M-Series Accessories

REMOTE CONTROL STATION 

CE-SMARTTM SYSTEM  

The CE-Smart system includes a lockable NEMA 1 enclosure (9"W x 14"H x 5"D) equipped with a three position selector switch (Summer Ventilation - Off - Heating); a combination seven day programmable timer and thermostat (TSS); an override timer; intermittent/continuous control; and indicating lights for blower operation (green), burner operation (red), and reset (amber).
The operator can control the heater from this panel provided the heater mounted disconnect is in the “ON” position and the service switches are in the “REMOTE” position. The TSS utilizes an encapsulated thermistor to sense space temperature. The adjustable differential is set by the selection of the ON and OFF temperatures. This control can accommodate separately programmed schedules for both the ventilation and heating modes. See the operating and programming instructions for the TSS Controller (page 20).
The intermittent/continuous control allows the heater to be operated in two modes. During unoccupied hours it operates intermittently based on a thermostat at maxi- mum discharge temperature (see EDL - Space Heating Mode) for space heating. During occupied hours it operates continuously at modulating discharge temperature for make-up air (see EDSM - Continuous Make-Up Air Mode).  

REMOTE CONTROL STATION COMPONENTS 

THERMISTOR (RTS) 

The thermistor is wired to the temperature sensor terminal block. If remote location of the sensor is desired, the connecting cable must be wired between the thermistor and this point. The thermistor enclosure (SH-1) is packed in the remote control station for shipment. It can be mounted on the exterior sides or bottom of the remote control station or a remote location within 500 feet using 18 gauge stranded, twisted-pair, shielded cable. 

GAS CONTROL SYSTEM

The gas control system utilizes Maxitrol's Series 44 modulation con- trols. The discharge temperature sensor, which is mounted in the discharge duct, transmits a resistance signal back to the amplifier that corresponds to the discharge temperature. The amplifier creates a voltage output to drive the modulating valve to maintain the preselected temperature. The system can be operated either intermittently as a space heater at maximum discharge temperature (EDL - Space Heating Mode) or continuously as a make- up air heater with the discharge temperature modulating to maintain the space temperature (EDSM - Continuous Make-Up Air Mode). 

EDL - Space Heating Mode 

The discharge temperature is controlled by the MAX setting on the amplifier (100-160 ̊F). The heater cycles on and off based on the temperature settings of the space thermostat.  

EDSM - Continuous Make-Up Air Mode (requires CE-Smart)

The discharge temperature modulates to maintain the space temperature selector. The adjust- able temperature selector is typically mounted inside the remote control station and is set to the desired space temperature and it transmits a resistance output to the amplifier to control the discharge temperature. The non- adjustable space sensor is mounted in the space and transmits a resistance signal back to the amplifier that corresponds to the space temperature. The discharge temperature sensor is mounted in the discharge and transmits a resistance signal back to the amplifier that corresponds to the discharge temperature. The amplifier creates a voltage output to drive the modulating valve to maintain the selected space temperature by controlling the heater output between the MIN and MAX setting on the amplifier. The MIN dial setting determines the mini- mum discharge temperature the heater will deliver (40 to 80 ̊F). The MAX dial setting determines the maximum discharge temperature the heater will deliver (100 to 160 ̊F). When the space temperature drifts from the temperature selector setpoint by more than 3 ̊F, the modulating valve is driven to the MIN or MAX discharge temperature, as applicable. 

GAS CONTROL COMPONENTS AMPLIFIER (AMP) 

The amplifier creates a voltage output to drive the modulating valve to maintain the selected discharge temperature. For EDL Mode, the discharge temperature is set at the amplifier. For EDSM Mode, the range of the dis- charge temperature is set at the amplifier, however, the adjustable temperature selector controls when more or less heat is required. 

COMBINATION VALVE 

The combination valve serves as a manifold pressure regulator and redundant gas shut-off valve. The valve operates on 24 Volts AC power. The combination valve is rated for a maximum gas supply pressure of 14" WC. 

DISCHARGE AIR TEMPERATURE SAMPLING BOX  

The discharge air temperature sampling box is located on the side of the dis- charge, and is accessible from the electrical control enclosure side of the unit. The sampling box houses the high limit and the DTS. This box should not be tampered with unless performing the Calibration Procedures (page 17). 

