Onix Tubing Installation Manual

ManualsBrandsWatts Radiant ManualsHeatingOnix - 1/2" Diameter - Radiant Tubing - 250' Length

page 8Watts Radiant: Onix Installation Manual

Step 1:

Initial Design

Considerations

There are three primary considerations

in a radiant design.

1. Heat Loss - how much energy

do we have to impart to the

system to keep the occupants

warm or the surface snow

and ice free.

2. Tubing - how much and what

type of tubing is required to

deliver the needed heat.

3. Control and Performance -

system operation will vary greatly

depending on how the system is

controlled and operated.

To answer these questions, some initial

information is needed. This informa-

tion primarily relates to the heat loss

calculation. It is important to gather

as much project information as possi-

ble. Even though this information is

conveyed to the end-user via the

RadiantWorks Assumption Report,

it saves time and effort to have the

correct information at the beginning.

To perform an accurate heat loss and

radiant design, the following informa-

tion is required.

Heating:

1. Wall R-Values

2. Ceiling R-Values

3. Window R-Values and Sizes

4. Amount of exposed wall

5. Fireplaces or other high

infiltration sources, such as

overhead hoods and vents

6. Floor Cross Section: It is

important to know how many

separate layers make up the

floor. Different floor coverings

may have anywhere from one

to four distinct layers

7. Floor Covering Materials

8. General Site Information

Snowmelting*

1. Slab construction details

2. Amount of snowfall

3. Desired response time

4. General Site Information

*Additional criteria concerning snowmelting

systems will be discussed in the Snowmelting

section.

Floor Coverings

More questions arise concerning floor

coverings than any other item. The

main misconception regarding floor

coverings tend to center on whether or

not carpet or wood can be used over a

radiant floor.

Virtually any floor covering can be

used if the insulative value for that

covering is accounted for in the radi-

ant design and installation process. In

a radiant floor heating system, the

floor is the room s heat source. The

floor gives off heat (energy) to the

room because it is warmer than the

surroundings - hot moves to

cold. If we want to maintain a

room temperature of 70¡F, the

floor has to be warmer than

70¡F. The warmer the floor,

the more energy it will emit

into the space. So, the higher

the heating load, the warmer

the floor needs to be. The

room does not care what the

floor type is, or what the con-

struction details are as long as

the required floor surface tem-

perature is achieved.

There is a limit. In theory, we

could heat any room to any

temperature with the use of a

radiant floor heating system.

The limiting factor is us. The

maximum temperature we can

allow the floor surface to reach

is 85¡F. Temperatures above

this point become too warm

for our bodies and in turn

make the floor uncomfortable

to stand on. This 85¡F floor limit in

turn limits the maximum BTU output

of the floor to around 45 BTU/sq.ft.

With this in mind, let s return to the

floor itself and look at the different

floor coverings. All floor coverings

have different conductivity values.

Conductivity values relate a material s

ability to transfer energy. The higher

the conductivity, the better the material

conducts, or transfers energy. For

example, wood has a conductivity

value of approximately 0.078

Btu/hr/ft./¡F while tile has a conduc-

tivity of 0.41 Btu/hr/ft./¡F. In this

example, tile will transfer energy

faster. But does that make tile a better

choice? Not really. Both the hardwood

floor and the tile floor will perform

exactly the same if we maintain the

same surface temperature. To do this,

we have to vary the supply water tem-

perature depending on the floor cover-

ing and construction. A hardwood

floor may require 120¡F supply tem-

Floor Coverings

Carpet and pad are

generally the most

difficult of the floor

coverings. This

means a higher

supply fluid

temperature.

Hardwoods are the