Anti-Freeze or Water?

[AOTO]

I am about to hook up a radiant system in my barn to my boiler. I have 3/4" Pex-AL-Pex installed in the cement and it has nothing in it at this time. I want to hook up my boiler system and put some water to it, but someone said that the water could freeze by the time it reaches the return manifold. I'm not sure about that since there is nothing to stop the water from moving and it's going in at 160 F. So with that said, my loops are 275-300' of the Pex. The cement is cold enough to water when it drips on it it freezes so...

a) Do I worry about this?
b) Not worry about this?
c) Put in 10-20 gallons of RV anti freeze into my whole system? Bear in mind I have no idea what it will do to the rest of my system.

I already have the boiler circulating inside the barn...I just have to either throw the lever or do something else.

Any idea on warranty data from TACO or Wilostar on using a glycol based product? What will it do in the boiler, if anything?

 

[reaperman]

First off if you choose water, it wont freeze as long as the pump is running. Water transfers heat much better than anti-freeze and is much easier on components. Are you heating with a wood boiler or electric/gas water heater or boiler? If you are using a gas or electric boiler, you cant use just any ol' anti-freeze.

 

[Valhalla]

Hey MHVFD,

If you ever loose power, the anti-freeze will certainly be necessary. With this winter that happens once a month, at least! I would add the right stuff for sure. Try searching (broken link removed) for more info on this.

It is also one of my projects for my new PEX radiant system this spring!

Nice barn!

 

[jklingel]

You may want to read a little on (broken link removed to http://www.healthyheating.com/before) you do anything. I just read some articles on using/not using antifreeze over there, and what kind to use/not use. Just what you needed, right? Another delay. Man, you sure have a heap of circuits there! Must be a big barn; good luck w/ it. j

 

[ezoffshore]

I chose not to use anti-freeze in my system because of the loss in heat transferability. I dont have to wory about the power loss aspect becouse I have a backup generator and I also have my propane boiler that will kick in if my water temperature drops down to 100 deg. That way I didnt have to wory about going on vacation for a couple weeks in the winter and trying to find sombody to keep filling my stove.

 

[jebatty]

Isn't 160 for radiant loops a little high? A 30% antifreeze solution has about 90% or a little better heat capacity of water, so if you go the antifreeze route, you may need a higher rate of circulation to make up the difference, depending on the design of your system.

 

[Hydronics]

If you intend to heat the building constantly, there is little risk of freezing. If you'll be away & not heating, it may be worth using anti freeze, you'll want to use propylene glycol w/ 1/2 water for freeze protection.
The non pex components above the slab (iron & copper) are actually at the greatest risk of freeze damage because they can't expand as much without failure.
With respect to temperature in the tubing: typically it is best to temper down below 125*F in concrete because the high temps. over time can break down the concrete.
As long as you flush the system well before loading with glycol and check the ph annually, you should have no problems with corrosion. Mixing with hard water and allowing the ph to drop excessively is what causes corrosion.

 

[AOTO]

Hey Folks - I mentioned that there is nothing in the pipes at the moment. I want to fill the pipes so I can get some warmth going out there but am afraid of the initial fill freezing as I am filling it, know what I mean? It is 1.8F outside right now and I'm sure the concrete isn't much above that temperature. I will be tempering down the temperature once everything is filled and circulating, but I am afraid to put the water to it, today.
I am debating on attempting to fill one loop to see what happens. If I put water in it and it doesn't come out the other end, I know it's frozen somewhere in there for sure, and then I'll know. Of course, that loop will probably be toast too. I do have 5 other loops. The cement slab is 32' x 48'. The Question of the day is; Will my Pex-AL-Pex freeze the hot water once I start to fill the loops or, will the heat from the water transfer into the Pex and warm it up so it won't freeze? Should I wait for Spring or Mix the whole system w/some kind of anti-Freeze. I don't want to waste money on an additive I don't need, then again I don't want to ruin a loop because of my ignorance. I was very late in getting my wood boiler hooked up, but now that it is, I'm frustrated as this is the last piece of the project.

