How long does it take a microwave oven to warm up?

M

micky

Guest
How long does it take a microwave oven to warm up?

I often cook things that take maybe 7 or 8 seconds. Maybe if they're
really small they take 5 but it's hard to know in advance and I really
dislike most overcooked things. Undercooked, one can just cook it some
more but is two 5-second zappings the same as one 10-second zap?

Or does it take a second (or 2 or 3 or more) to get the waves churning,
so two 5-seconds is more like 9 seconds (or 8 or 6)?

I need to know so that eventually I'll know the proper time for a
particular food, without stopping and checking**.

Has anyone read about this? Or other oscillators?


**This actually raises another question. I'm pretty darn good at
predicting how much time I need to microwave something, and once in a
while I can even remember from experience. (Cocoa from refrigerated
milk is 2 minutes. An eggroll of a given size is 2 minutes 40 seconds,
even though wrapper says 4 minutes.)

But what if part of something much bigger than 10-second food is cooked
enough and I take it to the table and start eating and when I get to
another part, find that it is not cooked enough. By this time all of it
has cooled some. In that case, it's not the microwave warm-up time that
would matter, but am I right that there is still food warm-up time? If
the food is 70^, it might not even start cooking until the part that
cooks reaches, what, let's assume 110. (Or maybe someone has a real
number for a given food)

So if one is eating for 15 minutes, the 120 degree food will have cooled
off to 80 degrees, and if I put it back in, it still has to get back up
to 110 again, before it even starts cooking again, is that right? That
could take 20 or 30 seconds or more, depending on how much food there is
and other details. I dont' mind the extra time, but I would like it if
someone could provide real-life numbers so I could better estimate how
long the 2nd part of the cooking will take.
 
When you get down to thing that only take a few seconds, the fact that it takes about two seconds for the magnetron filament to warm comes into play.

Usually you can hear the fan slow down once the microwaves are really being produced.
 
On Wednesday, November 30, 2016 at 3:41:20 PM UTC-8, Frank wrote:
On 11/30/2016 5:45 PM, FromTheRafters wrote:
micky explained on 11/30/2016 :
How long does it take a microwave oven to warm up?

I now have a new microwave oven with a turntable (the other had a
reflector) to help avoid the spottiness. The ovens power output is also
an important factor to consider.

I find it easier to microwave for longer periods of time at a lower
setting to get even heat.
Click to expand...

It takes a few seconds to heat the filament of the vacuum tube. So, it's advisable
to use longer times, but NOT lower setting (which just adds multiple ON/OFF switching
to the problem).

To get something a 5 second zap, you might be well advised
to put a cup of water in next to your nibble, and give the pair ten seconds.
The water load will slow the nibble heating, and the longer time means the turnon
variability is less important. It also gives your turntable a chance to do a full
revolution under full magntron power (better hotspot control)
 
"I find it easier to microwave for longer periods of time at a lower
setting to get even heat. "
Click to expand...

Yeah but they generally only turn it on and off. The duty cycle controls the power level.

I have only see one microwave in my life that actually had separate taps on the transformer for lower power.
 
>"Stick an old CD in the MW and you can see exactly when the RF power starts. "

Really. Never thought of that.
 
micky explained on 11/30/2016 :
> How long does it take a microwave oven to warm up?

The energy transfer is nearly immediate. The oven only warms up because
of the food warming up.

Some items which I microwave would end up having cold or cool spots, so
I used to cook say a three minute item by cooking for two minutes and
then allowing the heat to spread for a couple of minutes, and then zap
for another minute or so.

I now have a new microwave oven with a turntable (the other had a
reflector) to help avoid the spottiness. The ovens power output is also
an important factor to consider.
 
micky wrote:

How long does it take a microwave oven to warm up?
Click to expand...
The heater in the magnetron tube takes a couple seconds to warm to the point
where it will emit electrons. You can hear it easily on the old transformer
microwaves, the fan starts and it begins to hum, then a couple seconds later
the hum gets much louder. That louder hum is when the magnetron tube starts
conducting.

Newer microwaves with switching power supplies may delay turning on the HV
until the heater has warmed up, and they may not have that transformer hum,
so it may be harder to tell when the RF comes on.

Jon
 
On 11/30/2016 5:45 PM, FromTheRafters wrote:
micky explained on 11/30/2016 :
How long does it take a microwave oven to warm up?

The energy transfer is nearly immediate. The oven only warms up because
of the food warming up.

Some items which I microwave would end up having cold or cool spots, so
I used to cook say a three minute item by cooking for two minutes and
then allowing the heat to spread for a couple of minutes, and then zap
for another minute or so.

