Heated Driveway

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  #1  
Old 10-12-09, 08:49 AM
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Heated Driveway

Am installing a heated driveway in the cold Northeast and seem to be going into somewhat unchartered waters. I placed 2000 feet of half inch pex and blacktopped over it. I purchased a LP tankless hot water outside heater. This is a closed system which will be filled with anti freeze and connected to the manifold. I could use some advice from the experts (I basically know where to go next but could use some suggestions). What is the best way to go before proceeding? I know I need a circulating pump as well as an expansion tank. Is there anything else or is there any thing I missed? Remember, this is a closed system and the only source of liquid is what I put in.
 
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Old 10-12-09, 04:39 PM
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Assuming that your heat source is rated for the service that you are pressing it into... is it?

Are you concerned about the heater condensing the flue gases during operation?

You also need a way to pressurize the system. You probably want to treat this as you would any other heating system, where the minimum pressure when cold would be around 12 PSI or so.

I think you will need an air scoop and automatic air vent to get the air out of the system.
 
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Old 10-12-09, 05:19 PM
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Heated Driveway

Heater is outside model. Gas and venting is not problem unless I am missing something. Wouldn't the pump from the heater purge the system and into a holding tank? The fluid goes through a loop, with two manifolds. There are 6 different separate runs through the driveway. I can isolate any of the lines. First maniflod delivers, second recovers sends it back through the heater and back out the system. The temperature will run about 50 or so degrees, just enough to warm the blacktop until the storm is over. What kind of tank would I need to hold anti freeze?
 
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Old 10-12-09, 06:51 PM
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Question

If you have a tankless heater why would you want a tank ?
 
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Old 10-12-09, 07:09 PM
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On what basis did you design this system? Such as (in no particular order):

temperature required (50F? Guess again. At least double, up to triple that.)

flow rate and designed temperature drop through loops

BTU/ft^2 required

BTU/hr supplied by heat source

thickness of asphalt over tubing

amount of insulation beneath the tubing (if none, you are in for some bad news...)

amount of insulation along the edge of the driveway (if none, you are in for some more bad news...)

Control system and sensors used

did you really pour hot asphalt on 1/2" pex?

what kind of pex? oxygen barrier or non-barrier?

is there a secondary heat exchanger (if non-barrier pex, you'll need one)

Need more details.
 

Last edited by xiphias; 10-12-09 at 07:34 PM.
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Old 10-15-09, 01:32 PM
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Talking

Xiphias, I think you scared this guy away with your questions. I was hoping to learn from this thread. Guess not. Keep up the good help guys, love to read and learn about my and all boilers.

Buzz
 
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Old 10-15-09, 02:30 PM
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Yeah, Xiphia is pretty scary! j/k...

Happens a lot actually, sometimes it's just one post and they're gone. I think they expect instant gratification and when they don't get the answers they want right away, they move on.

It would make for interesting reading though!
 
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Old 10-15-09, 06:26 PM
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Sorry dudes.

Snow melt, like radiant flooring, isn't hard to get right, but very easy to get wrong. Even easier to get wrong than radiant flooring.

The RPA (Radiant Panel Assoc) puts out several things that are relevant to snow melt design. And of course Siggy's book is a trove of info.
 
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Old 10-15-09, 07:03 PM
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Naahhhh, nuttin to be sorry about!

There's some info on snowmelt over at tekmarcontrols.com also.

Look on the literature page.
 
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Old 10-16-09, 03:40 PM
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Heated Driveway

Thanks for all the suggestions. Maybe I was misunderstood on some things I wrote. The tank is to store the antifreeze. This is a closed system and a tankless heater has no place for excess or shortage. As far as the heater, this is an outside water heater, venting to an outside source is not necessary. When I said I need 50 degrees, this is what I need to melt whatever comes down in the form of solid stuff. As far as insulation, pex under blacktop, etc., I said that this is unchartered waters. I researched this for many months and the only thing I found was laying an electric blanket down in concrete and connecting it to heat sidewalks, or doing pex in the floors in my house. I could not find one word about doing this under blacktop. I must have asked a hundred people, including my boiler man, the local plumbing suppliers and anyone remotely connected to this subject. I even spoke to the people who make Pex, and not one had an answer relating to this method. Will it work ? I really don't know until I am finished. All I am trying to do is add warm liquid under my driveway so that I can throw my snowblower away. Like raising children, there is no manual out there, this is why I am asking this community for there input. Thanks
 
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Old 10-16-09, 04:38 PM
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As for a source of information, did you try typing "RADIANT SNOW MELT" into Google? I just did, and came up with 34,000 'hits'.

