I'm at the thinking about heating stage of my barn build...

[Raspy]

Mark,

You made the comment that my amount of rebar was overkill.

Well maybe, but not really. Here's why; I never build to minimum standards. Concrete cracks and mine did too, even with this amount of bar. And the bar defines the tube spacing by offering a perfect place to tie to that also protects the tubing during the pour. PEX is vulnerable during the time a bunch of guys are stomping around in the mix handling pumper hose and shovels. If the tubing is just running randomly around it will get stretched and kinked or dented over and over during the pour. The bar is up on dobies and the tube gets pushed down to the ground under large boots. Scary. Tied securely against rebar is way better. It's not so much about how much bar is commonly done in non radiant slabs, it's about the tubing. Also, radiant slabs are often left as bare concrete or tiled. Controlling the cracks reduces tile cracking and improves the final appearance on bare slabs.

It just makes sense to use a lot of rebar.

 

[mx842]

mx,

Sounds like you are on the right track to me. Floor sensing, in your case, makes perfect sense.

To install the sensor, bury a 3 foot piece of PEX in the slab with one end sticking out where you can always get to it. Tape the buried end closed with electrical tape and position the buried end half way between two of the heating lines in the slab. If you have 1' spacing the closed end of this tube would be 6" from each loop line, somewhere in the slab. Then slide the thermister down into the tube to the end and have the wires sticking out to connect to your controller. This will allow you to always be able to replace it if needed and it will control the slab well. This sensor can tie into a thermostat with remote sensing capability and the thermostat can mount up on the wall and send a signal to a relay to start the pump. Simple and repairable. Easy to adjust and accurate. The thermostat will display the floor temperature and you can even program it if you wish.

You can simply install an 8 loop manifold and keep your loops at no more than 300' each to stay within reasonable restrictions. Or a 10 loop with 240' each would be fine or better.

Since yours will be able to flow all the time and the recovery rate is not really important, you only need 1 GPM max for each loop and 1/2 GPM would work. I simply go by experience and don't calc each system. Assuming you have 1" copper feeding the manifold and a low restriction boiler or heat exchanger system, you could use TACO 008 cast iron circulator as the smallest size. Another slightly more powerful and possibly easier to get unit would be a Grundfos 15-58, 3 speed pump. If your system has a bit more restriction in the heat exchanger go to a Grundfos 26-64.

Since it will always be able to circulate, and recovery can be slow with no negative affect, you won't need water at over 100 degrees. 120 degrees would give aggressive recovery and 90 would be just about the lowest you could get by with in cold weather with constant flow. You'll be looking for an average floor temp of about 75 degrees from what I can make of your intended use.

The next thing might be plumbing strategies, corrosion resistance or something along those lines.

Boy! I'm sure getting my moneys worth out of this one. thanks!

I had just about settled on the pump you mentioned, the Taco 008 that is. Although I didn't know why other than just combing over the countless post and web sites I have looked at mentioned this pump many times. I'm sort of like you with respect to the over building thing but sometimes a little more actually hurts you rather than making things better.

I have a lot of the things already for my stove I want to build but a lot of the more technical stuff I haven't gotten around to and I have purposely left some of that stuff out of the picture until I get ready to actually put it together. I plan on placing it half way between the house and the barn, about 125' both ways and as I said I plan on doing a little floor work in the house also but that will be a ways away.

I haven't gotten to the corrosion aspect of the project just yet but while you are primed up you may as well give me a crash course in this important part of the project. I plan on using 1" pex from the boiler to the manifold at both the house and the barn with a copper and brass manifold. And oh yes I will take your suggestion and use those 3/4" electrical conduit 90* bends as protectors as the tube leaves the slab. I was wondering about that anyway but I am glad you mentioned that because now I'm sure to do it.

 

[Raspy]

mx,

Just a brief response about corrosion and a couple of things.

Be sure to make your system a closed loop.

If there is any chance of freezing the piping or the manifold, as in the system being off during a power failure for a couple of days or while you are gone, then you must use some propylene glycol in the system. If freezing is not a problem, another non-toxic corrosion inhibitor would be a nice addition. Not too important, but is does help the pumps a bit and reduces long term contaminants. I have a single-dose-per-life, non toxic inhibitor that I've used for 25 years or so and had excellent results with. This is based on the idea that you'll be using oxygen barrier PEX tubing to begin with. Any non barrier, non metallic tubing will have severe corrosion problems if not addressed properly.