 

[AOTO]

First off if you choose water, it wont freeze as long as the pump is running. Water transfers heat much better than anti-freeze and is much easier on components. Are you heating with a wood boiler or electric/gas water heater or boiler? If you are using a gas or electric boiler, you cant use just any ol' anti-freeze.

I am using a wood boiler at the moment, which is hooked into my existing oil burner in the house as a manifold (which has the burner turned off) to feed the zones with nice hot water.

 

[Jim K in PA]

I think the risk is low that you will freeze the water in the PEX while filling it. It is moving fast enough that the heat loss to the concrete will not be significant enough to pose a risk. However, you will need to keep it moving once you fill, and start heating it once the circuits are all full. There is no exposed surface area, so it is not a comparable condition to water drops freezing on the surface.

However, if you want to add a level of confidence, run your DHW out to the slab and fill the circuits with warm water. Then get that water moving and heated ASAP.

 

[AOTO]

If you intend to heat the building constantly, there is little risk of freezing. If you'll be away & not heating, it may be worth using anti freeze, you'll want to use propylene glycol w/ 1/2 water for freeze protection.
The non pex components above the slab (iron & copper) are actually at the greatest risk of freeze damage because they can't expand as much without failure.
With respect to temperature in the tubing: typically it is best to temper down below 125*F in concrete because the high temps. over time can break down the concrete.
As long as you flush the system well before loading with glycol and check the ph annually, you should have no problems with corrosion. Mixing with hard water and allowing the ph to drop excessively is what causes corrosion.

I will be tempering it down once I get it filled and circulating, probably down into the 80's? Right now the boiler is at 181F and by the time it get's to the manifold, 175 feet away, I am expecting to fall into ~160F -165F range. I've already installed my return loop and circulation loop, going thru the tempering valve to the Taco 007.

 

[AOTO]

I think the risk is low that you will freeze the water in the PEX while filling it. It is moving fast enough that the heat loss to the concrete will not be significant enough to pose a risk. However, you will need to keep it moving once you fill, and start heating it once the circuits are all full. There is no exposed surface area, so it is not a comparable condition to water drops freezing on the surface.

However, if you want to add a level of confidence, run your DHW out to the slab and fill the circuits with warm water. Then get that water moving and heated ASAP.

See above quoted reply. Hot water is right there, ready to go in. I just need to move one valve and it's the point of no return after that (actually I have the return, it was just a figure of speech).

 

[Sting]

Isn't 160 for radiant loops a little high?

When I first read this question last night I wondered how long it would take to get a lucid answer!

Did you ever fill a glass with ice cubes and then pour a hot liquid over them?????

I love a forth of July fireworks just as much as the next guy but more for the pretty lights then the booms and the cracking noises!

Then -- If I were the owner here, there would be fireworks after the booms and the cracks showed up - maybe the leaking !

Never add energy bearing liquid to a solid mass at at greater than 40 degree differential -- in this case I would even add at a closer delta T because its a first fill and the slab is below freezing.

- And them loops are too long -- but there isn't much you can do about it now - this thing is going to be a difficult puppy to balance and the pump needed to circulate at a hi enough GPM so there is still energy left in the return of the loop is going to be very costly to run.

But I am just a figment of the public internet -- What do I know?

 

[slowzuki]

I'll weigh in. I've got 1/2 loops that are longer so haven't dared hit my slab with the heat yet. My sister uses a 400 ft 5/8" garden hose to fill water buckets using 50 degree F water and it doesn't freeze even at -20 F laying out on the ground. When turned off you have about 5 minutes to get it all pulled downhill and unhooked to drain. BTW it wraps nicely around a 7 ft snowblower auger in about 15 seconds.

I'm not worried about the thermal shock. My slab has cured for 3 years and shrunk down. It also has shrunk from the cold weather so there is room for it to expand. Locally they use the infloor heat to heat slabs that are curing that are poured in the winter. They use 80 F water though. They also use hot water ground thaw tubing to melt the ground below a pour before it happens so no concrete will freeze.