This one offers some info... among the other 33,999:

Heated Driveways and Radiant Snow Melting Systems

INSULATION under the pex... rigid foam boards... is used to prevent heating the ground underneath... you want the heat to go UP, not down!

I could not find one word about doing this under blacktop.
Perhaps because it's never done? Perhaps because the hot blacktop is hot enough to melt and deform the PEX? (I don't know this to be true, but it sounds plausible) Perhaps because the blacktop is not rigid and will move over time and stress the pex to the point that leaks develop? (again, don't know, but plausible).

You really think that 50 liquid is all you will need? Or, do you mean you want the water to be hot enough to bring the surface of the blacktop to 50? Any idea how hot the water needs to be to achieve that? I don't...sorry, just asking.

there is no manual out there
I'm sure there is, you just weren't looking in the right places!

Off topic... does Troop 32 mean anything to you?
 
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Old 10-16-09, 04:45 PM
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Please let us know how it comes out.

I have an off topic but related question when you get it up and running. On very cold mornings will you see a bunch of critters from opossums to cats to squirrels curled up asleep on your nice warm driveway.?

I would suggest an old fashioned well pressure tank with out the bladder. The no-bladder type because you can't be sure how the heat or antifreeze would affect the bladder.
 
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Old 10-16-09, 04:54 PM
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That's funny Ray! I can picture it now! Heck, he might even find ME out there, living in a cardboard mansion.

One thing I wanted to mention... commercial snow melt controllers have what is called 'cold weather shutdown' that is set up to turn OFF the snow melt when the weather gets so cold that it can't keep up. You don't want to create a hazardous condition of forming 'black ice' on your driveway... LAWSUIT TIME!
 
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Old 10-16-09, 05:12 PM
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Ray's quip reminded me of a place I used to work. (The facility is long gone now.) We had a "high temperature" hot water system servicing several buildings. The water temperature in the winter was about 300 degrees and two of the buildings were served by direct burial piping. On the rare occasions it snowed you could tell exactly how the piping ran underground. Parking spots over that piping were fought over.
 
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Old 10-16-09, 06:29 PM
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As Trooper said, there is a wealth of information out there for snowmelt applications. The list of questions posed above is drawn from that, in part.

Some things to understand about snowmelt:

1) it ain't cheap to run.
2) it ain't hard to design, but there's a fair bit of homework involved.

The first thing I would do is see if your tubing is even functional. Fill it up, make sure water that goes in one end comes out the other, and do a pressure test.

Hot asphalt will soften or melt pex. The typical installation procedure is to run cold water through the pex during paving and maintain a pressure of at least 40-60 psi. (i.e., city pressure). Did you do that?

The binder layer is often hand-applied around/over the tubing
until there's sufficient coverage to allow a paver and a roller to cover with the finish surface. If you've already softened or melted your pex, and not run cold water through it, the paver and roller will probably have crushed it.

So if your tubing's not functional, game over.

But if it is, figure out what kind of BTU output you need per square foot. 100-150 BTU/sf is common. You can get that output with high water temperature, and/or close spacing of the tubing. There are tables out there somewhere that give the conductivity of asphalt. All I can remember is that it's a lot worse than concrete. Concrete is much preferred over asphalt for snowmelt for this reason (and others).

When you figure out how many BTU/sf you need, then you need to figure out what kind of flow rate, water temperature, and heat source you need to get there. Since you already ran your loops, there's no adjusting that....

I'm willing to be that a tankless heater ain't gonna do it. Not even close. Say your driveway is 2000 square feet, and you need 125 BTU/sf. That's 250,000 BTU....