Once you decide on closed loop, you get some nice benefits. The pumps and any other metal in contact with the radiant water can simply be iron. So the pumps are cheaper and you can use a cast iron boiler or steel heat exchanger. Plus you never get any mineral build-up, no doses of chlorine to the PEX, and you can address the possible freeze problem with additives. It goes on and on, so build use a closed loop system.

Since you will be adding another thermostat the the house area, you'll need a couple of 24 volt zone valves and a controller that can manage them and two thermostats. Start out with that equipment now and you can easily add the other zone later. The house zone might just be a wall thermostat, but it will function the same as the floor sensing stat.

Here's the logic: The stat call for heat and closes a circuit to the controller t-stat terminals. The controller sends 24 volts to the zone valve. The valve moves to the open position and signals the controller it's ready. This is called the end switch function. Then the controller signals the boiler to start or the pump relay to start, depending on your system. Minimum wiring is 2 conductors between the stat and controller, 4 conductors between the controller and the zone valve and two conductors between the controller and the pump relay or boiler. You will also have two conductors between the floor sensor and the thermostat. I like to use #18 bell wire for these and include extras in case of damage. Get a spool of 18-5 or other and run the leads.

When you lay the tubing think about where you will actually be walking or standing, add an extra and closer spaced run at high loss points like in front of doors. In the house you will also need more in the bathrooms for maximum comfort. Also remember, in the house, you'll be interested in programming and recovery rates as opposed to a constant setting in the shop. Don't fall for the old myth that you'll set the temp and just let it always run. You won't. Timing is very important in the house.

Prepare to smile every time you go out to the shop on a cold morning.

 

[Ranger Rick]

mx,

Also remember, in the house, you'll be interested in programming and recovery rates as opposed to a constant setting in the shop. Don't fall for the old myth that you'll set the temp and just let it always run. You won't. Timing is very important in the house.

Have you ever used geothermal instead of a boiler as a heat source? We are planning on renovating an old barn into a recreation building and living space and would like to use radiant heat with possibly geothermal. Would recovery be too slow so you would want to leave the temperature at one setting or would you be able to set it back. Any thoughts. I have found all of the discussion very interesting. I am one of those reader that some of this might be useful for.
Thanks for the insight.
Rick

 

[SPIKER]

Mark,

You made the comment that my amount of rebar was overkill.

Well maybe, but not really. Here's why; I never build to minimum standards. Concrete cracks and mine did too, even with this amount of bar. And the bar defines the tube spacing by offering a perfect place to tie to that also protects the tubing during the pour. PEX is vulnerable during the time a bunch of guys are stomping around in the mix handling pumper hose and shovels. If the tubing is just running randomly around it will get stretched and kinked or dented over and over during the pour. The bar is up on dobies and the tube gets pushed down to the ground under large boots. Scary. Tied securely against rebar is way better. It's not so much about how much bar is commonly done in non radiant slabs, it's about the tubing. Also, radiant slabs are often left as bare concrete or tiled. Controlling the cracks reduces tile cracking and improves the final appearance on bare slabs.

It just makes sense to use a lot of rebar.

John: a couple issues with your idea that the rebar will protect the tubing. assuming that concrete is going to crack the rebar is there to hold it together. now you tie semi soft PEX to the rebar in fact right on top of it. now the rebar is not going to move but the dead space and soft PEX is now forming a "crush zone" right where your rebar is laid out. Any movement or cracking of the concrete will put a lot of pressure right onto the PEX at that point where the crack PEX and Rebar meet. It will render the Rebar almost non-existent inside the slab to the point that the PEX is crushed.

The PEX-AL-PEX is rather hard much harder than standard PEX and is the O2 Barrier for closed systems.

You have underestimated the fluid dynamics of the bends in the tubing. Each bend in a tube, hose or PEX adds resistance to flow. There are standard calculations that shows this and is well known that the more bends there are the greater the resistance to flow of water. Tighter the bend the worse it is, sweeping bends and or curves are not as bad.

