Pex tube and a frozen floor...

[milkman636]

http://www.dow.com/heattrans/pdfs/DispellingTheMyths.pdf

Here is a little slide show about antifreeze.

 

[milkman636]

In my past I have cut and welded on 8 inch pipes containing 50% glycol (Dowtherm SR-1) solution that were sealed with ice plugs created by liquid nitrogen collars. The pipes were frozen solid for a short length so we could cut and drain the lines to add isolation valves. There was about 35 psi on the upstream side of the freeze with active flow through the bullheads of two tees feeding air cooled chillers that couldn't be shut down without impacting an expensive process. The freezing sealed the pipes for over an hour on each line while we welded flanges and bolted on shut-off valves. Afterward the collars were removed and the plugs thawed without any damage to the pipes. So the moral of this story is that freezing is not an automatic death sentence for pipes, or tubing encased in concrete for this thread.

 

[nybirdman]

To protect your domestic water make-up you need a "back flow preventer"which is basically two check valves with a drain between them.I would add anti-freeze to your system to prevent any further problems/protection.

 

[Raspy]

Gary,

I'm with you. The term "efficiency" really isn't applicable in that situation. I believe the reason it is said is because with propylene glycol or other fluids, the viscosity is slightly raised and the specific heat is slightly lowered. In two solar systems that were exactly the same in every way, but one had a higher viscosity fluid with lower specific heat, like silicone oil vs water, the collector would run at a higher temp while collecting and be less efficient. Less efficient meaning more energy was lost to the environment.

With radiant delivery and a 50-50 mix of Propylene glycol, it might be the same delivery rate as water or so close it didn't matter, but there is no loss off efficiency that I can see. I guess they'd have to define the word efficiency before they could make the argument.

 

[mx842]

Wow! Three pages while I was out. I'm still chucking wood in the boiler and running it as hot as I can to get enough hot water into the manifold as I can. There are so many things I have going against me right now that it's hard to keep up. This cold spell is one of them which is something we don't see too often here where I live. We normally get one good freeze sometime just before or right after Christmas. By that I mean a period of days where the temps don't get above freezing. It gets cold here and at times it will get down into the teens but its usually just a night or two then it warms back up. The short lived cold spells are easy to deal with with propane heaters and blankets as a few guys have suggested but when it gets cold and stays that way for over a month it's hard to catch up.

I've had this old wood boiler for awhile and I knew it needed some work but I had been putting it on the back burner because there were more pressing projects at the time. I waited for a long time for some help to get my big doors built and put up and I guess I should have been working on the stove then but just kept putting it off because I really didn't think it would take that much to get it going and I had so many other things to get done I kept putting that off too.

I had been working on putting up insulation, OSB, shelves, cabinets, and other stuff so that I could start putting my junk away so I had a place to work and find stuff when I needed it. I was so tired of moving stuff from one place to another just to make room for something else or make a hole to work on something. The thing that really messed me up was I got in a couple jobs that people wanted me to do.....to make money so that I could fund the rest of my barn build. I had just about decided to not do anything else until I at least got my doors up and the heat working because everything I did took three times longer than it should the way I had to do it the way the shop was.

Anyway this brings me to where I am right now. As of last night when I came in for the night I still had two loops that water will not flow through but I have have high expectations that they will finally thaw out and not be damaged.......that's me thinking positively. LOL I'm going out in a few minutes to see what has happened overnight and hopefully things will be good because it was warmer last night and today it's supposed to get in the 40's so maybe I can catch up to it, or hopefully so, because it's supposed to get cold again tonight and not get out of the 20's again for the next few days. If I can finish getting all my gable ends sealed up, the spaces between where the rafters and the top of my walls meet; the soffit area, and the corners where I still need to trim out so that the wind doesn't blow in as easily as it has been able to do I should be okay. I still need to seal up around my doors because there are some places that need caulking and weather strip.

Sadly for me all the work I have done on pipping the boiler for now is temp because I ended up having to put it in a part of the building it's not going to stay. I was working on building another shed off to the back of the building that was going to hold the boiler, air compressor and a acid dip tank but I ran out of money before it was completed so I had to go this route. I am going to post some pictures of the process when I get caught up but for now I have to get ahead of this next cold snap.

Thanks for all the replies, yesterday when I did this thread I was completely wore out from 5 days and nights working on this junk trying to get ahead of a complete floor failure. It was mostly a flustration rant than anything else but thanks for all the replies. Between those and a good nights sleep I feel better and ready to face what ever I find at the barn as I ready myself to head down there. Thanks!!