I now have a new microwave oven with a turntable (the other had a
reflector) to help avoid the spottiness. The ovens power output is also
an important factor to consider.
Click to expand...

I find it easier to microwave for longer periods of time at a lower
setting to get even heat.
 
"Jon Elson" <jmelson@wustl.edu> wrote in message
news:0sidnaf7d81CwaLFnZ2dnUU7-UednZ2d@giganews.com...
micky wrote:

How long does it take a microwave oven to warm up?

The heater in the magnetron tube takes a couple seconds to warm to the
point
where it will emit electrons. You can hear it easily on the old
transformer
microwaves, the fan starts and it begins to hum, then a couple seconds
later
the hum gets much louder. That louder hum is when the magnetron tube
starts
conducting.

Newer microwaves with switching power supplies may delay turning on the HV
until the heater has warmed up, and they may not have that transformer
hum,
so it may be harder to tell when the RF comes on.

Jon
Click to expand...

Stick an old CD in the MW and you can see exactly when the RF power starts.
 
Frank formulated the question :
On 11/30/2016 5:45 PM, FromTheRafters wrote:
micky explained on 11/30/2016 :
How long does it take a microwave oven to warm up?

The energy transfer is nearly immediate. The oven only warms up because
of the food warming up.

Some items which I microwave would end up having cold or cool spots, so
I used to cook say a three minute item by cooking for two minutes and
then allowing the heat to spread for a couple of minutes, and then zap
for another minute or so.

I now have a new microwave oven with a turntable (the other had a
reflector) to help avoid the spottiness. The ovens power output is also
an important factor to consider.

I find it easier to microwave for longer periods of time at a lower setting
to get even heat.
Click to expand...

Yes, the new MW oven has programmable settings for power level and rest
periods and such for better results. The old one only had a single knob
with minute marks on it and a bell that softly, almost inaudibly, went
'click' when the time expired.

The old one is 26 years old, but it still works.
 
On Wed, 30 Nov 2016 18:57:51 -0500, "tom" <tmiller11147@verizon.net>
wrote:

>Stick an old CD in the MW and you can see exactly when the RF power starts.

Good idea. Another way would be to cram a wad of paper between the
door and the oven, and use a microwave leakage detector to measure the
resultant leakage. It there's a slow rise in output, you'll see it on
the meter, which you won't see on the CD.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
In sci.electronics.repair, on Wed, 30 Nov 2016 15:09:58 -0800 (PST),
jurb6006@gmail.com wrote:

>When you get down to thing that only take a few seconds, the fact that it takes about two seconds for the magnetron filament to warm comes into play.

Sure. That's what I had in mind.
Usually you can hear the fan slow down once the microwaves are really being produced.
Click to expand...

I'll pay more attention.

Thanks and thanks all.
 
In sci.electronics.repair, on Wed, 30 Nov 2016 18:57:51 -0500, "tom"
<tmiller11147@verizon.net> wrote:

"Jon Elson" <jmelson@wustl.edu> wrote in message
news:0sidnaf7d81CwaLFnZ2dnUU7-UednZ2d@giganews.com...
micky wrote:

How long does it take a microwave oven to warm up?

The heater in the magnetron tube takes a couple seconds to warm to the
point
where it will emit electrons. You can hear it easily on the old
transformer
microwaves, the fan starts and it begins to hum, then a couple seconds
later
the hum gets much louder. That louder hum is when the magnetron tube
starts
conducting.

Newer microwaves with switching power supplies may delay turning on the HV
until the heater has warmed up, and they may not have that transformer
hum,
so it may be harder to tell when the RF comes on.
Click to expand...

I'll go with "a couple". Thanks.

Jon

Stick an old CD in the MW and you can see exactly when the RF power starts.
Click to expand...

That sounds like it might work
 
In sci.electronics.repair, on Wed, 30 Nov 2016 19:33:00 -0500,
FromTheRafters <erratic@nomail.afraid.org> wrote:

Frank formulated the question :
On 11/30/2016 5:45 PM, FromTheRafters wrote:
micky explained on 11/30/2016 :
How long does it take a microwave oven to warm up?

The energy transfer is nearly immediate. The oven only warms up because
of the food warming up.

Some items which I microwave would end up having cold or cool spots, so
I used to cook say a three minute item by cooking for two minutes and
then allowing the heat to spread for a couple of minutes, and then zap
for another minute or so.

I now have a new microwave oven with a turntable (the other had a
reflector) to help avoid the spottiness. The ovens power output is also
an important factor to consider.

I find it easier to microwave for longer periods of time at a lower setting
to get even heat.