DISCHARGE TEMPERATURE SENSOR  

The DTS is mounted in the discharge of the heater. It senses the average discharge temperature and transmits a resistance signal back to the amplifier that corre- sponds to the discharge temperature. 

FLAME ROD (FR) 

The flame rod senses the presence of flame and signals the flame safeguard relay. The presence of flame is detected by the flame rectification of the AC signal that is sup- plied to the flame rod thus creating the DC response. The resulting current flow produced can be measured with a DC microammeter. The reading should be steady and between 2.0 and 6.0 microamps (A. 

FLAME SAFEGUARD RELAY (FSR) 

The flame safeguard relay supplies 24 Volts AC to the igniter for 4 seconds before the gas valve is energized. If the burner does not light (flame is not established within 7 seconds), this control will lock out gas flow until the control is reset. If flame signal is lost during burner operation, the control will allow one retry for ignition. 

HIGH PRESSURE REGULATOR (HPR) 

The HPR option is required when the gas supply pressure exceeds the name- plate rating for the heater. Unless other- wise specified, the HPR assembly is also furnished with a high gas pressure manual shut-off valve and a tap for measuring the upstream gas pressure. The HPR must be a positive lock-up type regulator which must be vented to outdoors. It is sized according to the gas supply pressure and the capacity requirements of the heater. 

IGNITER (IGN)  

The hot surface igniter is the ignition source for lighting the gas in the burner. It is made of silicon carbide which is very fragile. Care should be used in handling. It operates on 24 Volts and the current ranges from 1.3 to 1.7 amps. It will reach temperatures in excess of 2400 ̊F during the ignition trial. 

MODULATING VALVE (MV)  

The MV responds to a 4 to 24 Volt DC signal from the amplifier to modulate the flow of gas to the burner. The low fire adjusting screw is located on the side of the valve under the dust cover. 

HEATER COMPONENTS AIRFLOW SWITCH (AF)  

The airflow switch senses the pressure drop across the burner. It is factory set and not adjustable. It is designed to pre- vent burner operation if the airflow drops significantly below the minimum design airflow of the heater. 

DAMPER MOTOR  

The damper motor operates on 24 Volts AC and switches power to the motor starter when the damper blades are fully open by the closure of the damper end switch. The damper end switch is an auxiliary Switch Which has been factory set to operate when the damper is fully open. The damp- er will spring closed when the heater cycles off. 

HIGH TEMPERATURE LIMIT (HL) 

The high limit opens when discharge temperature exceeds 180 ̊F. This limit must be manually reset. 

MOTOR STARTER (MS, OL, AUX)  

For SA250 heaters, the motor starter is a motor rated contactor that switches power to the blower motor. For SA350 heaters, the motor starter assembly consists of a motor rated contactor, overload relay and auxiliary con- tact. The overload relay protects motor from excessive current or single phasing. If overload relay trips, it must be reset manually. The auxiliary contacts are used in gas valve safety circuit as an indication blower is operating, and as an optional exhaust fan con- tact for interlocking other equipment with operation of the heater. 

MULTI-FUNCTIONAL PC BOARD 

The multi-functional PC board provides five (5) separate functions as follows: 1) Blower Relay (CR1) which is energized on “call for blower” from the remote control station. 2) The LTC (Low Temperature Cutout) circuit functions to shut down blower in approximately 31/2 minutes if either of the following occurs: (a) Inlet temperature drops below LTC setpoint (40, 45, 50, or 55 ̊F) in ventilation mode; or (b) the gas valve fails to remain energized during a heating cycle. 3) The EAT (Entering Air Thermostat) circuit functions automatically to turn off the burner when the out- door temperature reaches the EAT setpoint (45, 50, 55, 57.5, 60, 62, 64, 66, 68 or 70 ̊F). 4) The PT (Purge Timer) circuit function is preset at the factory to provide four air changes within the heater cabinet prior to an ignition attempt (normally set at 4 seconds). If inlet ducting is attached to the heater, the delay time can be increased to 8, 16, or 32 seconds, as applicable. 5) The patented LFS (Low Fire Start) circuit function is provided to limit the initial heater firing for the first 15 seconds of a heating cycle. The voltage to the modulating valve is adjusted between 9 and 13 Volts DC by an adjustable potentiometer on the PC board. 

