Lennox G61MP User Manual

G61MP

Service Literature

Corp. 0308−L6

Revised 10−2004

G61MP SERIES UNITS

G61MP series units are high−efficiency multi−position (upflow, downflow, horizontal right and left) gas furnaces manufactured with Lennox Duralok Plust heat exchangers formed of aluminized steel. G61MP units are available in heating capacities of 44,000 to 132,000 Btuh (13.0.0 to 38.6 kW) and cooling applications from 2 to 5 tons (7.0 kW to 17.5 kW)) up to 5 tons. Refer to Engineering Handbook for proper sizing.

Units are factory equipped for use with natural gas. Kits are available for conversion to LPG operation. G61MP model units are equipped with the Two−Stage Integrated SureLight control. All G61MP units meet the California Nitrogen Oxides (NOx) Standards and California Seasonal Efficiency requirements. All units use a redundant gas valve to assure safety shut−off as required by C.S.A.

All specifications in this manual are subject to change. Procedures outlined in this manual are presented as a recommendation only and do not supersede or replace local or state codes. In the absence of local or state codes, the guidelines and procedures outlined in this manual (except where noted) are recommendations only and do not constitute code.

TABLE OF CONTENTS

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Blower Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Parts Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

I Unit Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

II Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

III Start Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

IV Heating System Service Checks . . . . . . . . . . . . . . 31

V Typical Operating Characteristics . . . . . . . . . . . . . . 34

VI Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

VII Wiring and Sequence of Operation . . . . . . . . . . . . 38

VIII Field Wiring and Jumper Setting . . . . . . . . . . . . . 46

IX Control Board Troubleshooting . . . . . . . . . . . . . . . . 48

IMPORTANT

Improper installation, adjustment, alteration, service or maintenance can cause property damage, personal injury or loss of life. Installation and service must be performed by a qualified installer, service agency or the gas supplier.

WARNING

Electric shock hazard. Can cause injury or death. Before attempting to perform any service or maintenance, turn the electrical power to unit OFF at disconnect switch(es). Unit may have multiple power supplies.

WARNING

Sharp edges.

Be careful when servicing unit to avoid sharp edges which may result in personal injury.

Page 1

♥ 2003 Lennox Industries Inc.

SPECIFICATIONS

	Gas		Model No.	G61MP−36B−045	G61MP−36B−070	G61MP−48C−090	G61MP−60C−090
	Heating	High	Input − Btuh (kW)	44,000 (12.9)	66,000 (19.3)	88,000 (25.8)	88,000 (25.8)
	Performance
		Fire	Output − Btuh (kW)	41,000 (12.0)	62,000 (18.2)	83,000 (24.3)	84,000 (24.6)
		Temperature rise range − _F (_C)		25 − 55 (14 − 31)	35 − 65 (21 − 39)	35 − 65 (21 − 39)	25 − 55 (14 − 31)
		Low	Input − Btuh (kW)	30,000 (8.8)	45,000 (13.2)	60,000 (17.6)	60,000 (17.6)
		Fire	Output − Btuh (kW)	28,000 (8.2)	43,000 (12.6)	57,000 (16.7)	58,000 (17.0)
		Temperature rise range − _F (_C)		10 − 40 (6 − 24)	20 − 50 (12 − 30)	25 − 55 (14 − 31)	15 − 45 (9 − 27)
			1 AFUE	94.1%	94.1%	94.1%	94.1%
			California Seasonal Efficiency	83.5%	86.0%	87.3%	84.4%
		High static (CSA) − in. w.g. (Pa)		0.5	0.5	0.5	0.5
	Connections		2 Intake Pipe (PVC)	2	2	2	2
	in.		2 Exhaust Pipe (PVC)	2	2	2	2
		Condensate Drain Trap (PVC pipe) −		1/2	1/2	1/2	1/2
			i.d.
		with field supplied (PVC coupling) − o.d.		3/4	3/4	3/4	3/4
		hose with hose clamp − i.d. x o.d.		1−1/4 x 1	1−1/4 x 1	1−1/4 x 1	1−1/4 x 1
			Gas pipe size IPS	1/2	1/2	1/2	1/2
	Indoor	Wheel nominal diameter x width − in.		10 x 8 (254 x 203)	10 x 8 (254 x 203)	10 x 10 (254 x 254)	11−1/2 x 10 (292 x 229)
	Blower		(mm)
			Motor output − hp (W)	1/3 (249)	1/3 (249)	1/2 (373)	1 (746)
			Tons (kW) of add-on cooling	2.5 − 3 (8.8 − 10.5)	2.5 − 3.5 (8.8 − 12.3)	3 − 4 (10.5 − 14.0)	4 − 5 (14.0 − 17.5)
	Shipping Data		lbs. (kg) − 1 package	136 (62)	146 (66)	168 (76)	176 (80)
	Electrical characteristics			120 volts − 60 hertz − 1 phase (less than 12 amps)

OPTIONAL ACCESSORIES − MUST BE ORDERED EXTRA

	3 Air Filter and Rack Kit		Horizontal (end)	87L96 − 18 x 25 x 1 in.			87L97 − 20 x 25 x 1 in.
	Size of filter			(457 x 635 x 25 mm)			(508 x 635 x 25 mm)
			Side Return	Single 44J22 or Ten Pack 66K63 − (1) 16 x 25 x 1 in. (406 x 635 x 25 mm)
	Condensate Drain Heat		6 ft. (1.8 m)	26K68		26K68	26K68	26K68
	Cable		24 ft. (7.3 m)	26K69		26K69	26K69	26K69
			50 ft. (15.2 m)	26K70		26K70	26K70	26K70
	Heat Cable Tape Fiberglass − 1/2 in. (38 mm) x 66 ft. (20 m)			39G04		39G04	39G04	39G04
		Aluminum foil − 2 in. (25 mm) x 60 ft. (18		39G03		39G03	39G03	39G03
			m)
	EZ Filter Base	Catalog Number − Ship. Weight − lbs.		73P56 − 7 (3)		73P56 − 7 (3)	73P57 − 8 (4)	73P57 − 8 (4)
			(kg)
		Dimensions − H x W x D − in. (mm)		4 x 17−5/8 x 28−5/8		4 x 17−5/8 x 28−5/8	4 x 21−5/8 x 28−5/8	4 x 21−5/8 x 28−5/8
				(102 x 448 x 727)		(102 x 448 x 727)	(102 x 549 x 727)	(102 x 549 x 727)
		Size of field provided filter − in. (mm)		16 x 25 x 1		16 x 25 x 1	20 x 25 x 1	20 x 25 x 1
				(406 x 635 x 25)		(406 x 635 x 25)	(508 x 635 x 25)	(508 x 635 x 25)
	Down−Flow Additive Base			11M60		11M60	11M61	11M61
	4 High Altitude Orifice Kit − Natural Gas			59M16		59M16	59M16	59M16
	4 High Altitude Pressure Switch Kit − Order two each			− − −		56M06	− − −	− − −
			7501−10,000ft. (2286−3048m
	Horizontal Support Frame Kit − Ship. Weight − lbs. (kg)			56J18 − 18 (8)		56J18 − 18 (8)	56J18 − 18 (8)	56J18 − 18 (8)
	LPG/Propane Kit		0−7500 ft. (0−2286 m)	59M13		59M13	59M13	59M13
			7501−10,000 ft. (2286−3048 m)	59M14		59M14	59M14	59M14
	Natural to LPG/Propane Kit			59M87		59M87	59M87	59M87
	RAB Return Air Base			− − −		− − −	− − −	RAB60C (12M71)
	5 Termination Kits Concen-		1−1/2 inch (38 mm)	60G77		60G77	− − −	− − −
	Direct Vent	tric	2 inch (51 mm)	− − −		− − −	33K97	33K97
	Applications Only
			3 inch (76 mm)	− − −		− − −	60L46	60L46
		Wall	Close Couple − 2 inch (51 mm)	22G44		22G44	− − −	− − −
			3 inch (76 mm)	44J40		44J40	44J40	44J40
		Close Couple WTK − 2 inch (51 mm)		30G28		30G28	− − −	− − −
	5,6 Termination Kits	Roof	2 inch (51 mm)	15F75		15F75	15F75	15F75
	Direct Vent or		3 inch (76 mm)	44J41		44J41	44J41	44J41
	Non−Direct Vent
		Wall	Wall Ring Kit 2 inch (51 mm)	15F74		15F74	15F74	15F74
NOTE − Filters and provisions for mounting are not furnished and must be field provided.
1	Annual Fuel Utilization Efficiency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized furnaces.
2	Determine from venting tables proper exhaust pipe size and termination kit required.
3	Cleanable polyurethane frame type filter.
4	Required for proper operation at altitudes from 7501 to 10,000 ft. (2286 to 3048 m).
5	See Installation Instructions for specific venting information.
6	Kits contain enough parts for two, non−direct vent installations.