 

[AOTO]

Isn't 160 for radiant loops a little high?

When I first read this question last night I wondered how long it would take to get a lucid answer!

Did you ever fill a glass with ice cubes and then pour a hot liquid over them?????

I love a forth of July fireworks just as much as the next guy but more for the pretty lights then the booms and the cracking noises!

Then -- If I were the owner here, there would be fireworks after the booms and the cracks showed up - maybe the leaking !

Never add energy bearing liquid to a solid mass at at greater than 40 degree differential -- in this case I would even add at a closer delta T because its a first fill and the slab is below freezing.

- And them loops are too long -- but there isn't much you can do about it now - this thing is going to be a difficult puppy to balance and the pump needed to circulate at a hi enough GPM so there is still energy left in the return of the loop is going to be very costly to run.

But I am just a figment of the public internet -- What do I know?

Okay so you think I might be better off waiting for it (the slab) to warm a bit or bring the water temp way down before I try to fill? I never thought of the Ice-Cube thing before...it gave me shivers from just envisioning it. Egads!

 

[Tarmsolo60]

i've had slabs freeze on initial fill with pure water.

 

[AOTO]

I'll weigh in. I've got 1/2 loops that are longer so haven't dared hit my slab with the heat yet.
I'm not worried about the thermal shock. My slab has cured for 3 years and shrunk down. It also has shrunk from the cold weather so there is room for it to expand.

You have a radiant slab but it's not heated or filled with anything...? Do you plan on filling it this winter or wait until you can fill it with a garden hose in Spring?

 

[slowzuki]

In the shop the tubes just have air pressure in them. The slab sat open one winter, next winter just a roof over it, next winter walls, this winter 95% enclosed. It usually is about 5-10 C warmer than outside. Part of the reason is I need to jackhammer into the slab.

Now that someone on the last page had a freezeup during a fill, I certainly won't be trying it! My loops are way, way, way too long, as in one is 1000 ft of 1/2". Yup. You read right. The max should have been 500 feet for the heat load in the shop.

 

[DaveBP]

Never add energy bearing liquid to a solid mass at at greater than 40 degree differential—in this case I would even add at a closer delta T because its a first fill and the slab is below freezing.

The problem of heating the slab too fast is "striping". If you put heat into the slab faster than it can move through the whole mass of concrete and achieve an even temperature throughout you will have stripes of warm concrete and cold concrete next to each other. It's the uneven thermal expansion that stresses the concrete, not the whole slab expanding.

If you have all your system hooked up and ready to turn valves to fill and purge the air out of the PEX circuits I think you'll have plenty of time to avoid the water freezing in the pipes. If you plan to fill it with a garden hose and you have a good well or town water you could just run DHW through the whole floor for a while to start heating it gently. If you don't already have thermometers on your manifolds to measure water temp in and water temp out of the floor adding them will let you know what's happening. If your slab is really cold the water coming out is going to be 32F for quite a while before it climbs from there. You'll get some idea of how slowly slabs react.

If your system is currently set up to feed 165F water into the slab with on/off control your are going to go nuts trying to anticipate the heat loads on the building. It will take hours to catch up if it gets colder in the building than you want, and it can get warmer in there than comfortable (maybe not in January!) before it starts to cool off. The best way to run radiant floors is with a mixing valve that varies the temperature of the water going into the PEX to match the heat needs of the building. Much more even heat in the building without stressing the concrete with wild temperature swings.

Of course, as with most 'best' ways to do anything, it costs more money for the valves and controls. But to start off, a manually adjusted 3-way or 4-way mixing valve on the input manifold would let you watch the temperature drop with those thermometers and use the lowest temp water that will do the job. On an automatic system the circulator ends up running almost continuously but varying the water temperature all the time. Puts a more even load on your boiler so you have more capacity to heat the varying loads on your house.

Long winded post. I don't think you'll shatter your slab, but for lots of reasons it's better to heat as gently as possible at all times, not just at startup.

