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Hydronic Pipes in the floor: Material and Heating options  RSS feed

 
Rob Irish
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We're looking at putting some pipes into an earthen floor to run hot water through in the winter for toasty toes.

Probably heating the water simply by wrapping some coil around a RMH chimney shaft or the main barrel, and pumping it via solar or something like this. I have read here on the forums this can be unsafe, as the water pressure can build up and you get explosions - but aren't there pressure safety valves or something like this if it gets too much?

With the piping in the earth floor, I have seen people use PEX, PVC and Copper. Personally I would lean towards copper. I'm biased towards less manufactured things, but I'm open to something else if it does the job better.

Would anyone mind to share a bit about the advantages and disadvantages of these materials for this purpose? Or any other pointers?

Many thanks,
Rob
 
Rob Irish
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I have read from some other comments that you might need more PEX pipe compared to Copper.

PEX is more flexible than copper, and breaks less?

PEX is cheaper than copper?

PEX could leech petrol toxins into the water? Copper is more a friend of water in this regard?
 
tel jetson
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RMH wrap: at first blush, it seems like a pressure release valve would make this safe, but those really only work to relieve the pressure in a large vessel like a water heater, not in a tube. if it were my project, I think I would heat an open tank of water with the RMH and run your hydronic tubing through that water for heat exchange. that way, your water tank will never be above boiling, so steam explosions are not a risk.


pex and copper: when I was looking into it, prices and embodied energy were comparable. pex is cross-linked polyethylene, and I believe it's recyclable. most sources seemed to think the pex was a bit easier to work with than copper. copper is mined, which isn't a friendly scenario. pex is likely made from petroleum, which also isn't great. I would guess that copper conducts heat a bit better, but I don't actually know if that's an advantage in this application.
 
R Scott
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The poorer heat transfer of PEX is actually a good thing in the floor tubes. It allows you to have a longer run in the circuit and have more even heat. Copper will dump the heat too fast so the start of the loop is HOT while the end is COLD. You can have about 100' per run with 1/2" PEX before your heat loss and backpressure get too high. Run parallel loops if you need more than that.

Around here, PEX is a little cheaper up front but installs in WAY less time. You need a special tool to make connections, or buy the stupid expensive sharkbite connectors. Spend the money for the crimp tool if your plan is complicated, it will pay for itself in about a dozen connectors or less. But you can do a simple heat system in fewer connections than that.

It also is much more robust against mechanical damage like pounding it into a floor, although it still needs to be pressurized (or filled and capped) while packing the dirt to prevent collapse.

+1 on an open storage tank, or picking up heat from the bench area of the RMH. RMH + water is DANGEROUS. BOOM SQUISH as Paul, Ernie, and Erica refer to it. The problem is the RMH is SO hot the water flashes to steam and a valve simply can't react fast enough. We are talking EXPLOSION of steam here, same speed and energy as gunpowder.

 
Mike Cantrell
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tel jetson wrote:pex and copper: when I was looking into it, prices and embodied energy were comparable.


Embodied energy might be, but price is definitely not.

For a starting place (you can do better than these prices, but they're convenient):

Copper, $1.28/foot
http://www.homedepot.com/p/1-2-in-x-10-ft-Copper-Type-L-Pipe-LH04010/100354232#.UgJq523_2ZQ

PEX, $.30/foot
http://www.homedepot.com/p/SharkBite-1-2-in-x-10-ft-PEX-Pipe-U860W10/202033036#.UgJs3W3_2ZQ

I just replumbed my house with PEX and it was pretty fast and easy. Much faster and easier than PVC.
It cost roughly double what PVC would have, but it was worth it for the ease.
 
tel jetson
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Mike Cantrell wrote:
tel jetson wrote:pex and copper: when I was looking into it, prices and embodied energy were comparable.


Embodied energy might be, but price is definitely not.


it's been a couple of years since I looked. the two used to be much closer. I don't know if copper has gotten more expensive, or pex has gotten cheaper.
 
R Scott
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tel jetson wrote:
Mike Cantrell wrote:
tel jetson wrote:pex and copper: when I was looking into it, prices and embodied energy were comparable.


Embodied energy might be, but price is definitely not.


it's been a couple of years since I looked. the two used to be much closer. I don't know if copper has gotten more expensive, or pex has gotten cheaper.


NOTHING has gotten cheaper!!! Pex has gone up slightly, but copper has plain skyrocketed.

There are a couple online plumbing supplies that have PEX and fittings considerably cheaper than local sources like home depot, etc. www.pexuniverse.com and www.pexsupply.com are a couple that I've ordered from without incident, but there are more.