Page 2

SPECIFICATIONS

	Gas		Model No.	G61MP−48C−110	G61MP−60C−110	G61MP−60D−135
	Heating	High Fire	Input − Btuh (kW)	110,000 (32.2)	110,000 (32.2)	132,000 (38.7)
	Performance
			Output − Btuh (kW)	104,000 (30.5)	104,000 (30.5)	124,000 (36.3)
		Temperature rise range − _F (_C)		45 − 75 (25 − 42)	35 − 65 (21 − 39)	40 − 70 (24 − 42)
		Low Fire	Input − Btuh (kW)	75,000 (22.0)	75,000 (22.0)	90,000 (26.4)
			Output − Btuh (kW)	72,000 (21.1)	72,000 (21.1)	86,000 (25.2)
		Temperature rise range − _F (_C)		30 − 60 (18 − 36)	25 − 55 (14 − 31)	30 − 60 (18 − 36)
			1 AFUE	94.1%	94.1%	94.1%
			California Seasonal Efficiency	88.4%	87.0%	87.7%
		High static (CSA) − in. w.g. (Pa)		0.5	0.5	0.5
	Connections		2 Intake Pipe (PVC)	2	2	3
	in.		2 Exhaust Pipe (PVC)	2	2	3
		Condensate Drain Trap (PVC pipe) − i.d.		1/2	1/2	1/2
		with field supplied (PVC coupling) − o.d.		3/4	3/4	3/4
		hose with hose clamp − i.d. x o.d.		1−1/4 x 1	1−1/4 x 1	1−1/4 x 1
			Gas pipe size IPS	1/2	1/2	1/2
	Indoor	Wheel nominal diameter x width − in. (mm)		10 x 10 (254 x 254)	11−1/2 x 10 (292 x 229)	11−1/2 x 10 (292 x 229)
	Blower		Motor output − hp (W)	1/2 (373)	1 (746)	1 (746)
			Tons (kW) of add-on cooling	3 − 4 (10.5 − 14.0)	4 − 5 (14.0 − 17.5)	4 − 5 (14.0 − 17.5)
	Shipping Data		lbs. (kg) − 1 package	178 (81)	186 (84)	206 (93)
	Electrical characteristics			120 volts − 60 hertz − 1 phase (less than 12 amps)

OPTIONAL ACCESSORIES − MUST BE ORDERED EXTRA

		3, 4 Air Filter and Rack Kit −		Horizontal (end)	87L97 − 20 x 25 x 1 in. (508 x 635 x 25 mm)		87L98 − 25 x 25 x 1 in.
		Size of filter					(635 x 635 x 25 mm)
				Side Return	5 Single 44J22 or Ten Pack (66K63) − (1) 16 x 25 x 1 in. (406 x 635 x 25 mm)
		Condensate Drain Heat		6 ft. (1.8 m)	26K68	26K68	26K68
		Cable		24 ft. (7.3 m)	26K69	26K69	26K69
				50 ft. (15.2 m)	26K70	26K70	26K70
		Heat Cable Tape	Fiberglass − 1/2 in. (38 mm) x 66 ft. (20 m)		39G04	39G04	39G04
			Aluminum foil − 2 in. (25 mm) x 60 ft. (18 m)		39G03	39G03	39G03
		4 EZ Filter Base	Catalog Number − Shipping Weight		73P57 − 8 lbs. (4 kg)	73P58 − 10 lbs. (5 kg)	73P58 − 10 lbs. (5 kg)
			Dimensions − H x W x D − in. (mm)		4 x 21−5/8 x 28−5/8	4 x 24−5/8 x 28−5/8	4 x 24−5/8 x 28−5/8
					(102 x 549 x 727)	(102 x 625 x 727)	(102 x 625 x 727)
			Size of field provided filter − in. (mm)		20 x 25 x 1	24 x 24 x 1	24 x 24 x 1
					(508 x 635 x 25)	(610 x 610 x 25)	(610 x 610 x 25)
		Down−Flow Additive Base			11M61	11M61	11M62
		5 High Altitude Orifice Kit − Natural Gas Only			59M16	59M16	59M16
		6 High Altitude Pressure Switch Kit − Order two each			− − −	− − −	56M93
				4501−10,000 ft. (1372−3048 m)
		Horizontal Support Frame Kit − Ship. Weight − lbs. (kg)			56J18 − 18 (8)	56J18 − 18 (8)	56J18 − 18 (8)
		LPG/Propane Kit		0−7500 ft. (0−2286 m)	59M13	59M13	59M13
				7501−10,000ft. (2286−3048m)	59M14	59M14	59M14
		Natural to LPG/Propane Kit			59M87	59M87	59M87
		RAB Return Air Base			− − − −	RAB60C (12M71)	RAB60D (12M72)
	7 Termination Kits −		Concentric	2 inch (51 mm)	33K97	33K97	− − −
	Direct Vent		Roof/Wall	3 inch (76 mm)	60L46	60L46	60L46
	Applications
			Wall Close−Coupled 3 inch (76 mm)		44J40	44J40	44J40
	7,8 Termination Kits		Roof	2 inch (51 mm)	15F75	15F75	− − −
	Direct Vent or Non−			3 inch (76 mm)	44J41	44J41	44J41
	Direct Vent
			Wall	Ring Kit 2 inch (51 mm)	15F74	15F74	9 15F74
	NOTE − Filters and provisions for mounting are not furnished and must be field provided.
	1	Annual Fuel Utilization Efficiency based on DOE test procedures and according to FTC labeling regulations. Isolated combustion system rating for non-weatherized furnaces.
	2	Determine from venting tables proper exhaust pipe size and termination kit required.
	3	Cleanable polyurethane frame type filter.

4Not for use with RAB Return Air Base or with 60C and 60D size units with air flow requirements of 1800 cfm (850 L/s) or greater. See Blower Performance tables for additional information.

