave shuts off.snip

I asked SailorSams.com (from which I am buying this model) about this.
He had no definitive answer but did say "The distributor is going to
send the Tappan microwaves to Xantrex, to let Xantrex specify which
of their inverters should be used with which Tappan microwave." If
you are not in a rush, you might want to ask them in a month or two.

- Walt Bilofsky