Pex has enough elasticity that it can be frozen and not burst (at least a couple times). And each turn/loop of the pipe is not a stack of fittings.

Except for high heat stuff (like the water-loop in my woodstove) I will probably never use copper again.
 
Rob Irish
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tel jetson wrote:RMH wrap: at first blush, it seems like a pressure release valve would make this safe, but those really only work to relieve the pressure in a large vessel like a water heater, not in a tube. if it were my project, I think I would heat an open tank of water with the RMH and run your hydronic tubing through that water for heat exchange. that way, your water tank will never be above boiling, so steam explosions are not a risk.


That makes sense come to think of it. But where I'm scratching my head is how then to heat up this open tank? Do you mean like it would sit on top of the big metal drum?

tel jetson wrote:
pex and copper: when I was looking into it, prices and embodied energy were comparable. pex is cross-linked polyethylene, and I believe it's recyclable. most sources seemed to think the pex was a bit easier to work with than copper. copper is mined, which isn't a friendly scenario. pex is likely made from petroleum, which also isn't great. I would guess that copper conducts heat a bit better, but I don't actually know if that's an advantage in this application.


Thanks for this comparison Tel.

R Scott wrote:The poorer heat transfer of PEX is actually a good thing in the floor tubes. It allows you to have a longer run in the circuit and have more even heat. Copper will dump the heat too fast so the start of the loop is HOT while the end is COLD. You can have about 100' per run with 1/2" PEX before your heat loss and backpressure get too high. Run parallel loops if you need more than that.

Around here, PEX is a little cheaper up front but installs in WAY less time. You need a special tool to make connections, or buy the stupid expensive sharkbite connectors. Spend the money for the crimp tool if your plan is complicated, it will pay for itself in about a dozen connectors or less. But you can do a simple heat system in fewer connections than that.

It also is much more robust against mechanical damage like pounding it into a floor, although it still needs to be pressurized (or filled and capped) while packing the dirt to prevent collapse.

+1 on an open storage tank, or picking up heat from the bench area of the RMH. RMH + water is DANGEROUS. BOOM SQUISH as Paul, Ernie, and Erica refer to it. The problem is the RMH is SO hot the water flashes to steam and a valve simply can't react fast enough. We are talking EXPLOSION of steam here, same speed and energy as gunpowder.


Wow, I didn't realise I would be able to have that long a pipe (100') in one loop. What would be the spacing for 1/2" Pex?

I also thought it would be the other way around, but that makes a lot sense that with something like copper that transfers quickly will create an uneven distribution.

We want to avoid sudden explosions of boiling water while relaxing if possible, so will definitely not try and be too innovative with the heating of water with the RMH

Just so I'm clear, is this the kind of method that is really unsafe? He seems to be using the heat itself to migrate the water in a loop i.e. no external pump to push the water around, just heat pressure:


I'm trying to get a visual of how this all might come together as I'm planning how the pipes will go in first, even though we probably won't have an RMH until much closer to winter.

 
Rob Irish
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I did a mockup of what I can see so far.

- An RMH that doubles as a day bed.
- Piping that is running under the floor, connected to a water tank



The only way so far I have seen to heat up the water in the tank in combo with the RMH is to wrap some sort of coil around either the RMH drum, or the chimney. Is that how its done, or how would you go about it?

I'm not sure if this sort of concept would work, but could a water tank be built inside the mass section of the RMH so that it gets warmed up just by the auxiliary heat? I made the bed see through so it hopefully makes sense:




I imagine there could be a problem having a tank embedded in a bunch of solid clay. Possible breakages... leaks... Just trying to think how to avoid having a room with too many circular cylinders... Would love a warm room that doesn't look like a basement.

I don't know what kind of temperatures it gets up to inside the clay mass if it would be enough to heat up a tank like that. I think it could be easy enough to simply have a wooden door above the tank so that it can be opened and accessed for water changes or repairs if needed.

Probably it would make more sense to have the water tank closer to where it is hottest:



Thanks for taking any time to think about this and for any feedback.
 
tel jetson
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Rob Irish wrote:
That makes sense come to think of it. But where I'm scratching my head is how then to heat up this open tank? Do you mean like it would sit on top of the big metal drum?


that's one option, and probably a good one. a water jacket partially or completely surrounding the barrel could work, too, and I would guess that it would increase the draft of the unit by cooling the exhaust a lot more than air would. you might also be able to use a gas hot water tank as the down-draft portion instead of a barrel. route the exhaust downward through the flue. never tried any of these, but I will at some point.
 
tel jetson
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Rob Irish wrote:
I'm not sure if this sort of concept would work, but could a water tank be built inside the mass section of the RMH so that it gets warmed up just by the auxiliary heat?


that could also work. an easier option would be to run coils of tubing through the mass. less mass of water to heat up, so less lag before the hydronics can heat. just don't run it close to the exhaust so you don't risk steam. you'll rob heat from your bench, so factor that into the design.
 
