Carrier 38EV024320 User Manual

HEATING A COOLING

38EV,QV Variable Speed Systems

Operation, Service and Troubleshooting

For Models 38EV024320, 38EV036320, 38QV024320, 38QV036320

	CONTENTS
INTRODUCTION
Step 1 —General System Description..............................		1
Step 2—Component Functional Description....................		1
•	Outdoor Unit Components
•	Indoor Unit Components
Step 3—Sequence Of Operation........................................		7
Step 4—VVT-II Thermostat Operation Troubleshooting. 13
Step 5—System Troubleshooting.......................................		15

•Self-Diagnostics—Error Codes

•System Malfunctions—No Error Code

Step 6—Service and Maintenance....................................

40

NOTE: Malfunction of certain electronic control compo­ nents can cause lack of Automatic Emergency Heat initia­ tion. See Service and Maintenance section for corrective servicing procedures.

INTRODUCTION

This publication is designed to provide the information nec­ essary to understand and troubleshoot Carrier’s 38EV and s 38QV Variable Speed Split System Heat Pump and Air

'Conditioning Systems. The text covers variable speed 38EV condensing and 38QV heat pump outdoor units, coupled with 40QV Fan Coil or 28RD/RN Coil and 58SS Furnace with blower accessory package. AU system combinations are controUed in a similar manner utilizing the same elec­ tronic components for both heat pump and cooling only sys­ tems. System Diagrams are shown in Figs. 2 and 3.

Thermostat:

The 38EV/QV system must be installed with a VVT-II ther­ mostat Model MST-04 or MST-16 with software revision 6.7 or higher, available through your Carrier distributor.

General Operation:

The abflity of the system to control compressor and blower speeds as described above allows it to adjust its output capacity to match the varying load requirements of an installation.

This type of operation results in less on-off cycling (ref. Fig. 1), quieter operation and improved temperature control at modera:te and low load conditions.

Fig. 1—Variable Speed System Matches Load

This guide covers single zone applications only. For multi­ ple zone instaUation, see proper supplemental manual.

STEP 1—Gênerai System Description Outdoor Units:

The 38EV condensing and 38QV heat pump units are derived from standard Carrier single-speed units. The con­ trol box is slightly larger to aUow room for the induction inverter and system microprocessor control board.

Although the unit is 208/230 VAC single phase, the inverter supplies three-phase power at a wide r^ge of frequencies to control the speed of the three-phase compressor. By varying compressor speed, the system is able to control its output within a range of about one-half to fuU rated capacity. The outdoor fan motor is of standard single-phase, single-speed design.

Indoor Units:

The 40QV Fan Coü provides variable indoor airflow control for the system. This feature gives the system the capability not only to vary its output capacity, but to control humid­ ity levels throughout this capacity range.

The 58SSB Blower Accessory provides these same,features when coupled with a 58SSB Furnace and 28RD/RN Furnace Coil.

STEP 2—Component Functional Description
CONTENTS
	Page
38EV, QV Outdoor Units..........................................................	4
Main Control Board...............................................................	4
Compressor Inverter..............................................................	4
Compressors................................. .........................................	6
Outdoor Coil, Suction Thermistor (Tl, T2)..........................	6
Outdoor Fan Motor/Capacitor..............................................	6
Outdoor Solenoid Expansion Valve (SEV)..........................	6
High Pressure Switch (HPS).............................. ...................	7
Low Pressure Switch (EPS)....................................................	7
Emergency Stop Switch (ESS)....................... .......................	7
Crankcase Heater and Switch (CH, CHS)...........................	7
40QV Fan Coil, 58SSB Furnace Blower Accessory................	7
Interface Board ...................................................................	7
Blower Controller...................................................................	7
Blower Motor..........................................................................	7
Indoor Solenoid Valve (SEV) . .............................................	7
Indoor Coil Thermistor (T3)..................................................	7

Figs. 2 and 3 shows layout of components in the variable speed control system. This section will describe each compo­ nent and discuss its function in attaining proper system operation.

Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obiigations.

Book| 1 I 1 I 4 I 4 PC 101 Cataiog No. 533-895 Printed in U.S.A. FormSSEV, QV-1SM Pg 1 12-87 Replaces: New Tab I3al5al2al5a

38EV Variable Speed Air Conditioning System

FAN COIL	OUTDOOR UNIT
40QV024	38EV024
40QV036	38EV036

SERVICE VALVES,

&

SERVICE PORT

SERVICE VALVES

OUTDOOR FAN

THERMOSTAT

inrininTlTnili

iMTrifrilTTnW

felinui

™EIDEMH

N>1----	U
°----- GND ,	1 0 208/230 V.A.C.

ESS SWITCH (036 ONLY)

LOW PRESSURE SWITCH

SUCTION THERMISTOR

A87260

Fig. 2—Simplified System Schematic (shown with 40QV Fan Coil)

Fig. 3—Simplified System Schematic
(shown with 40QV Fan Coil)	A87215

38EV, 38QV Outdoor Unît Main Control Board:

The main control board is located in the front of the 38E V/ QV control box. It is fully visible and serviceable by simply removing the control box cover, as shovm in Fig. 4. All wir­ ing connections for components internal to the unit are at the top of the board as shown in Fig. 5. Low voltage connec­ tions are at thè white 17 pin connector, high voltage (O.D. fan relay) at the two push on terminals in the upper left. All connections to the indoor unit aré made through the 15 con­ ductor Interface Cable connector located in lower left of the board.

Thè main "control boárd receives information on system sta­ tus from 5 devices (including WT-II thermostat) and uses it to determine proper control for its 10 outputs. These I/O’s are listed below: •

Inputs:

1)Thermistor (T2), Suction Line.

2)Thermistor (Tl), O.D. coil (between expansion device and coil).

3)Thermistor (T3), I.D. coil (between expansion device and coil).

4)Compressor Inverter (over-current alarm).

5)Thermostat (cool/heat, capacity demand, etc.)

Outputs:

1)Inverter (compressor) speed signal.

2)I.D. Blower Speed Signal (via interface board).

3)O.D. Solenoid Expansion Valve* (refrig, expansion con­ trol, heat mode).