 

[BeezFun]

The math in post#6 is flawed.

My math was OK but my logic was completely flawed, not sure what I was thinking. To find the change in pressure for a fixed volume of water:
E = v(dp/dv) where E is the bulk modulus for water at room temp is roughly 300,000. So for a 1C change in temp, using the .0002 value from my other post for coefficient, the change in pressure is:
dp=.0002*E = 64psi
So that's quite a significant change for only 1 degree. I would guess the piping in these systems is good for a few hundred psi, so it wouldn't take much heat to get up to the point where you could damage piping. Some of the expansion of the water will be taken up by compression of the ice, but ice is anisotropic and I'm too lazy to try to figure out how much it will change volume for a given change in pressure. There's also air in the water that will absorb some of the expansion, so it's hard to know for sure what the net outcome would be.

 

[BeezFun]

Well, I've seen pipe split during the thawing process.

My guess is what you saw was the result of the ice plug melting. As the ice expands it splits the pipe, but also seals the hole so no water leaks out. As the ice melts, the hole is now exposed and water leaks out. I've only experienced one split pipe from freezing, and I was able to see ice through the split. The water did not leak out until a day later when I was able to thaw the pipe. So based on a vast statistical sample size of one, I've only seen a pipe split at the point where the ice is located.

 

[milkman636]

My math was OK but my logic was completely flawed, not sure what I was thinking. To find the change in pressure for a fixed volume of water:
E = v(dp/dv) where E is the bulk modulus for water at room temp is roughly 300,000. So for a 1C change in temp, using the .0002 value from my other post for coefficient, the change in pressure is:
dp=.0002*E = 64psi
So that's quite a significant change for only 1 degree. I would guess the piping in these systems is good for a few hundred psi, so it wouldn't take much heat to get up to the point where you could damage piping. Some of the expansion of the water will be taken up by compression of the ice, but ice is anisotropic and I'm too lazy to try to figure out how much it will change volume for a given change in pressure. There's also air in the water that will absorb some of the expansion, so it's hard to know for sure what the net outcome would be.

If you extend that math to cover a rise from 32°F to 72°F you'll have the increase just to room temperature. This phenomenon is exactly why torches should never be used to thaw pipes.

I believe the typical PEX lay line says something like 160 PSI at 73°F, and it drops off as temperature increases. I would guess that actual burst pressure would probably be at least double that #.

 

[Rustyiron]

The anti freeze slightly reduces the efficiency of the system, I was told by my radiant design Co. I used. I'm not sure if this is "splitting hairs" but if there is any chance of the system getting to that point, prolly a good option. Sounds like just dumb luck for the OP.
QUOTE]
I wonder about the truth of this. In a car radiator it increases the efficiency of cooling compared to plain water due to the wetting agents in anti-freeze. Why would it be different in a system that is basically doing the same thing, removing heat from hot water lines. I think your design company was blowing smoke up your ***** but don't know why they would do that, unless they wanted to come back to repair your lines after the froze and burst.

It might be Gary but think about it. In an automotive situation, you are trying to get rid of heat. In a hydronic heating aplication, you are counting on your water absorbing, storing & moving your heat from one point to another. I have read this same thing other places as well. Like I said, it might just be splitting hairs on efficiency. :confused3:
Well before I hit Post quick relpy, I did a search and the first result pretty much said that it is splitting hairs. Glycol treated water is "more viscous and less thermally efficient than pure water".
PS for those using automotive antifreeze, this site says it's a no no Anti-Freeze in Hydronic Systems

 

[Raspy]

It might be Gary but think about it. In an automotive situation, you are trying to get rid of heat. In a hydronic heating aplication, you are counting on your water absorbing, storing & moving your heat from one point to another. I have read this same thing other places as well. Like I said, it might just be splitting hairs on efficiency. :confused3:
Well before I hit Post quick relpy, I did a search and the first result pretty much said that it is splitting hairs. Glycol treated water is "more viscous and less thermally efficient than pure water".
PS for those using automotive antifreeze, this site says it's a no no Anti-Freeze in Hydronic Systems

Rusty,

An automotive system is the same as a radiant system. The "coolant" in a car absorbs heat from the hotter interior surfaces of the engine block and gives it up to the cooler interior surfaces of the radiator tubes. In a radiant floor, the "coolant" absorbs heat from the hotter interior surfaces of a boiler and gives it up the cooler interior surfaces of the radiant tubing. Same thing. In both cases energy is simply being transported between two objects that are at different temperatures, by a fluid. The energy is being absorbed and released by conduction.