BTW my background is Automotive body/engine repair then to Military Aircraft Hydraulics Systems on to Industrial Equipment Design/manufacturing (Heating systems/Powder coating Ovens/washers & ect.) Went back to school for Electronic Engineering degree. Currently working on Design & Engineering for heavy off road equipment as an electrical engineer. All of which just makes it much more fun to get out from behind the computers and into the barn to tear apart SOMETHING lol... on a bad note the engine I have on my stand I broke the dipstick tube off today! argh this engine has been a PITA

Mark

 

[Raspy]

Mark,

I don't want to go on endlessly about rebar. First I have too much, then it will cause tube damage and that's a problem. Well, no it won't. I use, and many of us use, the tube spacing to set the rebar spacing. There ends up more rebar than normally needed, but it's not a bad thing. We need the rebar to protect the PEX during the pour. PEX can take concrete cracks big enough to get a pencil into, for many years without damage. Partly because it doesn't adhere to concrete and partly because it is so elastic.

Crushed PEX because of too much bar that becomes non existent? What?

Argue the details all you want, but these methods have been well proven for many years and always work well. PEX is guaranteed in radiant heating applications for twenty-five years by the manufacturers, wheras metal piping is not guaranteed at all. There is a reason. Armchair theories are nice, but hard won proven methods should not be discounted. You, of course, are free to install your system with all the design characteristics you want and teach us all how to do it the right way. I guarantee my work for many years in the real world and have previously fought many of the battles you identify. Sometimes it is good to research proven methods and identify the reasoning before discounting them.

I have steered away from aluminum PEX for a couple of reasons. You should try it and report back.

As far as restriction in bends is concerned I'm left almost speechless. The industry standard of 300 linear feet for 1/2" ID tubing per loop, takes all that into account and it doesn't matter. It's not an issue. But you can run all your tubes straight if you want and teach us how to do it right. I'd like to see it and learn from you. No bends. OK. While you are at it, study turbulent flow vs. laminar flow in pipe and discover which is the most efficient at heat transfer. Then study tube-in-shell heat exchanger design and why they design in turbulence as an important factor.

I'm glad you have such a long list of personal accomplishments and so much hydraulic theory, and I'm sure you can see that hydraulic systems designed to transfer force are different than ones designed to deliver energy through a tube wall. It might be bit more useful, when you see something you don't understand, to study it instead of criticizing it. Personally, I don't care how you design your system. I only care about how I design my systems and I have always been glad to encourage others that are curious. My intention here is not to argue arcane theories, but to help a few interested and sincere folks who want a comfortable, simple system and are trying to cut through the static and hype. In other words, I'm a designer and an advocate as well as an installer.

Is there some way this conversation can continue without having repeated declarations of problems with my theories and methods? No offense intended, but I'd rather just call it as I see it and you take it for what it's worth to you.

I think I'm losing interest in this thread.

 

[Raspy]

Rick,

Yes, I have used geothermal on a house that is about 3,500 square feet. It sits at 5,000' elevation in Nevada and geo is the only heat source. I called out some specs to meet with the heat pump, but the equipment was not sized as I wanted. Much smaller in output. But it turned out OK, heats the house well.

I don't think they time the system with the thermostats, but more or less just leave them set. That method is less efficient and less comfortable in most cases, but is still nice. Their house is all electric except for the cook stove, and the last time I checked they were paying about $350./month in the winter for electric including hot water. The heat pump has a desuperheater function too.

Can't expand on it much more than that. I was mainly involved in the radiant delivery system, storage tanks and control logic.

We do have hot springs near here and some people have hot wells, but this system seems to not have those benefits. It is a large array of tubing buried about ten feet deep or so. I think it was 3,200 linear feet of 1" poly pipe. I measured the temperature at 185' down to be 61 degrees F.

Sorry I can't be more help with real numbers.

 

[mx842]

mx,

Just a brief response about corrosion and a couple of things.

Be sure to make your system a closed loop.

If there is any chance of freezing the piping or the manifold, as in the system being off during a power failure for a couple of days or while you are gone, then you must use some propylene glycol in the system. If freezing is not a problem, another non-toxic corrosion inhibitor would be a nice addition. Not too important, but is does help the pumps a bit and reduces long term contaminants. I have a single-dose-per-life, non toxic inhibitor that I've used for 25 years or so and had excellent results with. This is based on the idea that you'll be using oxygen barrier PEX tubing to begin with. Any non barrier, non metallic tubing will have severe corrosion problems if not addressed properly.

