(B) Size of Pipes                                                            Radiating Surface Supplied

11/4 inches.............       155 square feet

11/2 inches.............      225 square feet

2      inches.............      400 square feet

21/2 inches.............      620 square feet

3      inches.............      900 square feet

31/2 inches.............     1220 square feet

4      inches.............     1600 square feet

(C) Table of dimensions of standard wrought-iron pipe— For steam and water

1 inch and below, butt-welded ; proved to 300 pounds per square inch, hydraulic pressure.

1 1/4 inch and above, lap-welded; proved to 500 pounds per square inch, hydraulic pressure.

Table of Standard Sizes

The Heating of Greenhouses Continued 101

The preceding table gives the standard sizes and principal dimensions of wrought-iron pipe. From this table the amount required for a given amount of radiating surface can be readily computed. This pipe can be purchased of any dealer.

To design heating plant.

1.    Find radiating surface by dividing area of glass in square feet by results in table A. Hot water pipes can be kept at a temperature of 180° F. if desired.

2.    Find the size of grate by multiplying amount of radiating surface by number of pounds of coal per square foot of grate per hour divided by "radiation per pound " in table A.

3.    Find size of main pipes by table B, using size next larger when radiating surface comes between numbers given. It is usually better to have several main and return pipes, and divide the radiating surface in sections.