Rob Irish
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tel jetson wrote:
that's one option, and probably a good one. a water jacket partially or completely surrounding the barrel could work, too, and I would guess that it would increase the draft of the unit by cooling the exhaust a lot more than air would. you might also be able to use a gas hot water tank as the down-draft portion instead of a barrel. route the exhaust downward through the flue. never tried any of these, but I will at some point.


I had never heard of a water jacket until reading your post. I think I've got my head around it. So something perhaps like this?



There is a regular RMH cylinder as normal, but it is wrapped with a Water Jacket which seems to me to be some sort of cylindrical tank. The cold inlet is down low, with the hot outlet above. The thermal changes creates a natural water cycling so that colder water is constantly pushed into the Jacket. Both the Water Jacket and Water Tank have safety pressure valves on them.

Does the same thermal convection work with the hydronic pipes as well? Or does it require another kind of pump?
 
R Scott
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Rob Irish wrote:
Wow, I didn't realise I would be able to have that long a pipe (100') in one loop. What would be the spacing for 1/2" Pex?


Normally the spacing is 8-12 inches between runs. You can do a little more than that in deep earth floors but you will start to see uneven temps if you go too far apart for the mass..

Rob Irish wrote:
We want to avoid sudden explosions of boiling water while relaxing if possible, so will definitely not try and be too innovative with the heating of water with the RMH

Just so I'm clear, is this the kind of method that is really unsafe? He seems to be using the heat itself to migrate the water in a loop i.e. no external pump to push the water around, just heat pressure:


That way is safe for a typical exhaust temp, but not for the 1200 degree temps of an RMH bell. Drop a drip of water into a hot pan and it bounces and dances because the little bit of water that touched the pan first superheated and created a mini explosion to push the drop back into the air. Contain that inside a tube and it will get ugly quick.
 
Brian Knight
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Cool project you got going. Great diagram..Sketchup? Tend to agree that avoiding high temps is critical and challenging. Tej's suggestion of only running tubes through the bench portion is a good one.

The water jacket is just to create more surface area? Is that a certain product? I think for thermosiphoning with the two tanks one has to be completely below the other one. Large diameter tubing (3/4 thin wall copper as minimum) and avoiding 90 degree bends is critical.

It you attempt something like this it would be smart to put in a temp sensor at the closest part of the loop to the rmh vent along with the open tank advice. Pex does have temp restrictions too.

Not sure if your project is for new or existing but have to point out that a home where you can actually feel the heat or (toasy toes) from radiant floors has a very inefficient building envelope. There is a lot more science and repeated success of maintaining comfort and minimal fuel use with high performance building envelopes. You may want to consider focusing more in that area.



 
Rob Irish
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R Scott wrote:
Normally the spacing is 8-12 inches between runs. You can do a little more than that in deep earth floors but you will start to see uneven temps if you go too far apart for the mass..


To get this even spacing one would need to lay the pipes like I have in the diagrams I posted earlier. What I am unsure about is how to actually connect in this grid like manner. The only connectors I have seen are metal, and I was strongly advised against having these underground due to pressure bursts and major problems with repairs. I imagine the other issue would be rust.

Which makes me think that I would need to lay the PEX in some sort of snake-like manner, where there are no connectors under the floor, where the pipe meanders through the room without a single right angle or joint. Obviously then there would be some pretty big irregularities with heat distribution, some parts of the floor having pipe 8" apart, while some parts (based on how stiff the PEX I have is, limiting the bending circle) would be 24" - 30" apart.

e.g:


This is probably the easiest route, with least maintenance / problems in the long run, but at the expense of regular heat distribution.

If this was the method employed, would you want the piping to be closer to the surface?

Brian Knight wrote:
Cool project you got going. Great diagram..Sketchup? Tend to agree that avoiding high temps is critical and challenging. Tej's suggestion of only running tubes through the bench portion is a good one.

The water jacket is just to create more surface area? Is that a certain product? I think for thermosiphoning with the two tanks one has to be completely below the other one. Large diameter tubing (3/4 thin wall copper as minimum) and avoiding 90 degree bends is critical.

