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insulated underground pex

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by woodsmaster, Mar 7, 2010.

  1. woodsmaster

    woodsmaster Minister of Fire

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    Any recomendations for insulated pex underground oxygen barrior. Dont Know if I'd be better to put in lines and have closed cell ins sprayed or to bul one of the various preassembled pipes.

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  2. Frozen Canuck

    Frozen Canuck Minister of Fire

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    Suggest you go with option A as it should cost less per ft than option B as well as perform better if done right. Check out the threads here on that topic. From what I have read option B is mostly used when option A is unavailable, or time is very short.
  3. patch53

    patch53 New Member

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    Option A for sure. I've heard nothing but negative feedback on the pre-insulated (if you can call it that) pex. I'm going with closed cell spray foam when I re-do my lines this summer. Its a bit pricey, but if you have to dig up 100' of undrground line to re-do the insulation, it'll seem dirt cheap. Like they say, "do it once, do it right" !

    Pat
  4. altheating

    altheating New Member

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    The closed cell foam filled pipe is the way to go. No wasted time, the good stuff is worth the extra money spent. Last fall my eight year old underground pex failed (homemade, foam insulated pex inside a 8" pvc pipe) We installed triple wrap pre insulated pipe above ground. The last snow storm yielded 24" of snow. The next day I was shocked the snow had melted off the pipe and around it 6" on either side. I called to see what a local spray foamer would charge me to spray it after I get the trench dug this spring. About $400 for 75'. I'll just put in PEX Flex Foam Filled pipe in. Much less work. I have seen several Central Boiler installations that were done in mid winter with their version of the spray foam filled insulated pipe, no snow melt on the pipe. Do it right the first time!
  5. taxidermist

    taxidermist Minister of Fire

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    I used Logstor insulated underground pipe. Make sure you put in at least 1 1 to 1 1 lines. I went wiith the good stuff the first time but no one ever told me to go bigger. Now I cant move the BTU that I can make with my boiler plus I had to run a taco 13 pump when I cols have used a 009.

    Rob
  6. woodsmaster

    woodsmaster Minister of Fire

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    rob,
    I was thinking 1 1/4 lines from shed to storage in shop about 20',and 1 " from storage to house about 140'. House design load is 40,000 btu plus dhw and small hot tub. Would 1" be suffecient for the house load?
    planing on 200,000 btu boiler will 1 1/4 move the btus to storage.
  7. patch53

    patch53 New Member

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    Remember, that if you're going to be using Pex, the inside diamater is considerably smaller than the pipe size. And depending what kind of fittings you go with, you may well end up with less than 1" of actual flow capacity. I'm trying to figure out currently how to get a full 1 1/4" flow from my boiler into my storage tank using Pex, and it looks like even using 1 1/2 pex I'd still end up with less than 1 1/4" flow because of the reduced ID and the fittings. I'll probably end up using 1 1/4" blackpipe.

    I'm not sure 1" would be sufficient with DHW + hot tub and 140' run, you might be stretching it. For only a 20' run from boiler to storage, I'd go with 1 1/2", and 1 1/4" from storage to house. It's much better to ensure you have enough BTU's getting to where you need them than to scrimp a bit and end up regretting it later. You might also consider going with just 1 1/4" blackpipe from your boiler to storage since you have a nice short run. Would be cheaper than 1 1/2" pex also. jmho.

    Pat
  8. taxidermist

    taxidermist Minister of Fire

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    With my system the head number say this should not work but it does. I have a much larger pump than I would like to be using. I think you would be safe going with 1 1 in that short run. I would bet you could also run 1" to the house as your not trying to transfer tons of btu to the house like you would be if your storage was in the house like mine is. Talk to heaterman he could tell you what to use.

    Rob
  9. rowerwet

    rowerwet Minister of Fire

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    I have 85' of thermopex it cost $12.50/foot, it doesn't loose any heat and the ground stays frozen over it all winter, the manuf. says it will only loose 1 degree per 100'.
  10. flyingcow

    flyingcow Minister of Fire

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    i only had to go about 75ft, no foam guys in area. Went with thermopex. Happy with it, some places only 1ft underground. But I also put clean fill around it, and "2 x 2ft wide blue board over it. We get 3 to 4ft of frost, sometimes more, ok so far. If i had the option, from what i've learned here I'd go with closed cell. Be careful. I.D. of pex varies from company to company. Get a true 1 1/4 or 1 1/2 id.
  11. shawntitan

    shawntitan Member

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    Glad you guys could get spray foam contractors to return your calls, I never could, LOL... most wouldn't even return my initial inquiries, and the one that did never came up with an estimate... guess it's a busy industry... maybe I should start a spray foam company, LOL... ended up doing it myself with one of those do-it-yourself kits.
  12. juddspaintballs

