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Old 11-28-2008, 09:06 AM   #1
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Installing pex radiant floor heat, questions.


Towards the end of dec ill be installing a radiant heat system. This coming week a representative from .radiantec.com will be calling me so i can get a quote from them. What are some things i should be looking out for or questions i should be asking. I do not know alot about radiant heat.

Heres the project.
Mater bedroom roughly 480 sqft.
3/4 t&g plywood (plywood not OSB) subfloor, quartersawn Oak Hardwood and Tile finish, joist are 11-7/8 TGI's spaced 12 on center and 16 on center with two LVL (3-1/2 thick) beams to be crossed..

Current house is 800 sqft.
Boiler (Peerless Pinnacle PI-80 (REV1)) and central air, air handler/heater coil in atic.
Hot water is held in new hot-water holding tank heated by boiler.


For the project....

What would a good heat source be ?
House has NG.
Currently have a Peerless Pinnacle PI-80 but that will be sitting about 40' away from the floor which will be heated.
Plan on getting a small tankless for the project to supplie hot water to a single master-bath (will have two shower heads) but thats it.

Should i get a bigger tankless, can the PI-80 handle the 40' hike ?


Attaching the pex to the floor?
Read about this in two different ways.
One way uses plastic 1/2 round fasteners that are nailed up
Second is staples and that allumeno heat reflector.

Would it be wise to glue and staple the reflector sheet ?


As time goes by and more questions pop into my head and more information is learned, ill post it here.


Thanks for any help.


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Old 11-29-2008, 05:48 AM   #2
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Installing pex radiant floor heat, questions.


The boiler should be piped primary/secondary, then hte 40' doesn't matter.
Next, you need to know how much heat your current set up really needs, to determine if the boiler can handle the increased load.

You need to do a load calc on the addition to see how much heat it needs, to know if you can get enough radiant heat to heat it.

Your radiant supply should be able to determine what water temp you need, and if you need a second source of heat for design conditions.

Do not try and use temp set back with a radiant system.

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Old 11-29-2008, 06:07 AM   #3
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Installing pex radiant floor heat, questions.


it sound as tho you will be installing this system under your subfloor. you will have to contend with the flooring cleats or staples that are sticking through the floor. I did this system to my house, and no mater how you fasten the heat transfer plates to the underside of the subfloor your going to be hearing the plates expanding when they start to heat up. but the comfort out ways the 4 minute noise. Good choice with the 1/4 swan oak. the heat will rise much easier and less movement with the flooring. BOB
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Old 11-29-2008, 06:12 AM   #4
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Installing pex radiant floor heat, questions.


Which type of plates did you use.

Single or double tube.

The thin plates, should only be fastened by 1 fastener. Weather it be nail, or staple.

More then that, and you get noise.
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Old 11-29-2008, 06:33 AM   #5
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Installing pex radiant floor heat, questions.


they where the single tube type. for 1/2" pex. and I believe they where 18" long. one fastener would not of worked. the weight of the pex pulled the plates away from the subfloor. so i used 6 3/8" long crown staples per plate 2 @ each end and 2 in the middle. this was back about 8 years ago. They did come along way with there technology. plus the fact I grounded down all the flooring nails that where in the way of the plates,which I was worried about having the floor buckle. but 8 years latter still as new. BOB
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Old 11-29-2008, 06:51 AM   #6
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Installing pex radiant floor heat, questions.


Yea, some of the plate designs, well, they were just worthless.
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Old 11-29-2008, 06:56 AM   #7
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Installing pex radiant floor heat, questions.


I love the warm board set up for the wood flooring, with the 3/8" pex.
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Old 11-29-2008, 10:06 AM   #8
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Installing pex radiant floor heat, questions.


Thanks for your responses...

Quote:
Originally Posted by beenthere View Post
The boiler should be piped primary/secondary,...

Do not try and use temp set back with a radiant system.
Can you explane what you mean for both of those ? I dont understand.
I can sweat pipes, run lines, etc. but know nothing about heat sources or how they work.

Quote:
Originally Posted by buletbob View Post
it sound as tho you will be installing this system under your subfloor. you will have to contend with the flooring cleats or staples that are sticking through the floor.
Yes from under. I havnt installed the oak, was gonna do that last. The plan, snap chalk lines under the subfloor to make sure the pex is run nice and strait, then snap red-lines on the top NOT to nail and blue lines where all the joists lay to make things go alittle easier and safer (not to nail any pex), if that a wise thing ?
Did alittle reading on a radiant site and they said for new installs its best to have the radiant system runn for alittle while to dry out the subfloor of any moisture, which im sure i have been the subfloor got wet from teh rain a few times durning construction.

Quote:
Originally Posted by buletbob View Post
I love the warm board set up for the wood flooring, with the 3/8" pex.
If thats the subfloor with the grooves, yea...
Looked into this alittle and it looks like it could be a bit costly.


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Old 11-29-2008, 10:53 AM   #9
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Installing pex radiant floor heat, questions.


Quote:
Originally Posted by iMisspell View Post
Thanks for your responses...