SERVICE SWITCH (SS)  

The service switches are mounted in the electrical control enclosure. In the “LOCAL” or “OFF” position, the service technician has local control of the heater. These switches must be placed in the “REMOTE” position for normal control from the remote control station.  

TRANSFORMER (T1) 

 SA250 heaters are furnished with a 24 Volt secondary transformer. SA350 heaters are furnished with a dual 115/24 Volt secondary trans- former. A FLM-6.25 secondary fuse is provided in the Class I transformer circuit to protect downstream components from short circuit. Do not increase the fuse rating over that which is specified.

TRANSFORMER (T2)  

The Class II transformer provides 24 Volt supply for gas modulation and remote control circuits. The transformer output current is inherently limited to protect downstream components from short circuit.

 

GAS CONTROL SYSTEMS

MAXITROL SERIES 14

The Maxitrol Series 14 controls electronically modulate the burner input to maintain a selected dis- charge temperature. The discharge temperature is set on the amplifier (AD1014) between 55°F and 90°F with the standard controls. As an option, the discharge temperature can be set on a Remote Heat Adjust (TD114) control between 55°F and 130°F. The Remote Heat Adjust control can be mounted in the heater control enclosure or in the Remote Control Station. 

MAXITROL SERIES 44

The Maxitrol Series 44 controls electronically modulate the burner input to maintain a constant space temperature by increasing or decreasing the discharge temperature. The Space Temperature Selector (T244A) is set to maintain the space temperature of the heated space by controlling the heater output between the MIN and MAX setting on the amplifier. The MIN dial setting determines the minimum discharge temperature the heater will deliver (40°F to 80°F). The MAX dial set- ting determines the maximum discharge temperature the heater will deliver (80°F to 140°F)

INTERMITTENT/CONTINUOUS CONTROL

The Intermittent/Continuous Control allows the burner input to be modulated to be operated continuously at modulating discharge temperature for make-up air (see Maxitrol 44 above) or operated intermittently based on a thermostat at maximum discharge temperature for space heating.  Requires Maxitrol 44 controls and a signal to switch between modes (Exhaust Fan Interlock, Temperature Setback System, Manual Make-Up Air Switch, etc.)

REMOTE CONTROL STATION COMPONENTS

REMOTE CONTROL STATION

The Remote Control Station is a lockable NEMA 1 enclosure (9" wide x 14" high x 5" deep) equipped with a three position key lock selector switch (Summer Ventilation – Off – Heating) and indicating lights for blower operation (green), burner operation (red), and reset (amber). An auxiliary contact wired between terminals Z1 and Z2 is required to control heater operation in the heating mode. This can be accomplished by an Exhaust Fan Interlock, a Manual Make-up Air Switch, an Operating Electronic Thermostat, etc.

**IMPORTANT**

A number of the components listed below can be combined to yield a custom Remote Control Station to address a wide variety of applications.

MAXITROL SERIES 14 REMOTE HEAT ADJUSTMENT DIAL

The adjustment dial on the remote heat adjust (TD114) is either mounted on the exterior of the door of the Remote Control Station or mounted inside the Remote Control Station for tamperproof applications. The remote heat adjustment control permits manual adjustment of the dis- charge temperature from 55 ̊F to 90 ̊F. The override temperature selector dial, visible from the top of the remote heat adjustment control, increases the discharge temperature above the setting on the dial face by the increment selected (10 ̊F to 40°F) when a jumper or switch contact is provided across terminals 20 and 22.

MAXITROL SERIES 14 SPACE TEMPERATURE OVERRIDE

The Maxitrol Series 14 with Space Thermostat control system uses the Maxitrol Series 14 controls described above along with an electronic space thermostat switch contact to automatically increase the discharge temperature.

MAXITROL SERIES 44 / TAMPERPROOF

The Maxitrol Series 44 / Tamperproof controls function identically to the Maxitrol Series 44 controls (see gas control system) except the space temperature selector (T244A) is replaced with two devices. The adjustable portion, the space temperature selector (TD244A), is mounted inside the Remote Control Station, and the non-adjustable.