4)I.D. Solenoid Expansion Valve (refrig, expansion con­ trol, cool model).

5)Main Contactor (inverter/compressor on-off control).

6)O.D. Fan (on-ofif control).

7)Reversing Valve* (on-off control).

8)Aux. Heat (electric or furnace heat on-ofif).

9)On-Board LED (on-off for diagnostics codes, etc.)

10)Thermostat (display of diagnostics codes, etc.)

*38QV Heat Pump Units Only

Compressor Inverter:

NOTE: The following text describes disassembly of the con­ trol box for purposes of explaining inverter, coniponent func­ tion only. Inverter components are not serviceable, and shoüld not be removed from the control box.

Serviceable items include only the main control board, con­ tactor and fan capacitor.

Failure of any other component requires replacement of the entire control box. See instructions included with replace­ ment control box for this procedure.

The inverter is made up of 6 components, all mounted in the 38EV/QV control box. , ~

With the main system control board and backpanel removed (3-screws) the inverter board is clearly visible (See Fig. 6). _ w,, /;

Removal of the inverter board allows a view of the rest of the inverter components, which are pointed out in Fig. 7.

(Refer to Fig. 8) The inverter operates with 208-230VAC, single-phase input power provided to the Diode Module (or diode bridge). Here the AG power is converted to high volt­ age DC (325V approx.).

The large (black) Smoothing Capacitor in upper right of the control box is required to Smooth the DC voltage and is at this 325 VDC potential.

SUB-BOARD it2

SMOOTHING CAPACITOR

SUB-BOARD tn

CONTACTOR

CONTROL BOX-TO-UNIT	FAN CAPACITOR
CONNECTORS	A87438

Fig. 4—Control Box, Cover Off

17 PIN	DIAGNOSTIC
CONNECTOR	LED

INTERFACE

CABLE

CONNECTOR &

RETAINER

LATCH

A87216

Fig. 5—Control Board

The DC power is then provided to the Power Modules (3) or Power Transistors via a buss mounted across all 3 modules. The power modules drive the 3-phase compressor when the Inverter Board receives a signal from the main control board requesting a certain compressor speed. The inverter board switches each power module on-ofif into a signal simu­ lating a single-phase signal. (See Fig. 9A). Each power mod­ ule is switched in the same pattern, but 120-deg. out-of­ phase from the other two modules, so the total output is in 3-phase form. (See Fig. 9C).

POWER

MODULES (3)

HEAT SINK

A87440

A87441

Fig. 6—Control Board Removed Fig. 7—Inverter Board Removed

38EV/QV COMPRESSOR INVERTER OPERATION

. - . .... SERIAL ................................................................- -..........

ON (325VDC) —

		VOLTAGE OUTPUT
/	\	(Average of ON-OFF
		■ voltage)

OFF (OVDC) —

o

A87443

Fig. 9—Inverter Power Module Switching

A change in the speed signal from the main control board causes thé inverter board to switch the power modules at a different rate, thus changing the 3-phase output frequency, and compressor speed. (Ref. Fig..9B),

In summary, the inverter takes a 230V, single-phase, 60 Hz. frequency input and converts it'to high voltage DC. It then converts it to 3-phase AC power at frequencies of 30-90 Hz. to drive the 3-phase compressor at speeds of 1800 to 5400 RPM.

Although other inverter components (shown in Fig. 4) were not needed in the above'functional description, they are still necessary to maintain inverter integrity and reliability. Sub-board #1 is used to suppress electrical noise caused by power module switching to prevent interference with the inverter microprocessor. It also contains 2'current loops so the inverter can monitor its own current output. Sub-board #2 is an under-voltage protector for the inverter bbardr

Compressors—are of a spedial design to operate reliably over the 180Ô-540Ô RPM (30-90 Hz. frequency) speed range. They are driven by a standard design 3-phase motor. ,

—38EV024, 38Qy024 Models—have a reciprocating 'com­ pressor with internal PTC heater and internal overload feature. It has specially hardened valves for high speed operation, and special oil pump to retedn proper lubrica­ tion at low speeds.

Its internal current and temperature sensitive overload resets automaticaUy when internal compressor motor temperature drops to a safe level (overloads may require

. .. up to 30 minutes to reset). When an internal overload is suspected of being open, check by using an ohm-meter or continuity tester. - - ..:... ■

The internal high Pressure Relief Valve opens at a pres­ sure differential of approximately 450-f-50 psig between suction (low side) and discharge (high side) to

. allow pressure equalization..

See Table 1 for proper oil charge.

—38EV036, 38QV036 Models—have a scroll compressor. This type of compressor contains no valves, similar to a rotary type. The “movable” vane osciQates in a cam fash-

ion to force refrigerant around from outer edge to the cen­ ter discharge, while compressing it.

The scroll compressor contains no internal overload devices. Instead, an emergency stop switch (ESS) is mounted to the top of the compressor (see description below).

It also requires no high' pressure relief valve. At exces­ sive pressure the scroll vane is hfted from its seahng surface, allowing high tolow'side bypass.

Table 1—Refrigerant and Oil Charge

Unit	Charge	Oil	Oil Charge (oz)
Model	R-22(lb)	Type	New/Recharge
38EV024		Calumet RD-15 or	( , : 55/51
38QV024 ;	, 8;5	Sontex2000
38EV036	: 8.1	Sunisco 4GS	41/39
38QV036	9.5

Thermistors:

Three thermistors are utilized by the main control board to monitor refrigerant temperatures at locations shown in Figs. 2, 3 and 10. The same model thermistor is used at all three locations. Each is mounted in a %6” O.D. tube secured to the refrigerant hne for improved accuracy and protection of the device, and then heavily insulated (armaflex tube).

O.D. Fan Motor/Capacitor:

The totally enclosed fan motor is of standard 208-230 single-phase design for single-speed operation. Its related capacitor, located in lower right of the control box, is also of standard design.

Outdoor Solenoid Expansion Valve (SEV)—38QV Heat

Pumps Only.

This device is identical to that used at the indoor unit, except for accurator piston size. Refer to Indoor Solenoid Expansion Valve Description.

