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June 30, 2014

Radiant Tubing

Temporary Coupling for Pressurization
Radiant Tubing is installed.

The guys had to work in a pretty steady rain all day, but they persevered. The mud on their boots makes the puddle on the vapor barrier look like a swamp.

The tubing is Wirsbo hePEX, a tough cross-linked polyethelene tubing with an oxygen barrier coating. It is attached to the slab reinforcing with wire ties to hold it in place at the middle of the concrete slab.  We added extra rebar above the places where we will cut control joints, so that if we hit anything at all with the saw, it will hopefully be the steel bar instead of a radiant tube. 

Areas of the building slabs are divided into zones - each zone allows individual temperature control.  In our case we have 3 zones: the kitchen / entry, the guest bedroom / bathroom, and the living / dining room. 

Living & Dining Rooms
The living / dining room was large enough that it was divided into 2 piping runs, though it will be controlled as a single zone.  Piping runs are limited to ~300 sq.ft. to keep the water temperature from cooling down too much at the far end of the loops.

Entry, Bathroom & Bedroom

We laid out the tubing so that the hottest water - the beginning of the loop nearest the boiler - runs around the perimeter, particularly by the windows, to better warm these colder zones.  We also space the tubing closer together in these zones to put more heat into the slab there.  Our guideline spacing is 6" at the cold zones, and 9-12" in the field.  We avoid the locations of walls and cabinets.

We used rebar reinforcing in the slab for higher quality and crack resistance, but it gives less support to the radiant tubes than a closer-spaced wire mesh reinforcing.  This means the tubing sags a bit in some locations, and I had to add quite a few extra bars in trouble spots to pick them back up.  They are "fine" if they sag lower in the slab, but we want to strive for the ideal placement.

All the tubing runs end up back in the Utility Room, where they will be connected to pumps, manifolds, controls and the boiler.  For the time being however, they are coupled together and pressurized with air to 95 psi.  This way the tubes are stiff when the concrete pour happens, and a quick look at the gauge will let us know if someone damaged a tube somewhere; my nightmare scenario.  These tubes are tough, and it would take a real bad mistake to damage one.
Pressure Gauge

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