    juddspaintballs Member

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    which kit and how much did that cost you to do how many feet?
  13. shawntitan

    shawntitan Member

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    I bought the 600 bd ft. Tiger Foam kit (tigerfoam.com) Cost like $750 with shipping and everything. Worked well, but did come out to be about 20% less foam than advertised.
  14. woodsmaster

    woodsmaster Minister of Fire

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    Been looking for insulated dual 1-1/4 pex. Its not easy to find. looked at thermopex and at $24.00/ foot theres no way in hell im going with that. It comes to almost $3,600.00 U.S. for 140' Still waiting to hear from logstor for there price. Does any one Know of a better deal on 1 1-4" ? Thinking I will probably do my own. Figured I can do my own for $1,900. that other $1,600 could buy a lot of wood !! Thanks for the addvise and ideas.
  15. Tony H

    Tony H New Member

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    I used the Logstor stuff and it seems to be pretty good my run is about 75' . I have never heard of the spray in application or the idea of using larger pipe back then. When the weather warms up I can see a little evidence of heat loss when the pipe rises to enter the basement but the temp gauges on each end read within 1 degree F of each other. I think the logstor was about 12.00 per foot.
    If I was doing it now would run 4 - 1" pipes and insert them 2 ea in a 4" water pipe for protection then lay blue foam down like forms for concrete and spray foam filling in the forms and cover with blue foam then gravel and dirt and lay a couple strips of buried cable marking tape next to the run about 4" from the surface and also would lay a couple of empty pipes for any future add-ons. I saw a listing for a DIY kit for 575.00 I think .
  16. Tennman

    Tennman Minister of Fire

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    Will be digging up my 1 1/4" hePEX and home brew insulation system. I'm sure I have significant water penetration into my corregated pipe which I put over my PEX with insulated sleeves. My hurry up method for the '09 season allowed to heat with wood this year, but now I have the time and expense of redoing. I was at a home improvement show last Friday and found a local polyurethane foam contractor who will foam my PEX in the trench for about $500. Wish I had found this contractor back in October/November 09. Bottom line with about 160'-170' underground I couldn't justify the $14/ft insulated products, rolled my own, and now will do the foam in a 6" wide trench with about 3" foam around the PEX. With this method I'm confident next season we will get an addition 10-20k/btus/hr into our home instead of warming the ground. Haven't found ANY method for the bigger PEX as either better insulation or better cost. I also invested $600 in Tiger foam and the product is good stuff. But this time around I'm just gonna hire the foam contractor I didn't know about last time around. BOTTOM LINE from a labor standpoint, I would much rather swap out my boiler than the underground lines. DO IT RIGHT and DO IT ONCE. It's not just the trenching but the lawn restoration time and dollars.

    Best Wishes from a DIY installer with PEX lessons learned the hard way.
  17. in hot water

    in hot water New Member

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  18. woodsmaster

    woodsmaster Minister of Fire

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    + 1 On letting the contractor foam it. It takes skill, the right mix, and the right temps for that stuff to be applied right. I was around it in manufactured housing and it had to be just right.
  19. heaterman

    heaterman Minister of Fire

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    Guys. There is no variation in ID of pex that complies with ASTM standards. There are different products on the market that confuse the issue but if you buy a 1" pex product that is ASTM listed you are getting standard 1" pex. Now, that being said, the size refferred to is a NOMINAL or industry standard size. The ASTM standard is based on the OD of the tube conforming to copper tube sizes for commonality of fittings. The fact that the wall thickness is much greater than copper absolutely means that the ID is smaller than a given copper tube size. True 1" pex is a shade above 3/4" ID in reality. 1-1/4" is only a tickle above 1" ID and so on. This is no different than any other type of pipe. Go and measure for example, the ID and OD of a piece of 3/4" black pipe. The fact that 1" pex is not 1" ID doesn't mean you got screwed.

    Some manufacturers have brought out proprietary products that take special fittings such as Kitec. They made a big deal of the fact that their product was a true 1" ID. ......So what............just buy the size you need for your application. Don't let some salesman confuse you.

    Under "normal circumstances" with total loop lengths under 200'.......

    1" (nominal) Pex is good for 6-8 GPM
    1-1/4" pex will do 12-13
    1-1/2" will flow 17-22

    Working with a 20 degree supply/return temp drop that means you max out 1" at about 80,000 btu's, 1-1/4" at 130,000 and 1-1/2" at about 220,000. Stick with those number and you'll stay out of trouble.
  20. adenowski

    adenowski New Member

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    Heaterman,

    I have 1" pex coming from outside boiler into the house. Then secondary loop for the 120,000btu HX in furnace plenum and another loop for 60,000btu HX for basement.

    If both are supplying heat, they are not at max? They will only be supplying 80,000btu between the both of them? I don't understand, please explain.

