Gas Pressure Adjustment Locations; Pipe Sizing For Gas Connections; Flow Rates; Heat Exchanger Pressure Drop Tables - Raypak 259 Installation & Operating Instructions Manual

GAS PRESSURE ADJUSTMENT LOCATIONS

GAS INLET
GAS CONTROL
SWITCH SHOWN IN
"OFF" POSITION

PIPE SIZING FOR GAS CONNECTIONS

Maximum Equivalent Pipe Length (ft)
Natural Gas 1000 BTU/FT
0.60 Specific Gravity @ 0.5 in. WC Pressure Drop
Propane Gas 2500 BTU/FT
1.53 Specific Gravity @ 0.5 in. WC Pressure Drop
Input 3/4"
Model (KBTU) N P
259 250.0 15 35
409 399.0 * 15
*A 3/4" gas line can be used for up to 5 ft maximum length from the
gas valve in addition to the sediment trap.

HEAT EXCHANGER PRESSURE DROP TABLES

BRASS HEADER
PRESSURE DROP (FT OF HEAD)
FLOW
GPM
20
25
30
35
40
50
60
70
80
90
100
110
120
125
3
3
1" 1-1/4" 1-1/2"
N P N P N
50 125 210 480 445
20 55 95 225 215 480
259 409
4.4
5.2
5.3
5.4 9.9
5.8 10.2
6.4 10.8
7.6 11.6
8.6 12.5
10.6 13.6
11.8 15.0
21.0 23.5
26.0 28.5
28.0 30.0

FLOW RATES

MODEL PIPE SIZE
259 1-1/4"–1-1/2" - 2"
409 1-1/4"–1-1/2" - 2"
*When flow rates exceed maximum GPM an external auxil-
iary bypass valve is required. See external bypass valve
section for details.

INTERNAL AUTOMATIC BYPASS VALVE

A built-in automatic bypass valve is provided in the
in/out header. The internal bypass valve automatical-
ly responds to changes in water flow in the piping sys-
tem. Proper amount of water is maintained through
the heater under varying flows dictated by the condi-
tions of the pump and filter.
BYPASS
SPRING
P

EXTERNAL AUXILIARY BYPASS VALVE

(Where Required)
An auxiliary bypass valve should be used when flow
rates exceed 125 GPM. Usually a high-performance
pump size larger than two horsepower will exceed this
flow rate. This valve is required to complement the
function of the automatic bypass valve, particularly
when starting the heater in winter or early spring when
the spa or pool temperature is below 50°F. It also
serves to eliminate needless pressure drop through
the heater and accompanying reduction in the flow
rate to the spa jets, etc.
From Heater
To
Pool/Spa
AUXILIARY BYPASS VALVE
(DO NOT USE GATE VALVE)
25
MIN. GPM MAX. GPM*
25 125
40 125
BYPASS
VALVE
To Heater
From
Pool/Spa