Thomas & Betts RZ405, RGM 405 Gas Piping and Pressures, Manifold or Orifice Pressure Settings

9. Gas Piping and Pressures

WARNING: This appliance is equipped for a maximum gas supply pressure of 1/2 pound, 8 ounces, or 14 inches water column. Supply pressure higher than 1/2 pound requires installation of an additional lockup-type service regulator external to the unit.

PRESSURE TESTING SUPPLY PIPING

Test Pressures Above 1/2 PSI: Disconnect the heater and manual valve from the gas supply line which is to be tested. Cap or plug the supply line.

Test Pressures Below 1/2 PSI: Before testing, close the manual valve on the heater.

All piping must be in accordance with requirements outlined in the National Fuel Gas Code ANSI Z223.1a (latest edition) or CAN/CGA- B149.1 and B149.2 (See Paragraph 1). Gas supply piping installation should conform with good practice and with local codes.

Unit heaters are orificed for operation with natural gas having a heating value of 1000 (± 50) BTUH per cubic ft or propane gas with a heating value of 2550 BTUH per cubic ft. If the gas at the installation site does not meet these specifications, consult the factory for proper orificing.

Pipe joint compounds (pipe dope) shall be resistant to the action of liquefied petroleum gas or any other chemical constituents of the gas being supplied.

Install a ground joint union and manual shutoff valve upstream of the unit control system as shown in Figure 13. The 1/8" plugged tapping in the shutoff valve provides connection for a supply line pressure test gauge. The National Fuel Gas Code requires the installation of a trap with a minimum 3" drip leg. Local codes may require a minimum drip leg longer than 3" (typically 6"). Bleed gas lines of trapped air.

Gas connection is either 1/2" or 3/4" depending on size and type of gas.

Size	Gas	Gas Connection
150-200	Natural	1/2"
250-400	Natural	3/4"
150-400	Propane	1/2"

Leak-test all connections by brushing on a leak-detecting solution.

Immediately upstream of the gas		From Gas Supply
supply connection, install a manual
shutoff valve with a 1/8” NPT
plugged tap accessible for test
gauge connection.
To Controls		From
		Gas
Ground Joint Union	Manual	Supply
	Gas Valve
		NOTE:
	6” Drip Leg	Connections
Figure 13 -		shown are by
Supply Piping		the installer.

Connection

WARNING: All components of a gas supply system must be leak tested prior to placing equipment in service. NEVER TEST FOR LEAKS WITH AN OPEN FLAME. Failure to comply could result in personal injury, property damage or death.

Manifold or Orifice Pressure Settings

Measuring manifold gas pressure cannot be done until the heater is in operation. It is included in the steps of the "Check-Test-Start" proce- dure in Paragraph 22. The following warnings and instructions apply.

WARNING: Manifold gas pressure must never exceed 3.5" w.c. for natural gas or 10" w.c. for propane gas.

For Natural Gas: Manifold gas pressure is regulated by the combina- tion valve to 3.5" w.c. Inlet pressure to the valve must be a minimum of 5" w.c. or as noted on the rating plate and a maximum of 14" w.c.

For Propane Gas: Manifold gas pressure is regulated by the combina- tion valve to 10" w.c. Inlet pressure to the valve must be a minimum of 11" w.c. and a maximum of 14" w.c.

Before attempting to measure or adjust manifold gas pressure, the inlet

Sizing a Gas Supply Line

Capacity of Piping - Cubic Feet per Hour based on 0.3" w.c. Pressure Drop

Specific Gravity for Natural Gas -- 0.6 (Natural Gas -- 1000 BTU/Cubic Ft)

Specific Gravity for Propane Gas -- 1.6 (Propane Gas -- 2550 BTU/Cubic Ft)

Length

of

Pipe

Diameter of Pipe

1/2"3/4"1"1-1/4"1-1/2"2"

Natural Propane Natural Propane Natural Propane Natural Propane Natural Propane Natural Propane

20’	92	56		190	116	350	214	730	445	1100	671	2100	1281
30’	73	45		152	93	285	174	590	360	890	543	1650	1007
40’	63	38		130	79	245	149	500	305	760	464	1450	885
50’	56	34		115	70	215	131	440	268	670	409	1270	775
60’	50	31		105	64	195	119	400	244	610	372	1105	674
70’	46	28		96	59	180	110	370	226	560	342	1050	641
80’	43	26		90	55	170	104	350	214	530	323	990	604
90’	40	24		84	51	160	98	320	195	490	299	930	567
100’	38	23		79	48	150	92	305	186	460	281	870	531
125’	34	21		72	44	130	79	275	168	410	250	780	476
150’	31	19		64	39	120	73	250	153	380	232	710	433
175’	28	17		59	36	110	67	225	137	350	214	650	397
200’	26	16		55	34	100	61	210	128	320	195	610	372
	Note: When sizing supply lines, consider possibilities of future expansion and increased requirements.
			Refer to National Fuel Gas Code for additional information on line sizing.

Mfg No. 164771, Page 13