EcoRenovator  

Go Back   EcoRenovator > Improvements > Renovations & New Construction
Advanced Search
 


Blog Register 60+ Home Energy Saving Tips Recent Posts Search Today's Posts Mark Forums Read


Reply
 
Thread Tools Display Modes
Old 07-10-13, 07:14 AM   #11
Mikesolar
Master EcoRenovator
 
Mikesolar's Avatar
 
Join Date: Aug 2012
Location: Toronto
Posts: 958
Thanks: 40
Thanked 158 Times in 150 Posts
Default

Defo, got to weigh in on this one. First, the only issue with PEX is that of the wall thickness and its conductivity. As there is a VERY large ratio between the surface area of the tube in an average system and the walls heat transfer, the only issue is the time it takes to transfer the heat and we have lots of time because all we have to do is match the heat load. As we know, this is easily done otherwise the Germans wouldn't have gone with the system to start with as the benefits and longevity of PEX outweigh copper in cement (preferred) over copper (or anything) and aluminum plates.

For best radiant cooling, running the cold water through a fin-tube rad with a drip pan underneath it would work well if the cooling load is not great. You must remove the humidity but to do so without a fan requires way more surface area. Floor heating controls exist for cooling but you still have to get rid of the humidity and watch the set point very carefully.


Last edited by Mikesolar; 07-10-13 at 07:32 AM..
Mikesolar is offline   Reply With Quote
Old 07-10-13, 10:24 AM   #12
Minimac
Lurking Renovator
 
Join Date: Oct 2012
Location: Upstate NY
Posts: 29
Thanks: 7
Thanked 2 Times in 1 Post
Default

Quote:
Originally Posted by Mikesolar View Post
First, the only issue with PEX is that of the wall thickness and its conductivity.
It's not the only issue, but its conductivity is the issue here. I stated it's not very efficient. But, I agree that for HEATING in concrete, it works. Concrete will erode most metals rather quickly, unless it is properly encased. The question posed by the O.P. however involved it's use for cooling in the area where his ductwork will run. He also stated that the first floor concrete is already heated.
Unless he is prepared to encase the pex in something to serve as a heatsink to transfer the "coolness", I don't see it being of any meaningful value with regards to cooling. Just running Pex in a dead air space, even with additional controls, monitors, pumps and fans and what ever else you can think of, will provide little, if any practical cooling. Of course copper,aluminum, steel( all much better conductors) or any other piping won't do it either without a lot of extras.
The idea of "radiant cooling" is a good one, but I'm reminded of a picture I saw, the redneck air conditioner. A fan ducted into a cooler filled with ice, ducted into the room. How's that for bragging rights?
Minimac is offline   Reply With Quote
Old 07-10-13, 11:00 AM   #13
randen
Uber EcoRenovator
 
Join Date: Apr 2011
Location: Strathroy Ontario Canada
Posts: 654
Thanks: 9
Thanked 182 Times in 127 Posts
Default

I agree with Minimac The cooled pex with aluminum spreaders may at some point reach the dew point and rain on the ceiling wall board. Not good. If you have the space open, run ducts and drop vents from the ceiling. Install a air-handler. Some have the ECM fan multi speed that's very efficient. They are nearly silent. From your heat pump circulate the chilled water through the HX and the cool dry air will fall from the ceiling vents and condition your space with little striation. The added bonus to this is during winter heating season you can circulate hot water through the air handler for quick boost of heat as the floor will be slower to respond and heat the area. Or add some solar hot water panels and have FREE HEAT.

We have been living with this type of system for 6 yrs. and highly recommend it. Been there, Built it, Did it, Can say it works extremely well!!

Randen
randen is offline   Reply With Quote
Old 08-23-13, 02:53 AM   #14
daliti
Lurking Renovator
 
Join Date: Jan 2011
Location: BElgium
Posts: 8
Thanks: 0
Thanked 3 Times in 3 Posts
Default