Also likely that your 330+ foot loops will have an unacceptably high temperature drop, but you won't be able to pump water fast enough to counteract the temperature drop, because the head (resistance) at higher flow velocities is really, really high and you'll have velocity issues and/or require a truly monstrous circulator.

If you have non-barrier pex, you will need a secondary heat exchanger, or the system requires zero ferrous components or it's toast in short order. That will add a bunch more parts.

So let's hear some more details about how the pex was installed, and firstly if it's even functional.
 
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Old 10-19-09, 07:44 AM
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Heated Driveway

Listening to all the gloom and doomers out in never land, is something I have encountered since I started this project. The web site Heated Driveways was visited by me many times, but says nothing about blacktop. Again, there is nothing out there that addresses this specific project. I appreciate Trooper and all those experts who know the business, but, like most people whom I turned to for advice, the attitude is "you can't build it and if you do, it won't run". Yes, the pex is oxyen barrier, no the runs are not 300 or so feet. I kept them short, all under 200 feet. Yes, the pex did move and distort in some places, but it all went down under the asphalt and all the lines are intact. The pex was grooved into the item #4, just below the surface, and after trial and error, I found out that screwing into the item 4 worked like screwing into wood. I used 5 inch deck screws and clamps to keep the pex place. This worked out perfectly. To all those who told me I need insulation , etc., Blacktop is a different than cement. It needs a firm, basically smooth footing, with no bumps or valleys or the asphalt will eventually or immediately either buckle or sink in those places over time. I also took into account the steam roller that is used to pack this down. I also found out that rocks and pex do not like each other, so I had to make sure that no rocks were in the grooves, as pressure over one of the would cut the pex. Also, I had to keep the pex out of sunlight, as exposure breaks down the pex after 7 days, so I had to keep covering it with dirt until I finished. Taking this all into account, what else can the experts tell me about what I did wrong? The anti freeze to be used is propylene glycol, which is not harmful to the pex. I am currently puting the heating system together, with the Taco Pump and the Rheem. Again, all I am trying to do is send some warm water under my driveway.
 
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Old 10-19-09, 10:12 AM
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You have now provided some information that suggests this is not necessarily a fool's errand. Thanks for that. See, here on the other side of the internet it's hard to see that kind of information. We only know what you tell us. "2000 feet of pex in asphalt" as in the first post doesn't give us much to go on.

Now you need to do the flow rate, temperature drop and output calculations. That will require an understanding of the output capabilities of your medium.

Don't think asphalt snowmelt with pex hasn't been done. There's thousands of them out there. A quick example is the Uponor install guide at

http://www.uponor-usa.com/~/media/Fi...spx?sc_lang=en

See the asphalt example? As you describe it, you're not too far off that, except for the insulation.

What is the model of the Rheem?

What kind of manifold? What Taco circ?

Happy to help here, but you need to feed the internet void more info.
 
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Old 10-19-09, 05:26 PM
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Exactly what Xiphias said... and I don't think you've really gotten 'gloom and doom' here at all... SKEPTICAL perhaps, gloom and doom, no... and, you've gotten a lot of GOOD, PRACTICAL advice, haven't you?

And, backing up to my first post in this thread, I asked a few questions that seemed to go right on by...

Is the heater you plan to use rated for this service?

How do you intend to mitigate any problems that may occur with flue gas condensation by returning too cool water back to the unit?

How do you plan to pressurize the system?

These questions were more 'food for thought' than anything else.

So, understand where we are coming from, and don't take it personal. Whether you think so or not, we have been trying to help.
 
