Food Safety Experiment Number 2 - Norcold Refrigerator

[TucsonJim]

In July of 2015, there was a lot of discussion on this forum about whether is was safer to run with your LP gas and refrigerator turned off, or to leave it on. One side of the discussion believed that food safety was important and the refrigerator (and gas) needed to be left on, while others believed that it was safer to run with the gas turned off. Many people didn't understand the difference between spoilage bacteria and pathogenic bacteria. Spoilage bacteria will make your milk go sour. Pathogenic bacteria such as Salmonella, Campylobacter, E.coli, and Listeria can make you very sick or kill you. And many of us RV'ers aren't youngsters any more. So these diseases can treat us worse than others.

There were many assumptions regarding this topic that weren't backed with a lot of data. Some folks felt that "my food was still cool to the touch", or "my ice was still hard in the freezer", or "I've never gotten sick". While on the other side of the coin there was "I've been driving with the gas turned on for over 30 years and I've never had a problem".

In order to bring some real world data to the discussion, I ran an experiment to see how long it would take for food to reach an unsafe level with the gas and refrigerator turned off on a hot day. The results of that experiment can be found here:

https://www.mygrandrv.com/fo...r+temperatures

Since that time, we acquired a 2017 Reflection 297RSTS travel trailer that is equipped with a Norcold refrigerator. The Norcold is approximately the same size as the Atwood. Since this topic is still frequently discussed and debated, I felt it was a good idea to repeat the experiment with the Norcold refrigerator to see if the results were different. You can find the results of the new experiment in the reference library at the following link:

https://www.mygrandrv.com/fo...810#post179810


In the 2015 Atwood experiment, food reached an unsafe temperature over 40°F in approximately one hour! In this most recent experiment, the Norcold refrigerator fared slightly better, but the refrigerator temperature still exceeded the established safe limits in just two hours. A 1/2 gallon container of water was over 40°F in just four hours. And the internal temperature of the refrigerator hit 55°F before the refrigerator was turned back on. And even though the refrigerator was turned back on at the end of nine hours, the interior temperature did not return to below 40°F until midnight.

I also added a second experiment to this one. After letting the refrigerator stabilize for a couple of days I reran the experiment with Blue Ice placed in the refrigerator. It delayed the time before the refrigerator was once again at an unsafe temperature, but did not prevent it from occurring.

Of course, as with any experiment, there are always variables such as:
- Make and model of refrigerator
- Exterior temperature
- Food density in the refrigerator
- Sunny or cloudy
- Driving times
- How often the refrigerator/freezer doors are opened.
- Starting temperature of the refrigerator - Does yours even get to a safe temperature of 40°F or lower?
- The setting on the refrigerator.

My personal observations are as follows:

1. On a hot day, your refrigerator will exceed unsafe storage temperature in just one to two hours if not left running.
2. On a hot day, Blue Ice will delay the temperature increase, but will not prevent it.
3. In order to keep your food safe, you will need to run your refrigerator on a hot day. If you are fearful of doing so on LP gas, the only option when it comes to food safety is to run an inverter or replace your refrigerator with one that runs on 12VDC.

If you want to challenge the data, I'd really like to see you run a similar experiment and publish your findings.

Your thoughts?

Jim

[Cate&Rob]

Hi Jim - Great experiment . . . just like the first one. If you leave the fridge running, what would these temperature profiles look like as the RV interior temperature climbs to 110/115 F?

Rob

[livinthelife]

In July of 2015, there was a lot of discussion on this forum about whether is was safer to run with your LP gas and refrigerator turned off, or to leave it on. One side of the discussion believed that food safety was important and the refrigerator (and gas) needed to be left on, while others believed that it was safer to run with the gas turned off. Many people didn't understand the difference between spoilage bacteria and pathogenic bacteria. Spoilage bacteria will make your milk go sour. Pathogenic bacteria such as Salmonella, Campylobacter, E.coli, and Listeria can make you very sick or kill you. And many of us RV'ers aren't youngsters any more. So these diseases can treat us worse than others.

There were many assumptions regarding this topic that weren't backed with a lot of data. Some folks felt that "my food was still cool to the touch", or "my ice was still hard in the freezer", or "I've never gotten sick". While on the other side of the coin there was "I've been driving with the gas turned on for over 30 years and I've never had a problem".

In order to bring some real world data to the discussion, I ran an experiment to see how long it would take for food to reach an unsafe level with the gas and refrigerator turned off on a hot day. The results of that experiment can be found here:

https://www.mygrandrv.com/fo...r+temperatures

Since that time, we acquired a 2017 Reflection 297RSTS travel trailer that is equipped with a Norcold refrigerator. The Norcold is approximately the same size as the Atwood. Since this topic is still frequently discussed and debated, I felt it was a good idea to repeat the experiment with the Norcold refrigerator to see if the results were different. You can find the results of the new experiment in the reference library at the following link:

https://www.mygrandrv.com/fo...810#post179810


In the 2015 Atwood experiment, food reached an unsafe temperature over 40°F in approximately one hour! In this most recent experiment, the Norcold refrigerator fared slightly better, but the refrigerator temperature still exceeded the established safe limits in just two hours. A 1/2 gallon container of water was over 40°F in just four hours. And the internal temperature of the refrigerator hit 55°F before the refrigerator was turned back on. And even though the refrigerator was turned back on at the end of nine hours, the interior temperature did not return to below 40°F until midnight.

