YFG255 SERIES GAS RETHERMALIZERS
CHAPTER 1: SERVICE PROCEDURES
1-1
1.1 Functional Description
YFG255 Series gas rethermalizers contain a welded stainless steel cookpot that is heated by gas
flames diffused evenly through tubes built into the cookpot.
Flames originate from orifices in a burner manifold positioned beneath the burners. The burners are
positioned in the tube openings, at the front of the cookpot. The diameter of the orifices differs for
natural (CE:G20/G25) and LP (CE:G31) gas as indicated in the accompanying table.
NON-CE (Altitudes of 2000 feet or less)
MODEL
INPUT
(BTU)
GAS
TYPE
ORIFICE
MM
(INCH)
ORIFICE
PART NO.
QTY
EQUIPMENT
PRESSURE
MBAR INCH
W.C.
YFG255 90
NAT
LP
2.38(#42)
1.51(#53)
810-2926
810-2941
2
2
10
27.5
4
11
CE ONLY (Altitudes of 2000 feet or less)
MODEL
INPUT
(kW)
GAS
TYPE
ORIFICE
MM
(INCH)
ORIFICE
PART NO.
QTY/
COLOR
EQUIPMENT
PRESSURE
MBAR INCH
W.C.
YFG255 26.4
G20
G25
G31
2,38
2,38
1,51
810-2926
810-2926
810-2941
2/BLUE
2/BLUE
2/RED
10,0
15,0
27,0
4,0
6,0
10,8
An electromechanical gas valve regulates gas flow to the manifold. YFG255 Series gas
rethermalizers are equipped with a 24-volt valve system with an electronic ignition system.
Electronic Ignition Configuration
An ignition module connected to an ignitor assembly controls ignition. The ignition module
performs three important functions: it provides an ignition spark, supplies voltage to the gas valve,
and proofs the pilot flame.
The module contains a 60-second time delay circuit and a coil that activates the gas valve. The
ignitor assembly consists of a spark plug, a pilot, and a flame sensor element.
At start-up the power switch is placed in the "ON" position, supplying 12 VDC to the heat control
circuitry in the controller. Current is supplied to the other leg of the heat relay coil which then closes
an electronic switch in the 24 VAC circuit to provide current to the ignition module.
Circuitry in the ignition module sends 24 VAC current to the gas valve via a normally closed float
switch. Simultaneously, the module causes the ignitor to spark for up to 60 seconds to light the pilot
flame. A flame sensor verifies that the pilot is lit by measuring the flow of microamps through the
flame. If the pilot does not light (or is extinguished), current to the ignition module is interrupted,
preventing the main valve from opening, and the ignition module "locks out" until the power switch
is turned "OFF", then back "ON".