5	Required for proper operation at altitudes from 7501 to 10,000 ft. (2286 to 3048 m).
6	Required for proper operation at altitudes over 4500 ft. (1370 m).
7	See Installation Instructions for specific venting information.
8	Kits contain enough parts for two, non−direct vent installations.
9	Non−direct vent applications only.

Page 3

BLOWER DATA

G61MP−36B−045 PERFORMANCE (Less Filter)

External Static					Air Volume / Watts at Different Blower Speeds
Pressure			High			Medium−High			Medium−Low			Low
in. w.g.	Pa	cfm	L/s	Watts	cfm	L/s	Watts	cfm	L/s	Watts	cfm	L/s	Watts
0.00	25	1555	735	630	1410	665	585	1190	560	520	1030	485	435
0.10	25	1515	715	605	1385	655	555	1190	560	485	1020	480	415
0.20	50	1470	695	580	1345	635	520	1170	550	455	1010	475	400
0.30	75	1410	665	555	1310	620	495	1155	545	440	1000	470	385
0.40	100	1350	640	535	1250	590	465	1120	530	410	980	465	360
0.50	125	1290	610	505	1205	570	450	1080	510	390	950	450	345
0.60	150	1220	575	485	1145	540	420	1020	480	365	905	430	320
0.70	175	1145	540	460	1080	510	400	975	460	345	860	405	300
0.80	200	1050	495	425	985	465	365	870	410	320	785	370	285
0.90	225	945	445	410	900	425	345	825	390	305	730	345	270
NOTES −	All air data is measured external to unit without filter (not furnished − field provided).
	Air volume based on bottom air return air. Actual air volume may vary on side return air applications.

G61MP−36B−070 PERFORMANCE (Less Filter)

External Static					Air Volume / Watts at Different Blower Speeds
Pressure			High			Medium−High			Medium−Low			Low
in. w.g.	Pa	cfm	L/s	Watts	cfm	L/s	Watts	cfm	L/s	Watts	cfm	L/s	Watts
0.00	0	1640	775	660	1415	665	575	1160	545	485	1005	475	410
0.10	25	1600	755	635	1395	660	550	1160	545	460	1000	470	385
0.20	50	1540	725	605	1370	650	525	1160	545	445	995	470	375
0.30	75	1495	705	580	1345	635	505	1145	540	425	990	465	365
0.40	100	1420	670	545	1275	605	480	1125	530	395	965	455	345
0.50	125	1360	640	525	1245	590	450	1080	510	375	945	445	325
0.60	150	1275	600	490	1165	550	410	1025	485	350	900	425	305
0.70	175	1170	555	465	1085	515	385	965	430	335	860	405	295
0.80	200	1080	510	440	1010	475	360	865	410	310	775	365	270
0.90	225	945	445	400	840	395	320	765	360	275	710	335	245
NOTES −	All air data is measured external to unit without filter (not furnished − field provided).
	Air volume based on bottom air return air. Actual air volume may vary on side return air applications.

G61MP−48C−090 PERFORMANCE (Less Filter)

External Static						Air Volume / Watts at Different Blower Speeds
Pressure			High				Medium−High			Medium−Low			Low
in. w.g.	Pa	cfm	L/s	Watts		cfm	L/s	Watts	cfm	L/s	Watts	cfm	L/s	Watts
0.00	0	2180	1030	930		1835	865	790	1520	715	630	1280	605	510
0.10	25	2135	1005	885		1825	860	750	1510	710	610	1275	600	495
0.20	50	2085	985	840		1810	855	720	1505	710	580	1270	600	475
0.30	75	2030	955	800		1775	835	685	1500	705	565	1265	595	460
0.40	100	1940	915	760		1735	820	650	1480	700	535	1250	590	440
0.50	125	1865	880	725		1660	785	600	1430	675	505	1215	575	425
0.60	150	1740	820	670		1590	750	575	1380	650	475	1175	555	410
0.70	175	1645	775	640		1475	695	520	1290	610	450	1105	520	375
0.80	200	1540	725	600		1340	630	465	1175	555	405	1020	480	355
0.90	225	1335	630	540		1170	555	440	1070	505	375	950	450	330
NOTES −	All air data is measured external to unit without filter (not furnished − field provided).
	Air volume based on bottom air return air. Actual air volume may vary on side return air applications.
G61MP−48C−110 PERFORMANCE (Less Filter)
External Static						Air Volume / Watts at Different Blower Speeds
Pressure			High				Medium−High			Medium−Low			Low
in. w.g.	Pa	cfm	L/s	Watts		cfm	L/s	Watts	cfm	L/s	Watts	cfm	L/s	Watts
0.00	0	2160	1020	880		1880	890	755	1490	705	602	1235	580	485
0.10	25	2100	990	850		1855	875	730	1480	700	585	1230	580	475
0.20	50	2035	960	805		1815	860	690	1475	695	560	1225	580	460
0.30	75	1965	925	750		1755	830	650	1475	695	545	1220	575	445
0.40	100	1885	890	725		1715	810	625	1465	690	510	1215	575	430
0.50	125	1780	840	680		1630	770	580	1420	670	490	1150	540	400
0.60	150	1690	800	660		1550	735	550	1360	640	460	1110	525	380
0.70	175	1575	745	620		1410	665	505	1210	570	405	1035	490	350
0.80	200	1375	650	550		1230	580	450	1125	530	380	970	460	325
0.90	225	1225	580	520		1120	530	415	1050	495	365	885	420	310
NOTES −	All air data is measured external to unit without filter (not furnished − field provided).
	Air volume based on bottom air return air. Actual air volume may vary on side return air applications.

Page 4

BLOWER DATA

G61MP−60C−090 PERFORMANCE (Less Filter) − Single Side Return Air − Air volumes in bold require field fabricated transition to accommodate 20 x 25 x 1 in. (508 x 635 x 25 mm) air filter in order to maintain proper air velocity.

External Static					Air Volume / Watts at Different Blower Speeds
Pressure			High			Medium−High			Medium−Low			Low
in. w.g.	Pa	cfm	L/s	Watts	cfm	L/s	Watts	cfm	L/s	Watts	cfm	L/s	Watts
0.00	0	2835	1335	1495	2340	1105	1155	1800	850	895	1440	680	695
0.10	25	2785	1315	1475	2345	1105	1135	1805	855	865	1515	715	690
0.20	50	2715	1280	1435	2275	1075	1080	1825	860	845	1560	735	685
0.30	75	2620	1235	1380	2260	1065	1035	1840	870	825	1600	755	680
0.40	100		1205	1350		1055	1015		870	815		765	670
		2550			2230			1845			1620
0.50	125	2450	1155	1305	2175	1025	990	1850	870	790	1615	765	655
0.60	150	2365	1115	1270	2130	1005	940	1830	865	775	1615	760	640
0.70	175	2240	1060	1205	2070	975	915	1815	855	760	1595	755	620
0.80	200	2185	1030	1190	1965	925	865	1775	840	745	1555	735	605
0.90	225	2015	950	1150	1820	860	820	1690	800	715	1440	680	580
NOTES −	All air data is measured external to unit without filter (not furnished − field provided).

G61MP−60C−090 PERFORMANCE (Less Filter) − Bottom Return Air, Side Return Air with Optional RAB Return Air Base, Return Air from Both Sides or Return Air from Bottom and One Side.

