## APPENDIX A

## APPENDIX B

This appendix presents a simple method for estimating the head loss of piping paths or circuits constructed of smooth tubing, such as copper tubing or PEX.

The head loss of a piping path or circuit can be determined using Formula B-1.

**Formula B-1**

$$ H_L = (acl)f^{1.75} $$

$H_L$ = Head loss of circuit (ft of head)

$a$ = a factor that depends on the average water temperature

in piping (see Figure B-1)

$c$ = a factor determined by the type and size of tubing in

the circuit (see Figure B-2)

$l$ = total equivalent length of the circuit (ft)

$f$ = flow rate (gpm)

$1.75$ = an exponent of flow rate

The values of “a” read from **Figure B-1** should be based on the average water temperature in the piping. Thus, for a recirculation loop with a supply temperature of 130ºF and a return temperature of 120ºF, the value of “a” would be determined at the average fluid temperature of 125ºF.