 

[Tarmsolo60]

If you have all your system hooked up and ready to turn valves to fill and purge the air out of the PEX circuits I think you'll have plenty of time to avoid the water freezing in the pipes.

Thats what I thought but I've had it freeze in the slab, I'd bring the room up to temp for a good day or more to warm up the slab a little before filling.

 

[AOTO]

Here is what I am dealing with and let me know your thoughts on the set-up. The white lines on the left are 1 1/4" pex. They go thru a valve body I made that is currently circulating water from the OWB. The bottom is the supply and the top is the return.
The other valves on the right are closed since I don't want the hot water going into the actual system just yet. I removed the tempering (mixing) valve so I can extend the one copper pipe about 1/4 of an inch because I sweated the joints too close. Once I re-connect it, the Hot water will go thru the mixing valve on the left and then down to the Taco 007. It will then be pumped upwards into the lower manifold. The lower manifold will supply the loops with the mixed water that will feed back into the top manifold. This cooler fluid will return thru the mixing valve when needed and/or the rest of it will go back to the OWB for reuse. I need to hook up the circ. pump to the single zone switch and the Tstat. I have to still hook up one of the return loops (Left top manifold) to the bypass loop, like I did on the lower right side. I can use these bypass loops to purge air from either manifold, or I can use them to suck the water out (with a vacuum) when I want to work on the system.

 

[DaveBP]

DaveBP - 14 January 2009 11:57 AM

If you have all your system hooked up and ready to turn valves to fill and purge the air out of the PEX circuits I think you’ll have plenty of time to avoid the water freezing in the pipes.

Thats what I thought but I’ve had it freeze in the slab, I’d bring the room up to temp for a good day or more to warm up the slab a little before filling.

...freeze in the slab with new water (well water at 50F or whatever) running through it while filling/purging? Or the same unheated water recirculating? Or sitting in the pipes? I'm fully prepared to stand corrected at a gut guess but now that I see from the newer pics that the building is insulated, I'd wind 10 or 20 bucks worth of kerosene through a salamander to warm the slab a little just in case.

mhvfd, I see you used styrofoam on the perimeter but what was that underneath? Bubblewrap?

 

[Tarmsolo60]

DaveBP - 14 January 2009 11:57 AM

If you have all your system hooked up and ready to turn valves to fill and purge the air out of the PEX circuits I think you’ll have plenty of time to avoid the water freezing in the pipes.

Thats what I thought but I’ve had it freeze in the slab, I’d bring the room up to temp for a good day or more to warm up the slab a little before filling.

...freeze in the slab with new water (well water at 50F or whatever) running through it while filling/purging? Or the same unheated water recirculating? Or sitting in the pipes? I'm fully prepared to stand corrected at a gut guess

Freezing happened during initial purging with water, new construction, basement, foam under slab, insulated and backfilled basement walls. Piping was installed and concrete poured in the fall, I went back during the winter after house was framed but not heated. warmed mechanical room with electric while I did all required work aound boiler. The slab manifold was in the mechanical room and the loops could be blown through before hooking to the manifold. when charging the floor with cold water the loops froze before the water made it back to the return manifold.

I didn't measure the temp of the slab (it was pretty cold out)before trying to purge figuring the water would be moving and boiler was ready to heat. The OP said his slab was probably about 1 degree F.

We ran some propane salamanders in the basement for a day and all turned out well. The loops started to thaw and flow one at a time.

Trust me I've been there

 

[DaveBP]

Trust me I’ve been there

Under those conditions (sounds like you did everything right ) I would have had no hesitation to fill the lines. And I would have been just as stunned as you probably were. I don't swear much, almost always at myself, but I would have tried language to thaw those lines.

Recollect how long the loops were?

 

[AOTO]

DaveBP - 14 January 2009 11:57 AM



mhvfd, I see you used styrofoam on the perimeter but what was that underneath? Bubblewrap?

The Pex-Al-Pex is sitting on top of "Tekfoil" (White, Bubble, Foil) which supposedly refracts back 95% of the heat, and then it is on top of 2" blue board. I think it's separated from the ground pretty good.