I also added a second experiment to this one. After letting the refrigerator stabilize for a couple of days I reran the experiment with Blue Ice placed in the refrigerator. It delayed the time before the refrigerator was once again at an unsafe temperature, but did not prevent it from occurring.

Of course, as with any experiment, there are always variables such as:
- Make and model of refrigerator
- Exterior temperature
- Food density in the refrigerator
- Sunny or cloudy
- Driving times
- How often the refrigerator/freezer doors are opened.
- Starting temperature of the refrigerator - Does yours even get to a safe temperature of 40°F or lower?
- The setting on the refrigerator.

My personal observations are as follows:

1. On a hot day, your refrigerator will exceed unsafe storage temperature in just one to two hours if not left running.
2. On a hot day, Blue Ice will delay the temperature increase, but will not prevent it.
3. In order to keep your food safe, you will need to run your refrigerator on a hot day. If you are fearful of doing so on LP gas, the only option when it comes to food safety is to run an inverter or replace your refrigerator with one that runs on 12VDC.

If you want to challenge the data, I'd really like to see you run a similar experiment and publish your findings.

Your thoughts?

Jim

Thanks so much for this. We got lectured while in Canada about running with our fridge running on propane. According to the RV "expert" there, you can go up to 4 hours and have no risk in the temperature rising too much in there.

Nice to see that's not the actual fact.

[gordofuchs]

Your findings scare the s--t out of me. I have just ordered one of the remote monitors that supposedly will give you high and low readings over a time period that can be reset. It's supposed to also sound an alarm if it goes outside the limits.

[TucsonJim]

Hi Jim - Great experiment . . . just like the first one. If you leave the fridge running, what would these temperature profiles look like as the RV interior temperature climbs to 110/115 F?

Rob

Rob - That is a great question. Fortunately, everything was still in place, so I'll run some data tomorrow. But I have pretty high confidence that it's going to be great. When I truncated the second experiment today (five and 1/2 hours ago), I turned the refrigerator back on, but left the AC off. I mean after all, there was no sense in abusing that beer anymore than I already had. I just checked, and the interior of the RV is 111°F, and the interior of the refrigerator has already cooled back down to a safe temp of 38°F.

Jim

[TucsonJim]

By the way, I found it interesting food-borne illness in the USA sickens 48 million, causes hospitalization of 128,000 and kills 3,000 people each year! Source: Centers for Disease Control:

https://www.cdc.gov/foodborneburden/...-overview.html

Jim

[sande005]

Having run a really big food operation (50+ locations, population of 90,000, etc.) where it seemed like I was welded at the hip to our Health Department for decades...everything Jim said is true. Thankfully, never had a food illness outbreak in almost 30 years. A few other tidbits:

1. The critical temperature range is 40-140 (F). Perishable food should not be in that range for more than 3 hrs. And that time is cumulative. So the time in the grocery cart, getting it home, on the counter during prep - all count. The CDC says only 2 hrs. Some debate, as that may be conservative to allow for times that people don't normally think about - like the grocery cart. Or the time you don't know about at the store, on a truck, etc. Whichever benchmark you use, throw it out. Period.

2. Things that will make you sick growing in food almost never make it appear to be spoiled. There is some evidence that the bacteria causing spoilage actually inhibit the growth of disease organisms. It is the food that seems perfectly fine that will get you.

3. There is no such thing as "stomach flu" - it is food poisoning.

4. Think about how long something may take to cool in the middle when put in the fridge. That pot of chili or big hunk of ham may be in the danger zone for many, many hours (plus warming up everything else in the fridge). Store it in shallow containers, or drop zip-lock bags of ice into it to cool it faster.

[powerscol]

Jim - have you ever tried dry Ice in the fridge. Its available around here and I can usually find it on the road at the bigger grocery stores or Ice companies. Just a thought?
Great experiment - I appreciate your work.
Keith

[TucsonJim]

Jim - have you ever tried dry Ice in the fridge. Its available around here and I can usually find it on the road at the bigger grocery stores or Ice companies. Just a thought?
Great experiment - I appreciate your work.
Keith

Keith. It is a possible solution, but doesn't seem to be a practical way to tackle the problem. First of all you'd need to have a fresh supply each time you hit the road. If you purchase it the night before, you'll need to get a fairly large quantity because it will sublimate overnight.

Another issue is that any refrigerated foods in close proximity would be prone to freezing. So quantity and placement would be pretty important. If anyone has ever experimented with it, maybe they can share their results.

Jim

[DaveMatthewsBand]

Interesting read Jim.
But wouldn’t it be simple enough to just run the fridge off a small inverter?








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