If I have thawed a 21 pound frozen turkey in fridge for 30 hours. How much longer should I submerge in cold water every 30 minutes before it is completely thawed to cook

Defrosting them in what, the fridge, the microwave?

If in the fridge, just put them in the fridge for 48 hours. Or in winter you can leave them on your worktop for 8 hours. Or, just drop them into a sink of warm water for 2 hours and cook straight way.

Defrosting by weight and measurement would depend on where you live?

Andrew - famous 50 year career chef (retired), and Fixya Admin.

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How to Cook a 21.5-Pound Turkey at 325 Degrees Fahrenheit ...

https://www.livestrong.com > Food and Drink

Nov 20, 2017 - Expect it to take 4.5 to 5 hours to cook a 21.5-pound turkey at 325 degrees Fahrenheit -- if your turkey is unstuffed. If it's full of your favorite stuffing, add at least 15 minutes to the total cooking time.
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This table from the USDA is based on a 325°F oven, and a fully defrosted or fresh bird. (For an unstuffed bird, we're talking roughly 15 minutes per pound.) If you want to cook a frozen turkey, it will take at least 50 percent longer than the recommended times.

Thaw it before cooking then plan on 13 minutes of cooking time for every pound of turkey if roasting empty and 15 minute per pound if stuffed. Heat the oven to 450°F to preheat and then drop the temperature to 350°F when putting the turkey into the oven. The turkey is done when it registers a minimum of 165° in the deepest part of thigh.

Here's How It Works:

1. Run hot tap water into a bowl.
2. Check the temp with a thermometer. You're looking for 140 degrees.
3. Submerge the frozen chicken.
4. Stir the water every once in a while (this keeps pockets of cold water from forming).
5. It should be thawed in 30 minutes or less.

How to thaw a frozen chicken the fast and easy way

How do DEFROST CHICKEN TENDERS Google Search

According to the USDA, when thawing your turkey in the refrigerator, you'll need to allow 24 hours for every four to five pounds. Don't bother with the math-here's a table: 4 to 12 pounds: 1-3 days. 12 to 16 pounds: 3-4 days.14 Aug 2012

How long does it take for a turkey to thaw? ' MyRecipes

www.myrecipes.com/how-to/cooking-questions/how-long-turkey-to-thaw How long does 16lb turkey need to defrost in the refrigerator Google Search

No way!!! To quick thaw, set it in cold water in a deep pan and change the water every few hours--could still take 24 hours. Thawing a turkey in the refrigerator can take as long as a week.

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Is it frozen or thawed? The NuWave oven takes 12 minutes per pound thawed

This is the site for the manual:
http://www.rivalproducts.com/manuals/MANUALS/RO188BR_43_81844057.PDF

However,
The Rival manual suggested 375 for pre basted or 350 for fresh 9-14 minutes per pound. In my experience this is too hot. I use 325 for 4 to 4 3/4 hours at 325 for an 18 pound turkey; a 21 pounder takes about 35-45 minutes more. The USDA now uses 165 as the end point temp (down quite a bit from a few years ago), but if you stuff, that has to be in the middle of the stuffing, and the turkey will overcook somewhat while it gets there. Stuffing adds about 2 minutes per turkey pound to the cooking time.
All experts agree that turkeys cook better and safer if unstuffed, so considering that you will have to make an extra pan of stuffing to have it for everyone, you would be well advised to cook your turkey unstuffed and use some of the drippings to flavor the pan of stuffing while the turkey rests.

This turkey is bigger than recommended for this roaster, so first, check the fit- you need about an inch all around including the top to get good cooking. Any place it touches the sides it will tend to overcook.

The Rival manual suggested 375 for pre basted or 350 for fresh 9-14 minutes per pound. In my experience this is too hot. I use 325 for 4 to 4 3/4 hours at 325 for an 18 pound turkey; a 21 pounder takes about 35-45 minutes more. The USDA now uses 165 as the end point temp (down quite a bit from a few years ago), but if you stuff, that has to be in the middle of the stuffing, and the turkey will overcook somewhat while it gets there. All experts agree that turkeys cook better and safer if unstuffed, so considering that you will have to make an extra pan of stuffing to have it for everyone, you would be well advised to cook your turkey unstuffed and use some of the drippings to flavor the pan of stuffing while the turkey rests.