External Static					Air Volume / Watts at Different Blower Speeds
Pressure			High			Medium−High			Medium−Low			Low
in. w.g.	Pa	cfm	L/s	Watts	cfm	L/s	Watts	cfm	L/s	Watts	cfm	L/s	Watts
0.00	0	2840	1340	1450	2345	1105	1105	1895	895	900	1515	715	700
0.10	25		1305	1415		1115	1080		920	885		745	700
		2765			2365			1950			1580
0.20	50	2695	1270	1385	2345	1105	1050	1985	935	870	1620	765	695
0.30	75	2605	1230	1335	2315	1090	1030	1990	940	850	1645	775	690
0.40	100	2530	1195	1300	2265	1070	990	1990	940	825	1665	785	675
0.50	125	2420	1140	1260	2210	1045	955	1970	930	800	1675	790	665
0.60	150	2330	1100	1220	2145	1010	925	1930	910	775	1665	785	650
0.70	175	2250	1060	1190	2050	965	885	1875	885	745	1645	775	630
0.80	200	2135	1010	1140	2000	945	865	1810	855	715	1620	765	615
0.90	225	2030	960	1090	1885	890	830	1720	810	685	1560	735	590
NOTES −	All air data is measured external to unit without filter (not furnished − field provided).

G61MP−60C−110 PERFORMANCE (Less Filter) − Single Side Return Air − Air volumes in bold require field fabricated transition to accommodate 20 x 25 x 1 in. (508 x 635 x 25 mm) air filter in order to maintain proper air velocity.

External Static					Air Volume / Watts at Different Blower Speeds
Pressure			High			Medium−High			Medium−Low			Low
in. w.g.	Pa	cfm	L/s	Watts	cfm	L/s	Watts	cfm	L/s	Watts	cfm	L/s	Watts
0.00	0	2625	1240	1350	2310	1090	1080	1885	890	885	1515	715	700
0.10	25	2570	1215	1330	2325	1095	1060	1910	900	865	1575	745	700
0.20	50	2410	1135	1305	2285	1080	1035	1930	910	845	1620	765	690
0.30	75	2425	1145	1265	2230	1055	990	1925	905	825	1635	770	675
0.40	100	2335	1100	1220	2175	1025	950	1910	900	810	1640	775	660
0.50	125	2270	1070	1195	2120	1000	935	1895	895	785	1640	775	640
0.60	150	2170	1025	1155	2045	965	885	1860	875	765	1630	770	630
0.70	175	2110	995	1130	1950	920	855	1795	845	730	1590	750	610
0.80	200	2035	960	1090	1885	890	820	1745	825	705	1540	725	580
0.90	225	1900	895	1055	1760	830	780	1665	785	680	1470	695	565
NOTES −	All air data is measured external to unit without filter (not furnished − field provided).

Page 5

BLOWER DATA

G61MP−60C−110 PERFORMANCE (Less Filter) − Bottom Return Air, Side Return Air with Optional RAB Return Air Base, Return Air from Both Sides or Return Air from Bottom and One Side.

External Static					Air Volume / Watts at Different Blower Speeds
Pressure			High			Medium−High			Medium−Low			Low
in. w.g.	Pa	cfm	L/s	Watts	cfm	L/s	Watts	cfm	L/s	Watts	cfm	L/s	Watts
0.00	0	2720	1285	1385	2410	1135	1090	2055	970	935	1620	765	710
0.10	25	2665	1255	1355	2385	1125	1075	2025	955	885	1730	815	735
0.20	50		1220	1315		1110	1015		955	865		795	690
		2585			2350			2030			1680
0.30	75	2505	1180	1275	2290	1080	990	2025	955	840	1695	800	675
0.40	100	2435	1150	1250	2235	1055	940	2030	960	830	1695	800	660
0.50	125	2350	1110	1205	2170	1025	930	1975	930	790	1735	820	665
0.60	150	2255	1065	1185	2100	990	895	1915	905	765	1720	810	650
0.70	175	2160	1020	1150	2005	945	840	1865	880	730	1680	795	635
0.80	200	2020	955	1090	1905	900	825	1810	855	710	1625	765	610
0.90	225	1910	900	1050	1820	860	795	1705	805	675	1540	725	590
NOTES −	All air data is measured external to unit without filter (not furnished − field provided).

G61MP−60D−135 PERFORMANCE (Less Filter) − Single Side Return Air − Air volumes in bold require field fabricated transition to accommodate 20 x 25 x 1 in. (508 x 635 x 25 mm) air filter in order to maintain proper air velocity.

	External Static					Air Volume / Watts at Different Blower Speeds
	Pressure			High			Medium−High			Medium−Low			Low
	in. w.g.	Pa	cfm	L/s	Watts	cfm	L/s	Watts	cfm	L/s	Watts	cfm	L/s	Watts
	0.00	0	2665	1260	1440	2325	1095	1100	1865	880	890	1410	665	690
	0.10	25	2615	1235	1405	2310	1090	1065	1915	905	865	1465	690	685
	0.20	50	2530	1195	1370	2280	1075	1055	1925	910	850	1570	740	675
	0.30	75	2470	1165	1330	2235	1055	1015	1920	905	825	1590	750	670
	0.40	100	2380	1125	1290	2175	1025	985	1910	900	805	1590	750	655
	0.50	125	2310	1090	1265	2120	1000	965	1890	890	790	1595	755	645
	0.60	150	2200	1035	1230	2055	970	935	1835	865	765	1580	745	630
	0.70	175	2120	1000	1190	1970	930	900	1790	845	740	1545	730	605
	0.80	200	2025	955	1160	1890	890	875	1720	810	710	1515	715	590
	0.90	225	1930	910	1110	1800	850	835	1655	780	685	1440	680	570
	NOTES −	All air data is measured external to unit without filter (not furnished − field provided).

G61MP−60D−135 PERFORMANCE (Less Filter) − Bottom Return Air, Side Return Air with Optional RAB Return Air Base, Return Air from Both Sides or Return Air from Bottom and One Side.

External Static					Air Volume / Watts at Different Blower Speeds
Pressure			High			Medium−High			Medium−Low			Low
in. w.g.	Pa	cfm	L/s	Watts	cfm	L/s	Watts	cfm	L/s	Watts	cfm	L/s	Watts
0.00	0	2730	1290	1465	2425	1145	1125	2055	970	915	1560	735	680
0.10	25	2670	1260	1440	2400	1135	1100	2065	975	890	1590	750	675
0.20	50	2600	1225	1400	2365	1115	1070	2045	965	865	1620	765	665
0.30	75	2525	1190	1360	2315	1095	1045	2035	960	845	1615	760	655
0.40	100	2445	1155	1325	2260	1065	1015	2020	955	820	1615	760	645
0.50	125	2360	1115	1280	2195	1035	985	1960	925	790	1610	760	635
0.60	150	2290	1080	1255	2130	1005	965	1900	895	755	1600	755	615
0.70	175	2205	1040	1220	2035	960	910	1825	860	730	1570	740	600
0.80	200	2110	995	1195	1945	915	880	1765	830	710	1540	725	580
0.90	225	1970	930	1120	1835	865	830	1680	795	690	1540	725	545
NOTES −	All air data is measured external to unit without filter (not furnished − field provided).