Fig. 10—Thermistor Locations

	High Pressure Switch (HPS)—is provided for high pressure
	protection of the system. It is located on the hquid line in
	38EV units, and the discharge hne in 38QV units, (ref. Figs.
	2 and 3). Its setting is 425 (+ -10) psig.
	Low Pressure Switch (LPS)—is included to provide loss-of-
(	charge protection.
	In 38QV heat pumps the LPS is located in the hquid line
	between the outdoor coil and outdoor SEV (ref. Fig. 3). Its
	setting is 5 + (+ -3) psig and provides protection in the heat­
	ing mode.
	In 38EV coohng units, the LPS is located in the suction line
	between suction service valve and accumulator (ref. Fig. 2).
	Its setting is 27 (4--5) psig.
	Emergency Stop Switch /EiSSj—Is used only on 38ÉV036
	and 38QV036 model units. It is mounted to the top of the
	scroU compressor to provide over-temperature protection,
	as the scroll has no internal overload. It is located in the
	safety electrical circuit in series with LPS and HPS
	switches. The ESS is set to open on temperature rise at
	265 + -10 deg.F and reclose at 210 + -20 deg.F.
	Crankcase Heater and Switch (CH,CHS)—is connected
	across the input side of the line filter and operates continu­
	ously except above the setting of the crankcase heater
	switch (70-deg.F) which is located on the liquid hne.
	The purpose of the heater is to keep the crankcase warm
	during the off cycle and thus prevent dilution of the oil with
	refrigerant. This assures good lubrication and prevents loss
	of oil from the crankcase during startup. To energize crank­
	case heater, turn the indoor thermostat to OFF position and
	energize electrical disconnect to the outdoor unit. If the elec­
	trical disconnect switch to the outside unit has been off for
	an extended period of time, the crankcase heater should
	be always energized for 24 hours before starting the
	compressor.
	INDOOR UNIT COMPONENT DESCRIPTION
	40QV Fan Coils—Are essentially standard Carrier indoor
	units with motor replaced by the variable speed motor and
	208-230 VAC controller and interface board (ref. Figs. 11
	and 12.)

58SSB Furnace Blower Accessory—Includes the same motor as the 40QV fan coil. Its controller and interface board are 115 VAC versions of the fan coil components, mounted as shown in Fig. 13.

Interface Board—serves three major functions in the system.

Whenever gas or electric heat is energized, the interface board takes over control of the blower from the outdoor unit. It then forces the blower to high heating speed, which is adjusted at the blower speed trimpot (ref. Fig. 14).

The board also contains the VVTTI thermostat power supply.

Last of all, it acts as a connection point for input power, and the control circuit between outdoor unit and indoor compo­ nents (i.e., indoor SEV, thermistor, transformer, and blower motor).

Blower Controller—serves a function similar to the outdoor unit compressor inverter. It converts single-phase, 60 Hz. power into a variable frequency output to control blower motor speed. High and low motor speed settings are adjust­ able at a 10-pin connector on the controller.

Blower Motor—is of unique design, containing a permanent magnet rotor for superior eflBciency.

A CAUTION

An extremely hard or sharp blow to the casing or drop­ ping the motor may affect motor operation due to mag­ net damage.

Indoor SEV Assembly—Is provided with the 38EV or 38QV outdoor unit. It must be mounted to indoor unit liquid con­ nection during installation. The 38EV SEV assembly pro­ vides two expansion orifices in parallel; a main orifice, which is controlled by the solenoid, and a b3q)ass orifice (See

Fig. 15).

The b5qiass orifice is sized to meter refrigerant properly at low compressor speeds with valve de-energized. At high Compressor speed, the solenoid is energized, allowing paral­ lel flow through a second, main orifice, sized properly for the additional refrigerant flow needed. At intermediate com­ pressor speeds, the solenoid is cycled on-off to control mid­ range flow rates.

The 38QV heat pump valve functions in much the same manner, except the fixed bypass orifice is replaced by a standard accurator piston. This allows the capability for non-expanded flow in the reverse direction needed in heat pumps. This valve, with cutaway, is shown in Figs. 16 and 17. See Table 3 for piston sizes.

The SEV solenoids are energized by a 24 VDC coil, driven directly by the main control board.

Indoor Coil Thermistor (T3)—Mounted to the SEV assem­ bly, it is identical to the outdoor unit thermistors.

STEP 3—Sequence Of Operation

Startup—Once the system is properly installed or serviced, there are two methods available to start the system and check operation.

The first method is the “Run Test” function, which is highly recommended for operational checkout after initial installation or servicing. The Run Test automatically oper­ ates the system in both the heat (including aux. heat) and cool modes, thus eliminating the need to adjust the thermo­ stat a number of times to force system into the desired oper­ ating conditions. “Run test” operation is detailed below.

ACC ELECTRIC	HEATER
AND CONTROLS
LOW-VOLTAGE
TERMINAL AREA i|
FAN DECK WIRING-^^
PASSAGE HOLE
(HIDDEN)
	MOTOR LEADS
OUTDOOR CABLE	ECM MOTOR
ENTRY HOLE
	CONTROLLER
	BLOWER ASSEMBLY
INTERFACE BOX
REFRIGERANT LINE	INDOOR COIL
CONNECTIONS
	FILTER SECTION
SEV ASSEMBLY'
CONDENSATE
DRAINS	A87445
Fig. 11—40QV024 Fan Coil

	ACC. ELECTRIC
	HEATER AND CONTROLS
	jr LOW-VOLTAGE
OUTDOOR CABLE	TERMINAL AREA
ENTRY HOLE	1^'

	FAN DECK WIRING
MOTOR LEADS	PASSAGE HOLE
ECM MOTOR
CONTROLLER	INTERFACE BOX
	BLOWER
	ASSEMBLY
	INDOOR COIL
REFRIGERANT
LINE CONNECTIONS
SEV ASSEMBLY	FILTER SECTION
CONDENSATE
DRAINS	A87446
	Fig. 12—40QV036 Fan Coil

R

INTERFACE CABLE

LOW VOLTAGE TERMINAL

BLOCK (TO ACCESSORT

HEATERS OR FURNACE)

