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Time to pull the trigger


Hello Everyone.

I have been lurking and reading and re-reading and trying to make heads or tails of anything weezbo says. ;)

But now I have to get off my butt and actually do this project. My buddy is a plumber and is going to help, but I am in charge of making sure I have a grasp on all this.

The details seem to help people cut to the chase it seems, so here you go:

Purchased a little building a few years ago and reno'd it into a half livable place to hang my hat. There was Pex in the floor already, but never hooked up. The guy who sold it to me kept excellent records of the install so this helps I hope.

Now I want to get the floor heat going.

Did heat loss calculations and I am looking at 19 btu/hr by the book.

I rounded it up to 24 in the real world when the insulation settled etc...etc...

Just under 1000 sq. feet of slab

One zone

Four circuits, roughly 225' per of Non O2 Barrier pex

Looking at the Cadet 40 with a low loss header set-up.

The "near boiler piping" (just some of the great lingo thrown around here) looks pretty simple really, but the devil is in the details from what I have gleaned from reading.

Anyone open to making sure I have a few details sussed out?

My first question is about low loss headers.

The manifold is 3/4" copper as is the roughly 24" of copper soldered onto that.

The Low Loss headers are, at the smallest end of the market, 1". Is this Kosher?

Will reducing the in/out make a difference?

Thank you.


  • GordyGordy Member Posts: 9,530
    edited May 2014
    Non o2 barrier tubing

    You need to isolate the tubing via a heat exchanger.......or use non ferrous components circulator etc. I'd use the HX keeps component costs down.

    3/4" copper can carry 42000 btus so it's big enough.
  • ZmanZman Member Posts: 6,318
    Low Loss

    To answer the low loss header question. The header should be designed for 2 ft/sec. with 3/4" copper that would be 3.2 gpm. With 4 loops that would be .8 gpm per loop.That would work just fine for the floor. A Grundfos 15-58 on setting 1 get's you there.

    If you want higher flow, you could either go with a 1" manifold or pipe your manifold reverse/return.

    As Gordy said, the 3/4 is plenty big for the delivery pipe.

    Keep reading Weezbo's posts. I have learned to  read  "weazbo" he is  very knowledgeable.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • NYplumberNYplumber Member Posts: 503
    pro design

    Good morning,

    If your buddy is a good "truck plumber", get a pro design so he stays your buddy.

    If you dont mind me asking, where are you located?
  • tiredofchoppingwoodtiredofchoppingwood Member Posts: 32

  • EastmanEastman Member Posts: 927

  • tiredofchoppingwoodtiredofchoppingwood Member Posts: 32
    Ok, got it to work

    thats better.


    I will give that some thought. I like "keeping costs down" within reason. I know this stuff costs cold hard cash to make work properly.

    With a heat exchanger, what kind of loss in efficiency do people face?


    Thats even more info than I was hoping for, thank you.

    Weezbo is without a doubt knowledgeable, I am not, so his savant like delivery is lost on me.


    Ha! Oh he is plenty knowledgeable, but he treats every project as a learning experience that I am forced to research myself. I have learned a lot over the years! He basically makes sure I don't flood the house, or blow myself up. Though I appreciate your point.

    I am in Canada, middle of nowhere, nearest a Place called Calgary.
  • tiredofchoppingwoodtiredofchoppingwood Member Posts: 32
    LP / cadet / regulator

    The manual for the cadet says: "Ensure that the high gas pressure regulator

    is at least 6 - 10 feet upstream of the


    Later it also states: "If an in-line regulator is used, it

    must be a minimum of 10 feet from the Cadet heating boiler."

    So I can't find anything on "in-line regulators"

    The typical set-up is a regulator at the tank and another as the line enters the building.

    Does this mean the boiler needs to be ten feet from the last regulator on a typical install?

    If so, this becomes a near impossible situation for me. Can I run ten feet of meandering black iron to get ten feet of linear distance? Even though the reg and the boiler are almost back to back.
  • Tim PotterTim Potter Member Posts: 258
    Hot water needs also???

    What are you doing for hot water - shower, washer, dishwasher ?

    What is your heat loss on the building?

    Winter Park, CO & Lenexa, KS
  • tiredofchoppingwoodtiredofchoppingwood Member Posts: 32
    Just need it

    for radiant heat.

    No dishwasher, no washing machine, one shower on an on demand.
  • tiredofchoppingwoodtiredofchoppingwood Member Posts: 32
    heat loss

    is, more or less, 20,000 btu/hr for design loss, worse case scenario, end of days, too cold to even stick my head out the door, ice zombie apocalypse.
  • ZmanZman Member Posts: 6,318

    That is a strange note. Who decides if it should be 6 or 10?