Haven't read all the posts. We installed several PEX floorcooling systems in Belgium.
You don't have to install moisture sensors in the slab, they will be useless. Condensation needs measurement of the ambient temperature and RH to use this as a dewpoint controller.
Dewpoint controllers are ready available on the market.
Practical: we don't go lower than 18C for the floor because otherwise this will feel unpleasant.
We use 8 cm PU foam, than PE foil, tubes of 18 x 3 mm with tackers, 10 cm wide and 6 rows of 5 cm around outer walls.
You can place these tubes also in the walls as long as the walls are made of stone or concrete.
You will face +/- 20 to 30 W/m cooling effect with radiant cooling.
Burry PE pipes ( we use the same 18 x 3) at a depth of +/- 1 m and fill it with a glycol/water mix. You install a PHE on the radiant heating and a pump on the burried captation net outside. You then will have free cooling.
daliti is offline   Reply With Quote
The Following User Says Thank You to daliti For This Useful Post:
philb (08-26-13)
Old 08-23-13, 06:08 AM   #15
Mikesolar
Master EcoRenovator
 
Mikesolar's Avatar
 
Join Date: Aug 2012
Location: Toronto
Posts: 958
Thanks: 40
Thanked 158 Times in 150 Posts
Default

Quote:
Originally Posted by daliti View Post
Haven't read all the posts. We installed several PEX floorcooling systems in Belgium.
You don't have to install moisture sensors in the slab, they will be useless. Condensation needs measurement of the ambient temperature and RH to use this as a dewpoint controller.
Dewpoint controllers are ready available on the market.
Practical: we don't go lower than 18C for the floor because otherwise this will feel unpleasant.
We use 8 cm PU foam, than PE foil, tubes of 18 x 3 mm with tackers, 10 cm wide and 6 rows of 5 cm around outer walls.
You can place these tubes also in the walls as long as the walls are made of stone or concrete.
You will face +/- 20 to 30 W/m cooling effect with radiant cooling.
Burry PE pipes ( we use the same 18 x 3) at a depth of +/- 1 m and fill it with a glycol/water mix. You install a PHE on the radiant heating and a pump on the burried captation net outside. You then will have free cooling.
Right, we have done this as well but since we also use the system for heating, the cooling tube layout is the same as for heating and it is more important.

Older cooling systems just tried to keep the slab temp 2-3C cooler than the ambient regardless of the RH which doesn't work well.
Mikesolar is offline   Reply With Quote
Old 08-23-13, 06:17 AM   #16
Mikesolar
Master EcoRenovator
 
Mikesolar's Avatar
 
Join Date: Aug 2012
Location: Toronto
Posts: 958
Thanks: 40
Thanked 158 Times in 150 Posts
Default

Quote:
Originally Posted by Minimac View Post
It's not the only issue, but its conductivity is the issue here. I stated it's not very efficient. But, I agree that for HEATING in concrete, it works. Concrete will erode most metals rather quickly, unless it is properly encased. The question posed by the O.P. however involved it's use for cooling in the area where his ductwork will run. He also stated that the first floor concrete is already heated.
Unless he is prepared to encase the pex in something to serve as a heatsink to transfer the "coolness", I don't see it being of any meaningful value with regards to cooling. Just running Pex in a dead air space, even with additional controls, monitors, pumps and fans and what ever else you can think of, will provide little, if any practical cooling. Of course copper,aluminum, steel( all much better conductors) or any other piping won't do it either without a lot of extras.
The idea of "radiant cooling" is a good one, but I'm reminded of a picture I saw, the redneck air conditioner. A fan ducted into a cooler filled with ice, ducted into the room. How's that for bragging rights?
I've been called in to fix copper radiant tubing in 60 year old concrete floors and it is not fun when you have to tell the owner that it is not worth fixing. The will need an overpour of gypcrete and new tubes. Given the amount of galvanic corrosion I have seen over the years, I am really reluctant to have copper in contact with aluminum for any period of time. I just had to remove a copper sensor well from a 5 year old SS tank because the copper had corroded through. It had a small piece of steel inside to push the sensor to the tube wall.

Anyway, in the end, it is all about measurement and controls.
Mikesolar is offline   Reply With Quote
Old 08-23-13, 07:30 AM   #17
daliti
Lurking Renovator
 
Join Date: Jan 2011
Location: BElgium
Posts: 8
Thanks: 0
Thanked 3 Times in 3 Posts
Default

Quote:
Originally Posted by Mikesolar View Post
Right, we have done this as well but since we also use the system for heating, the cooling tube layout is the same as for heating and it is more important.