THERMOSTAT

TERMINAL BLOCK

INTERFACE CABLE

GROUND WIRE

SEV/THERMISTOR

CONNECTOR

ISOLATOR GROMMET

A87447

Fig. 13—58SSB Furnace Blower Assembly

	LI, L2 POWER INPUT PRM,
„	PR1-2 POWER TO INTERFACE

CONNECTOR FOR HEATER BOX TRANSFORMER
ACCESSORY OR FURNACE
BLOWER LEADS	CONTROL POWER FROM
	INTERFACE BOX
	TRANSFORMER
	A87448

Fig. 14—Interface Board

TO OUTDOOR

UNIT

LIQUID LINE

INDOOR

THERMISTOR

THERMISTOR	A87449	A87450

Fig. 15—38EV SEV Cutaway

Fig. 16—38QV SEV Cutaway

Fig. 17—38QV SEV Parts

The second method involves setting the thermostat setpoint for a high demand (4-deg.F or more from room temperature) in the heat or cool mode. To accomplish this, refer to ther­ mostat setup instructions, Step 4. This will allow the sys­ tem to start and operate normally.

A “Speed-Up” function is available to aid in operational checkout if the normal startup method is used. The “SpeedUp” function shortens the delays and timing sequences of the normal startup routine, and is described in this section.

The system Self-Diagnostic feature (Eef. Troubleshooting, Step 5) is incorporated in both the Run Test and normal startup operation.

Run Test-

Initiation—Remove the outdoor unit control box cover, then apply power to indoor and outdoor units.

A WARNING

High Voltage power is supplied to control box compo­ nents immediately upon closure of external main dis­ connect. The main contactor is bypassed fqr initi^ charge-up of inverter capacitor (ref. Fig, 8). Electrical shock or death may result,, ,,

The Red LED on Main Control Board will illuminate for approximately 30 seconds, and then extinguish.

To initiate “Run Test” function, remove yellow jumper (board is labeled “Run Test” as ishowri in Fig. 5). Unit will start soon after jumper is reinstalled in its proper position on the board. _ v

Operating Sequence;

In the absence of any diagnosed problems, the system will operate in the Cool Mode for 7 minutes. It will then switch to Heat with auxiliary heat on (gas or electric) and immedi­ ately ramp the compressor down and off. Auxiliary heat remains energized for about 3 minutes. See Fig. 18 for a pic­ torial of Run Test sequence.

Influence of Diagnostics:

If a problem is diagnosed by the main control board, the Red LED will flash an error code. Refer to Section 5, “Trou­ bleshooting” for interpretation of the flashing code.

one of the following responses:

a)The unit may not start (Error Codes 3-5,8).

b)The unit may shut down prematurely (Error Codes 9, 10). Compressor and/or indoor fan speed may fluctuate before shutdown as the system attempts to verify or clear the problem (Error Codes 11, 14).

c)The unit may complete the Run Test properly, but flash an Error Code during operation. Some diagnos­ tics, such as low cheu-ge indication (Error Code 15), are designed to warn the serviceman of potential problems but may not affect system operation.

Manual Checkout During Run Test:

Although the system is equipped with self-diagnostic capa­ bilities, it should stül be visually and audibly inspected for proper installation and operation during the Run Test.

A check list of system operational functions is included below. Refer to Fig. 18 for the sequence of these functions and check each item. To complete the list, the Run Test can be initiated more than once.

a) Verify that compressor and outdoor fan operate with­ out excessive vibration of the outdoor unit in its mounted position.

b)Verify indoor blower operates in both the Cool and Heat Mode.

c)Verify indoor solenoid expansion valve operates prop­ erly by listening closely for valve clicking off-on at about 3-second intervals.

d)Reversing valve switches off (detected by “woosh” sound) when unit changes to Heat Mode. This sound

also ensures valve was properly energized for cooling operation (38QV only). /

e)Verify that indoor blower speed override for gas or elec­ tric heat operates properly (blower jumps from medium to high speed). This function is necessary to guarantee full blower speed operation when electric heat or fur­ nace is on. (Blower control is different for gas vs. elec­ tric heat as shown in Fig. 18).

f)Verify that electric heaters or furnace burners operate.

Once the “Run Test” has completed and the unit, including auxiliary heat is off, the main control board LED will illumi­ nate. When it extinguishes, system can be started normally by adjusting thermostat.

A87452

The system may, however, react in different ways, depend­
ing upon the problem diagnosed. Certain errors wiU cause	Fig. 18—Run Test Sequence

A WARNING

Unit is capable of restarting on normal thermostat demand soon after Run Test is completed. Personal injury can result.

Normal System Startup Sequence

Apply power to indoor units via main disconnect switches.

If outdoor unit control box cover is removed, main control board LED wiU light and extinguish after 30 seconds.

Thermostat will display HPOO (for 38QV units) or ACOO (for 38EV units).

Set up thermostat in heat, cool or automatic mode for room temperature desired (Ref. Thermostat Operation, Trouble­ shooting Section 4).

Thermostat setpoint must be 2-deg.F or more away from room temperature for the system to initiate a startup. (Room temperature can be displayed on thermostat by pressing both heat setpoint adjustment buttons to right of display simultaneously).

Startup Sequence

NOTE: Startup delays and sequence times can be shortened for system checkout by initiating “Speed-Up” jumper, described below.

	a)	Time Guard-
		Normal Ambient Startup—Mter applying power and/
		or adjusting thermostat setpoint, the system will
		undergo a 5-minute delay before starting. This will also
		occur any time the system cycles off normally, to pre­
		vent unnecessary on-off cycling.
		Low Ambient, Initial Startup—When outdoor tempera­
		tures are near or below 20-deg.F, the system will
		undergo a 26-minute delay bn initial power-up only.
		This allows the crankcase heater to at least partially
		warm up compressor before startup.
		Siartop—Compressor wffl start and ramp up to low
		speed, outdoor fan wffl come on. Indoor blower will
		start in a similar manner to compressor, 30 seconds
		later.
	b)	Low	Speed LOCA-ITI—After starting, the' unit will	lock
		in at low speed for a period of 8 minutes. This is done
		for the following reasons:
		1. System self-diagnostics wffl monitor system condi-
		tionis during this period to verify proper system
		operation.
		2. Allows indoor blower time to circulate and slowly
		mix possibly cold ductwork air with room air, thus
		avoiding erratic speed fluctuations due to unstable
		thermostat readings.
	c)	Transition to Normal Control—li the thermostat is sat­
	isfied during the Srminute period at low speed, the sys­
	tem wffl remain at low speed for 4 more minutes and
	then shut down. If not, it wffl speed up depending upon
	thermostat demand. The startup sequence is complete.
	“Speed-Up” Function
	The “Speed-Up" jumper is a yellow jumper, similar to the
	“Run Test” jumper. It’s located on the outdoor unit main
(J	control board next to the label “Speed-Up” (ref. Fig. 5). The
	function is		initiated by removing and reinstalling	the
	jumper during the sequence period you want to eliminate.