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Old 10-19-09, 07:10 PM
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Heated Driveway

Thanks for the info on the web site, thats the first time I saw anything about this subjet. The heater I purchased is a Rheem 141,000 BTU with a 5.3 GPM flow rate. The Taco pump is a standard one purchased at Home Depot. I do not understand what you mean by having a problem with the outside heater. The instructions given, basically say it was designed to be outdoors. It has three outlets, one for in, one for out and one for the gas. Is there something I am missing about putting it out there? There is no flue pipes or other exhaust vents other than what comes with the self contained unit. Please explain what problems I can get with this. Also, filling it up with anti freeze. I spoke to my local plumbing supply house and the man there told me to make a 1" flue sweat, about 5 inches tall with a bleeder. He said this would take the expansion. He also suggested a new type bleeder valve that goes on the outflow, where I can add fluid. I did not add insulation because of the logistics of the installation. My blacktop man said that anything soft under the driveway will eventually shift or collapse or cause creases. The insulation to be used is of a foam board nature and I did not want to ruin the job. The pex can always be cut off and left dead, but the insulation can cause me to dig a new driveway if it shifts. Thanks for all the help.
 
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Old 10-19-09, 08:28 PM
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The unit you are installing... it's a DOMESTIC WATER HEATER, right? and it's spec'd, rated, and approved for that service by all the appropriate agencies. If it's NOT specified, approved, and rated for snow melt applications, well... you could have problems later on... just saying, cuz it seems to me that you would like to do this right, right?

FLUE GAS CONDENSATION: perhaps the best way to explain this is by asking you to google the term. I don't have the energy right now to explain it again... but think DEW POINT. When the HOT FLUE GASES contact a surface that is below their dew point (which for gas fired appliances is around 135) the water vapor that is in those gases will condense on that surface. The condensate is ACIDIC due to the nature of combustion... carbonic acid, nitric acid, etc... allowing this to occur will pretty quickly destroy the appliance. Bringing all that cool water back from the driveway, it will DEFINITELY be below 135, and the flue gases WILL condense. Google for more information.

I spoke to my local plumbing supply house and the man there told me to make a 1" flue sweat, about 5 inches tall with a bleeder. He said this would take the expansion.
Has he done this before? Does he know what you intend to do? If you set it up that way, you darn sure better put a pressure gauge on it, and be there when you fire it up, and be ready to pull the plug when the pressure spikes up... a CLOSED heating system is a world apart from an OPEN domestic water system.
 
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Old 10-19-09, 11:11 PM
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I'm less concerned about condensation than I am about some other stuff, like:

is this unit rated/approved for propylene glycol, or do you need a secondary heat exchanger?

what kind of output do you need?

what will be the temperature drop through the loops?

what kind of output will you get with glycol or a glycol mix (it has ~15% less heat capacity than water)?

how many square feet is the driveway?

how will you control the system? i.e., what tells it to turn on, off, idle, provide hotter water when it's colder, etc.?

where will the pump, controls, expansion tank, etc. be located?

how many gallons of fluid in the system? (That determines the size of expansion tank needed.)
 
  #22  
Old 10-21-09, 07:53 AM
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Heated Driveway

Thanks again for the info, the tank came from Pex Supply. They are the ones who sell all of this stuff. The anti freeze info is from their bible. The system will only be used for inclement weather, as needed or when the sun does its magic, no more no less. The temp is controlled by the thermostat that comes with the heater. The heater is recommended for the anti freeze (its in their instructions). The expansion is something I am still working on. As I said, this is new ground and there are 10 different opinions as to how to go about this. If there was a place I could turn for a definitive answer, there is not. Thats why come here and to other places to get to the experts. Believe me there are many different suggestions on how to attack this thing.
But each and everyone has a different opinion or suggestion. Stay tuned.
 
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Old 10-21-09, 06:56 PM
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Expansion tank sizing is not new ground. It's ancient. Expansion tank size is based on the volume of fluid in the system.

Go to the Amtrol site and use their sizing guide.
 
  #24  
Old 10-21-09, 09:11 PM
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Wow what a thread.

I have done too many snow melt systems to not chime in.
We do snowmelts under asphalt all the time. We have even done one or two commuter train platforms.

1/2" tubing is a problem as it causing high pumping restrictions the colder it gets. Normally we use 5/8" or 3/4" tubing.
Typically 1/2" tubing would need around 8" spacing due to the lower btu capacity of it. 3/4" can be easily used at 12" centers.