MAXITROL SERIES 44 / HAZARDOUS AREA

The Maxitrol Series 44 / Hazardous Area is the same as the Maxitrol Series 44 / Tamperproof, except the space sensor (TS244A) is replaced by a space sensor with epoxy coated circuitry (ES225A). The standard Remote Control Station is not suitable for hazardous areas and would need to be mounted outside of the hazardous area.

OPERATING ELECTRONIC THERMOSTAT

The operating electronic thermostat is wired between terminals Z1 and Z2 to control heater ON/OFF operation in the heating mode (see pages 65).

NON-ADJUSTABLE THERMOSTAT

The non-adjustable thermostat is a fixed temperature, solid state, epoxy sealed thermostat with a specified temperature setpoint, either: 41°F, 50°F, 55°F, 60°F, or 65°F. It is wired between terminals Z1 and Z2.

TEMPERATURE SETBACK SYSTEM

The temperature setback system is a combination seven-day programmable timer with independent programs for summer ventilation/heating modes and integral electronic thermostat with separate selectable day/ night setback temperatures (see page 67). The thermostat contact is wired between Z1 and Z2.

CLOGGED FILTER LIGHT

The clogged filter light is an alarm light mounted in the Remote Control Station to indicate a clogged filter condition. Includes an adjustable pressure switch mounted in the make-up air heater control enclosure to monitor the pressure drop across the filters.

MANUAL MAKEUP AIR SWITCH

A manual make-up air toggle switch is used to manu- ally turn the heater on and off. It is either mounted on the exterior of the door of the Remote Control Station or mounted inside the Remote Control Station for tamper- proof applications.

EXHAUST FAN INTERLOCK

An exhaust fan interlock is used to interlock the make- up air heater as a slave to an exhaust fan. Terminals are provided in the Remote Control Station for wiring of dry contacts (by others).

INDIVIDUAL HEATER COMPONENT DESCRIPTIONS

AIR FLOW SWITCH (HIGH AND LOW)

The air flow switches sense the pressure drop across the burner profile plate. They are factory set and not adjustable. They are designed to pre- vent burner operation if the pressure drop across the burner drops below 0.40 inch WC or increases above 0.85 inch WC for natural gas applications or below 0.60 inch WC or above 1.12 inches WC for LP gas applications.

AMPLIFIER

The amplifier creates a voltage output to drive an electronic proportioning gas valve to maintain the selected discharge temperature (Maxitrol Series 14) or space temperature (Maxitrol Series 44). On Maxitrol Series 14 control systems, the discharge temperature is set either on the amplifier (AD1014) or the Remote Heat Adjust (TD114). On Maxitrol Series 44 control systems, the range of the discharge temperature is set on the amplifier (A1044), but the space tempera- ture selector controls when more or less heat is required.

CONVENIENCE OUTLET

A convenient 115 volt GFI duplex receptacle is provided inside the heater’s electrical enclosure. The electrical supply source for this device can be either the heater’s control power transformer (5 amps max.) or a separate outside source (15 amps max.).

DAMPER MOTOR

The damper motor operates on 24 Volts AC and transmits power to the motor starter when the damper blades are fully open by the closure of the damper end switch. The damper end switch is an adjustable internal auxiliary switch which has been factory set to operate when the damper is fully open. The damper motor will power closed when the heater cycles off. The damper motor will not close unless the blower service switch is in the REMOTEposition. Refer to detailed instructions regarding the replacement and adjustment of the damper motor (see page 53).

DISCHARGE TEMPERATURE SENSOR

The discharge temperature sensor is mounted on the fan housing and is a component of the Maxitrol Series 14 and Series 44 temperature control systems. It senses the average fan dis- charge temperature and transmits a resistance signal back to the amplifier that corresponds to the dis- charge temperature. The Maxitrol Series 44 and Maxitrol Series 44/Tamperproof temperature control systems use the Maxitrol Series 44 sensor (TS144). The Maxitrol Series 14 control systems use the Maxitrol Series 14 sensor (TS114).

DISCONNECT SWITCH

The non-fused disconnect switch is provided on all heaters and includes a lockable operating knob. The disconnect must be off before accessing the electrical control enclosure. Once the control enclosure is open, experienced service technicians may activate the electrical circuit to assist in troubleshooting.