Once you decide on closed loop, you get some nice benefits. The pumps and any other metal in contact with the radiant water can simply be iron. So the pumps are cheaper and you can use a cast iron boiler or steel heat exchanger. Plus you never get any mineral build-up, no doses of chlorine to the PEX, and you can address the possible freeze problem with additives. It goes on and on, so build use a closed loop system.

Since you will be adding another thermostat the the house area, you'll need a couple of 24 volt zone valves and a controller that can manage them and two thermostats. Start out with that equipment now and you can easily add the other zone later. The house zone might just be a wall thermostat, but it will function the same as the floor sensing stat.

Here's the logic: The stat call for heat and closes a circuit to the controller t-stat terminals. The controller sends 24 volts to the zone valve. The valve moves to the open position and signals the controller it's ready. This is called the end switch function. Then the controller signals the boiler to start or the pump relay to start, depending on your system. Minimum wiring is 2 conductors between the stat and controller, 4 conductors between the controller and the zone valve and two conductors between the controller and the pump relay or boiler. You will also have two conductors between the floor sensor and the thermostat. I like to use #18 bell wire for these and include extras in case of damage. Get a spool of 18-5 or other and run the leads.

When you lay the tubing think about where you will actually be walking or standing, add an extra and closer spaced run at high loss points like in front of doors. In the house you will also need more in the bathrooms for maximum comfort. Also remember, in the house, you'll be interested in programming and recovery rates as opposed to a constant setting in the shop. Don't fall for the old myth that you'll set the temp and just let it always run. You won't. Timing is very important in the house.

Prepare to smile every time you go out to the shop on a cold morning.

Heck! I'm already smiling just thinking about it.:laughing:

I'm sorry for the delay in getting back to you its just that here lately I don't have much time for the computer. I wish I could say it's because I'm out making money, fishing or something else fun. Right now I am in the process of grading out the floor area in the 10x40 space I added for the small office and machine shop area. When I first graded that area I had a skid steer loader that a friend was kind enough to let me use while he wasn't using it too much and I had it graded real close.

The problem now is, that was before I decided to put this last addition on and that means I have a lot of dirt to move. I thought about just making it a raised area and putting a step up to enter the area but decided against that because a lot of this material is not that good, (topsoil/roots) and needs to be removed anyway so I'm just taking it all out. It's just a pain because it's all hand work and some of this dirt has packed like rock. I'm trying to get as much of this done now so when my ship comes in or I win the lotto I can get my floor in without delay.

As I mentioned in a post earlier I may have to run this system off of a hot water heater the first year, that is until I get my boiler stove built and hooked up to the system. It will be summer time now if I am lucky and don't have any big delays before I get into this building and won't need any heat for awhile. Once I do get in it will still be awhile before I finish everything and can get to work. I have a lot of equipment to put in and a lot of that has to be finished or built all together. It just doesn't seem possible to get all this done and then come up with a boiler stove by the time winter comes rolling around next year.

My thinking is that I want to have hot water out there anyway so the heater won't be a waste but do you see any negatives with this plan other than the extra cost on the electric bill?

Hopefully I can up date my photo gallery pics soon as I haven't done so in awhile but for now I guess I will just wait until I get my piping done.

 

[mx842]

Mark,

I don't want to go on endlessly about rebar. First I have too much, then it will cause tube damage and that's a problem. Well, no it won't. I use, and many of us use, the tube spacing to set the rebar spacing. There ends up more rebar than normally needed, but it's not a bad thing. We need the rebar to protect the PEX during the pour. PEX can take concrete cracks big enough to get a pencil into, for many years without damage. Partly because it doesn't adhere to concrete and partly because it is so elastic.

Crushed PEX because of too much bar that becomes non existent? What?

Argue the details all you want, but these methods have been well proven for many years and always work well. PEX is guaranteed in radiant heating applications for twenty-five years by the manufacturers, wheras metal piping is not guaranteed at all. There is a reason. Armchair theories are nice, but hard won proven methods should not be discounted. You, of course, are free to install your system with all the design characteristics you want and teach us all how to do it the right way. I guarantee my work for many years in the real world and have previously fought many of the battles you identify. Sometimes it is good to research proven methods and identify the reasoning before discounting them.

