Energy Tech Laboratories MR212 Manuale Utente

 

8

Gas Pressure Type 

Gas Pressure 

Size 1-3 Inlet Pressure 

7 in. w.c. – 14 in. w.c. 

Size 4-5 Inlet Pressure 

7 in. w.c. – 5 psi. 

Max. Manifold Pressure - Natural Gas 

5 in. w.c. maximum 

Max. Manifold Pressure - Propane 

2.5 in. w.c. maximum 

Unit Size 

Gas Pipe Size (NPT) 

Size 1 

¾” 

Size 2 

1” 

Size 3 

1” 

Size 4 

1-1/4” 

Size 5 

1-1/2” 

Installation of gas piping must conform with local building codes, or in the absence of local codes, with the 
National Fuel Gas Code, ANSI Z223.1 (NFPA 54) – latest edition.  In Canada, installation must be in 
accordance with CAN/CGA-B149.1 for natural gas units and CAN/CGA-B149.2 for propane units. 

1. Always disconnect power before working on or near a heater.  Lock and tag the disconnect 

switch or breaker to prevent accidental power up. 

2.  Piping to the unit should conform with local and national requirements for type and volume of gas 

handled, and pressure drop allowed in the line.  Refer to the Gas Engineer’s Handbook for gas 
line capacities. 

3.  The incoming pipe near the heater should be sized to 

match the connection on the outside of the unit. Unit inlet 
sizes are shown in the table to the right.  Avoid multiple 
taps in the gas supply so the unit has a steady supply of 
gas at all times. 

4.  Install a ground joint union with brass seat and a manual 

shut-off valve external to the unit casing, as shown below, 
adjacent to the unit for emergency shut-off and easy 
servicing of controls. 

5.  Provide a sediment trap, as shown below, before each 

unit and where low spots in the pipe line cannot be avoided.   

6.  Blow out the gas line to remove debris before making connections.  Purge line to remove air 

before attempting to start unit.  Purging of air from gas lines should be performed as described in 
ANSI Z223.1-latest edition “National Fuel Gas Code”, or in Canada in CAN/CGA-B149. 

7.  All field gas piping must be pressure/leak tested prior to unit operation.  Use a non-corrosive 

bubble forming solution or equivalent 
for leak testing.  The heater and its 
individual shut-off valve must be 
disconnected from the gas supply 
piping system during any pressure 
testing of that system at test 
pressures in excess of ½ psi.  The 
heater must be isolated from the gas 
supply piping system by closing its 
individual manual shutoff valve 
during any pressure testing of the gas supply piping system at test pressures equal to or less 
than ½ psi. 

8.  This unit requires a constant 7 in. w.c. minimum 

natural gas supply, when the unit is operating at 
maximum gas flow.  If the gas supply exceeds 14 in. 
w.c. (5 psi. for sizes 4-5 housings) it will damage the 
internal valve components, and if it is below 7 in. 
w.c., the heater may not perform to specifications.