McQuay SuperMod IM-685-1 Installation And Maintenance Manual Download

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IM 685-1

Installation and Maintenance Manual

IM-685-1

Group:

Applied Systems

Part Number:

IM685

Date:

June 2001

SuperMod

Forced Draft Gas Fired Furnace

on McQuay Applied Rooftop Systems

HT***A* with RM7895A Flame Safeguard

Summary of Contents for SuperMod IM-685-1

Page 1: ...n and Maintenance Manual IM 685 1 Group Applied Systems Part Number IM685 Date June 2001 SuperModTM Forced Draft Gas Fired Furnace on McQuay Applied Rooftop Systems HT A with RM7895A Flame Safeguard 2001 McQuay International ...

Page 2: ...Air Gas Adjustments 14 Gas Supply Pressure 14 High Pressure Regulator 14 Gas Adjustment 14 Air Adjustment 14 Air and gas Control Linkage 14 Actuator Crankarm 15 Switch Adjustments 15 Altitude Considerations 15 Gas Valve Pressure Regulator Adjustment 16 Adjustment Procedure for Parallel Valves 16 Check Manifold Pressure at Minimum rate 16 Combustion Testing 17 Verify Input Rate 17 Check CO2 CO and ...

Page 3: ...ill void all warranty coverage by the manufacturer Questions regarding specific con taminants should be referred to your local gas utility If the burner was specified for operation at higher altitudes combustion air adjustments were compensated to result in proper settings at the higher altitude This checkout nor mally eliminates on the job start up problems however the equipment is subject to var...

Page 4: ... be run from the meter to the gas burner without reductions Undersized piping will result in inadequate pressure at the burner The pressure will be at its lowest when it is needed the most at times of maximum demand Therefore it can cause intermit tent hard to find problems because the problem may have left before the service technician has arrived Avoid the use of bushings wherever possible WARNI...

Page 5: ... by IRI for over 1000 MBH input units must always be routed to the outdoors This is field piping Table 1 Capacity of pipe natural gas CFH WITH PRESSURE DROP OF 3 W C SPECIFIC GRAVITY OF 0 60 PIPE LENGTH FT PIPE SIZE INCHES IPS 1 1 1 2 2 3 4 10 132 278 520 1050 1600 2050 4800 8500 17500 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 ...

Page 6: ...ors etc Through The Curb Piping Models 020 140 1 Remove bottom access panel 5 See Figure 3c 2 Remove knockout 4 and make an opening 6 through bottom deck directly below knockout hole 3 Route gas pipeline through these openings and seal them off with suitable grommets 7 See Figure 3a Section A A 4 Replace bottom access panel 5 Typical Piping Connections Figure 4 A Shutoff Cock ball valve B Union Fu...

Page 7: ... be routed up to the burner from within the curb on Models 150 through 200 Gas piping must be routed across the roof to under the burner vesti bule or a pitch pocket can be provided there The installer must cut a hole in the bottom panel of the overhanging burner vestibule through which to route the gas line up to the burner gas train The bottom panel of the vestibule is at approximately the same ...

Page 8: ...he burner is controlled for proven low fire start The actua tor will position the modulating gas valve and the modulat ing air valve to the low fire position each time the burner is to light off Switch LS1 proves the air and gas valves are at the low fire position If LSl is not made at light off the gas valves cannot open and the flame safeguard will lock out requiring manual reset Pilot is Main F...

Page 9: ...ble 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 dis turbed during shipment etc Flame Start up 1 Open the gas line cocks and position switch S3 to AUTO The flame safeguard will go through the 10 second Ini tiate period after which the burner motor will start The modulating air and gas...

Page 10: ...the unit through several start ups with the temperature controls calling for first minimum rates and finally maxi mum rates Be alert for any hints of trouble or unexplained inconsistencies that could indicate future problems Record Data 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...

Page 11: ...l go out on safety lockout After completion of the 60 second prepurge period there will be a 10 second trial for ignition during which terminal 8 combination gas valve GV1 and terminal 10 ignition transformer IT will be energized If flame is being detected through the flame rod FD at the completion of the 10 second trial for ignition period terminal 10 ignition transformer IT will be de energized ...

Page 12: ...r heat by the temperature control system Normal Start up Prepurge Upon a call for heat the prepurge period will begin If the air switch does not detect fan operation in the first 10 seconds into the prepurge period a recycle to the beginning of the prepurge will occur Ignition Trial The start combination gas control and the ignition transformer are powered for 10 seconds following the prepurge Fla...

Page 13: ...he grommet Flame Rod Adjustment The gun assembly is removed for flame rod inspection or service When correctly adjusted the flame rod insulator will be concentric with the hole it passes through not be shorted out against the disc the 0 75 inch long end tip will point toward the 0 086 inch diameter alignment hole and the end tip will clear the disc according to dimension C Figure 9 Figure 9 Flame ...

Page 14: ...as train Air Adjustments Airflow and the resultant combustion characteristics have been preset and tested at the factory and no further adjust ments should be required Airflow to the burner is deter mined by the characterized plate on the air valve outlet 1 and an adjustable plate 2 on Figure l0a The adjustable plate can increase or decrease airflow across the entire stroke of the valve If burner ...