I have steered away from aluminum PEX for a couple of reasons. You should try it and report back.

As far as restriction in bends is concerned I'm left almost speechless. The industry standard of 300 linear feet for 1/2" ID tubing per loop, takes all that into account and it doesn't matter. It's not an issue. But you can run all your tubes straight if you want and teach us how to do it right. I'd like to see it and learn from you. No bends. OK. While you are at it, study turbulent flow vs. laminar flow in pipe and discover which is the most efficient at heat transfer. Then study tube-in-shell heat exchanger design and why they design in turbulence as an important factor.

I'm glad you have such a long list of personal accomplishments and so much hydraulic theory, and I'm sure you can see that hydraulic systems designed to transfer force are different than ones designed to deliver energy through a tube wall. It might be bit more useful, when you see something you don't understand, to study it instead of criticizing it. Personally, I don't care how you design your system. I only care about how I design my systems and I have always been glad to encourage others that are curious. My intention here is not to argue arcane theories, but to help a few interested and sincere folks who want a comfortable, simple system and are trying to cut through the static and hype. In other words, I'm a designer and an advocate as well as an installer.

Is there some way this conversation can continue without having repeated declarations of problems with my theories and methods? No offense intended, but I'd rather just call it as I see it and you take it for what it's worth to you.

I think I'm losing interest in this thread.

Oh no you don't.....you ain't getting off that easy.:laughing: I don't think mark meant any harm in his comments, he seemed to just be making observations and commented on what he saw and threw out his thoughts. It's really hard to get a point across in a setting like this without sometimes it coming out the wrong way or it reading like it maybe intended as combative. I truly don't believe he meant any harm and I'm sure you guys have a lot in common and would get along really well together in real life. There is too much good information being passed around here to have it squashed so can we all just get along. I've never been afraid of a good debate and often times learn a little in the process and I could be the poster child for hardheaded anonymous.

I know you have put a lot of time into this thread and I do appreciate it as well as others that may be reading this thread as it progresses. Concrete slabs are something that has always peaked my interest and then add heating tubing into them and I want to know more. I have poured a few floors in my life and one thing I know is that you never know where it is going to crack you just know it will at some time in the future. I have seen floors poured on solid rock crack and then there was this floor we did that was poured over really crappy dirt of which was almost wet that didn't show a crack for almost two years and then it was small one that ran from one corner to the other. That slab was supposed to be just temporary but it held up so well it was never replaced. The small crack just showed up one day and in places you could hardly feel it with your fingernail but it ran from one corner to the other and it never changed after that.

I have concrete all the way across the back of my house and I graded and formed it with all sorts of angles to break up the lines to keep it from cracking. I had someone else pour and finish it and they probably should have been in another line of work. It was a hot day and he only had two women helpers and the stuff got away from him and I ended up with some of it too high and some spots were too low. I never got any cracks in it but now there are blocks that have sunken down and are a inch and a half lower than it was. I have been putting off fixing this for a couple years now but I know one day I need to address this.

 

[mx842]

Have you ever used geothermal instead of a boiler as a heat source? We are planning on renovating an old barn into a recreation building and living space and would like to use radiant heat with possibly geothermal. Would recovery be too slow so you would want to leave the temperature at one setting or would you be able to set it back. Any thoughts. I have found all of the discussion very interesting. I am one of those reader that some of this might be useful for.
Thanks for the insight.
Rick

Hey neighbor!

I guess you could call us neighbors, I live in Varina a little east of Richmond. I pass through Lousia every other week when I go to Culpeper to visit a friend. I heard you guys had another 3.5 shaking the other day. I don't know what it felt like there when the big one hit but here, I thought at first a helicopter was landing on my roof full of ATF agents coming to take my guns but then the shaking got so bad that I knew a train had jumped the track and was crashing through the house then as I looked out I saw the trees moving back and forth and the wavy lines and knew we were having an earthquake. I have felt a few before in other parts of the country but never seen one that lasted so long and made such a noise.

That old brick house in Cuckoo sure took a beating. That was such a beautiful place and hopefully they can put it back together. I see they are finally starting to work on it and now it looks like there is a major operation going on there. Anyway i just wanted to say hi and I hope your project goes well.