Older cooling systems just tried to keep the slab temp 2-3C cooler than the ambient regardless of the RH which doesn't work well.
It's of course used in winter for heating as well (GSHP) because we have -10C outside in winter. For cooling you need narrower spacing because DT is smaller when cooling.
daliti is offline   Reply With Quote
Old 08-24-13, 08:48 PM   #18
AC_Hacker
Supreme EcoRenovator
 
AC_Hacker's Avatar
 
Join Date: Mar 2009
Location: Portland, OR
Posts: 4,002
Thanks: 303
Thanked 712 Times in 532 Posts
Default

Quote:
Originally Posted by Mikesolar View Post
I've been called in to fix copper radiant tubing in 60 year old concrete floors and it is not fun when you have to tell the owner that it is not worth fixing.
I'm surprised the copper lasted so long, because concrete always holds some moisture, and it is very alkaline... both of which should really do copper in.

Quote:
Originally Posted by Mikesolar View Post
I am really reluctant to have copper in contact with aluminum for any period of time.
I realize that aluminum and copper are pretty far aparton the Galvanic Table:


NOTE: The table is for metals in sea water!

But I have always thought that for the galvanic action to work its wickedness, moisture must be present.

Quote:
Originally Posted by Mikesolar View Post
I just had to remove a copper sensor well from a 5 year old SS tank because the copper had corroded through. It had a small piece of steel inside to push the sensor to the tube wall.
So the above statement is very interesting to me... was the tank you are referring to a wet tank or a dry tank, was it filled with some non-aquious fluid?

Reason I'm asking is that over on Build It Solar, Gary tested out a solar heat collector configuration that used stamped aluminum heat spreader plates with PEX pipes, and also an identical unit with copper pipes. The copper pipe version yielded a 15% increase in heat absorption, which in his way of thinking was not enough to justify neither the additional cost nor continuing the experiment, since cheaper PEX panels could be deployed in greater number and achieve more BTU for the buck.

But to my way of thinking, 15% is a really substantial improvement... especially when you are considering radiant flooring, where the option of deploying greater radiant area may not be available as an option.

In fact, I am considering extruded aluminum with copper pipes for a dry system floor.

Your thoughts?

-AC
__________________
I'm not an HVAC technician. In fact, I'm barely even a hacker...
AC_Hacker is offline   Reply With Quote
Old 08-24-13, 08:54 PM   #19
AC_Hacker
Supreme EcoRenovator
 
AC_Hacker's Avatar
 
Join Date: Mar 2009
Location: Portland, OR
Posts: 4,002
Thanks: 303
Thanked 712 Times in 532 Posts
Default

Quote:
Originally Posted by daliti View Post
...tubes of 18 x 3 mm with tackers, 10 cm wide and 6 rows of 5 cm around outer walls.
I'm unfamiliar with this way of specifying... can you please explain what these terms mean?

Quote:
Originally Posted by daliti View Post
Burry PE pipes ( we use the same 18 x 3) at a depth of +/- 1 m and fill it with a glycol/water mix. You install a PHE on the radiant heating and a pump on the burried captation net outside. You then will have free cooling.
This is a very interesting concept to me but I am not familiar with some of your terms...

"18x3" means what?

"...install a PHE on the radiant heating..." means what?

"free cooling" Yes, that one I understand!

-AC
__________________
I'm not an HVAC technician. In fact, I'm barely even a hacker...
AC_Hacker is offline   Reply With Quote
Old 08-26-13, 11:26 PM   #20
philb
Apprentice EcoRenovator
 
Join Date: Nov 2010
Location: Oklahoma City
Posts: 152
Thanks: 57
Thanked 17 Times in 14 Posts
Default

I'm also interested in using PEX for cooling for my container house. There's not much on the net about it. What's a good lightweight medium for pouring over PEX to make a sub floor? The more information at this stage of the game will be helpful.

Here's a primer. Radiant Floor Heating and Cooling - GreenGarageWiki and about moisture control and a link to moisture modeling software from Oak Ridge Nat'l Labs and Germany's Fraunhofer Institute of Bauphysics toward the bottom of the page. Moisture Control - GreenGarageWiki

Viega Heating & Cooling Design Manual (pdf | 19.92 MB) has a very good design manual that now includes cooling. It's under installation manuals. All 184 pages.


Last edited by philb; 08-26-13 at 11:56 PM.. Reason: adding link
philb is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 11:08 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.
Ad Management by RedTyger
Inactive Reminders By Icora Web Design