Page 6

		G61MP PARTS ARRANGEMENT
		TOP CAP
		DuralokPlusTM
		HEAT EXCHANGER
		ASSEMBLY
			CABINET
	BURNER BOX
	ASSEMBLY
	GAS VALVE
	AND MANIFOLD
	FLUE
	COLLAR
COMBUSTION
AIR PROVE PROVE			WARM HEADER
	SWITCHES*		(COLLECTOR)
			BOX
	COMBUSTION AIR
	INDUCER
			CONDENSER COIL
BURNER			PRIMARY LIMIT
ACCESS
PANEL
			COLD HEADER
			(COLLECTOR)
			BOX
BLOWER		DOOR
ACCESS		INTERLOCK
DOOR		SWITCH	SECONDARY
			LIMITS (2)
*G61MP−090 shown.
G61MP−045 and −070	SIGHT		BLOWER
are equipped with	GLASS		ASSEMBLY
two switches.
		CONTROL BOX

FIGURE 1

Page 7

I−UNIT COMPONENTS

G61MP unit components are shown in figure 1. The gas valve, combustion air inducer and burners can be accessed by removing the burner access panel. Electrical components are in the control box (figure 2) found in the blower section.

G61MP units are factory equipped with a bottom return air panel in place. The panel is designed to be field removed as required for bottom air return. Markings are provided for side return air and may be cut out in the field.

ELECTROSTATIC DISCHARGE (ESD)

Precautions and Procedures

3. Circuit Breaker (CB8)

A 24V circuit breaker is also located in the control box. The switch provides overcurrent protection to the transformer (T1). The breaker is rated 3A at 32V. If the current exceeds this limit the breaker will trip and all unit operation will shutdown. The breaker can be manually reset by pressing the button on the face. See figure 3.

CIRCUIT BREAKER CB8

PRESS TO RESET

CAUTION

Electrostatic discharge can affect electronic components. Take precautions during furnace installation and service to protect the furnace’s electronic controls. Precautions will help to avoid control exposure to electrostatic discharge by putting the furnace, the control and the technician at the same electrostatic potential. Neutralize electrostatic charge by touching hand and all tools on an unpainted unit surface, such as the gas valve or blower deck, before performing any service procedure.

A−Control Box

1. Control Transformer (T1)

A transformer located in the control box provides power to the low voltage section of the unit. Transformers on all models are rated 40VA with a 120V primary and a 24V secondary.

2. Door Interlock Switch (S51)

A door interlock switch rated 14A at 125VAC is wired in series with line voltage. When the blower door is removed the unit will shut down.

CONTROL BOX G61MP
	CIRCUIT
	BREAKER
DOOR INTERLOCK
SWITCH	TRANSFORMER
SURELIGHT
CONTROL
BOARD

FIGURE 2

FIGURE 3

WARNING

Shock hazard.

Disconnect power before servicing. Integrated

Control Board is not field repairable. If control is inoperable, simply replace entire control.

Can cause injury or death. Unsafe operation will result if repair is attempted.

4. Integrated Control Board (A92)

All G61MP units are equipped with the Lennox Two−Stage Integrated control board. The system consists of a ignition control board (figure 4 with control terminal designations in tables 3, 4 and 5) and ignitor (figure 7). The board and ignitor work in combination to ensure furnace ignition and ignitor durability. The board controls all major furnace operations. The board features two LED lights, DS1 and

DS2 for troubleshooting. The board also has two accessory terminals rated at (1) one amp. See table 6 for troubleshooting diagnostic codes.

Electronic Ignition

At the beginning of the heat cycle, SureLight control monitors the first stage and second stage combustion air inducer prove switch. The control will not begin the heating cycle if the first stage prove switch is closed (by−passed). Likewise the control will not begin the second stage heating cycle if the second stage prove switch is closed, and will allow first stage heat only. However if the second stage prove switch closes during the first stage pre−purge, the control will respond to second stage heat. Once the first stage prove switch is determined to be open, the combustion air inducer is energized on low (first stage) heat speed. When the differential in the prove switch is great enough, the prove switch closes and a 15−second pre−purge begins. If the switch is not proven within 2−1/2 minutes, the control goes into Watchguard−Pressure Switch mode for a 5−minute re−set period.

After the 15−second pre−purge period, the SureLight ignitor warms up for 20 seconds after which the gas valve opens for a 4−second trial for ignition. The ignitor energizes during the trial until flame is sensed. If ignition is not proved during the 4−second period, the control will try four more times with an inter purge and warm−up time between trials of 35 sec-

Page 8

onds. After a total of five trials for ignition (including the initial trial), the control goes into Watchguard−Flame Failure mode. After a 60−minute reset period, the control will begin the ignition sequence again.

The SureLight control board has an added feature that prolongs the life of the ignitor. After a successful ignition, the SureLight control utilizes less power to energize the ignitor on successive calls for heat. The control continues to ramp down the voltage to the ignitor until it finds the lowest amount of power that will provide a successful ignition. This amount of power is used for 255 cycles. On the 256th call for heat, the control will again ramp down until the lowest power is determined and the cycle begins again.

Two Stage Operation / Thermostat Selection Jumper

The control can be utilized in two modes: SINGLE−STAGE thermostat or TWO−STAGE thermostat. The thermostat selection jumper E20, located just below dip switches 1 through 4 (figure 4), must be positioned for the particular application. The jumper is factory set on TWO" for use with a two−stage thermostat with two stage heat. Re−position jumper to SINGLE" for use with a single stage thermostat with two stage heat.

While in the single−stage thermostat mode (single jumper setting), the burners will always fire on first−stage heat. The combustion air inducer will operate on low speed and indoor blower will operate on low heat speed. After a 10 minute recognition period, the unit will switch to second stage heat. While in the two−stage thermostat mode (two jumper setting) the burners will fire on first−stage heat. The combustion air inducer will operate on low speed and indoor blower will operate on low heat speed. The unit will switch to second−stage heat on call from the indoor thermostat. If there is a simultaneous call for first and second stage heat, the unit will fire on first stage heat and switch to second stage heat after 30 seconds of operation. See Sequence of Operation flow charts in the back of this manual for more detail.

Dip Switch Settings

Dip Switches 1 and 2 − Heating Fan off Delay − The fan on time of 45 seconds is not adjustable. Fan off time (time that the blower operates after the heat demand has been satisfied) can be adjusted by flipping the dip switches 1 and 2 located on the SureLight integrated control. The unit is shipped with a factory fan off setting of 90 seconds. Fan off time will affect comfort and is adjustable to satisfy individual applications. For customized comfort, monitor the supply air temperature once the heat demand is satisfied. Note the supply air temperature at the instant the blower is de−energized. Adjust the fan−off delay to achieve a supply air temperature between 90° − 110° at the instant the blower is de− energized. (Longer delay times allow for lower air temperature, shorter delay times allow for higher air temperature). See table 1 for dip switch settings.

TABLE 1

Heating Fan Off Delay

Delay (Seconds)	Switch 1	Switch 2
60	Off	Off
90	Off	On
120	On	Off
180	On	On

Switch 3 − Second Stage Delay (Used with Single−Stage

Thermostat Only) −− This switch is used to determine the second stage on delay when a single−stage thermostat is being used. The switch is factory−set in the ON position, which provides a 10−minute delay before second−stage heat is initiated. If the switch is toggled to the OFF position, it will provide a 15−minute delay before second−stage heat is initiated. This switch is only activated when the thermostat selector jumper is positioned for SINGLE−stage thermostat use.

Switch 4 − Cooling Fan off Delay − The fan on delay time of 2 seconds is not adjustable. Fan off time (time that the blower operates after the cool demand has been satisfied) can be adjusted by flipping dip switch 4. The unit is shipped with a factory fan off setting of 45 seconds. Fan off time will affect comfort and is adjustable to satisfy individual applications. See table 2 for cool fan off time settings.

