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Question

I am a GC with a radiant heat problem. My plumber installed a wirsbo radiant system throughout a new 900 sq. ft. residential addition. The Bathroom is separately zoned from the Master Bedroom & Hallway. On warmer days (above freezing) we can get the Bedroom temperature to about 68 degrees, max. On colder days however, we cannot get the Bedroom temperature above 61. After the engineering and installation of the tubing, the architect designed and installed a wood platform bed that covers up 63 sq. ft. the Bedroom floor. The Bedroom is 304 sq. ft. Currently, outgoing water temp. to the tubing is set at 150 degrees. The floor around the bed is reading at 80 degrees (83 degrees under 2 rugs), and under the bed at 91 degrees. The delta T returning water is 20 degrees less. What do you think is wrong with the system? Should I ask the plumber to bleed the system again to make sure that air is not in the system? What should the delta T be optimally? Thank you.

Submitted: 296 days and 1 hours ago.
Category: HVAC
Value: $9
Status: CLOSED
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Posted by Brian 296 days and 1 hours ago.

Answer

Hello XXXXXXXXXXXX,

Welcome to Just Answer.

Sorry to hear about your problem.

 

I just went through a similar situation on a job. It sounds like the system was not designed with enough tubing, since the design did not take into consideration the platform bed and the rugs; these items block a large amount of the radiant heat. I would recommend having a heat loss calculation redone or adding additional tubing. In my recent situation, we actually had to add additional tubing in the ceiling to get the adequate heat, because a built-in bench was added which surrounded the room. Since this bench sat directly on the floor, just like the bed and rugs, it was enough to block the existing radiant heat, so that more had to be added to compensate the difference.

 

If you need further help or clarification on this answer, please do not hesitate to reply to this post.

 

Thanks for asking your question at Just Answer.

Best of Luck, Brian

 

Please leave feedback at your convenience.

296 days and 1 hours ago.

Reply

Thanks Brian:

My HVAC guy thinks the problem is air in the tubes. I believe my plumber bled the system, but I am not sure. Does the Delta T of 20 degrees sound suspicious to you and the fact that the water temp. is set at 150 degrees while the wood flooring only reads 80? We're using Quik Trac and have R-30 insulation below the floor in the Basement. Shouldn't the floor heat up more?

Accepted Answer

XXXXXXXXXXXX,

 

There may be other issues that I cannot see because I cannot see it firsthand. The 20 degree difference is not that bad, but the floor reading of 80 degrees seems quite low; if the tubing was not spaced close enough however, you would get low readings. You have to remember that the 150 degrees is transferring over a larger area. I would verify that the air is indeed bled from the system, then I would remove the bed and rugs from the room to see if any drastic changes occur.

 

If you need further help or clarification on this answer, please do not hesitate to reply to this post.

 

Thanks for asking your question at Just Answer.

Best of Luck, Brian

 

Please leave feedback at your convenience.

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Expert: Brian
Pos. Feedback: 100.0 %
Accepts: 
Answered: 1/30/2009

Architect

12 years designing, specifying, troubleshooting HVAC systems

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