Click here to Find a Contractor in your area.
Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Will tube inside existing radiant tube heat floor?

Hello all,
I have radiant floor heating installed in a slab under a new kitchen remodel. After a couple of years it became apparent that there was a hole in the tubing (1/2" PEX). To fix the problem, I have spent the last three months pulling some smaller diameter tubing through the existing tubing. I used 5/16" OD nylon tube, so there is a 5/32" air gap between the inner tubing and the wall of the existing tubing. I am wondering, will what I have done even work once I get water flowing through? Will the small tube inside, heat the air inside the larger tube, which will then heat the slab? Or will that air gap prevent the heat from radiating to the slab?
I guess I will find out in 3 months when winter comes, but I'm hoping to know now if all my efforts are going to be in vain or not. Thanks.
Jeff
I have radiant floor heating installed in a slab under a new kitchen remodel. After a couple of years it became apparent that there was a hole in the tubing (1/2" PEX). To fix the problem, I have spent the last three months pulling some smaller diameter tubing through the existing tubing. I used 5/16" OD nylon tube, so there is a 5/32" air gap between the inner tubing and the wall of the existing tubing. I am wondering, will what I have done even work once I get water flowing through? Will the small tube inside, heat the air inside the larger tube, which will then heat the slab? Or will that air gap prevent the heat from radiating to the slab?
I guess I will find out in 3 months when winter comes, but I'm hoping to know now if all my efforts are going to be in vain or not. Thanks.
Jeff
0
Leave a Comment
Categories
- 80.9K THE MAIN WALL
- 2.5K A-C, Heat Pumps & Refrigeration
- 36 Biomass
- 394 Carbon Monoxide Awareness
- 2.6K Controls
- 1.4K Domestic Hot Water
- 3.7K Gas Heating
- 100 Geothermal
- 130 Indoor-Air Quality
- 2.3K Oil Heating
- 30 Pipe Deterioration
- 561 Plumbing
- 4.2K Radiant Heating
- 333 Solar
- 12.1K Strictly Steam
- 36 Water Quality
- 7 Industry Classes
- 50 Job Opportunities
- 7 Recall Announcements
Comments
The tube in a tube will be insulated. Due to air space, and the wall of the old pex.
The 5/16" tube would require much shorter loops to obtain a reasonable flow rate with a reasonable head loss for the existing circulator.
That being said unless you swapped out the existing circulator for a mining pump your flow rates will be very low, or non existent.
Due to the above hurdles much higher water temps would be required to even try to see any performance.
Did you try to isolate loops if there is multiple loops?
Finding the leak is not impossible, and is repairable.
How long are your 5/16" loops now?
I was hoping the existing pump would be fine since it was pumping less water than before. You think I might have an issue with the pump now that I have smaller tubing?
Just out of curiosity - besides ripping up the floor, is there another way I could have fixed this? Thanks.
If this is pex a you used
.5 gpm is about 17' of head. What pump are you using?
I agree with Gordy. Your flow rate will be very low, There will be less surface area and, the extra air and tubing will have an insulating effect.
Albert Einstein
Here is what is printed on the pump:
Bell and Gossett
NRF-25 103417 1K21
225 F/107 C
150 PSI/10 BAR
A W
3 1.1 125
2 .8 90
1 .7 72
There is a switch on the side that has 1, 2, 3 with a line next to each, 1 being the shortest and 3 the longest. The switch is set to 1 right now.
Was the original zone calculated accurately to the heat load? Did it ever run during design conditions? How did it heat?
I'm amazed how well some of the Lieutenant Dangle, suspended pex tube systems work. Bare pex heating a big air space, you at least have some convection going for you.
trainer for Caleffi NA
The magic is in hydronics, and hydronics is in me
So bottom line is, it certainly did not "fix" it, but it is better than doing nothing. Thanks to all who replied.
It may be best in the long term to come up w a long term solution.
ME