If thats the subfloor with the grooves, yea...
Looked into this alittle and it looks like it could be a bit costly.


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They do make a sub floor with the grooves, but what I was referring to was the 1/2"thick plywood with the heat transfer plate attached to the bottom . this hole thing gets screwed down over the subfloor. and when you install your flooring the pex is visible so you don't have to worry about looking for it when nailing down the floor. It will be a lot more easier then doing it from under the subfloor. try this link. BOB http://www.pexsupply.com/Categories.asp?cID=819&brandid=
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Old 11-29-2008, 11:57 AM   #10
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Installing pex radiant floor heat, questions.


Temp set back. If you lower the temp during the day when your not using the bedroom, and try to raise it for sleeping. It could take several hours to recover 4.


Primary/secondary piping example.
Attached Files
File Type: pdf PrimarySecondaryExample.pdf (3.6 KB, 249 views)
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Old 11-29-2008, 02:01 PM   #11
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Installing pex radiant floor heat, questions.


Quote:
Originally Posted by buletbob View Post
They do make a sub floor with the grooves, but what I was referring to was the 1/2"thick plywood with the heat transfer plate attached to the bottom . this hole thing gets screwed down over the subfloor. and when you install your flooring the pex is visible so you don't have to worry about looking for it when nailing down the floor. It will be a lot more easier then doing it from under the subfloor. try this link. BOB http://www.pexsupply.com/Categories.asp?cID=819&brandid=
Ahh... i see.
Seen something simulare but the transfer plate was mended on the top, like a full 3/4 t&g subfloor, think it was called warmboard (which seams alittle different then the link you posted (thanks for the link)).

I like those 1/2 panels, which bring me to a couple questions.

Insulation in the joist bays below.
Heres a thread i started questioning how to insulate with the tubing stapled from below. If i was to go with the 1/2 planks could i just put R38 in the joist bays and not worrie about anything (that would be nice) ? One thing about the 1/2 that looks the most appealing is not having to work with my arms over my head

Installing the planks. Since hardwood will be installed on top and that and will be running perpendicular to the joists, those planks will run parallel with the joists ?

As for "mass" for absuorbing heat, how does that 1/2 compair to tubing under 3/4 ? Seams like there would be more mass to hold the heat with the pex below heating the 3/4 and the hardwood compaired to the 1/2.

One thing which will suck if i head the 1/2 rout, just got done hanging three pocket doors and left 1" to play with off the subfloor Looks like i might be trimming off the tops of a few doors when it comes time to stain them (solid 6 panel pine) lol.




Quote:
Originally Posted by beenthere View Post
Temp set back. If you lower the temp during the day when your not using the bedroom, and try to raise it for sleeping. It could take several hours to recover 4.


Primary/secondary piping example.
Understand the temp set back now (currently do that with the hot air heat).

The primary/secondary piping is still above my head right now, thanks for the diagram, will have to do a little more research when i get some more time.


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Old 01-07-2009, 10:01 PM   #12
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Installing pex radiant floor heat, questions.


Quote:
Originally Posted by beenthere View Post
Which type of plates did you use.

Single or double tube.

The thin plates, should only be fastened by 1 fastener. Weather it be nail, or staple.

More then that, and you get noise.
Just read your post about only using one fastener....my crew totaly didn't do this and I wake up every morning to the noise of a really bad troop of boyscouts tap dancing under my bed!

I have 3 systems on my home. In cement in the basement, staple up with the noise issues on under the 130 year old fir floors in the joists and the "warm boards" in the attic.

The heat is GREAT...the noise not so much.

The basement ceiling is still open right now and I am trying to figure out insulation. I read the other post about the plates not staying on with one fastener and think that would be the case here too.

Any advise? I can still remove them but I paid BIG BUCKS to have them and my installers have told me that I wanted the plates and I got the plates and too dang bad it they make noise...... so much for customer service??

Oh well I have to decided what to do from here. Do I remove them before I close in the ceiling? Do I leave them enjoy the heat and get used to the start up noise? Do I take some staples out and see if just hanging there not snug to the floor is quiet?

HELLP HELP HELP

thanks

Maria
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Old 01-07-2009, 10:16 PM   #13
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Installing pex radiant floor heat, questions.


Remove the staples.

Use a short drywall screw instead. It won't put out.
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Old 01-07-2009, 11:01 PM   #14
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Installing pex radiant floor heat, questions.


Quote:
Originally Posted by beenthere View Post
Remove the staples.

Use a short drywall screw instead. It won't put out.

But if I use just one the plates would hang down as they are long like the other person posted about. The crew who installed it did change some over to sheet metal screws but it didn't help with the noise. I think the noise comes from the tube expanding in the plates (is that right?)

thanks so much for your help with these questions!!

Maria
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Old 01-08-2009, 12:09 AM   #15
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Installing pex radiant floor heat, questions.


Some times its just the tube expanding.
Other times its the plate.
And some, its both.

The plates will hang down.
But, the plates will still radiate more heat, then just a stapled tube system.

If you want.
You can pull the tube out, put some talc or baby powder on the tube, and put it back in teh plate.
See if it stops the noise.

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