Making some assumptions,
2000 feet of tubing = 2000 Sqft ?
2000 SqFt*150 btu/sqft = 300,000 btu.
300,000 at 30 degrees delta T yields a flow rate of 20.6 GPM (based on glycol).
I can tell you that you will NEVER get 20 GPM thru a resi. instantaneous hot water maker.
But, your in luck, as you can utilize a high delta t method of injecting 180 degree water into the secondary loop.
Let's just hope that you don't need 180 degree F to melt the driveway snow.
You do not need any kind of storage tank, thought you may want an axiom glycol feeder to top up pressures should they fall, or there is slight leaks. A simple ET60 or ET90 should do.

My real worry are that many of these products are not rated for exposure to the outdoor elements nor the temperature range they will be subject to.

I have to tell you, I doubt you will make this work right. Sounds like you may have had a bad start. Somehow I think you probably will not care and forge ahead. I say good luck and if I can help I will be glad to.
 
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Old 10-21-09, 10:22 PM
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very interesting read but honestly, if you can make this work, all I am seeing is dollar signs running out the vent of the heater.


The heater is going to have a very difficult time keeping this whole thing up to temp (it will simply run continuously).

have you figured out how much money it will cost to run this thing for 24, 48, 96 hours continuously?

Is the unit rated to run continuously that long?
 
  #26  
Old 10-23-09, 09:30 AM
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Heated Driveway

Once again, thanks again for the help. Everyone seems to have a somewhat different opinion on or if this thing is going to work. The heater will only be on just enough for the stuff to melt. Hopefully with the help of the sun, which I get all day. The half inch was from the pex people recommendation. Remember, I only want it to weather the storm (no pun intended). Why would I run it for 36 consecutive hours? The expansion tank $40 bucks, can't hurt and it will take any fluid that is in excess. I also installed a pressure valve and two 3/4 inch circuator valves for feeding and purging. Again will it work? Remember it is the regrets of things you didn't do. Investment is around $1500. I received estimates of over $15,000 from the professionals to do it. If it fails, I still have a tankless heater to keep and a bunch of dead pex buried under my driveway. And out comes the snowblower and salt. Stay tuned.
 
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Old 10-23-09, 03:54 PM
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There is a reason why you where getting quotes of 15,000.00 bucks.
We ( heating contracts are not crocks, not all of us anyways :-)...), if you have 4 inches of snow on the driveway, and its 20 degrees out there it will take hours for it to melt.
First you have to raise the slab temperature from 20 degrees to about 34 degrees in order to melt. The you have to overcome the heatloss of the driveway at 20 degrees F. If you think that is not going to take some horsepower, flow and time, you are going to be putting gas in the snow blower.
 

Last edited by NJT; 10-23-09 at 04:29 PM. Reason: I think TO meant 'not CROOKS' instead of 'CROCKS'?
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Old 10-23-09, 04:36 PM
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OPINIONS versus REALITY and FACT

One last point I would like to make...

You keep saying that you are getting OPINIONS, and of course you know what they say about those...

Yes, you have gotten some opinions... and these are based on real world experience. You have also gotten some hard, cold, advice, again from real world experience.

I sense (as TO also does) that you will do what you will do, rather than take a step back and re-evaluate what you are planning to do, in spite of the opinions and advice that you've asked for and received... so be it I guess!

Happy Winter!
 
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Old 10-23-09, 05:11 PM
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This is so far out of my realm of experience I am not going to give any advice of my own. I will however suggest you read what TOHeating had to say as it sounded as if he knew what he was talking about. His basic math (with very few details from you) suggested you need 300,000 BTU and you said your unit is rated at 141,000 BTU. Doesn't that concern you at all?

As for an expansion tank, I would guess a tank rated for boiler systems would work fine but as I said, I have never seen one used outside so don't know how it would stand up to the elements. If nothing else just make an expansion tank and add air pressure as needed?

Lastly you said the heating unit was rated at 5.3 GPM but what temperature rise is that calculated at? I know my tankless unit is rated based upon temperature rise required. Basically the lower the temp of the incoming water the less it will heat at any given flow rate. In your case however I am guessing you COULD maybe move more water than that but it will all depend on the temp differential of the input and output designs.