For instance, if you want to ehminate the time guard period before startup, wait for the LED to extinguish after powerup. Then pull and reinstall the “Speed-Up” jumper. This wffl shorten the respective period, (i.e., 5 minutes down to 2

minutes for the normal time guard, or 20 minutes down to 4 minutes for low ambient initial startup).

If the jumper is pulled and reinstalled during a sequence period listed in Table 2, it wffl shorten that period as indi­ cated. The speed-up function will then cancel automatically when the next event listed in the table occurs. To shorten subsequent sequence periods, the jumper must be initiated again.

Table 2—Speed-Up Function

Initiate The	Period Wiil	Speed-Up Function
Jumper During	Shorten From	Will Cancel
This Period	Normalto Speed-Up	When
—Prestart	5 Min.—2 min.	Compressor Starts
Time Guard	OR* 20 Min.—4 Min.
—Low Speed	8 Min.—	Compressor Begins
Lock in At	40-50 Seconds	Ramping Above
Startup		Low Speed, Or
		Shuts Down
— Between Defrost	45 Min.—4-5 Min.	Unit Initiates
Periods (Beiow	(1st Defrost)	A Defrost
32-Deg.F	30 Min.-4 Mrs.-
Ambient)
	3-24 Min.
	(Subsequent
	Defrosts)
—During Defrost	4-10 Min.-	Defrost Termination
	24 Sec-1 Min.

*Low Ambient Initial Startup

Cooling Operation Compressor—

During normal operation, the compressor speed will vary, based on thermostat demand, from 2200 RPM at low speed to 5000 RPM at high speed.

Indoor Blower-

Blower speed (or airflow) wffl “track” or follow compressor speed; i.e., when the compressor is at low speed, so is the blower. If the compressor ramps^oTiigh.speed, the blower ramps to high speed simultaneously. This speed signal is sent from the outdoor unit main control board, through the indoor unit interface board to the blower controller. (See Fig. 19).

Outdoor Fan—

The outdoor fan cycles on-off with the compressor.

Solenoid Expansion Valves (SEV)—

In the cooling mode only, the SEV at the indoor unit is oper­ ated. SEV operation “tracks” or follows compressor speed directly. At low compressor speed operation, the solenoid remains off and aU refrigerant flow is directed through a bypass orifice in the valve body (38EV systems). In 38QV systems, the bypass orifice is located in the accurator piston (Ref. Component Description, Section 3). At high compres-

sor speed, the solenoid is energized on continuously, allow­ ing the extra refrigerant flow required through a second oriflce in parallel to the bypass orifice. At intermediate com­ pressor speeds, the SEV is cycled on-off at different rates, depending upon compressor speed. This rate is based on a 5-secpnd on-off period, with the on-time increasing (with compressor speed) from zero (at low speed) to the full five seconds on (i.e., continuous on) at high speed. For instance, at lower speeds, the SEV is on 1 second, off 4 seconds; at medium speed, on 2.5 seconds, off 2.5 seconds, and so on.

Proper vsllve operation can be checked by listening closely for the “clicking’’ at the indoor SEV during intermediate speed operation. - --— -----

The system will cycle on-off at low speeds at moderate^ (75deg.F) outdoor temperatures. It will operate continuously at increasingly higher speeds as outdoor temperatures increase.

Heating Operation—38QV Systems Heat Pump

Heat pump operation is executed in the same manner as in the coohng mode. Indoor blower speed and SEV control “track” or follow compressor speed directly. However, in the heat mode, only the outdoor unit SEV is operated. It is cycled in the same pattern as cool mode control, except cycling on-time is shortened at colder ambients, (i.e. At low ambients, the SEV may also be cycling on-off rather than remaining full on when the unit is at high speed).

The system will cycle on-off at low speeds during normal operation at moderate (50-deg.F) outdoor temperatures. It will operate continuously at increasingly higher speeds as outdoor temperatures drop.

When outdoor temperatures drop to a point where supple­ mentary heat is required, dr the optimizer function is ena­ bled, electric or gas heat is initiated. Electric heat and furnace operation are described in the following sections.

When the electric heat (“W”) is cycled off, normal sequencer operation retains blower control from the interface board until the heaters cool down. When terminals C and 1 are de­ energized by heater package, blower control reverts back to the outdoor main control board.

Supplemental (2nd Stage) Heat—(38QV Heat Pump/40QV

Fan Coil Systems Only)

I

Supplemental heat is required when the outdoor tempera­ ture drops too low for the heat pump to handle the load alone. At this point, the system begins cycling electric heat, in addition to continuing full speed heat pump operation. This is done by energizing heater package terminal “W.” The heaters and blowers are controlled as described above.

A change in blower speed when the interface board takes over control may not be noticeable, since the outdoor unit is already operating it at high speed.

It may be noticeable if the blower heating speed trimpot is adjusted below its maximum setting.

Heating Operation—(38EV Cooling Systems) and Emergency Heat—(38QV Heat Pump Systems)

Electric or gas heat is operated directly on thermostat demand on 38EV systems or whenever the 38QV outdoor unit operation is locked out due to a diagnostic problem. The blower is controlled by the interface board as described above. However, since the blower is not being operated by the outdoor unit during electric heat off cycles, the blower will cycle fuU-on-off similar to standard systems.

NOTE: Malfunction of certain electronic control compo­ nents can cause lack of Automatic Emergency Heat initia­ tion. See Service & Maintenance section for corrective servicing procedures.