    Some modulating boilers have issues with an annoying harmonic hum when they are to close to the regulator. I suspect that is what the note refers to.

    There is no reason I know of that the 6 to 10 could not be a loop in the boiler room.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • tiredofchoppingwoodtiredofchoppingwood Member Posts: 32
    Think I get it

    The10 foot reg problem seems to be in LP systems with PSI in the 2 range. (High pressure)

    Not sure what mine is to be honest, but it seems to me most residential setups are 1/2 psi

    Though I could be wrong.

    Now the inline reg 6-10 foot thing seems to be about needing enough gas in the line between the reg on the exterior of the house and the reg in the boiler so the boiler reg is not having to react to the exterior reg...Maybe?
  • ZmanZman Member Posts: 6,318

    Here in the lower 48, the pressure in the line from the tank to the house is reduced to approx 8-10 psi.

    The house pressure is then lowered to approx 11 inches of water column. 1 PSI = 27.68 in/wc.

    I don't know what specifically causes the noise. I suspect it has to do with the low volume of gas in the line and the lack of resistance .

    There are folks on hear that have a better understanding.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • tiredofchoppingwoodtiredofchoppingwood Member Posts: 32
    Too be safe

    I will just add a loop of Black iron. There that problem solved.

  • tiredofchoppingwoodtiredofchoppingwood Member Posts: 32
    edited May 2014
    Low loss header

    I am looking at has a vent and a sediment trap/purge built in.

    Good idea or bad?

    Normally, I see the expansion tank under the air vent, but since this isn't possible with the sediment trap, where does the expansion tank fit in the flow of things?
  • SWEISWEI Member Posts: 7,356
    Combination hydraulic separator w/ air and dirt separation

    works great.  Just tee off from one of the cold legs near where they connect to the separator.  Don't forget a shutoff valve and a union so you can easily test or replace the expansion tank.
  • tiredofchoppingwoodtiredofchoppingwood Member Posts: 32
    Thats easy

    Is it best to have it (expansion tank) before or after the vent/low loss header/sediment trap?

    I Am all about isolation valves and unions. Has made my life so easy in the past.

  • SWEISWEI Member Posts: 7,356
    Before or after

    is really your choice.  I use whichever works out best for the particular system layout.  Don't want to block access to the boiler, might get in the way of the lines to the indirect, etc.  You can even tee it off of the drain line, though I worry about sediment somehow ending up in the tank.
  • Tim PotterTim Potter Member Posts: 258
    Low Loss Headier vs Buffer Tank

    Being as you are over-sized by a factor of 2 even in worst case scenario design day with one of the smallest Mod-Con boilers made, you might compare & contrast the cost vs benefit of a small buffer tank in place of the LLH. Mine absolutely eliminates short cycling & give you LONG run times & LONG off times.

    Just another concept to keep you up at night thinking about.......

    Good luck,

    Winter Park, CO & Lenexa, KS
  • tiredofchoppingwoodtiredofchoppingwood Member Posts: 32
    So much

    good advice!

    Buffer tank huh?, ok I will look into it as well. Though space is a bit of an issue. But, I could probably frame a little bump out on the house and slide it in there.



    Any idea if You need to or have to have a water line feeding into the system? Or can you just fill it up and periodically make sure there hasn't been water loss?


    I'm sure nobody needs to or wants to rehash this again and again for people, so do any of you have a rock solid link to a site or thread or PDF that will help me sort out the head loss/pump selection etc.? As simple one that a simpleton can figure out.
  • ZmanZman Member Posts: 6,318

    I see where Tim is heading with the buffer tank and generally think they are a good idea.

    In your case you have a single zone high mass panel and a boiler that turns down to 9k/btu input.

    My math (actually Siggy's) is saying that you can lower your boiler supply temp to 92 degrees before the boiler would cycle at all. The boiler will never "short cycle".

    As far as the piping goes,pipe it primary/secondary just like the manual. The 15-58 will work for both circulators. Most systems have a backflow preventer/fill valve assembly.

    It can be done without one but usually is not.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • tiredofchoppingwoodtiredofchoppingwood Member Posts: 32
    edited May 2014
    never short cycle!


    I like the sound of that, though I don't expect perfection, so if I get even close to "never" I would be happy.

    Huh - I am currently struggling to think of anything else to ask. Seems simple enough! hahaha.

    No doubt I will post a question at the end of the instal wondering what these "left over doodads are for".

    I might come up with something a bit later, but thanks a tonne everyone.
  • tiredofchoppingwoodtiredofchoppingwood Member Posts: 32
    Ya but!

    Ok, so I was doing some poking around the net and what Gordy mentioned about a HXer sent me off on another tangent, which led me to a little slant/fin CI unit in the range of 29k btu.

    It is plenty small enough at +/- 9" wide and would fit into the space I have to work with. If I did something like this instead of the Mod con how would it - Hmmmm?

