Radiant Concrete in Sub zero temps Help!

Petro55

Hi everyone,

I moved into a house that has 3 radiant zones all in concrete. Updated the entire distribution panel 3 years ago using the following config, I have a conventional boiler 160BTU, running a primary secondary loop, controlling with Taco 705, taco 007 for each zone controlled with a thermostat. Overall the system works great except when we get subzero temps.

I am having problems with 1 zone, it has 3 1/2 pex runs(not sure the length) I typically run 120 degree supply and get ~ a 10 degree delta with ~80 degree slab 68 degree thermostat.

Now that it is -13 degrees out I am seeing 66 degree air temps 76-78 degree floor I have tried cranking up the supply temp to 140 and I am seeing a 20 degree delta but air temps are not rising.

My questions is should I swap out the Taco 007 for something larger? Does increasing the gpm help with he slab temp, or was not enough pex or slab insulation used for the extreme temps?

hot_rod

What supply temperature are you seeing at the manifold, you mentioned 140f?

Any idea of the heat load in that area? Or the design temperature for your area?

Petro55

On the Taco 705 mixing control you can adjust the manifold hot side distribution. I have it set to a target of 140F and it is supplying 140f verified by laser temp gun on the return I am seeing 120f, slab is ~76 degrees . I live in Chicago area, dont have any background on what the design really looks like as far as pex lengths, pex configuration, concrete thickness or insulation under the slab. This is a 25 year old system that was originally sending boiler output right to the floor!

hot_rod

140 is about the upper limit for concrete supply. Increasing flow would pick up some additional output any of the small multi speed circulators would get you additional flow

Petro55

How much flow would I pick up swapping in a Taco 0015E over a 007? Would that help bring the slab up 2-3 degrees? Thank you for your support.

hot_rod

Petro55 said:

How much flow would I pick up swapping in a Taco 0015E over a 007? Would that help bring the slab up 2-3 degrees? Thank you for your support.

Maybe. What is the diameter of the radiant tubing. That would give you some idea on what gpm you could push.

Alan (California Radiant) Forbes

It could be that your heat loss is overwhelming what your radiant system can provide. Is the house fully insulated?

kcopp

What do you have for windows in that room? What do you have for ceiling height?

Joe Mattiello

Contact Taco 401-942-8000 for technical support