It you attempt something like this it would be smart to put in a temp sensor at the closest part of the loop to the rmh vent along with the open tank advice. Pex does have temp restrictions too.

Not sure if your project is for new or existing but have to point out that a home where you can actually feel the heat or (toasy toes) from radiant floors has a very inefficient building envelope. There is a lot more science and repeated success of maintaining comfort and minimal fuel use with high performance building envelopes. You may want to consider focusing more in that area.


Cheers! Those diagrams I've done in Cinema 4D.

I think I will go with the simplest option of running tubes through the bench. I don't know if the water jacket is a product you can buy, and I'm not a metal worker so I don't really trust my ability to create something from scratch.

This project is a renovation on a wooden house which already has some earth insulations in the wall. We're going to be adding to this by thickening the walls even more with more cob. Hopefully the building envelope isn't too inefficient in the end because winters here are cold and long.



 
tel jetson
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you can buy or build manifolds that allow multiple parallel runs of pex. you wouldn't want to bury those in the floor, but you could frame them into either the floor or the wall so that they're still accessible.


and water jackets accomplish a couple of things. a lot of surface area is one advantage. improving draw of the stove is another. because water at atmospheric pressure won't ever get above the boiling temperature, neither will the outside of the heat exchanger/barrel. cooling the exhaust at that point in the stove provides part of the draw that drives the system.

and yeah, it would likely have to be a custom job unless you tore apart a gas water heater.

fortunately, running tube through the mass should work just as well for heating water. it won't increase the draw of the stove, but that isn't necessarily bad.
 
Rob Irish
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tel jetson wrote:you can buy or build manifolds that allow multiple parallel runs of pex. you wouldn't want to bury those in the floor, but you could frame them into either the floor or the wall so that they're still accessible.


I did a search to find what manifolds are. That makes sense. Does a manifold system require more pressure or a more powerful pump?

Are all manifolds pretty much the same or is there a certain type of manifold which is ideal for this sort of system?

And more probably stupid questions: Say on one wall you have a manifold, on the other side of the floor where you need to turn the pipe around with 2 right angle turns, would that be done with another manifold connected the same way? Or would you bring those pipes out of the ground, and into another frame or into the wall and then turn them and loop them back to the one manifold ?
 
Rob Irish
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In the following video he demonstrates how to turn PEX without using joints. The second one looks like plastic - I think this would be great - any problems with these?

 
tel jetson
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Rob Irish wrote:Does a manifold system require more pressure or a more powerful pump?


I don't actually know, but I wouldn't think so. I would guess that you'll have the same total length of tube in the system, but more of it will be in parallel, so it might actually require less power due to less friction loss.

Rob Irish wrote:Are all manifolds pretty much the same or is there a certain type of manifold which is ideal for this sort of system?


there are purpose-built radiant floor manifolds, and you could most likely jury rig one yourself if you're relatively handy. I haven't taken the time to compare prices.

Rob Irish wrote:And more probably stupid questions: Say on one wall you have a manifold, on the other side of the floor where you need to turn the pipe around with 2 right angle turns, would that be done with another manifold connected the same way? Or would you bring those pipes out of the ground, and into another frame or into the wall and then turn them and loop them back to the one manifold?


I think you could do it many ways. you could do an out-and-back run (or any multiple of that) and have the supply and return manifolds right next to or on top of each other. you could also do just a single run (or any odd number of runs) and have your supply and return manifolds on opposite sides of the room. unless you find or make a really fancy contraption, though, I would guess that you will need two or more manifolds. more than two would be if you wanted to have more than one heating zone so you could heat only specific parts instead of the whole system.
 
R Scott
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Those bend supports are great for holding tight bends, but you don't even need that for most turns. Normally the pipe gets zip-tied to the re-mesh for concrete floors. For an earthen floor, you could use landscape staples, or the plastic pegs, or sandbags (removed after you have packed around them) to hold it down as you build up the floor. To hold a fairly tight bend, you could tie it with twine to hold the loop. They definitely help where you come up out of the floor to the manifold.

There is a science to how you run the pipes, it isn't a straight back and forth zig zag. You skip runs and then loop back to get them--it helps distribute heat more evenly and reduces the number of tight bends. Youtube and the library are your friends. They also show how to unroll pipe without kinking it.

Manifolds can run from simple (basically a stack of Tee's) to insane (flow meters and adjusting valves and shutoff valves and pressure meters and ...) Running parallel circuits may mean you need a bigger volume pump, but probably not, as the reduced backpressure usually evens things out. Usually the problem is finding a small enough pump for a DIY system. The big pump manufacturer's (Taco, Grundfos, etc) have pump sizing tools on their websites. If you want a solar/DC pump, take the numbers from their tool and then find the DC pump with acceptable specs. www.builditsolar.com has a lot of info on DC pumps.