    Let me work this out.

    The cadet:

    boiler, LLH, two bronze or SS pumps, strainer, exp tank, various check and isolation valves etc

    it modulates down to more or less the correct output.

    = Warm floor.

    CI boiler:

    Boiler, HXer, Two pumps (one SS or Bronze for the boiler side, one Iron for the non Barrier Pex side of the HXer) 2 exp tanks, various check and isolation valves etc

    it blasts away at full throttle and the temp into the floor is controlled with a?

    Anyone have a link or can explain how this kind of set-up looks and functions?

    This is an interesting option if it can be made to work for my load as the cost of the CI boiler is a lot less upfront and my guess the ongoing maintenance would also be less. Probably last a lot longer as well. (if I can keep it from short cycling to an early grave. Let me guess - a buffer tank is about to be mentioned. now I am in a space crunch again)
  • EastmanEastman Member Posts: 927
    edited May 2014

    Thermostat calls for heat. --> Boiler fires, heating water to the set point which may be adjusted according to the outside temperature if an ODR is used.

    A modulating boiler would throttle back as it approaches the set point. There is no link between the thermostat and the set point. The set point is something you would program as part of the installation and probably adjust later if required.

    Is there insulation under the slab? --something other than bubble foil like product?
  • ZmanZman Member Posts: 6,318

    If you do the slant fin boiler you would need something like the Taco I series mixing valve to do outdoor reset and boiler condensing protection.

    It looks like the cost of the 2 options would be similar.

    with the slant fin,You would be right about  6 cycles per hour with 92 degree water and a 25 degree boiler differential.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • tiredofchoppingwoodtiredofchoppingwood Member Posts: 32

    Oh, I get it.

    I think I meant more how do you get the appropriate temperature of water into the floor, from either boiler now that I think about it. But specifically the CI boiler?

    The Ci Boiler probably has some degree of turn down adjustment, but I am guessing there is a mixing valve and or maybe it has to do with the size of the HX'er or flow rate or a combo of all the above? The more I think about that one the more I get confused actually.

    So maybe a CI boiler is not really possible in this application?

    Yes, the floor has, what looks like, 2" foam board in the pictures. Taped between seams.

    The exterior perimeter has foam board as well.

    Overall, it seems like a pretty well done installation, except for the Non O2 barrier pex and there is no insulation between were the slab and the frost wall intersect. So I am guessing a certain amount of the energy goes down to the footing. But maybe that helps with frost heave in the end.
  • tiredofchoppingwoodtiredofchoppingwood Member Posts: 32

    6 cycles per hour, do you mean 6 on/off cycles of the boiler or do you mean 6 circulations of the water volume in the system.

    If you mean the boiler cycles on/off 6 times per hr, do you mean it basically goes 24hrs a day on and off every 10 minutes to maintain the floor temp or it would just do the cycle until it hit the set point temp then shut off until it called for heat again.

    Sorry folks, I'm sure you are used to a more educated line of questioning.

    I am super glad Weezbo has not commented. I am confused enough.
  • EastmanEastman Member Posts: 927
    no direct control

    There isn't a tight control on the water temperature. It's constantly rising or falling around the set point. The swing in temps is kept within reason by a differential value. A small modulating boiler can make good use of a tight differential, keeping a more even output to the floor. A bigger fixed fire boiler would make better use of a larger differential to prevent excessive cycling.
  • tiredofchoppingwoodtiredofchoppingwood Member Posts: 32
    modcon tight diff

    Ci larger diff, same price more or less once all the stuff is factored in, which is a wiser buy?
  • ZmanZman Member Posts: 6,318
    CI Boiler

    In the scenario where you have a 29,000BTU boiler and the outdoor temp is fairly warm, I was assuming the output water temp on the floor side would be 92 degrees. In that event, the slab should be absorbing about 9,000 BTU while the boiler is producing 29,000 BTU. This will cause the boiler to cycle. The length of the cycles is dictated by the amount of mass the boiler and the amount of water in the system  as well as the on/off differential setting on the boiler. In my rough calculation, you would pretty close to 6 on and 6 off cycles per hour which is what many people use as the definition of "shortcycling". A buffer tank would resolve this issue.

    As far as the stability of the water temps to the slab, the I valve will handle that.

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • RobGRobG Member Posts: 1,850
    Cadet boiler

    Another thing is that with the Cadet you will not have to use a heat exchanger as it does not contain any ferrous components. Just use copper, brass and stainless and you will be fine.

  • tiredofchoppingwoodtiredofchoppingwood Member Posts: 32

    back on track.

    I will put aside the fantasy that somehow I can save a buck or two thousand by getting a CI boiler.