I can help you with friction loss though if you need it. Did you "sweep" all the PeX tubing? Any 90 deg elbows are gonna really hurt your friction loss but if you did "sweep" it and the loops lengths are 200' I will be happy to give you some info on the pressure loss of the piping itself at a given flow rate.
 
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Old 10-23-09, 06:34 PM
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Well, good luck. IMHO, this has a snowball's chance in [a very hot place] of providing adequate performance.

Please post some pictures of the final installation. Would like to see how it all looks.

And don't forget to have this LP/gas-fired combustion appliance installation inspected by your local Authority Having Jurisdiction.
 
  #31  
Old 10-23-09, 07:11 PM
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I understand where everyone is coming from. I started this project without any misconceptions. I never accused anyone of being crooks or crocks. The essence of DIY is to both save money and learn. I would rather put $14000.00, in my pocket rather than bury it under my driveway. I also have seemed to hit a raw nerve on some of you. If it does not work, so let it be. I blew more money in Vegas, than I spent on this entire project. And learned a lot. What I cannot understand is why most of you saying it will be so difficult in sending warm water under the blacktop to raise it just above freezing (the melting point). I am not building a sauna.
 
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Old 10-23-09, 07:49 PM
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Hey give it a whirl! You never know it may work for what you are trying to do.

I think some people on here are problem upset because they would have rather you come on before the project asking questions than in the middle, especially given the size of this project.

Even if it fails like you said you just pull the heater out and use it elsewhere or sell it so no loss there.

Your definately gonna flow higher than if it was in a normal domestic hot water situation as the return temp will obviously be a lot hotter than 35-40 degree freshwater so who knows

I think the achilles heal on this is the 1/2 inch pex though.
 
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Old 10-23-09, 08:09 PM
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I have 1/2" pex in my house slab. Say the slab and heat in the house is 68 degrees, if I move the thermostat up just one degree it takes the boiler my be two to three hour to catch up. My water goes in at 110 degrees and comes out about 80. And thats on a slab thats at 68* already.

Now if my slab was say at just freezing temp 32* It would take days for the house to get to 68*

Now I think of your slab outside, no insulation under it or over it. Maybe say 20* outside after a snow fall. 110* water going in and what coming out ? maybe 40-50*. By the time that heat makes it to the suface, I would think, not knowing for sure,but just guessing, would take days to melt snow.
 
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Old 10-23-09, 08:14 PM
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What I cannot understand is why most of you saying it will be so difficult in sending warm water under the blacktop to raise it just above freezing
I don't 'get' that anyone is saying that it's particularly difficult.

What I do get is that they are saying that your heat source, and possibly your distribution system may not be up to the task. The surface which you are heating has a very specific HEAT LOSS, expressed in BTU. In order to WARM that surface, you must be able to input MORE BTU than it is losing. The estimates that have been given range around 300K BTU. Your heat source is capable of outputting 141K BTU.

If you aren't able to counter the LOSS with the INPUT, the surface won't warm.

It's the exact same scenario in heating the interior of a building. Your home has a certain heat loss. Your heating system has a certain heat output. If the heat loss of your home was to exceed the output of your heat source, your home would not get warmer, no matter how hard the boiler worked at it. It would get cooler! BTU IN must exceed BTU OUT in order for something to get warmer.

I mentioned COLD WEATHER SHUT DOWN as a function that the commercial snow melt controllers offer. This function is added so that when the weather gets cold enough that that heat loss exceeds the capacity of the system to counter the loss, it simply shuts down. It does this so as not to cause hazardous ICE conditions. Instead of a snow covered surface, you would have an ICE covered surface. I'd rather have the snow.

You may well find that your system is capable of handling small accumulations, in relatively warmer weather... let's say down to 30 or so as an example... (or maybe it won't!) ... I'm afraid that what you will find though is that once the weather gets colder, and a heavier accumulation rate of snow, you will find that you end up with a layer of ice UNDER the heavy accumulation of snow. And that's gonna REALLY suck, cuz you won't even be able to hit that with your snow blower!