Zero joints in the floor. Pressure/leak test every run before you cover them up (pipes do get pinholes in shipping and install). Have them pressurized while putting in the floor.

 
Brian Knight
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Great advice above. Was thinking more about your system. One of my main concerns is creating an overly complicated plumbing system to distribute heat from a source that is already going to be distributing well enough on its own. How much useful benefit will there be to heating the floors in an already heated room? Now if youre talking about a different level or distant room that's different..

DC pumps powered by PV are in a world all themselves. DC pumps last a very long time and the PV is running it outside of the grid power. The minute you hook up a grid tied AC pump to any heating distribution system you are introducing some serious concerns.

AC pumps tend to break down a lot and can represent a surprising amount of energy use. Its possible that an AC pump in this type of system would use as much or more power than a mini-split heat pump. The mini split would heat (and cool) the area almost instantly and could be dialed back instantly unlike a slowly responding radiant floor.

So that leaves you with DC pumps powered by PV or a completely passive and thermosiphoning system. DC with PV is a problem because it wont work very well when you need it the most (cold, cloudy dark).

A system that circulates itself would obviously be the ticket but presents its own challenges. The main thing is that the RMH would need to be below the floor area to be heated (warm water rises, cold water drops). Again, back to my original big picture problem that a RMH will probably be heating the upstairs just fine depending on the building envelope.
 
Rob Irish
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R Scott wrote:Those bend supports are great for holding tight bends, but you don't even need that for most turns. Normally the pipe gets zip-tied to the re-mesh for concrete floors. For an earthen floor, you could use landscape staples, or the plastic pegs, or sandbags (removed after you have packed around them) to hold it down as you build up the floor. To hold a fairly tight bend, you could tie it with twine to hold the loop. They definitely help where you come up out of the floor to the manifold.

There is a science to how you run the pipes, it isn't a straight back and forth zig zag. You skip runs and then loop back to get them--it helps distribute heat more evenly and reduces the number of tight bends. Youtube and the library are your friends. They also show how to unroll pipe without kinking it.

Manifolds can run from simple (basically a stack of Tee's) to insane (flow meters and adjusting valves and shutoff valves and pressure meters and ...) Running parallel circuits may mean you need a bigger volume pump, but probably not, as the reduced backpressure usually evens things out. Usually the problem is finding a small enough pump for a DIY system. The big pump manufacturer's (Taco, Grundfos, etc) have pump sizing tools on their websites. If you want a solar/DC pump, take the numbers from their tool and then find the DC pump with acceptable specs. www.builditsolar.com has a lot of info on DC pumps.

Zero joints in the floor. Pressure/leak test every run before you cover them up (pipes do get pinholes in shipping and install). Have them pressurized while putting in the floor.



I found an example of piping that was laid out like my great sketch here. This setup is the room I'm currently working on, where the pipes will be coming through a door section, with the RMH in the other room.



I imagine this method actually be quite good as there isn't that many hard turns and would create a fairly even heat distribution.

The learning curve is quite steep at the moment, so adding manifolds into the mix is feeling a bit much at this stage. I want this to be real simple, perhaps in another house down the track that is more complex I will look at manifolds.

We are definitely getting solar panels so a small DC pump sounds like the way to go.

Thanks for the link and advice!
 
Rob Irish
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Brian Knight wrote:Great advice above. Was thinking more about your system. One of my main concerns is creating an overly complicated plumbing system to distribute heat from a source that is already going to be distributing well enough on its own. How much useful benefit will there be to heating the floors in an already heated room? Now if youre talking about a different level or distant room that's different..

DC pumps powered by PV are in a world all themselves. DC pumps last a very long time and the PV is running it outside of the grid power. The minute you hook up a grid tied AC pump to any heating distribution system you are introducing some serious concerns.

AC pumps tend to break down a lot and can represent a surprising amount of energy use. Its possible that an AC pump in this type of system would use as much or more power than a mini-split heat pump. The mini split would heat (and cool) the area almost instantly and could be dialed back instantly unlike a slowly responding radiant floor.

So that leaves you with DC pumps powered by PV or a completely passive and thermosiphoning system. DC with PV is a problem because it wont work very well when you need it the most (cold, cloudy dark).

A system that circulates itself would obviously be the ticket but presents its own challenges. The main thing is that the RMH would need to be below the floor area to be heated (warm water rises, cold water drops). Again, back to my original big picture problem that a RMH will probably be heating the upstairs just fine depending on the building envelope.