The 58SSB furnace will operate as described in the litera­ ture provided with it. The only difference is control of the variable speed blower. The standard 58SSB furnace bypasses its fan relay to lock-in blower operation when the burner is on, just like an electric heat package.

Table 3—38QV Piston Sizes

UNIT	LOCATION	■ PISTON#
38QV024	Outdoor	42
, - - •	Indoor	49
38QV036 ,	. . '„ Outdoor ,,	. 52
	. Indoor...............	63

Electric Heat Control—(38EV and 38QV ¡Systems)

Electric heat is initiated and controlled by energizing “W” in the same manner as in standard systems. However, since the variable speed blower heeds a speed input signal to oper­ ate, blower control is considerably different.

Blower Control—In.=a standard 'heat package, energising ‘‘W)’’ energizes the heater sequencer(s). When this is done, the ian relay is b3^assed-by 230V power to drive the blower directly. Therefore, if the fan relay is faulty, the blower still operates for safe electric heat operation.

40QV Fan Coil Units operate in a similar manner (Ref. Wir­ ing Diagrams). However, instead of operating the blower directly, this ■'230VAC power is apphed to the interface board at terminals C and 1 (see Figs. 14 and 19). When these terhiinals are energized by the electric heat sequencer, the interface board relay breaks the speed signal connection from the outdoor unit and allows the interface board to drive the board at a speed set by the adjustable pot on the board. ; '

The variable speed blower package switches blower control to its interface board when “W” is energized, in the same manner as described above for “Electric Heat Control.” (The furnace interface board design is identical to that for the 40QV fan coil, except it is a il5VAC yersioh)/

The blower will remain off for 2r3 minutes while the burner ignites and warms the heat exchanger. The blower wUl then start, and ramp to low speed for a short period before going to full speed. 'When “W” is de-energized, the blower will stay on for a short period to use the remaining heat from theexchanger.

Supplemental (2nd Stage) and Optimizer Control—(38QV Heat Pump/58SSB Furnace Systems)

Unlike fan coil operation, the furnace wiU not operate simul­ taneously with the heat pump. Therefore, whenever the out­ door temperature drops to where the heat pump cem no longer match the load, or the optimizer setpoint is reached, the heat pump wfll shut down when. furnace startup is requested (“W” is energized). At this point, the heat pump wfll also shut down the indoor blower (except if ,the thermo­ stat is in the fan-on position). The normal furnace delay of 2-3 minutes wfll then pass before the blower is cycled back on, to allow the heat exchanger to heat up. Once the thermo­ stat is satisfied by the furnace, it will cycle off. Operation wfll alternate between furnace and heat pump, until either the heat pump can handle the entire load, or the optimizer setpoint is reached. If the optimizer setpoint is reached, the heat pump wfll be locked out (a minimum of two hours) and the furnace will cycle directly on thermostat demand.

		Adaptive Defrost—
		38QV Heat Pump Systems utilize an adaptive defrost con­
		trol which clears the coil of frost only when necessary.
	•r■■	Based on coil conditions and outdoor temperature, the time
		between defrosts is adjusted between 30 minutes and four
		hours, as described below.
		Between Defrost Period Calculation-

--------------------------------------			---------------/
It				1 lO 'O oii—
—1
			^OWER HEAT
			SETPOINT

Defrost monitoring is begun when the O.D. coil thermistor temperature drops below 32 degrees F. The first defrost will occur 45 minutes later.

When the unit is ready to defrost, the pre-defrost O.D. coil thermistor temperature (frosted coU) is memorized, and thè unit then switches to defrost. A short time after defrost is completed, a post-defrost thermistor temperature (clear coU) is memorized.

The after-defrost (clear cod) temperature is used to estimate outdoor temperature and the optimum pre-to-post defrost coil temperature change (i.e. frosted coil vs. clear coU temperature).

The time period to the next defrost is then determined by:

a)If defrost time was less than 5 minutes, add 30 minutes to previous period.

b)If defrost time was maximum (10 minutes), and O.D. con temperature at termination was:

—more than 45 degrees F, divide previous period in half.

—less than 45 degrees F, next period will be 30 min­ utes.

c)If defrost time was greater than five and less than 10 minutes, the new time is calculated by:

. . , optimum temperature change * previous peno x actual post-defr. temp..minus pre-defrost temp.

*The new period calculated by this method cannot be less than half, or more than double the previous period.

Other Limitations:

Maximum period between defrosts is 4 hours. Minimum period between defrosts is 30 minutes, except:

The initial defirost after coming out of optimizer mode will occur 15 minutes after startup.

Defrost Sequence—

When a defrost is initiated, compressor speed is dropped to medium speed. This is done to mininiize shock to the com­ pressor. The reversing valve and heat (terminal “W”) relays are energized, the outdoor fan relay de-energized, and com­ pressor then ramped to full speed for a rapid defrost. Defrost is terminated on any of the following occurrences:

a)O.D. coil thermistor rises to 80 degrees F (when out­ door temperature is above 10 degrees F).

b)O.D. coil thermistor rises to 60 degrees F (when out­ door temperature is below 10 degrees F).

c)10-Miuute maximum defrost period.

The system then ramps down to medium speed, returns to heat mode, and returns to the pre-defrost speed.

Heat/Cool/Auto Control-

This thermostat function controls as in standard systems. Heat or cool operation may be requested separately. The “Auto” position allows the' system to switch between these two modes automatically as required to satisfy thermostat setpoint demand.

Fan-On/Auto-

With the fan-auto mode selected, the indoor blower will

•HP’OBQV)	\ /		\ /		\ /		COOL	\	4 ’HP' or 'AC:.		V /
•AC’(38EV).	■HP		65		HP			•66			HP
	00		56		;;			56	-HEAT		05
	z' \				N			' \	SETPOINT		N
	NORMAL POWER-UP			IMPROPER							SYSTEM
				CONFIGURATION						DIAGNOSTIC

ERROR CODE

ON I OFF I
68	69	70	71	72	76	77	78	79

ROOM TEMPERATURE
Fig. 20-VVT-ll MST Thermostat	A87454

cycle on-ofil with the outdoor unit and/or the electric/gas indoor unit.