Yes, the new MW oven has programmable settings for power level and rest
periods and such for better results. The old one only had a single knob
with minute marks on it and a bell that softly, almost inaudibly, went
'click' when the time expired.

The old one is 26 years old, but it still works.
Click to expand...

I had an Amana Model 2, that looked just like the drawings of microwaves
that were used for decades. It lasted many years. I got it used around
1975 and met its earthly demise around 2000. . Although the insulation
on the diodes had failed** and it sparked, so I covered the open parts
with GE silicon sealant, and something else I fixed, and eventually the
power transformer broke, I think it was. They wanted 300 dollars for it
and my pointing out that they should take 80 since I coudl buy a new one
for 80 didn't help. They lowered the price to the repairmans price of
200 roughly.

**Amanda didn't want to send me a schematic. I had to beg, and promise
I knew what I was doing and wouldn't kill myself. She relented.
 
On Wed, 30 Nov 2016 17:16:05 -0600, Jon Elson wrote:

The heater in the magnetron tube takes a couple seconds to warm to the point
where it will emit electrons. You can hear it easily on the old transformer
microwaves, the fan starts and it begins to hum, then a couple seconds later
the hum gets much louder. That louder hum is when the magnetron tube starts
conducting.

Newer microwaves with switching power supplies may delay turning on the HV
until the heater has warmed up, and they may not have that transformer hum,
so it may be harder to tell when the RF comes on.
Click to expand...

+1, You are the only one who did not lambast the OP for using the term
'warm up' to mean 'cause the ambient MW intensity to reach its operational
range'.

When I am judging time for extremely small loads (like softening butter
without liquifying it), I allow 4 seconds for my oven.

I find that the hum does not get louder though. Instead, I notice that the
fan speed lowers a bit, presumably because the supply voltage for the fan
is then being loaded down by the power consumption by the magnetron.
 
On Wednesday, November 30, 2016 at 5:23:50 PM UTC-5, micky wrote:
> How long does it take a microwave oven to warm up?

YIKES!!

This is a single question with two separate answers.

a) Less than 4 seconds for the magnetron tube to reach full output. There will be a sequence as others have noted: Fan-Start, relay click, magnetron start.

b) Then, it depends. We have a 1,100 watt Panasonic that is very fast-cooking to the point that we are very careful of the setting as even 10 seconds makes a difference. A 500-watt device will provide an entirely different experience.

So, it is a combination of the onset time and the actual power of your microwave that will give you the answer. But what is obvious is that 2 @ 5 seconds is NOT 1 @ 10 seconds. The reality is that a 5-second setting will give ~1~2 seconds of actual full-output heat. 10 seconds will give ~6~9 seconds..

Peter Wieck
Melrose Park, PA
 
Micky,

Heating improves the physical "eatability" of products and also beats the
crap out of bacteria. If you cook for under the prescribed time to suit your
tastes then you need to understand about the bacteria.. Don't poison
yourself.
Sorry, can't help you with cooking times.

Dave M.
 
On 11/30/2016 4:23 PM, micky wrote:
An eggroll of a given size is 2 minutes 40 seconds,
even though wrapper says 4 minutes.)
Click to expand...

Pan fry your egg rolls, roll so four sides get crispy.
Microwaved egg rolls just aren't worth eating. IMHO
Mikek
 
On 11/30/2016 04:23 PM, micky wrote:

[snip]

**This actually raises another question. I'm pretty darn good at
predicting how much time I need to microwave something, and once in a
while I can even remember from experience. (Cocoa from refrigerated
milk is 2 minutes. An eggroll of a given size is 2 minutes 40 seconds,
even though wrapper says 4 minutes.)
Click to expand...

I have an older microwave, that has only 700W. Most directions are for
higher power. I find most things are OK if I add 25% to the cooking
time. For example, if it says 3 minutes I use 3:45.

BTW, some people have said that if I got a new microwave, it would
probably fail before the old one.

[snip]

--
24 days until the winter celebration (Sunday December 25, 2016 12:00:00
AM for 1 day).

Mark Lloyd
http://notstupid.us/

"If fascism ever comes to America, it will be wrapped in the flag and
carrying a cross." -- Upton Sinclair, Huey P. Long, and others.
 
On 11/30/2016 06:33 PM, FromTheRafters wrote:

[snip]

> The old one is 26 years old, but it still works.

I have a 30 year old JCPenney microwave (from the time they sold a lot
of things rather than just clothes and related stuff).

--
24 days until the winter celebration (Sunday December 25, 2016 12:00:00
AM for 1 day).

Mark Lloyd
http://notstupid.us/

"If fascism ever comes to America, it will be wrapped in the flag and
carrying a cross." -- Upton Sinclair, Huey P. Long, and others.
 
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