I don't think we'll be having the RMH below the floor level. And it is just a one story (ground level) house. I think I understood correctly, but just to clarify, are you saying that unless the RMH is down below the radiant pipes that passive thermosiphoning doesn't work?

Thanks for explaining this difference between AC and DC - I really had no idea. I will see if they have them here in Estonia otherwise I'll order it online. So much to learn! This is great. Thanks again.
 
Rob Irish
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tel jetson wrote:
I think you could do it many ways. you could do an out-and-back run (or any multiple of that) and have the supply and return manifolds right next to or on top of each other. you could also do just a single run (or any odd number of runs) and have your supply and return manifolds on opposite sides of the room. unless you find or make a really fancy contraption, though, I would guess that you will need two or more manifolds. more than two would be if you wanted to have more than one heating zone so you could heat only specific parts instead of the whole system.


That is actually a really awesome idea and I hadn't thought of the option of choosing which zones would be heated.

I think though after weighing up my super amateur plumbing skills, pump skills and general building skills this time I'm going to go with a very simple single loop that just goes through two rooms and a kitchen. But when we get one day to putting our skills to building a home from scratch and we have ample time and resources I think we will definitely choose the manifold path so we have more control over it all.

Thanks for explaining all of that!
 
Rob Irish
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R Scott wrote: Pressure/leak test every run before you cover them up (pipes do get pinholes in shipping and install). Have them pressurized while putting in the floor.


Just on this little valuable bit of advice.

To test the pressure holds, would you connect the piping to a water pump and run water through and see if any water comes out anywhere?
 
R Scott
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Normally we did it dry. We had a home-built pressure tester that included a pressure gauge from home depot from the irrigation/sprinkler aisle, a hose Tee (with no valves, just a cap on the other side), a tire valvestem, and an air pump.

Or you can buy this already done: http://www.homedepot.com/p/DANCO-0-15-psi-1-10-Increment-Gas-Test-Gauge-94352/100180536#.UgueftKkqss

You can use sharkbite adapters and plugs to temporarily close off the pipes.

Pump it up to 15 psi and leave it overnight. If it isn't 15 psi by morning, then you get to troubleshoot. Soapy water on every connection along the mainfold, that is probably the leak. If it isn't there, then you may want to fill with water to find the leak--but it can make fixing it messier.


 
Rob Irish
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R Scott wrote:Normally we did it dry. We had a home-built pressure tester that included a pressure gauge from home depot from the irrigation/sprinkler aisle, a hose Tee (with no valves, just a cap on the other side), a tire valvestem, and an air pump.

Or you can buy this already done: http://www.homedepot.com/p/DANCO-0-15-psi-1-10-Increment-Gas-Test-Gauge-94352/100180536#.UgueftKkqss

You can use sharkbite adapters and plugs to temporarily close off the pipes.

Pump it up to 15 psi and leave it overnight. If it isn't 15 psi by morning, then you get to troubleshoot. Soapy water on every connection along the mainfold, that is probably the leak. If it isn't there, then you may want to fill with water to find the leak--but it can make fixing it messier.




I understand now. I didn't know there was such a thing as sharkbite. I thought I was going to have to crimp ends and attach fittings which would have been a hassle!

Thanks for the tips.
 
R Scott
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Sharkbites are WONDERFUL tools, the same fitting works on copper and pex. Expensive to do a whole project with them, but oh so convenient for temporary work and patching.

Everyone with running water should have a couple sharkbite plugs, valves, and/or couplers to fix leaking plumbing ASAP. It always happens 10 minutes after the store closes and 10 minutes before company arrives.
 
Rufus Laggren
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Sorry if I missed it but what temperature do you plan on running through your radiant floor piping? What flow do you plan? Unless you wish to constantly monitor and modify your temperature/flow you need to have some idea of what you're shooting for and try to build to get somewhere in that ballpark by default. But regardless, you still need a way to control the heat into the radiant pipe. Otherwise you get either hot or cold feet.

"Open" tanks generally need topping up regularly, more so if temperatures are high; you may want to design in a fail safe so that a low water condition doesn't destroy things or at least "fails gracefully".

What effect will this heat have on your floor? Cracks due to thermal changes or moisture changes? Do you want insulation below the radiant piping to reduce the heat you send to China?

www.heatinghelp.com is a "clubhouse" of professional heating contractors where a lot of this stuff is discussed in more depth than any sane person needs - at least in the context of "standard" construction practice. A year or so ago they were still answering questions from polite and intelligent "home owners".