The fan-on mode will keep the indoor blower operating at all times. The blower will operate at low speed during systemoff intervals.

STEP 4 VVT-II Thermostat Startup/Troubleshooting

The MST-04 or MST-16 thermostat consists of a printed cir­ cuit board, a connector board, and a wall mounted case.

A thermostat software revision of 6.7 or higher is required.

AU wiring connections to the thermostat are made to the connector board. .

Mount the thermostat as described in 38EV or 38QV out­ door unit installation instructions, or follow the Installation Instructions included with each control. Thermostat must be wired as shown in Figs.. 36 and 37.

Fig. 20 shows front view of the VVT-II MST thermostat.

Start-Up Procedure:

Close indoor main disconnect.

Normal Display—The thermostat will. display HPOO (for 38QV systems), ACOO (for 38EV systems), or 4 zeros, then switch to the normal heating/cooiing setpoint as shown.

Blinking Display—If the thermostat display blinks on .and off or is erratic, it is an indication that a wiring connection is not correct, or that the thermostat is not receiving ade­ quate power. Check the wiring connections and the supply voltage (22VAC rninimum) at terminals SEC-1 and SEC-2 on the interface board. Make certain the thermostat ribbon cable has been inserted into the connector board correctly.

Display Four Zeros—If the display shows four zeros upon power-up, and then displays “HF-11,” it indicates that the thermostat is currently configured for a multiple-zone sys­ tem. It must be reset for single-zone control.

Setting Thermostat For Single-Zone Control—

To correct the configuration, set the rotary switch to posi­ tion #1 (ref. Fig. 20). A number and “ON” or “OFF” will

appear on the display. Press either of the right (“Heat”) setpoint buttons to change the display to “OFF.” This is the indication that the thermostat is now correctly set for single-zone control. Now adjust the displayed number to “2” by pressing the cool setpoint buttons; the lower one to decrease the number, upper one to increase. Return the rotary switch to position #0 and press any setpoint button to display the normal setpoints.

Adjust Heating/Cooling Setpoints—The setpoints for both heating and coohng can be easily adjusted by pressing the setpoint buttons as shown.

Installer Adjustable_Fe Clock Option—Each thermostat is equipped with a buüt-in instruction manual which explains the various installer adjustable features and how to set the time clock.

FoUow each page of the manual to configure the thermostat based on the application. Always set the “Local Set-back Control” to ON.

For single-zone control applications, the following features wül have no effect on the thermostat operation and can be disregarded at the time of installation:

#6—Duct Temperature Sensor Calibration #7—Max Damper Position/Min Ventilation Position #C—System Demand

#D—Communication Test - #E—Supplemental Heat

Error Codes—3ie displayed as HF, SF, HP or AC followed by a two digit number (ref. Fig. 20.) An HF or SF code indicates a thermostat malfunction (see Thermostat Trou­ bleshooting, below). A HP or AC code indicates a system diagnostic malfunction (see System Troubleshooting, Section 5).

Set-Back Feature—li the homeowner desires to use the set­ back feature, remove the “set-back override jumper” from the connector board at the back of the thermostat.

Operation—When an “OFF” time occurs, the thermostat displays the word “SETBACK” and the highest cooRng and lowest heating setpoints. When an “ON” time occurs the thermostat returns to the last setpoints that were displayed before set-back.

Overriding Set-Back—During set-back the heating'or cool­ ing set-back Setpoint can be manually 'overridden by adjust­ ing the setpoint through the use of the setpoint buttons. The setpoint selected becomes the new comfort setpoint that the thermostat uses when the next “OÑ” time occurs.

When the set-back setpdiiit is overridden the comfort setpoint chosen remains displayed until the next “OFF” time occurs; unless the' user manually adjusts the setpoint back to the set-back setpoint; ;

Programming Set-Back—Follow the built-in thermostat instruction mandai (behind front cover) to program the ON/ OFF times for set-back operation (and for programming the electronic time clock). ■ , - .

Set-Back Programming Tips—If it is desirable for a particu­ lar period to be in set back coiitinuóuály do not enter any ON/OFF times for that period;

If it is desirable, for a particular period to be in the comfort rnode continuoúsíy enter an ON time that is the same as an OFF time.

Heating/Cooling Cycles—The thermostat should be set to energize a heating cycle and a cooling cycle. Check to make certain the 38EV or 38QV system operates properly.

“HEAT,” “COOL,” or “FAN” may be shown in the lower left corner of the thermostat display depending on the sta­ tus of the system. The 38EV or 38QV system controls to 1.5-deg.F from setpoint in both heat and cool modes. It will start-up at 1.5 deg.F from setpoint (minimum run time is 12 minutes), and cycle off based on rate of room temperature change (ref. Fig. 20).

VVI-ll Thermostat Troubleshooting

Hardware Failures—HF-11 or HF-12. The thermostat is not properly configured for single-zone control application. Make certain that “OFF” is displayed when the rotary switcMs set to position #1.

HF-14, HF-15, or HF-16. There is a failure in the electronic circuitry on the thermostat. Replace the thermostat circuit board.

HF-13. The thermostat room temperature sensor is reading out of its normal range ... 30 to 180 F. (Ref. thermostat instructions).

Check the room temperature sensor to make sure that it is physically intact.

Attempt to calibrate the room temperature sensor by fol­ lowing the built-in instruction manual. If cahbration is not possible, replace the thermostat circuit board.

Storage Failures—The thermostat continuously checks its memory to make certain that stored information is valid. If information is ever determined to be invalid an error code of “SF” followed by a number is displayed.

When an “SF” error is displayed, the thermostat will also use a safe, substitute value appropriate to the particular code. (See instructions included with thermostat.)

To Clear An “SF” Error—FoUow the buUt-in thermostat manual to find the correct rotary switch position and reset the desired setting. Then return the rotary switch back to position #0.

Time Clock—The time clock should be accurate to within 10 minutes per year. During a power faUure, the time wiU be maintained for a minimum of 8 hours, after which it may be necessary to reset the clock, (Ref. thermostat instructions).

If the clock is not keeping accurate time, m^e certain the power has not been off for over 8 hours. If it has not, then replace the thermostat.

