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Related Manuals for McQuay IM 685
Summary of Contents for McQuay IM 685
- Page 1 Installation & Maintenance Manual IM 685 Group: Applied Systems Part Number: 629948Y-00 Date: March 1998 SuperMod Forced Draft Gas Fired Furnace on McQuay Applied Rooftop Systems HT****A* with RM7895A Flame Safeguard (Gas Burner) ® ©1998 McQuay International...
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Page 2: Table Of Contents
When writing to McQuay for service or replacement parts, refer to the model number of the unit as stamped on the serial plate, attached to the unit. If there is an in-warranty 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. -
Page 3: General
General This forced draft gas burner is specifically designed for use with the furnace on McQuay applied rooftop heating and air conditioning units which are for outdoor installation only. Each model size has unique burner head components to tailor the shape of the flame to each particular stainless steel combustion chamber, to match the capacity requirement, and to offer a 20 to 1 turndown ratio. -
Page 4: Flue Box
Use inner hinge screws on top hinged door (see Figure 2). Side hinged doors have holes for mounting (see Figure 5). Models 020 and 025 have a different style wind deflector. It mounts on the door and has a top opening flush with the roof of the unit (see Figure 14). Page 4 / IM 685... -
Page 5: Electrical
√ Electrical The McQuay burner receives its electrical power from the main unit control panel. No additional power wiring must be routed to the burner. The sequencing of the burner is also controlled through this panel and therefore is factory wired. No additional wiring will be required. Note that models 150 through 200 furnaces require reassembly of some electrical connections as the burner is removed for shipment. -
Page 6: Valve And Regulator Venting
0.60 1.000 0.70 0.936 0.80 0.867 0.90 0.816 1.00 0.775 Table 3. Pressure Drop Other than 0.3" PRESSURE PRESSURE MULTIPLIER MULTIPLIER DROP DROP 0.577 1.83 0.815 2.58 1.000 3.16 1.16 3.65 1.42 4.47 1.64 5.15 Page 6 / IM 685... -
Page 7: Gas Piping Routing Into Unit
A = Shutoff Cock. ball valve B = Union – Furnished. C = Gas Pipe – Routed in through front. D = Gas Pipe – Routed in through curb. E = Factory Piped Gas Trains. IM 685 / Page 7... -
Page 8: Gas Piping (Models 150-200)
At installation the burner must be re-mounted, the tagged electrical connections re-attached, and the vestibule re-assembled and mounted as shown in Figure 5. These items are packed in a crate and shipped as a separate item. Figure 5. Page 8 / IM 685... -
Page 9: Start-Up & Operating Procedures Start-Up Responsibility
Only qualified personnel should perform the start-up and service of this equipment. It is highly recommended that the initial start-up and future service be performed by McQuay certified technicians who are familiar with the hazards of working on live equipment. A representative of the owner or the operator of the equipment should be present during start-up to receive instructions in the operation, care and adjustment of the unit. -
Page 10: Set Control System To Enable Heating
Table 5, Column 6. Any appreciable deviation from these values would indicate a burner air problem that should be found before attempting to fire the burner. These problems could include linkages disturbed during shipment, etc. Page 10 / IM 685... -
Page 11: Flame Start-Up
After the gas burner has been successfully started up, checked out and is operating correctly, readings should be taken and recorded for future reference (see Table 6). If problems develop in the future, variations in these readings will indicate what has changed and where to start looking for problems. IM 685 / Page 11... -
Page 12: References
(LP5) and the optional manual reset high gas pressure switch (HP5), terminal 6 on the flame safeguard (FSG) is powered. The flame safeguard will go through a 10 second initiation period before the prepurge period will begin. Page 12 / IM 685... -
Page 13: Typical Piping Schematic
If the unit overheats, the combination fan–high limit control (FLC) will cycle the burner limiting furnace temperature to the limit control set point. Figure 6b. Typical Piping Schematic IM 685 / Page 13... -
Page 14: Typical Burner Control Box
