Zone In A System; Drawing 1-Example-Calculating Pressure Drop - Rinnai E50C System Piping And Applications Design Manual

Calculating the Resistance of the Longest Loop/Zone in a System
In order to correctly calculate resistance first determine the longest equivalent length loop in the system. The length
of this loop is calculated starting at the supply connection of the boiler and ending at the return connection to the boil-
er. Select this loop for your calculations.
The system/longest loop head pressure can be determined by adding up all the fittings in the longest loop and the total
length of straight pipe in the longest loop to get an equivalent length.
If the pressure drop in the loop/system is greater than the available head pressure from the boiler circulator a Low
Loss Header Plumbing kit part number: 804000061 must be used.
If the boiler is to be installed in a system that utilizes zone circulators and not zone valves, a low loss header
plumbing kit is required to be installed.
Rinnai strongly recommends the use of full port ball valve zone valves; these valves provide a lower pressure drop than
a gate valve type zone valve. The lower pressure drop will allow for longer loop lengths and better flow through the
zones.
specific weight of fluid at operating temperature (the specific weight of water is given in appendix B table 7)
=
Flow rate = flow rate through the device
C
value from the device manufacturer
=
v
To calculate the resistance for a fitting, reference Appendix A tables 5 and 6 (when using copper tubing).
ATTENTION
Example – Calculating the Pressure Drop
8
Drawing 1