Page 15: ...m out against the switch body When properly adjusted the lever can move an additional 0 02 inches as proven by slipping a feeler gauge between the switch lever and the collar when in the made position The collar on the control rod should be adjusted so the switch lever it is actuating will rest squarely on the outer surface of the collar but only 0 03 inches from the edge If the collar is located ...

Page 16: ...of the burner As the firing rate is increased the manifold pressure will be rela tively constant until the gas flow rate exceeds the capacity of that single valve and the manifold pressure starts to drop off The pressure adjustments should be made at the maximum gas flow rate just before the manifold pressure starts to drop off and the following should be considered a The manifold pressure does no...

Page 17: ...from inside one of the sec ondary tubes If the sample is taken from the flue box rather than the tube the sample 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 would cause high readings near the center of the tube and low readings near the edge Temp...

Page 18: ...O2 readings one with the supply fan running and one with the supply fan off If the CO2 increases with the supply fan off it could indicate leak age Note that CO2 samples must be taken from inside a tube not just from inside the flue box Checking for Leaks 1 Open up the rear casing panel while the unit is shut off and visually inspect the heat exchanger 2 Visually inspect the heat exchanger while t...

Page 19: ... the casing Furnace Condensation A furnace will produce condensation when the flue gas tem perature falls below its dew point temperature A more effi cient furnace will transfer more of its heat into the building and leave less heat in the flue gas This results in a lower flue gas temperature and more condensate A modulating burner will produce more condensate than an on off burner As the firing r...

Page 20: ...l screw hole is located 2 75 inches below the bottom of the inspection cover with the exception that several models are drilled at 3 15 inches below the inspection cover to avoid the no drill zone Install the Cover Channel Over Drain Pipe 1 Locate the copper channel 5 over the drain line The top of the channel should be approximately 75 inches below the bottom of the inspection cover and extend ap...

Page 21: ...stion chamber cleaning as required Keep burner vestibule clean Dirt and debris can result in burner air blockages Yearly 1 Gas Train Check all valves piping and connections for leakage Remove burner gun assembly Inspect and if required clean the flame rod ignition electrode main burner disc and blast tube Check tightness of linkage fas teners and bolts that could work loose from vibration and move...

Page 22: ... after 10 seconds and pressing the safety reset button has no effect replace the RM7895A BURNER MOTOR RUNS BUT 2 1 Burner motor runs valve actuator travels to the maxi mum rate position and stays there the Keyboard Display Module indicates Purge Hold a Switch LS2 is not being actuated by the collar on the control rod when at the maximum rate position b The air proving switch AS is not sensing burn...

Page 23: ...t for which the gas train is designed can also cause problems Line pres sure should not exceed 13 9 W C psi into the combination gas controls Pressures higher than this require an additional stepdown regulator to maintain the pressure below 13 9 W C even at no flow conditions The preferred pressure to the combination gas controls is 7 0 in W C A regulator that does not shut off tight at no flow wi...

Page 24: ...ly 1 0964148 04 040 Burner Gun Assembly 1 0964148 05 050 Burner Gun Assembly 1 0964148 06 064 065 Burner Gun Assembly 1 0964148 08 079 080 Burner Gun Assembly 1 0964148 10 100 Burner Gun Assembly 1 0964148 1 1 110 Burner Gun Assembly 1 0964148 12 140 Burner Gun Assembly 1 0964148 13 150 Burner Gun Assembly 1 0964148 14 200 Burner Gun Assembly 1 0373788 02 020 040 Blast Tube Assembly 4 00 x 20 1 03...

Page 25: ...1 25 1 25 HT 100 1250 62 5 15 000 61 1 63 2 09 4 60 3 20 3 72 6 5 7 5 1 25 1 25 1 25 HT 110 1375 68 8 10 100 100 2 50 2 60 4 45 2 90 3 50 5 0 7 8 1 50 1 25 1 25 HT 140 1750 87 5 21 000 61 2 25 2 45 4 45 2 80 3 30 5 0 7 8 1 50 1 25 1 25 HT 150 1875 93 8 13 700 100 2 32 2 50 4 50 3 10 3 60 5 0 8 4 1 50 1 25 1 25 HT 200 2500 125 0 30 000 61 2 60 3 65 4 90 3 70 4 10 6 0 11 2 2 00 1 50 1 25 Notes 1 Pre...

Page 26: ...s Manifold Pressure In W C 12 Gas Line Pressure In W C 13 Flame Signal DC Volts 14 Ambient Temperature Deg F 15 Flue Gas Temperature Deg F 16 Flue Gas CO 2 percent 17 Flue Gas CO PPM 18 Air Pressure in Box In W C 19 Min Rate Scale 5 Gas Manifold Pressure In W C 20 Gas Line Pressure In W C 21 Flame Signal DC Volts 22 Ambient Temperature Deg F 23 Flue Gas Temperature Deg F 24 Flue Gas CO 2 percent 2...

Page 27: ...IM 685 1 27 Notes ...

Page 28: ...28 IM 685 1 13600 Industrial Park Boulevard P O Box 1551 Minneapolis MN 55440 USA 612 553 5330 ...

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