6.
The low fire bypass and the Modulating Gas Valve are pre-set by the factory for a
minimum firing rate of 20 MBH. The flame signal at this firing rate should be
above 2 DC micro amps.
7.
Check the modulation tracking by modulating the burner to 4 Volts DC signal. The
manifold pressure should be approximately 0.8” to 0.9” W.C. If not, loosen the
7/16” nut on the Modulating Gas Valve Actuator and make necessary adjustment
with the green handle of the butterfly valve (see Figure 4). Retighten the nuts and
modulate the burner to low fire (2 Volts DC) and back up to 4 Volts DC again to check
the adjustments. If the manifold pressure is not as specified, repeat step 7 again.
8.
The damper should be flush with the low fire stop. The O
2
concentration of the flue
exhaust at the low fire rate should be approximately 10% +/-2. To adjust the O
2
level at
low fire (allow more air or reduce the air), vary the alignment between the damper and
the inlet ring. Minimum air shutter adjustment can be done by adjusting the three 8-18
screws on the inlet ring (see Figure 5). To increase or decrease the O
2
percentage
substantially loosen the air damper from the shaft and make necessary adjustment.
Check combustion readings to verify burner performance.
____________________________
Special equipment, either factory or contractor installed, may cause variation in the
procedures and descriptions given in this manual.
Consult the OEM's manual to identify the differences in the information.
____________________________
8
Part 2
Service Continued
Part 2 Service
XI
Special
Equipment
(OEM Versions)
X Start
Up
Continued
Midco
®
International Inc.
4140 West Victoria Street Chicago, Illinois 60646
1107
tel 773.604.8700 fax 773.604.4070 web www.midcointernational.com email [email protected]
8471 50
Printed in USA
Figure 4:
Valve Train Assembly
RE4400DS HTD
Figure 5:
Damper Location at High Fire Firing Rate - 250 MBH, 350 MBH and 400 MBH
RE4400DS HTD