EXHAUST FAN CONTACT

The exhaust fan contact is an auxiliary dry contact that is mechanically interlocked to operation of the heater’s motor starter and is provided with terminals located in heater’s electrical enclosure. The dry contact is typically wired into an exhaust fan control circuit to activate the exhaust fan as a slave to the make-up air heater.

FLAME SAFEGUARD RELAY

The flame safeguard relay supplies 24 Volts AC to the igniter for 4 seconds prior to the gas valve being energized. If the burner does not light (flame is not established within 7 seconds), this control will lock out. If flame signal is lost during burner operation, the control will allow one retry for ignition.

FLAME ROD

The flame rod senses the presence of flame, and signals the flame safeguard relay. The presence of flame is detected by the flame rectification of the AC signal that is supplied to the flamerod, thus creating the DC response. The resulting current flow produced can be measured with a DC microammeter. The reading should be steady and between 2.0 and 6.0 microamps (mA).

FUSE BLOCK

The fuse block provides line fusing for branch circuit protection. It is wired in conjunction with the non-fused disconnect switch.

HIGH GAS PRESSURE SWITCH

The high gas pressure switch is a manual reset safety device to lock out the burner operation should large gas pressure fluctuations occur. The high gas pressure switch should be set at 25% above manifold gas pressure. The adjustment screw is located under the top plate.

HIGH PRESSURE REGULATOR

The high pressure regulator is required when the gas supply pressure exceeds the nameplate rating for the heater. The high pressure regulator assembly is also furnished with a high gas pressure manual shut-off valve and a tap for measuring the upstream gas pressure. The high pressure regulator is a positive lock-up type regulator which must be vented to the outdoors. It is sized according to the gas supply pressure and the capacity requirements of the heater.

HIGH TEMPERATURE LIMIT

The high temperature limit opens when the discharge air temperature exceeds 150 ̊F. This limit must be manually reset.

An inclined manometer with a range of -0.1 to 1.0 inch WC is provided on each heater with manual profile damper adjustment to indicate the pressure drop across the burner profile plate. The pressure drop should be set without the burner operating (blower only) at 0.68 inch WC for natural gas applications and 0.90 inch WC for LP applications. If the heater is sup- plied with a filter section or filters in the rainhood, increase the manometer reading to 0.72 inch WC for natural gas and to 0.94 inch WC for LP gas heaters.

DIFFERENTIAL PRESSURE SWITCH/GAUGE

A differential pressure switch/gauge is available as part of the Automatic Pro le Adjust system to control the pressure drop across the burner pro le plate. The differential pressure switch drives a Pro le Damper Adjust Motor to maintain approximately 0.68 inch WC for natural gas applications, or approximately 0.90 inch WC for LP applications.

IGNITER

The hot surface igniter is the ignition source for lighting the gas in the burn- er. It is made of silicon carbide which is very fragile. Care should be used in handling. It operates on 24 Volts and the current ranges from 1.3 to 1.7 amps. It will reach temperatures in excess of 2400 ̊F during the ignition trial. It is furnished with a sleeve for shock mounting and sealing the igniter in the mounting tube.

INTERIOR LIGHT(S)

Available for the heater cabinet, electrical control enclosure, and/or gas train enclosure. Light switches are located inside the heater’s electrical enclosure. Furnished with safety guards. 100 watts maximum, each. A separate electrical supply source is required.

LEAK TEST FACILITY

The leak test facility is provided on all heaters over 400,000 Btu/hr and consists of a momentary switch for the first safety shut-off valve in the gas train and a gauge port between the first and second safety shut-off valve. By holding the gas valve momentary switch closed, the first gas valve is energized which allows gas pressure to build on the seat of the second gas valve. The gauge port between valves is used to determine if the first gas valve seat is properly sealed.

MODULATING VALVE

The modulating valve responds to a 4 to 24 Volt DC signal from the amplifier to modulate the flow of gas to the burner. On the Maxitrol M511 or M611 valve, the minimum fire adjusting screw is located on the far side of the valve under the dust cover. On the Maxitrol MR212 valve, the minimum fire adjusting screw is located under the large dust cover. The MR212 modulating valve also serves as the manifold pressure regulator to control the burner manifold pressure. The MR212 is rated for 5 PSIG.

