How cold is freezing?

[Layton100@gmail.com]

Hello, new to the forum with recently acquired 2016 Coachman Galleria.
In reading all manuals, especially the Truma furnace/water heater there is much talk about winterizing when temps get to “Freezing”.

My question is what experience have others had in using this type of vehicle & equipment in colder weather? We have had several other C and A RVs and have only worried about temps when they went below Freezing (32) for prolonged periods of time, say2-3 days.

Thoughts and suggestions are welcomed.

Thank you,

Layton

[avanti]

There are two opposing things going on that you need to consider:
1) The "danger point" is just below freezing. Contrary to what you might think, extremely cold weather is NOT in general more dangerous than "barely-below freezing" temperatures. The opposite is true: Ice is at its maximum volume just a degree or two below freezing--after that it contracts and becomes less likely to cause damage.
2) OTOH, your vehicle is a heat reservoir, and it takes time to chill it to the point at which freezing and associated damage can occur. The colder it is, the less time this takes. In frigid temperatures, a few hours suffice. If it is barely below freezing, then it could take days. But, if it is 31 degrees long enough, freezing will eventually occur, and when it does, it will do at least as much damage as would colder weather. Freezing is freezing.

[RossWilliams]

In reading all manuals, especially the Truma furnace/water heater there is much talk about winterizing when temps get to “Freezing”.

My question is what experience have others had in using this type of vehicle & equipment in colder weather? We have had several other C and A RVs and have only worried about temps when they went below Freezing (32) for prolonged periods of time, say2-3 days.

How long is very individual both in terms of weather conditions and your coaches design and features. Are there exposed pipes? Will they burst if frozen.

The pink RV antifreeze will freeze, it just doesn't expand when freezing so nothing gets broken. Water expands a lot once as it freezes and that magic point is 32 degrees. If the temperature is below that, the only question is how long it will take the water to get there. In some circumstances it might take a day or two and in others less than an hour if the temperature is low enough.

The low temperatures here are predicted to be slightly below freezing, around 30 degrees, the next few days with highs also in the 30's. But it was in the high 60's and low 70's the last few days. So the coach and the ground are starting out warm. Its doubtful it will get to freezing under the coach, especially with the heater running. So we haven't winterized.

On the other hand, when we reached below freezing temperatures on our trip last spring, we immediately winterized. The frozen ground was still a lot colder than the air and a moving vehicle creates its own windchill. And when I look under the coach, I see exposed pipes. Our furnace turned off on that trip while we were winterized and the cat's water dish sitting on the floor froze solid before we noticed the problem. It doesn't take long.

[Layton100@gmail.com]

Thanks, very good thoughts and info.

[hbn7hj]

Windchill is a parameter for exposed skin and nothing more. For Example if it is 34F and the windchill number is 25F contained water In a pipe will never freeze. But the skin will feel like it is 25F in still air. Windchill is not relevant.

Pipes will freeze quicker in 25F air and 10mph wind but the windchill number doesn’t tell you anything about that. It is a useless number to RV systems.`

You guys are smart enough to know that.

[magicbus]

In case you didn’t get it from the documentation, your Truma will work fine as a furnace, both gas and /or electric, even after you drain it. All you lose is hot water.

Regarding winterizing, our fresh water and feed line are completely exposed so we drain if it’s going near 32 and use bottled water for drinking and the pink stuff for flushing.

[RossWilliams]

From Wikipedia

"The first wind chill formulas ... were based on the cooling rate of a small plastic bottle as its contents turned to ice while suspended in the wind on the expedition hut roof"

That sounds an awful lot like what we are talking about.

Absent evaporation, wind alone will not cause water to freeze. So your pipes are safe at 34 degrees no matter how fast the wind is blowing. But at 28 degrees they will freeze much faster in a high wind.

Reported wind chills are based on the perceived heat loss of a 98 degree human body. So the reported wind chill will only reflect in a rough manner the relative effect on water at 32 degrees.

[booster]

Originally Posted by RossWilliams

Absent evaporation, wind alone will not cause water to freeze. So your pipes are safe at 34 degrees no matter how fast the wind is blowing. But at 28 degrees they will freeze much faster in a high wind.

This is not always true, as it all depends on radiation losses, also.



All things give off radiated heat based on their temp and other properties. If two thing face each other and have the same radiation properties, they will stay at the same temperature. If one radiates more than the other, it will get colder, barring any convection things.


Perfect example is the roof of the van if it is sitting out under a clear ski at night. It will get colder than the air around it get condensation or frost on it at air temps above freezing. This is because the van is radiating off heat and the sky is not as there is nothing there. In some cases you can even get water to freeze in a pan at close to freezing air temps if left under clear skies.


This is also an effect that happens to a lesser degree with cold ground and stuff above it as the ground will not radiate as much as the warmer stuff if the stuff is warmer.