    Thanks,

    Anthony
  21. rowerwet

    rowerwet Minister of Fire

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    just remember if you DIY, or buy a cheaper insulated pex, make sure the supply and return lines are not touching, or you will loose heat to the return line, my thermopex gets every degree to my house from my OPB, it was pricey but I didn't see taking a shortcut that could cost me big $$$ in lost heat, I put 7k into my OPB, another 1k for the thermopex was worth it to me. Thermopex doesn't need any special back fill and it only needs to be 12" or so down.
  22. heaterman

    heaterman Minister of Fire

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    Sorry. My ramblings get a little confusing. I guess I'd start by saying that regardless of what your HX is rated at, the thing you need to know the most is what the actual load of your house is.
    The thing to remember and realize is that your house is likely not going to need that 120K ....and by association, the 12 GPM to deliver it with. 1" pex is not going to supply that many BTU's unless you could drop the water temp in that coil by 30*. That is not likely to happen because most water to air coils are designed to work with a 10-15* drop max. If your going to actually need 180,000 btu total you would need to flow 18GPM and there's no way 1" pex is going to do that under normal circumstances.

    If you actually need that amount of heat and you were my client, I would be telling you that you need 1-1/4".


    For easy figuring, each gallon of flow will carry 10,000 BTU's if you drop the water temp 20* supply to return. So if for example you have 9 GPM flow rate and you drop the water temp 20* through whatever type of heat exchanger you are using, you have transferred 90,000BTU's. Doesn't matter if you drop it from 180 to 160 or 140 to 120. 20 degrees is 20 degrees.
  23. woodsmaster

    woodsmaster Minister of Fire

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    I decided to build the boiler shed in a different location to reduce the amount of line needed. May have to handle the wood slightly more but thats what I have kids for. lol
    Also decided to go with either logstor or thermopex both about the same price. Both seem to a good product and really not that much more than doing yor own.
    I think I would be OK with 1" but will probably go 1-1/4" in case I ever add on, and maybe I can get away with a smaller pump.
  24. Tennman

    Tennman Minister of Fire

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    Heaterman, Your last post made me feel somewhat better about my 1 1/4" piping system. Per the Taco TD10 data sheet I knew I'd be exceeding the TD10 maximum 1 1/4" recommended flow rate of 11.2 gpm. With my computed head loss of a little more than 22 feet and assuming my 210kbtu boiler could consistently put out about 170kbtu I computed a required flow rate of 17 gpm (20F deltaT). Those two numbers flow rate and head put me right on the Taco 0013 curve. I had not read of anyone here using more than 1 1/4" PEX so I presumed others were routinely exceeding the recommended flow rate on 1 1/4" PEX. The existing 115kbtu propane furnace was adequate to keep our downstairs adequately warm during our short heating season, so I didn't attempt to do a heat loss. Since I'm about to dig up my PEX to foam insulate, from your experience am I way over pushing the flow rate in that 1 1/4"? Until recently I don't recall ever hearing discussions about 1 1/2" PEX.

    The TD10 document implies the gpm limits are to keep flow noise at acceptable limits. But they also say keep flow velocity between 2-4 fps. At 17 gpm and 1 1/4" I'm at 6.25 fps! Now I'm wondering if I need to add a 1" line to my existing 1 1/4". Geez what a learning experience related to the underground part of this system.
  25. heaterman

    heaterman Minister of Fire

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    Reading between the lines of what info you have posted here I wouldn't get to concerned about it. 1-1/4" will give you plenty of flow to heat your house. Charging your storage with no other load on the system will be the only time you actually need the 17gpm. ......depending of course on how the piping is configured.
    As to the availability of 1-1/2 pex, I would say the the majority of our systems (mostly Garn based) go in with that size tube when the entire load is served via a single underground line, so it's out there if you need it.
    Remember also that you can reduce your flow requirements by over sizing your heat emitters. As an example, I just visited a job that was done in 2002 where we did the inside piping and HX's after the customer had installed the underground himself. The building is a big old farm house with 5 bedrooms and 2 full baths and the heat load was/is very high per sq ft of floor space. The guy had run a pair of 3/4" pex lines from the OWB to the house which for all intents and purposes is severely undersized. He didn't want to dig it back up and go with bigger tube so we went with plan B. We used one pair of lines for heating and the other for DHW. I ordered him a custom heat exchanger for his furnace, 24"x24" with a four row coil configuration, to help extract heat from the water. I would say we are lucky if the flow rate hits 5GPM on that system and it should be in the neighborhood of 10 under normal design parameters. Suffice to say the darn thing heats and heats well. We got a little over 30* drop by using that ginormous HX in the plenum and when you increase the temp drop the flow requirement of course, is reduced. More than one way to skin a cat

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