    Thanks guys.
  • tiredofchoppingwoodtiredofchoppingwood Member Posts: 32


    earlier in this thread you mentioned the Grundfos 15-58 as an ideal choice.

    I can only find this in cast iron. Unless I have misunderstood, for the cadet/non o2 Pex I will need ss or bronze pumps.

    I came across a bronze pump from b&g called the ecirc or something like that, but I am not sure if the curve is right.

    Any other pump options you or anyone can think of?

    (scrolling through the grundfos catalogue was mind blowing. They have a lot of pumps!)

  • ZmanZman Member Posts: 6,318

    The 15-55 is the stainless version
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • tiredofchoppingwoodtiredofchoppingwood Member Posts: 32
    edited May 2014

    that makes more sense. I was looking up 58 not 55.

    And if you just start browsing for random pumps on the site. Well, lets just say the pump gods love wondrous variety.

  • WeezboWeezbo Member Posts: 6,232
    edited May 2014
    i have something that you might like ,

    it allows you to look at two charts side by side , without brain strain .

    It may help ...

    There are times where i look at a pencil and consider that it has two ends , one with an eraser one with a sharpened end graphite point. Today when looking at an old boiler gravity system converted over to a "Pumped system" i considered the quest you were on and the problem in front of me and thought maybe this would help you as well.

    *~//: )

    Did heat loss calculations and I am looking at 19 btu/hr by the book.

    I rounded it up to 24 in the real world when the insulation settled etc...etc...

    i live in a completely different area of the world so some of the filtration of information i occasionally roll right past without reading between the lines . i apologize for that . my typing is not great either as i used to play Karate and Aikido in school and jammed my fingers into my hands so i had to try to type with my nose and the side of one of my thumbs in typing class.. my thinking is a bit different however i did not mean to blow by how you might feel ,it is just the way i think certain things.

    hope the charts side by side allow you to see two manufacturers circs flow and head .

    Many of us have books handy so we can piece things together by part numbers ,

    a miss read number can take even more time to find. i am fairly certain you were not deliberately given a run around .

    up until last Thursday, i was doing fine , until the guy i am working with started feeding me lunch , now i am addicted to food again and don't know how to get off of it . Even right now i think i might have fallen prey to another insidious trap due to some neglected aspect so today i asked my buddy what day it was and He Knew ! Now i am sure my days are numbered . !

    My last paragraph will definitely help just about anyone who is feeling like things did not go right in their day. i hope you are feeling refreshed , if not, try Onion News they have a video there that will relieve the doldrums .
  • tiredofchoppingwoodtiredofchoppingwood Member Posts: 32
    edited May 2014

    Thanks Weezbo!

    I am so happy you found my little thread and plucked it.

    I still have no idea what you are talking about, but it brought a smile to my face thinking about you nosing away at your keyboard. Might I suggest speech to text software?

    I rotated my laptop in the air several times to make out what the emoticon smiley face doodad is.

    Either a smiley face guy with a fancy turban on.

    Could be a poop on his head and a single fly buzzing around it I suppose

    Could be a guy with a scarf wrapped around his face if you rotate it counterclockwise.

    Or maybe you sneezed while typing.

    (if you really did have a Karate accident as a child and really are typing with your nose. Sorry to be insensitive)

    Thanks for the comparison link as well.

    These ss pumps are well expensive!

    Now that HXer is looking like an option.
  • ZmanZman Member Posts: 6,318

    You need to buy a ss circ and expansion tank for the heating side either way.

    If you don't use a  HX you need to upgrade the circ on the boiler side to ss for about $200.That's it

    If you use an HX, you need another;

    fill valve

    heat exchanger


    pressure gauge

    expansion tank

    misc fittings

    At least $800 more.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • tiredofchoppingwoodtiredofchoppingwood Member Posts: 32

    Thanks Zman. ( you know, as a Canadian, I am saying your name as Zedman. Damn Brits! )

    I might grumble a bit and plot a way around it, but deep down inside I know I have a whole fat stack of cash that needs to be spent on this little project. Which is fine in the end. I live in a frozen wasteland 9 months out of the year. I am just starting to see the leaves on trees this week and it's almost June.

    I think my ancestors were world class under achievers. It was a free for all when they arrived back in the day. They could have pretty much settled anywhere. They made it this far and called it quits when they should have banked a hard turn South and stopped when they heard the margaritas in the blender! So because of this laziness I have to shell out for an expensive boiler!

    Can you even imagine how shite it must have been for a peasant in Europe in the 1800's, that the bald arse tundra of Canada was a welcome sight!?

    Thanks Zman.
  • EastmanEastman Member Posts: 927
    electric rates

    How does electric compare to LP on a btu to btu basis there? There was a poster on this forum that had significantly cheaper dual fuel electric rates vs LP.

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