TABLE 2

Cooling Fan Off Delay

Delay (Seconds)	Switch 4
2	Off
45	On

Diagnostic LED’s (DS1 and DS2)

Two diagnostic LED’S are located on the two−stage integrated control board. See figure 4. These light flashes correspond with the codes detailed in table 6.

Factory Installed Jumper Y1 to Y2

A factory−installed jumper from Y1 to Y2 terminals on the integrated control board terminal strip must be clipped for two−stage cooling.

Page 9

TWO−STAGE INTEGRATED CONTROL BOARD

LEDs

DIP

SWITCHES 1 − 4

W915 FACTORY INSTALLED JUMPER (MUST CLIP FOR 2 STAGE COOL)

THERMOSTAT CONNECTIONS (TB1)

DIP SWITCH(ES)	FUNCTION
1 and 2	Blower Off Delay (Heating Mode)
3	Second Stage ON Delay (Single−stage t’stat)
4	Blower Off Delay (Cooling Mode)

FIGURE 4

TABLE 3

Integrated Control Board Terminals

120VAC Neutral

LINE	Line
XFMR	Transformer
EAC	Electronic Air Cleaner
CIRC	Indoor Blower
HUM	Humidifier
	120VAC Line
HUM	Humidifier
XMFR	Transformer
LINE	Line
PARK	For Unused Leads
COOL	Cooling Speed
EAC	Electronic Air Cleaner
HI HEAT	HIigh Heat Speed
LO HEAT	Low Heat, Low Cool and Continuous Fan
	Speed

TABLE 4

Integrated Control Board 5 Pin Terminal

PIN #	Function
1	Ignitor

2Combustion Air Inducer High Speed

3Combustion Air Inducer Low Speed

4	Combustion Air Inducer Neutral
5	Ignitor Neutral

TABLE 5

Integrated Control Board 12Pin Terminal

PIN #	Function
1	Gas Valve 2nd Stage (High Fire)
2	Second Stage Prove Switch
3	Not Used
4	Ground
5	24V Hot
6	Primary Limit In
7	Gas Valve 1st stage (Low Fire)
8	Gas Valve Common
9	24V Neutral
10	Ground
11	Primary Limit Out
12	1st Stage Prove Switch

Page 10

			TABLE 6
			DIAGNOSTIC CODES
		Diagnostic LEDs are labeled DS1 and DS2. See figure 4 for location of diagnostic LEDs.
	DS1	DS2	DESCRIPTION
	SIMULTANEOUS	SIMULTANEOUS	Power on − Normal operation.
	SLOW FLASH	SLOW FLASH	Also signaled during cooling and continuous fan.
	SIMULTANEOUS	SIMULTANEOUS	Normal operation − signaled when heating demand initiated at thermostat.
	FAST FLASH	FAST FLASH
	SLOW FLASH	ON	Primary, secondary, backup secondary or rollout limit switch open. Limits must
			close within 3 minutes or unit goes into 1 hour Watchguard.
			Low prove switch open;
	OFF	SLOW FLASH	OR: Blocked inlet/exhaust vent;
			OR: Low prove switch closed prior to activation of combustion air inducer.
			High prove switch open;
	OFF	FAST FLASH	OR: Blocked inlet/exhaust vent;
			OR: High prove switch closed prior to activation of combustion air inducer.
	ALTERNATING	ALTERNATING	Watchguard −− burners failed to ignite; OR limit open more than 3 minutes;
			OR lost flame sense 5 times in one heating cycle;
	SLOW FLASH	SLOW FLASH
			OR pressure switch opened 5 times in one heating cycle.
	SLOW FLASH	OFF	Flame sensed without gas valve energized.
	ON	ON
	ON	OFF	Circuit board failure or control wired incorrectly. Check 24 and 115 volts to board.
	OFF	ON
	FAST FLASH	SLOW FLASH	Main power polarity reversed. Switch line and neutral.
	SLOW FLASH	FAST FLASH	Low flame signal. Measures below 0.23 microAmps. Replace flame sense rod.
			The following conditions are sensed during the ignitor warm−up period only:
			1) Improper main ground;
	ALTERNATING	ALTERNATING	2) Broken ignitor; OR: Open ignitor circuit;
	FAST FLASH	FAST FLASH	3) Line voltage below 75 volts.
			(If voltage lower than 75 volts prior to ignitor warm-up, control will signal waiting on
			call from thermostat, and will not respond.

NOTE − Slow flash rate equals 1 Hz (one flash per second). Fast flash rate equals 3 Hz (three flashes per second).

Low flame sense current = 0.17−0.22 microAmps.

B−Blower Compartment

1. Blower Motor (B3) and Capacitor (C4)

All G61MP units use direct drive blower motors. All motors are 120V permanent split capacitor motors to ensure maximum efficiency. Ratings for capacitors will be on motor nameplate. See SPECIFICATIONS section for motor specifications.

NOTE − Shafts on 1 HP motors have 2 flat sides and are matched with blower wheels with 2 set screws.

2. Secondary Limit Controls (S21)

The secondary limits (S21) on G61MP units are located in the blower compartment on the back side of the blower housing.

See figure 5. All G61MP units are equipped with two secondary limts. When excess heat is sensed in the blower compartment, the limit will open. If the limit is open, the furnace control energizes the supply air blower and closes the gas valve. The limit automatically resets when unit temperature returns to normal. The switch is factory set to open at 125°F and cannot be adjusted.

SUPPLY AIR BLOWER

AND SECONDARY LIMITS

SECONDARY

LIMIT (S)

MOTOR/BLOWER ASSEMBLY

CAPACITOR

To Remove Blower From Unit: Disconnect Power, Remove Control Box, Remove Bolts and Unplug Motor Wires From Control Board.

Then Slide Out Front of Unit.

FIGURE 5

Page 11

C−Heating Components

3. Flame Sensor

A flame sensor is located on the left side of the burner support. See figure 6. The sensor is mounted through the bottom of the burner box and the tip protrudes into the flame envelope of the left−most burner. The sensor can be removed for service without removing any part of the burners. During operation, flame is sensed by current passed through the flame and sensing electrode. The SureLight control allows the gas valve to remain open as long as flame signal is sensed.

4. Ignitor

The SureLight ignitor is made of durable silicon nitride. Ignitor longevity is enhanced by controlling voltage to the ignitor. The board finds the lowest ignitor temperature which will successfully light the burner, thus increasing the life of the ignitor. Due to this feature of the board, voltage cannot be measured so ignitor must be ohmed. Ohme value should be 10.9 to 19.7. See 7 for ignitor location.

NOTE − The G61MP furnace contains electronic components that are polarity sensitive. Make sure that the furnace is wired correctly and is properly grounded.

NORMAL FLAME SIGNAL > 0.23 MICROAMPS

LOW FLAME SIGNAL	< 0.22 MICROAMPS
DROP OUT SIGNAL	= 0.16 MICROAMPS

5/16"

FIGURE 6

5. Burners (Figure 7)

All units use inshot burners. Burners are factory set and do not require adjustment. The manifold brackets are slotted so burners can be removed as an assembly for service. Burner maintenance and service is detailed in the MAINTENANCE section of this manual. Each burner uses an orifice which is precisely matched to the burner input and is threaded into the burner manifold. All G61MP natural gas units are fitted with

.089" sized orifices. See SPECIFICATIONS" tables for LP kits and high altitude.

