McQuay IM 685, Installation & Maintenance Manual

Page 1: ...Gas Fired Furnace on McQuay Applied Rooftop Systems HT A with RM7895A Flame Safeguard Installation Maintenance Manual IM 685 Group Applied Systems Part Number 629948Y 00 Date March 1998 1998 McQuay I...

Page 2: ...nty failure state the date of installation of the unit and the date of failure along with an explanation of the malfunctions and the description of the replacement parts required Parts are warranted f...

Page 3: ...ssembly and requires no additional chimney flue pipe Breidert cap draft inducer etc Factory Mounting This burner and gas train has been installed and wired at the factory See Gas Piping Also note that...

Page 4: ...the outside of the tube See Figure 1 Also apply a bead of high temperature silicone to seal both sides to the bottom of the flue box wrapper being careful not to obstruct the square drain holes in eac...

Page 5: ...e burner is shown in Table 5 under Column 13 thru 15 Gas piping must be sized to provide the minimum required pressure at the burner when the burner is operating at maximum input Consult the appropria...

Page 6: ...20 92 190 350 730 1100 2100 3300 5900 12000 30 73 152 285 590 890 1650 2700 4700 9700 40 63 130 245 500 760 1450 2300 4100 8300 50 56 115 215 440 670 1270 2000 3600 7400 60 50 105 195 400 610 1150 18...

Page 7: ...s to avoid interference with swinging of doors etc Through the Curb Piping Models 020 thru 140 1 Remove bottom access panel See Figure 3c 2 Remove knockout and make an opening through bottom deck dire...

Page 8: ...re only a connection to the supply gas line The manual shutoff valve is located within the burner vestibule If local codes require a manual shutoff valve that is accessible from outside the unit that...

Page 9: ...tc 2 Review the equipment and service literature and become familiar with the location and purpose of the burner controls Determine where the gas and power can be turned off at the unit and upstream o...

Page 10: ...electric gas valve in the line Open the gas line cocks upstream from there and bleed the gas line of all air Replace the 1 8 inch pipe plug 7 Leak check Using a rich soap water mixture and a brush ch...

Page 11: ...until after a period of main flame operation has further purged the gas lines before trying to adjust out something that may actually be caused by air in the lines Modulate Firing Rates Set the tempe...

Page 12: ...he flame safeguard FSG Upon a call for heat the control system will close OBA3 thus energizing relay R20 When 120 volt power is furnished through the system on off switch S1 through the burner on off...

Page 13: ...flame rod FD at the completion of the 10 second trial for ignition period terminal 10 ignition transformer IT will be de energized and terminal 9 relay coil R23 and main gas valves GV4 etc will be ene...

Page 14: ...history It can be mounted to the RM7895A and will retrieve information on the six most recent faults Consult the Honeywell bulletin 65 0090 1 7800 Series Keyboard Display Module and 65 0118 1 7800 Ser...

Page 15: ...e RM7895A which are energized to indicate operation as follows POWER The RM7895A is powered PILOT The prepurge period is complete and the terminal for the start combination gas control is powered FLAM...

Page 16: ...rly careful to correctly reinsert the air tube into the grommeted hole The tube should slip into the grommet so there is little leakage but it should not bear down on it or it can cause binding on the...

Page 17: ...ure is not an option the following discussion on the High Pressure Regulator would still apply High Pressure Regulator If a high pressure regulator is included as part of the burner gas train or is in...

Page 18: ...et that connects the air and gas valves must be correctly positioned on the control rod such that the bracket will be firmly held under tension against its stop when the actuator is in the minimum rat...

Page 19: ...of 2000 feet and higher the gas burner must be derated 4 for every 1000 feet of altitude Example Model HT080 at an altitude of 3000 feet is derated 0 04 x 3 0 12 At 1000 mbh input 1000 x 0 12 120 mbh...

Page 20: ...e adjusted to the flow rate used for this procedure is too high and must be reduced by repositioning the actuator to a lower firing rate or the gas supply line pressure is too low After adjusting valv...

Page 21: ...will be diluted with outside air and lower readings will result If flue gas temperature is to be measured this must be done in the flue box not in the tube The temperature gradient within the tubes w...

Page 22: ...bulator in each tube approximately flush with the tube end locking them in place with the wedge clips on each turbulator 8 Reinstall flue box front wrap Figure 14 Models 020 thru 025 Heat Exchanger Le...

Page 23: ...Rate 2 Control Failure The limit control does not function properly to shut off the burner when the heat exchanger temperature becomes excessive In most situations a properly controlled unit will nev...

Page 24: ...condensate However suitable steps should be taken to manage the flow of the condensate produced Most condensate will be produced in the secondary tubes where flue gas will sweep it into the flue box C...

Page 25: ...eyboard display module or a DC voltmeter Twice Yearly 1 Burner Air Check burner fan wheel for dirt build up and lint Check combustion air intake louver and flue box for dirt buildup and accumulation o...

Page 26: ...als 7 and L2 on the flame safeguard stays there the Keyboard when the burner fan is running Display Module indicates Purge Hold 2 2 Burner motor runs valve a Timer TD10 is not making after 20 seconds...

Page 27: ...ressure will build up on the downstream side thus exceeding the rating of the gas train components b Undersized piping can also cause problems by delivering reduced pressure during times of maximum de...

Page 28: ...64148A 04 040 Burner Gun Assembly 1 964148A 05 050 Burner Gun Assembly 1 964148A 06 064 065 Burner Gun Assembly 1 964148A 08 079 080 Burner Gun Assembly 1 964148A 10 100 Burner Gun Assembly 1 964148A...

Page 29: ...N n i M M F C x a M R T F g e D g n i r u D e g r u p e r P e t a R x a M r e n r u B g n i t a r e p O e t a R x a M g n i r u D e g r u p e r P e t a R x a M x a M e t a R n i M e t a R 5 e t o N 5...

Page 30: ...T t n e i b m A F g e D e r u t a r e p m e T s a G e u l F t n e c r e p 2 O C M P P O C C W n I x o B n i e r u s s e r P r i A Flue Gas Flue Gas s t n e m m o C y n a e z i r a m m u S k r o w e c...

Page 31: ...IM 685 Page 31 Notes...

Page 32: ...13600 Industrial Park Boulevard P O Box 1551 Minneapolis MN 55440 USA 612 553 5330...