I think the reason you perceive that there are some raw nerves is because you are asking for advice, and it seems that you have your own set of pre-conceived ideas that can't be shaken. That's what I see anyway...
 
  #35  
Old 10-23-09, 08:36 PM
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Originally Posted by Homefield View Post
What I cannot understand is why most of you saying it will be so difficult in sending warm water under the blacktop to raise it just above freezing (the melting point). I am not building a sauna.
You just aren't understanding (or doing) the math of this project. For the driveway to melt snow, you will need to get it up to temperature faster than the outside air can cool it down. The boiler you have will not be able to put enough heat into the driveway to do that. It's like expecting a lit match to heat a room based on the concept that fire is hot.
 
  #36  
Old 10-25-09, 09:13 PM
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Originally Posted by Homefield View Post
I understand where everyone is coming from. I started this project without any misconceptions. I never accused anyone of being crooks or crocks. The essence of DIY is to both save money and learn. I would rather put $14000.00, in my pocket rather than bury it under my driveway. I also have seemed to hit a raw nerve on some of you. If it does not work, so let it be. I blew more money in Vegas, than I spent on this entire project. And learned a lot. What I cannot understand is why most of you saying it will be so difficult in sending warm water under the blacktop to raise it just above freezing (the melting point). I am not building a sauna.
The poblem with these types of things (the web list) is you can't convey expressions well.
My comment about crooks was definately a joke.
Frankly I love the concept of DIY, I practice it all the time. I am frugal and like to save money.
What I don't like is doing something DIY and screwing it up and it not working. It's not about what I saved or blew in vegas, but more that I was able to DO IT MYSELF.

I am trying to help you, I have lots of experience with snowmelt systems and I do know what to do and how to make it work. It just seems like you are so set in your mind that you can just send warm water out to the slab and everything will melt.
As trooper said, the slab needs a certain BTU in order to raise it and keep it at melt temperature. If you don't have that horsepower its just not going to be able to bring the water temperature up enough to do what you ask.
Imagine trying to push a fully loaded dump truck up the hill with a small car with a V6 in it, what do you think is gonna happen.
Anyways, enjoy your efforts with your project.
Feel free to post / or PM me and I will help where I cam.

Your call.
 
  #37  
Old 10-26-09, 07:07 PM
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Heated Driveway

I never thought a project such as this would bring on so many responses. I understand the concepts, now that I have almost finished. Would I have done anything different knowing what I now know from this web and from others to whom I spoke? If I was spent big bucks, I would be worried. Putting down insulation under the pex was out of the question. My blacktop guy said it would not hold up, as the the base is not solid. Plan B was to dig it down just to the top of the item #4. This is what I did. The 1/2 inch pex was on the recommendation of the pex supplier. I made the manifolds myself by sweating copper. When it came to the heating supply, I had a choice of getting a large hot water system, inside my basement and hearing my wife, or the direct waterless outside Rheem system, which would fit anywhere, was out of sight and I could compact the whole plumbing job to a piece of 4x8 plywood. This would both hide the system outside and please the bride. Out of sight, out of mind. Knowing these constraints, I don't think I could have done things differently. If I fail, all I have to do is to cut the pex lines and dump the rest of the system. Nothing ventured, nothing gained.
 
  #38  
Old 10-26-09, 07:29 PM
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so, be sure to let us know how things work out. It is an interesting project but for myself and others, we just do not believe you understand the heat demands for system such as this.

there is a reason you were quoted $14k for a system and it was not all simply profit.

but anyway, hope it works for you well enough to do what you want and not cost t boone pickens paycheck to run.
 
  #39  
Old 11-12-09, 06:53 PM
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Originally Posted by nap View Post
so, be sure to let us know how things work out. It is an interesting project but for myself and others, we just do not believe you understand the heat demands for system such as this.

there is a reason you were quoted $14k for a system and it was not all simply profit.

but anyway, hope it works for you well enough to do what you want and not cost t boone pickens paycheck to run.

bwah ha ha t boone pickens that's rich!
 
  #40  
Old 12-21-09, 04:32 PM
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JUst wondering if this guy got his stystem up and running, and if it is working ?
 
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