Set-Back—If the thermostat never goes into set-back make certain: '

The set-back override jumper has been removed from the connector board. ,

The thermostat hasn’t been programmed to be continuously in the comfort mode.

The thermostat is set for the proper time of day.

If the thermostat never comes out of set-back make certain:

A set-back On/Off program has been entered.

The thermostat is set for the proper time of day.

STEPS System Troubleshooting
TABLE OF CONTENTS
Self-Diagnostics—Description
Diagnostic Error Codes	Page
Error Codes 3, 4—Outdoor Coil, Suction
Thermistor Failure.......................................................	.16-17
Error Code 5—Indoor Coil Thermistor FaUure..........	18-19
Error Code 8—Locked Compressor Rotor...................	20-21
Error Code 9—Overcurrent Trip............................ .	22-23
Error Code 10—Contactor Control FaUure.................	24-25

Error Code 11—Reversing Valve Failure...................	26-27
Error Code 14—Indoor Coil Freeze................................	28
Error Code 15—Low Refrigerant Charge..................	29-31
System Malfunctions with No Error Code
No LED on power-up.....................................................	32-33
No Indoor Blower Operation........................................	34-35
Electric/Gas Heat Failure..............................................	36-37
Miscellaneous Malfunctions..............................................	39

BEFORE TROUBLESHOOTING THE SYSTEM

This troubleshooting guide covers all components of the 38EV/QV variable speed system, including outdoor and indoor units.

See previous section for thermostat troubleshooting. (Ther­ mostat Error Codes HF and SF).

A WARNING

High voltage (300VDC) circuit remains energized after main disconnect is opened. Normal capacitive discharge time is ten (10) minutes, but this period may be extended indefinitely by component failure. Before servicing, always check with D.C. voltmeter between contactor terminal #23 (violet wire) and ground. Always reinstall safety shield in top of control box after servic­ ing. Electrical shock can cause personal injury or death.

Before replacing components to correct a system malfunc­ tion, always inspect circuit for damaged or oorroded wiring. Connectors should be inspected for improper mating. They should then be unplugged and examined for corrosion, dam­ age or incomplete terrhinal insertion. This procedure is espe­ cially required when a system malfunction is intermittent (does not occur consistently).

Clean and/or repair wiring as required. A special accessory terminal kit (Carrier Service Part No. 38QV660001) includ­ ing terminal extraction tools is available through your local, distributor.

Use high quality multimeter for troubleshooting electronic devices in this system.

Self-Diagnostic Error Codes—

Error codes are indicated at an LED located on the outdoor unit main control board (Ref. Fig. 5), and on the indoor ther­

mostat display (Ref. Fig. 20).

Control board LED error codes are shown as a series of % second on, % second off flashes, followed by a 10-second pause before repeating.

Thermostat display error codes are shown as a two-digit number, preceded by “HP” on 38QV heat pump systems or “AC” on 38EV coohng-only systems.

As an example, when an error Code #5 is diagnosed, “HP05” or “AC05” will be displayed at the thermostat when 5 flashes are indicated at the control board LED.

Automatic System Restarts on Diagnostic Shutdown—

AU diagnostic shutdowns described in this text wfll cause as many as five restarts before final shutdown and compressor lockout. The system wfll remain off for at least five minutes (time guard function) before attempting each restart.

Note that the control board LED wfll display the error code after each shutdown. The thermostat display will indicate an error code only after final compressor lockout.

A CAUTION

Whenever troubleshooting system with power on and control board LED flashing error code, check ther­ mostat display. If error code is not indicated at thermo­ stat, automatic restart is pending. Servicing of equip­ ment at time of automatic restart may cause personal injury.

How to “Clear"Error Codes—

Indoor unit power (i.e., controLpower) must be broken and reset in order to cancel system lockout on a diagnostic.

. The-Self-Diagnostics, feature is designed .to monitor inputs (thermistors and inverter alarm) and take over control of the system if these inputs go out of normal range.

Table 4 lists each of the Self-Diagnostic error codes, the con­ ditions, that cause the code, and how the system reacts to each condition.

Troubleshooting System withRower On—

Always bredk power to both indoor and outdoor units when servicing, except as indicated in the following procedures.

Table 4—Self Diagnostic Error Codes

ERROR		CAUSE	^ SYSTEM REACTION
CODE	DESCRIPTION
3	O.D. Coil Thermistor Failure	Thermistor reads greaterthan 160'’F or less than -dO^F '	: Immediate Shutdown or no startup*
4	Suction Thermistor Failure	Same as above	Same as above*' - - ■
5	i.D, Coil Thermistor Failure	Same as above	Same as above*
8	Locked Compressor Rotor	Inverter alarm—on within 2 minutes after contactor	Sameasabove* -
		energization
9	Overcurrent Trip -	Inverter alarm—on after 2 minutes of run time (See Note 1)	Compressor slows down to cancel alarm. If alarm stays on system shuts down.
10	Contactor Control. Failure	No change in thermistor readings (See Note 2)-	Immediate Shutdown or no startup*
11	Reversing Value Failure	O.D., IrD. Coii Thermistor readings change in wrong	Compressor speeds up to shift valve. If thermistor readings don't switch direction,
		directions (See Note 2).	system shuts down.* - - ■
14	indoor Coil Freeze	Suction Thermistor reads less than 32°F in Cool Mode.	Blower speeds up to raise suction temperature above 35°F. If so, blower continues
			operation at higher speed. If not, .system shuts down.*'
15	Low Refrigerant Charge	Suction thermistor reads much higher than I.D.	No effect on system operation. Error code on control board LED only.
		coil (cool), or O.D. coil (heat) thermistor.

NOTES:
* System attempts 5 restarts (each followed by 5 minute timeguard) before lockout and error code display on thermostat.
1. Inverter	alarm comes on	at 100% of rated inverter	output-current. Control board ramps compressor speed down until	alarm goes off at 85%	of rated
current.	If control board	drops compressor speed to	minimum and alarm remains on, it knows inverter has tripped,	and shuts system down.	(Inverter

trip requires reset of inverter power through contactor to shut off alarm).

2. Control board compares thermistor readings after 5 minutes of run time to readings taken at startup (contactor energization).

'I

Fig. 21 — Error Codes 3 and 4

16