A flame retention ring in the end of each burner maintains correct flame length and shape and keeps the flame from lifting off the burner head. In addition, the burner entrance to each clamshell is fitted with a corbel cup (orifice) used to direct the flow of combustion products.

	SureLight Ignitor Location
5/8"	MEASUREMENT IS TO I.D.
	OF RETENTION RING
13/32’
	5/16"
IGNITOR	BRACKET
BURNERS FRONT VIEW		BURNERS TOP VIEW

FIGURE 7

Page 12

6. Clamshell Heat Exchanger

G61MP units use an aluminized steel primary and stainless steel secondary heat exchanger assembly. Heat is transferred to the air stream from all surfaces of the heat exchanger. The shape of the heat exchanger ensures maximum efficiency.

The combustion air inducer pulls fresh air through the air intake box. This air is mixed with gas in the burner venturi and at the corbel orifices. The gas / air mixture is then burned at the entrance of each clamshell. Combustion gases are then pulled through the primary and secondary heat exchangers and exhausted out the exhaust vent pipe.

7. Flame Rollout Switches (S47)

Flame rollout switch S47 is a high temperature limit located on each side of the burner box. Each furnace is equipped with two identical switches. The limit is a N.C. SPST manu- al-reset limit connected in series with the primary limit S10. When S47 senses rollout, the circuit breaks and the ignition control immediately stops ignition and closes the gas valve.

If unit is running and flame rollout is detected, the gas valve will close and ignition control will be disabled. Rollout can be caused by a blocked heat exchanger, flue or lack of combustion air. The switch is factory set to trip (open) at 250°F and cannot be adjusted. The switch can be manually reset. To manually reset a tripped switch, push the reset button located on the control.

8. Primary Limit Control (S10)

Figure 8 shows the primary limit (S10) used on G61MP units located in the heating vestibule panel. S10 is provided with a shield on some models (figure 8) and must not be removed. Note orientation of shield and limit if limit is replaced. When excess heat is sensed in the heat exchanger, the limit will open.

Once the limit opens, the furnace control energizes the supply air blower and de−energizes the gas valve. The limit automatically resets when unit temperature returns to normal. The switch is factory set and cannot be adjusted.

9.Backup Secondary Limit Control (S113) (G61MP−090, 110, 135 only)

Backup secondary limit control S113 is a N.C. auto−reset switch located on the combustion air inducer. S113 acts as a backup to primary limit S10 in the event of an indoor blower failure. S113 contacts open when temperature on the CAI reaches 142°.

10. Gas Valve (GV1)

The G61MP uses a two−stage gas valve manufactured by Honeywell (figure 35) or White Rodgers (figure 36). The valves are internally redundant to assure safety shut−off. If the gas valve must be replaced, the same type valve must be used.

24VAC terminals and gas control knob or switch are located on the valve. All terminals on the gas valve are connected to wires from the electronic ignition control. 24V applied to the terminals energizes the valve.

Inlet and outlet pressure taps are located on the valve. A regulator adjustment screw is located on the valve.

LPG change over kit s are available from Lennox. Kits include burner orifices and a gas valve regulator conversion kit.

The burner box is sealed and operates under a negative pressure. A pressure hose is connected from the burner box to the gas valve. The gas valve senses the pressure in the burner box and changes gas valve outlet (manifold) pressure based on changes in the burner box pressure.

The intent is to compensate for different vent configurations which can greatly affect the rate of the unit.

PRIMARY LIMIT LOCATION

limit shield 090, −110 and

−135 only

limit faces shield

FIGURE 8

11. Combustion Air Inducer Prove Switch (S18)

All G61MP units are equipped with combustion air prove switches located on the combustion air inducer housing.

G61MP−045 and −070 (figure 10) units have two combustion air proving switches. G61MP−090, −110 and −135 units are equipped with two dual prove switch assemblies" consisting of two switches acting as one. See figure 9. The switches are connected to the cold end header box by means of a flexible hose that monitors negative air pressure in the cold end header box.

The switches are a single-pole single-throw proving switch electrically connected to the furnace control. The purpose of the switch is to prevent burner operation if the combustion air inducer is not operating or if the flue becomes obstructed.

Page 13

On heat demand (first or second stage) the switch senses that the combustion air inducer is operating. It closes a circuit to the furnace control when pressure inside the cold end header box decreases to a certain set point.

Set points vary depending on unit size. See tables 8, 9 and 10. The pressure sensed by the switch is negative. If the air intake vent pipe or outlet vent pipe becomes obstructed during operation, the switch senses a change of negative pressure and opens the circuit to the furnace control and gas valve. A bleed port on the switch allows relatively dry air in the vestibule to purge switch tubing, to prevent condensate build up.

The switch is factory set and is not field adjustable. It is a safety shut-down control in the furnace and must not be by− passed for any reason. If switch is closed or by−passed, the control will not initiate ignition at start up.

DUAL COMBUSTION AIR PROVE SWITCH

G61MP−090, −110 & −135

	first stage	negative
		pressure

second stage

positive pressure

FIGURE 9

To troubleshoot the prove switches, temporarily jumper them.

The unit will not fire with the switches jumpered. Therefore, the prove switches must be bypassed after the combustion air inducer is activated. This will determine if the prove switches and furnace are operating properly. However, this may not indicate if the sealed combustion system is operating properly.

Checks of pressure differential can aid in troubleshooting. When measuring the pressure differential, readings should be taken at the prove switch. Lack of differential usually indicates problems in the intake or exhaust piping, but may indicate problems in the heat exchanger, condensing coil, header boxes, combustion inducer or other components.

Measuring pressure differential

The differential pressure is the difference in pressure measured across the cold end header box orifice.

1 − Remove thermostat demand and allow unit to cycle off.

2 −	Install a tee in the negative (−) line and a tee in the positive
	(+) line running from one of the prove switches to the cold
	end header box.
3 −	Install a manometer with hose from the negative (−)
	side of the manometer to the tee installed in the nega-

tive (−) line and with hose from the positive (+) side of the manometer to the tee in the positive (+) line.

NOTE − Both sides of the cold end header box are negative.

However the (+) port reads less negative pressure than the

(−) port.

CAI & COLD END HEADER BOX ASSEMBLY
(−045 & 070 SHOWN)
	Install tee’s in the
	negative line and
	positive line then
	connect hoses to
	manometer.
_ +	+ _
cold end header box	prove switches orifice size

FIGURE 10

4 − Operate unit and observe manometer reading. Readings will change as heat exchanger warms.

a.Take one reading immediately after start-up.

b.Take a second reading after unit has reached steady state (approximately 5 minutes). This will be the pressure differential.

The pressure differential should be greater than those listed in table 8, 9 or 10.

5 − Remove thermostat demand and allow to cycle off.

6 − Remove manometer and tee’s. Reinstall combustion air sensing hoses to the prove switch.

7 − Repeat steps 1 through 6 for the other prove switch.

Page 14

12. Combustion Air Inducer (B6)

All G61MP units use a combustion air inducer to move air through the burners and heat exchanger during heating operation. The blower uses a PSC 120VAC motor. The motor operates during all heating operation and is controlled by the ignition control A3. Blower operates continuously while there is a call for heat. The burner ignition control will not proceed with the ignition sequence until combustion air inducer operation is sensed by the proving switches.