Like you said, steep/high learning curve. But on the other hand usually radiant fluid temps are low - 80F. to 110F IIRC which makes them relatively benign, at least in the floor piping.

Nice project. Best luck.


Rufus
 
Rob Irish
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Rufus Laggren wrote:Sorry if I missed it but what temperature do you plan on running through your radiant floor piping? What flow do you plan? Unless you wish to constantly monitor and modify your temperature/flow you need to have some idea of what you're shooting for and try to build to get somewhere in that ballpark by default. But regardless, you still need a way to control the heat into the radiant pipe. Otherwise you get either hot or cold feet.

"Open" tanks generally need topping up regularly, more so if temperatures are high; you may want to design in a fail safe so that a low water condition doesn't destroy things or at least "fails gracefully".

What effect will this heat have on your floor? Cracks due to thermal changes or moisture changes? Do you want insulation below the radiant piping to reduce the heat you send to China?

www.heatinghelp.com is a "clubhouse" of professional heating contractors where a lot of this stuff is discussed in more depth than any sane person needs - at least in the context of "standard" construction practice. A year or so ago they were still answering questions from polite and intelligent "home owners".

Like you said, steep/high learning curve. But on the other hand usually radiant fluid temps are low - 80F. to 110F IIRC which makes them relatively benign, at least in the floor piping.

Nice project. Best luck.


Rufus


Thank you for adding that insight and questions Rufus.

I am not wanting to run super hot water through the floor, as it isn't the only source of warmth, and I'd like to avoid any cracking from excess heating and cooling.

We are just wanting to take the chill out so that the floor isn't cold in the winter. It doesn't have to be hot. Warm would be nice.

I'm hoping that if I can run the pipe through the mass section of the RMH, in just the right place where temperatures don't get too hot, so that we can just get a nice warm water running through the pipes this won't cause any major dramas... even then if the water runs out of the tank for whatever reason... it wouldn't be an issue.. I hope.

Having next to no experience with RMH and radiant floor heating, at this stage it is a bit of a guessing game. Trying to soak in as much info as possible.
 
Rufus Laggren
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> warm water...

That's what radiant floor heating uses - at least compared with radiators which will use water anywhere from 140F to 170F when things get going in winter. Just remember that w/out insulation the heat is going to China as well as up into your room; may not matter if you don't mind burning a few extra BTU but the floor will maintain it's temp longer after the burn if you use insulation.

> just the right temp...

Yes that's always the hoped for scenario. It pretty much implies some sort of controls because the chance of you building your heat exchangers just right so it works perfectly right out of the box... If you can figure out how to control your water temps between about 85F and 110F you have solved the main design problem. After that it's just a matter of specific construction details.

FWIW vertical tanks (like a standard water heater) have two temperatures in them - top and bottom. IIRC there can be as much as 25F difference between the two. If you heat the tank by circulating water from and back into the tank near the top somewhat slowly (so as not to create a large mixing action in the tank) you can heat the tank water from the top down and may be able to maintain the thermocline (imaginary boundary in the tank where the water below and the water above differ significantly in temperature) while doing it. The point is that you then have a choice of drawing "cool" (from the bottom) or "hot" (from the top) water from the tank to mix and circulate in your floor. Be warned - I really don't know if this idea has merit; I never have seen it done this way. However heating system regularly utilize the difference between top and bottom temps to provide thermo-syphon flow; the two temperatures in the tank _may_ provide a somewhat passive way to obtain the particular temperature you want to circulate.


Rufus
 
Rob Irish
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Rufus Laggren wrote:> warm water...

That's what radiant floor heating uses - at least compared with radiators which will use water anywhere from 140F to 170F when things get going in winter. Just remember that w/out insulation the heat is going to China as well as up into your room; may not matter if you don't mind burning a few extra BTU but the floor will maintain it's temp longer after the burn if you use insulation.

> just the right temp...

Yes that's always the hoped for scenario. It pretty much implies some sort of controls because the chance of you building your heat exchangers just right so it works perfectly right out of the box... If you can figure out how to control your water temps between about 85F and 110F you have solved the main design problem. After that it's just a matter of specific construction details.

FWIW vertical tanks (like a standard water heater) have two temperatures in them - top and bottom. IIRC there can be as much as 25F difference between the two. If you heat the tank by circulating water from and back into the tank near the top somewhat slowly (so as not to create a large mixing action in the tank) you can heat the tank water from the top down and may be able to maintain the thermocline (imaginary boundary in the tank where the water below and the water above differ significantly in temperature) while doing it. The point is that you then have a choice of drawing "cool" (from the bottom) or "hot" (from the top) water from the tank to mix and circulate in your floor. Be warned - I really don't know if this idea has merit; I never have seen it done this way. However heating system regularly utilize the difference between top and bottom temps to provide thermo-syphon flow; the two temperatures in the tank _may_ provide a somewhat passive way to obtain the particular temperature you want to circulate.