Ignition Trial: The "start" combination gas control and the ignition transformer are powered for 10 seconds following the prepurge. Flame must be proven at the end of that 10 second period or safety shutdown will occur. Page 14 / IM 685... -
Page 15: Led Display
SWITCH ANNUNCIATOR CAPTIVE MOUNTING SEQUENCE SCREW STATUS PLUG-IN PURGE CARD SELECTABLE MESSAGE OR PREEMPTIVE MESSAGE KEYBOARD DISPLAY MODULE SEQUENCE RELAY STATUS MODULE LEDs FLAME RESET AMPLIFIER PUSH BUTTON FLAME FLAME SIMULATOR CURRENT INPUT TEST JACKS IM 685 / Page 15... -
Page 16: Service General
"Sequence of Operation" to get an overview. Gun Assembly The McQuay gas burner gun assembly is easily removable and includes the ignition electrode assembly, the flame rod assembly, and a "Base Air" fitting with orifice. The positioning of this assembly is not considered field adjustable. -
Page 17: Flame Rod Installation
If burner airflow is in question, measure the static pressure at Ports (4) and (5), Figure 16, and compare those readings with Columns 6 and 8 in Table 5. A significant difference should be checked out. IM 685 / Page 17... -
Page 18: Air And Gas Control Linkage
Return the actuator to the minimum rate position. The adjustable plate (2), Figure 10a is positioned to provide an opening per dimension "F". Figure 10. Air and Gas Control Linkage Figure 10a. Figure 10b. Page 18 / IM 685... -
Page 19: Actuator Crankarm
Clockwise rotation of the pressure adjusting screw on the combination gas controls will increase the pressure set point, and counter-clockwise rotation will reduce the pressure set point (see Figure 11). Figure 11. Combination Gas Controls IM 685 / Page 19... -
Page 20: Adjustment Procedure For Parallel Valves
After making this type of adjustment it is necessary to recheck the maximum firing rate manifold pressure and perhaps readjust it, making very small but equal adjuster movements on each valve. Page 20 / IM 685... -
Page 21: Combustion Testing
3. Clean each tube with a 2 ⁄ " round flue brush. 4. Remove the brushings and if required clean the combustion chamber and header through the rear inspection door port. IM 685 / Page 21... -
Page 22: Cleaning Heat Exchanger (Models 020-025)
During the time the furnace is on and the supply fan is off the leakage would be out off the furnace and then when the supply fan came on it would blow those products of combustion into the supply duct. Page 22 / IM 685... -
Page 23: Checking For Leaks
2. The burner is mounted on and supported by the heat exchanger studs with four nuts. When removing the heat exchanger, the burner must either be removed or blocked in place. Remove the four burner mounting nuts and the two exchanger bolts located 2" above the upper burner mounting nuts. IM 685 / Page 23... -
Page 24: Furnace Condensation
Instead, the condensate is to run down the drip shield and drip off its bottom edge, away from the rear casing door. Figure 15. Rear cleanout port (models 032 thru 200) Page 24 / IM 685... -
Page 25: Combination Fan And Limit Control
Re-oil each bearing with 150 drops (approximately 1 teaspoon) SAE-20 oil. 5. If the burner is to be out of service for the summer, turn off the burner control switch and close the manual gas cocks. IM 685 / Page 25... -
Page 26: Troubleshooting Guide
Verify that the contacts that control firing rate are calling for an increase rate. out but the burner remains b. Verify that Relay R23 is functioning properly. at the minimum rate. Page 26 / IM 685... - Page 27 Purge card missing or bad, terminals are energized that should not be at that stage, or there is an internal system is powered it locks out and fault. Replace purge card or RM7895A as indicated. the ALARM LED comes on. IM 685 / Page 27...
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Page 28: Typical Parts List - 60 Hz
020 – 200 Combination Gas Control 598613A-01 020 – 200 Control Rod, Sliding Bushing 594700A-01 020 – 200 Shoulder Screw 598621A-10 020 – 200 Crank Arm Extension 964149A-01 020 – 200 Air Damper Flex Link Page 28 / IM 685... -
Page 29: Capacities & Adjustments Table
Capacities & Adjustments IM 685 / Page 29... -
Page 30: Performance & Service History
Performance & Service History Table 6. Page 30 / IM 685... - Page 31 Notes IM 685 / Page 31...
- Page 32 ® 13600 Industrial Park Boulevard, P.O. Box 1551, Minneapolis, MN 55440 USA (612) 553-5330...
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