Wind under clear skies can actually prevent items from getting colder in marginal temps.

[SDDavis]

Actually not true. At 0mph wind there is a slight heat transfer from the pipes to the surrounding air that slows the freezing process. Wind above 0 mph will strip the thermal barrier much more quickly leading to quicker freezing

[booster]

Originally Posted by SDDavis

Actually not true. At 0mph wind there is a slight heat transfer from the pipes to the surrounding air that slows the freezing process. Wind above 0 mph will strip the thermal barrier much more quickly leading to quicker freezing

What are you saying is not true, I don't think anyone said wind wouldn't speed up cooling/freezing if the temps are below freezing, just that windchill temp as given on the news is more related to humans and not inanimate objects. If the temps are above freezing wind can actually help keep items that are out in the open and radiating to the sky at night from getting colder than freezing.

[RossWilliams]

"At 0mph wind there is a slight heat transfer from the pipes to the surrounding air that slows the freezing process."

Obviously, ALL the heat transfer from the pipes goes to the surrounding air, where else would it go, regardless of wind speed. The wind speed determines how quickly that heated air is dispersed and replaced by cold air.

Air that doesn't move at all is used for insulation. If you actually had zero air movement, it would take a very long time for the pipes to freeze since the only heat transfer would be by conduction and air isn't much of a conductor. There are a bunch of other things that will usually move the heated air away from the pipe, but wind speeds the process substantially.

[booster]

Originally Posted by RossWilliams

"At 0mph wind there is a slight heat transfer from the pipes to the surrounding air that slows the freezing process."

Obviously, ALL the heat transfer from the pipes goes to the surrounding air, where else would it go, regardless of wind speed. The wind speed determines how quickly that heated air is dispersed and replaced by cold air.

Air that doesn't move at all is used for insulation. If you actually had zero air movement, it would take a very long time for the pipes to freeze since the only heat transfer would be by conduction and air isn't much of a conductor. There are a bunch of other things that will usually move the heated air away from the pipe, but wind speeds the process substantially.

Yep, if air doesn't move it is called insulation. Unfortunately in our world when air heats up it rises and if it cools it falls, so convection will cause air movement. That is why the gaps in insulated glass are so important to be right gap for the gas used, to limit convection vs heat transfer through the air.


Back to the original question of skirting, the above would indicate that the skirting would have two benefits. First is obviously blocking any wind from going under the van, but it will also prevent heat from going out from under the van horizontally do to convection as it heats on the bottom of the van. A stagnate, warm at the van bottom, cold on the ground air mass could have a significant temperature gradient.


Of course we still don't know what was stated as incorrect, so might not apply.

[avanti]

Originally Posted by RossWilliams

Obviously, ALL the heat transfer from the pipes goes to the surrounding air, where else would it go, regardless of wind speed.

Not true. Some of the heat loss is RADIANT. Air is mostly transparent to radiant heat. Such heat travels in rays until it either hits something that absorbs it, or else escapes into outer space.

(This discussion illustrates why Thermo is a weed-out course in engineering school.)

[booster]

Originally Posted by avanti

Not true. Some of the heat loss is RADIANT. Air is mostly transparent to radiant heat. Such heat travels in rays until it either hits something that absorbs it, or else escapes into outer space.

(This discussion illustrates why Thermo is a weed-out course in engineering school.)

Exactly, and this is what I described in detail in a previous post. Most of the non engineers have no idea of the somewhat abstract idea that things will cool down or heat up based on only the criteria of what surface, or space, they are facing.


Without this property of thermodynamics, a radiant heater would not work and neither would the sun.

[Davydd]

Originally Posted by Layton100@gmail.com

Hello, new to the forum with recently acquired 2016 Coachman Galleria.
In reading all manuals, especially the Truma furnace/water heater there is much talk about winterizing when temps get to “Freezing”.

My question is what experience have others had in using this type of vehicle & equipment in colder weather? We have had several other C and A RVs and have only worried about temps when they went below Freezing (32) for prolonged periods of time, say2-3 days.

Thoughts and suggestions are welcomed.

Thank you,

Layton

Now that we had a lesson on heat transfer, why don't we get back to Layton's question at hand. Layton, I think your practical experience is right on. You don't have to fret freezing at least in overnight situations where the daytime temperatures go above freezing especially if you keep your van warm inside. I'm not familiar with the Coachman Galleria but I managed without winterizing to withstand temperatures below freezing for a week at all times other than putting pink anti-freeze in the bathroom drain trap and periodically in the black tank. I don't know about 2016 models but RV upfitters are getting more cognizant about water lines especially to design them to be more durable from freezing. I doubt my 2005 Pleasure-way was that way but I did travel with water in the tank when overnight temperatures got below freezing.

[SDDavis]

Apologies, I didn't read your post closely enough. I believe we are saying the same thing.

[Layton100@gmail.com]

Thank you all for this responses. Have a great winter season!