Rufus


I haven't rushed to respond to this because it has taken a while to seep in. And I've needed to wrap my head around what is involved.

Basically, there is a high probability I'm going to completely get the rocket heating combined with radiant floor heating wrong. Probably going to either melt the PEX, or it isn't even going to be hot. It is unlikely, with no previous experience in either RMH's or PEX floor heating that I'm going to get this right off the bat. And no experience with thermo-syphoning.

Which means I think for this project, we're going to need to look at using some more modern tech to do the job. Which I think involves:

1. A standard hot water heating unit.
2. A unit of some kind which measures the temperature of the water in the pipes, and brings in more hot water and cycles the water to maintain a constant temperature.
3. Since we currently have AC, and not DC, (solar coming down the track), a AC pump of some kind which connects to this 2nd unit, i.e. they talk to each other.

Is there a device like this already on the market?

Thanks for your time.
 
Rob Irish
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Rufus Laggren wrote:
What effect will this heat have on your floor? Cracks due to thermal changes or moisture changes? Do you want insulation below the radiant piping to reduce the heat you send to China?


I only thought about this now - we don't want to send heat to China (although I think the other side of the world from where we are right now is Australia, and it is probably hot enough down there).

What is a good insulation for a cob floor?

So currently we have sand, then rocks, then cob. Where would insulation go?

Where we are renovating, we told a neighbour we will have clay floors and he said that will be too cold. I'm guessing this cold can be reduced with insulation?

Any information greatly appreciated.

 
tel jetson
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Rob Irish wrote:Which means I think for this project, we're going to need to look at using some more modern tech to do the job. Which I think involves:

1. A standard hot water heating unit.
2. A unit of some kind which measures the temperature of the water in the pipes, and brings in more hot water and cycles the water to maintain a constant temperature.
3. Since we currently have AC, and not DC, (solar coming down the track), a AC pump of some kind which connects to this 2nd unit, i.e. they talk to each other.


for #1, I suggest considering a heat pump water heater. they're pretty expensive, but there may be subsidies available. ours ended up costing about $300 after all the rebates we got from the manufacturer, the local utility, and a region-wide efficiency organization. one of these would be much more efficient than an electric heater element, particularly if it was placed in a space also heated by you RMH.

for #2, yes, there are heat exchangers that manage all this automatically. the water in the floor is kept separate from the water in the water heater so that you don't end up with old, stale water in your sink or shower. there are two pumps: one for the loop connected to the water heater, and one for the floor loop. those loops intersect at the heat exchanger, but do not mix.

#3: yeah. there are contraptions that handle this for you. they can get expensive.
 
Ardilla Esch
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Rob Irish wrote:
Rufus Laggren wrote:

What is a good insulation for a cob floor?

So currently we have sand, then rocks, then cob. Where would insulation go?

Where we are renovating, we told a neighbour we will have clay floors and he said that will be too cold. I'm guessing this cold can be reduced with insulation?

Any information greatly appreciated.



Here is the profile of my earthen floor with radiant heat:

1/2" troweled earthen floor layer - fine finish, oiled etc.
1/2" troweled earthen floor layer
1/4 to 3/4" troweled earth floor leveling layer - checked with laser while applying
~2" clay-rich crusher fines placed moist and tamped with plate compactor
1/2" PEX tubing 9" on center tied to 6x6 concrete reinforcing mesh with rebar ties
~2" clay-rich crusher fines placed moist and tamped with plate compactor
Landscape fabric (fibrous, breathable stuff)
9" of 1/2"pumice for insulation (14" thick adjacent to foundation for about 24")
Compacted native ground / fill

This floor certainly isn't cold like your neighbor suggests. You could use 1.5" or 2" expanded polystyrene or the like to insulate the floor instead of pumice. We used pumice because it is natural, we needed material/fill to build up the floor/site anyway, there are pumice operations reasonably close. The thermal break the insulation provides is important IMO. Some people advocate no insulation for natural cooling. This really comes down to your local climate. In most temperate climates where you can count on cooler evenings in the summer - a well insulated building (floor included) with decent thermal mass will get you far.

Another note: Don't underestimate how much sand needs to go in your floor. If you use a similar mix of clay to sand as normal cob, adobe, earthen plaster, etc. you will get cracks.

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