The CAI is installed on the cold end header box. The cold end header box is a single piece made of hard plastic. The box has an internal channel where the combustion air inducer creates negative pressure at unit start up. The channel contains an orifice used to regulate flow created by the CAI. The box has pressure taps for the CAI prove switch hoses.

The prove switches measure the pressures across the CAI orifice or difference in the channel and the box. A window is provided on the bottom right hand side of the box to indicate orifice size. See figure 10. See table 7 for orifice size per unit. If replacement is necessary the gaskets used to seal the box to the vestbule panel and the CAI to the box, must also be replaced.

	TABLE 7
G61MP Unit		C.A.I. Orifice Size
−045		.719"
−070		.938"
−090		1.063"
−110		1.313"
−135		1.688"

TABLE 8 0’ to 4500’

	G61MP Unit	Set Point	Set Point
		Second Stage	First Stage
	−045	0.95"	0.95"
	−070
	−090	0.85"	0.50"
	−110
	−135	0.60"	0.35"
		TABLE 9*
		4501’ to 7500’
	G61MP Unit	Set Point	Set Point
		Second Stage	First Stage
	−045	0.95"	0.95"
	−070
	−090	0.75"	0.50"
	−110	0.85"	0.50"
	−135	0.55"	0.35"

*Unit may require conversion kit at this altitude. See High Altitude table.

TABLE 10* 7501’ to 10,000’

	G61MP Unit	Set Point	Set Point
		Second Stage	First Stage
	−045	0.95"	0.95"
	−070	0.85"	0.85"
	−090	0.60"	0.35"
	−110	0.85"	0.50"
	−135	0.55"	0.35"

*Unit may require conversion kit at this altitude. See High Altitude table.

Page 15

II−PLACEMENT AND INSTALLATION

TABLE 11

OUTDOOR TERMINATION KITS AND CORRESPONDING EQUIVALENCIES

					Vent Pipe Length Equivalency (feet)
			Outdoor	Outdoor						2" Wall
		VENT	Exhaust	Exhaust	1−1/2"	2" Con-	3" Con-
								2" Wall	3" Wall	Kit with	2" Wall
			Accelerator	Accelerator	Concen-	centric	centric
	UNIT	PIPE
								Plate Kit	Plate Kit	Vent Ex-	Ring Kit
	MODEL	DIA.	(Dia. X	(Dia. X	tric Kit	Kit	Kit
										tension
		(in.)	Length)	Length)
			1−1/2" X 12"	2" X 12"	71M80	60M29	60L46	22G44	44J40	30G28	15F74
									81J20
		2	4	Not	12	Not	Not	4	4*	4	4
				Allowed		Allowed	Allowed
		2−1/2	5	Not	15	Not	Not	5	5*	5	5
				Allowed		Allowed	Allowed
	36B−045
		3	7	Not	21	Not	Not	7	7*	7	7
				Allowed		Allowed	Allowed
		4	14	Not	42	Not	Not	14	14*	14	14
				Allowed		Allowed	Allowed
		2	4	Not	12	Not	Not	4	4*	4	4
				Allowed		Allowed	Allowed
		2−1/2	5	Not	15	Not	Not	5	5*	5	5
				Allowed		Allowed	Allowed
	36B−070
		3	8	Not	24	Not	Not	8	8*	8	8
				Allowed		Allowed	Allowed
		4	14	Not	42	Not	Not	14	14*	14	14
				Allowed		Allowed	Allowed
		2	Not	1	Not	3	3	Not	1	Not	1**
			Allowed		Allowed			Allowed		Allowed
		2−1/2	Not	2	Not	6	6	Not	2	Not	2**
			Allowed		Allowed			Allowed		Allowed
	60C−090
		3	Not	2	Not	6	6	Not	2	Not	2**
			Allowed		Allowed			Allowed		Allowed
		4	Not	4	Not	12	12	Not	4	Not	4**
			Allowed		Allowed			Allowed		Allowed
		2−1/2	Not	2	Not	6	6	Not	2	Not	2***
			Allowed		Allowed			Allowed		Allowed
	60C−110	3	Not	2	Not	6	6	Not	2	Not	2***
			Allowed		Allowed			Allowed		Allowed
		4	Not	4	Not	12	12	Not	4	Not	4***
			Allowed		Allowed			Allowed		Allowed
		3	Not	6	Not	Not	15	Not	6	Not	6***
			Allowed		Allowed	Allowed		Allowed		Allowed
	60D−135
		4	Not	10	Not	Not	25	Not	10	Not	10***
			Allowed		Allowed	Allowed		Allowed		Allowed

*Requires field−provided and installed 1−1/2" exhaust accelerator. **Requires field−provided and installed 2" exhaust accelerator.

***For use only in non−direct vent applications, when snow riser is

not required. Requires field−provided and installed 2" exhaust accelerator.

Page 16

A−Vent Piping Guidelines

The G61MP can be installed as either a Non−Direct Vent or a Direct Vent gas central furnace.

NOTE − In Non-Direct Vent installations, combustion air is taken from indoors and flue gases are discharged outdoors.

In Direct Vent installations, combustion air is taken from outdoors and flue gases are discharged outdoors.

Intake and exhaust pipe sizing in Direct Vent applications and exhaust pipe sizing in Non-Direct Vent applications −−

Size pipe according to tables 12 and 13. Table 12 lists the minimum equivalent vent pipe lengths permitted. Table 13 lists the maximum equivalent pipe lengths permitted.

Maximum vent length is defined as:

Total length (linear feet) of pipe,

Plus Equivalent length (feet) of fittings,

Plus Equivalent length (feet) of termination.

NOTE − Include ALL pipe and ALL fittings, both in doors and outdoors.

Regardless of the diameter of pipe used, the standard roof and wall terminations described in section Exhaust Piping

Terminations should be used. Exhaust vent termination pipe is sized to optimize the velocity of the exhaust gas as it exits the termination. Refer to table 14.

*NOTE − The exhaust pipe should be offset a minimum of 12 inches to avoid the possibility of water droplets being released from the exhaust termination. The minimum exhaust vent length is 15 ft. Shorter exhaust vent lengths may result in the discharge of water droplets from the exhaust termination, in spite of the 12−inch vertical offset.

Each 90° elbow (including those provided with the furnace) of any diameter is equivalent to 5 feet (1.52m) of vent pipe of the same diameter. Two 45° elbows are equivalent to one 90° elbow of the same diameter. One 45° elbow is equal to 2.5 feet (.76m) of vent pipe of the same diameter. In some applications which permit the use of several different sizes of vent pipe, a combination vent pipe may be used. Contact the Application Department for assistance in sizing vent pipe in these applications.

NOTE − The flue collar on all models is sized to accommodate 2" Schedule 40 flue pipe. When vent pipe which is larger than 2" must be used in an upflow application, a 2" elbow must be applied at the flue collar in order to properly transition to the larger diameter flue pipe. This elbow must be added to the elbow count used to determine acceptable vent lengths. Assign an equivalent feet value to this elbow according to the larger size pipe being used. Contact the Application Department for more information concerning sizing of vent systems which include multiple pipe sizes.

	Exhaust Pipe Offset
	12" Min.
12" Min.
Upflow and Downflow Application	Upflow and Downflow Application
Rooftop Termination	Side Wall Termination
12" Min.	12" Min.

Horizontal Application		Horizontal Application
Rooftop Termination		Side Wall Termination

FIGURE 11

Page 17