COMBINATION VALVE

The combination valve serves as a manifold pressure regulator and redundant gas shut-off valve. This control is typically used for gas capacities below 400,000 Btu/hr. The valve operates on 24 Volts AC power. The combination valve is rated for a maxi- mum gas supply pressure of 14 inches WC.

MANIFOLD PRESSURE REGULATOR

The manifold pressure regulator controls the burner manifold pressure. When the MR212 valve is used, this modulating valve also serves as the pressure regulator. The maximum gas supply pressure rating is normally determined by the exposed pressure rating of the regulating device. The RV61 and RV81 are rated at 1 PSIG; and the MR212 is rated at 5 PSIG. (For make-up air heaters rated at 400,000 Btu/hr or below, see the combination valve above.)

MOTOR STARTER, OVERLOAD, & AUXILIARY CONTACT

The motor starter assembly consists of a motor starter, overload relay and auxiliary contact. The overload relay protects the motor from excessive current or single phasing. If the overload relay trips, it must be reset manually. The auxiliary contacts are used in the gas valve safety circuit as an indication the blower is operating, and as an optional exhaust fan contact for interlocking other equipment with the operation of the heater.

MULTI-FUNCTIONAL PC BOARD

The multi-functional PC board provides five (5) separate functions for heaters with the Maxitrol Series 14 or Series 44 controls. The functions are as follows:

1) Blower Relay (CR1) which is energized on a “call for blower” from the Remote Control Station

2) The LTC (Low Temperature Cutout) circuit functions to turn off the blower in approximately 3 1/2 minutes if any of the following occurs: (a) The inlet temperature drops below the selectable LTC setpoint (40 ̊F, 45 ̊F, 50 ̊F, or 55 ̊F) in the ventilation mode; (b) the gas valve fails to remain energized during a heating cycle or (c) the high airflow switch contacts indicate the burner profile plate pressure drop is too high.

3) The EAT (Entering Air Thermostat) circuit functions automatically to turn off the burner when the outdoor temperature reaches the selectable EAT setpoint (45 ̊F, 50 ̊F, 55 ̊F, 57.5 ̊F, 60 ̊F, 62 ̊F, 64 ̊F, 66 ̊F, 68 ̊F or 70 ̊F).

4) The PT (Purge Timer) circuit function is preset at the factory to provide four air changes within the heater cabinet prior to an ignition attempt (normally set at 4 or 8 seconds). If inlet ducting is attached to the heater, the delay time can be increased to 8, 16, or 32 seconds, as applicable.

5) The patented LFS (Low Fire Start) circuit function limits the initial heater firing for the first 15 seconds of a heating cycle to obtain proper ignition. The voltage to the modulating valve is adjusted between 9 and 13 Volts DC by an adjustable potentiometer on the multi-functional PC board.

SERVICE SWITCH

The service switches are mounted in the electrical control enclosure. In the “LOCAL” or “OFF” position, the service technician has local control of the heater. These switches must be placed in the “REMOTE” position for normal control from the Remote Control Station.

SPACE TEMPERATURE SELECTOR

The space temperature selector is part of the Maxitrol Series 44 control system. The space temperature selector senses the space temperature. A 3 ̊F drift above the set temperature will cause the heater to modulate to the MIN setting on the amplifier and a 3 ̊F drift below the set temperature will cause the heater to modulate to the MAX setting.

TRANSFORMER

Heaters are furnished with a dual voltage transformer unless the primary voltage is 115 Volts. The transformer furnished depends on the primary voltage (208, 230, 460 or 575 Volts). This transformer pro- vides secondary control voltages of 24 and 115 Volts. Heaters supplied for 115 Volts are furnished with a 24 Volt secondary transformer only. Secondary fusing is provided in all Class I transformer circuits to protect the downstream components from short circuit. Fuse sizing is as follows: FNM-6.25 for 150 va 24 Volt and FNM-1.6 for 150 va 115 Volt. Consult the heater wiring diagram to identify the proper fusing for the heater in question. Do not increase the fuse rating over that which is specified.