Product Overview
This document provides installation, operation, maintenance, and troubleshooting information for the Nortron B Series Electric Furnace. It covers models including 21B10M, 21B15M, 21B18M, 21B20M, 21B25M, 21B27MS, 83B13, 83B24, and 83B27.
For service and support, contact Nortron in Sherbrooke, Quebec, visit www.dettson.ca, or call 800-567-2733.
The unit is certified by SP C US and manufactured in Canada.
Important Warnings and Cautions
WARNING:
- Do not tamper with the unit or its controls. Contact a specialized contractor for repairs.
- When using a humidifier, ensure it does not damage the heating element bank.
- Annual inspection by a specialized technician is recommended.
- Poor maintenance of air filters or unbalanced static pressure can decrease performance.
- Use only genuine Nortron parts for maintenance or service. Unbranded parts may void the warranty.
- Operating the unit without an air distribution duct will void the warranty.
- Do not use jumpers to simulate heat demand.
- Risk of electrical shock: Disconnect power before installation, servicing, maintenance, or field wiring. Replace all panels before operating to prevent severe injury or death.
- Wear safety glasses and gloves during installation, servicing, or cleaning.
- Use high-quality, name-brand thermostats for optimal performance.
- Comply with local regulations that may have more restrictive installation or certification requirements.
- Do not store or use gasoline or other flammable liquids/vapors near the unit or any other appliance.
- This manual is intended for qualified personnel trained in furnace installation. Installation by unqualified persons may lead to equipment damage or hazardous conditions.
- The furnace is not watertight and is not designed for outdoor installation. Protect electrical components from water to prevent hazardous electrical conditions and premature failure.
- Do not block combustion air openings. Blockages can lead to improper overheat situations, fire hazards, or bodily harm.
- Ensure an uninterrupted electrical ground connection for safety. Attach the ground conductor firmly to the ground lug.
- Do not use this furnace as a construction heater, as it exposes it to abnormal conditions, contaminated air, and lack of filters, potentially leading to premature failure or vent failure.
- The owner/user is responsible for maintaining the area around the furnace free from combustible materials, ensuring adequate air quality (not excessively dusty or humid), and always operating the unit with an air filter.
- Before servicing, ensure all utilities are turned OFF upstream of the appliance, unless operations specifically require power. Failure to do so can cause fire hazards or bodily harm.
- Address all questions regarding operation, maintenance, or warranty to the company where the product was purchased.
CAUTION:
- Never burn garbage or paper in the heating system. Keep rags or paper away from the unit.
- Return air grilles and warm air registers must not be obstructed.
IMPORTANT: Local and national code requirements for electrical installation, heating equipment, wiring, and flue connections must be followed. Applicable codes include ANSI/NFPA 70 (National Electrical Code) and CSA C22.1 (Canadian Electrical Code). Consult the latest issues of these codes, available from the National Fire Protection Agency or the Canadian Standards Association.
1. Dimensions
The furnace is designed with specific dimensions for installation. Various views are provided:
- Top View: Shows the discharge opening size (17" x 17" or 432 mm x 432 mm) and related dimensions (11½" or 38 mm).
- Front View: Indicates the overall height (39" or 991 mm) and width (20" or 508 mm), along with a 1" (25 mm) dimension. It also shows the filter frame location, which can be on the side, rear, or bottom.
- Side and Rear Views: Illustrate wiring knockout (KO) locations and dimensions, as well as the return air opening size (1½" x 1½" KO or 38 mm x 38 mm).
Wiring KO Values:
- A = 1⅜" (35 mm)
- B = 1¼" (32 mm) & 1¾" (44 mm)
- C = ⅞" (22 mm) & 2" (51 mm)
2. General Requirements and Specifications
Installation Environment:
- Install in a dry, non-corrosive, well-ventilated environment, free from excessive dust.
- Ambient temperature should be between 10°C and 27°C. If below 10°C, the plenum requires insulation for a minimum of 10 linear feet.
Location and Position:
- Locate the furnace centrally to the heating area.
- Installation can be vertical, horizontal, or downflow. For horizontal installations, position the furnace so the door is not on top, ensuring motor bearings are correctly oriented. For vertical downflow, use "L" or "T" shaped plenums without openings directly below the furnace.
Installation Clearances:
- The unit is approved for "zero inch" clearance as shipped. Refer to the data label for any additional clearance requirements.
Temperature Rise:
- Furnaces are set to operate at 0.20" W.C. (50 Pa) external static pressure and are certified for operation up to 0.50" W.C. (125 Pa). Adjustments may be needed based on temperature rise tables.
Service Clearance:
- Units are serviced from the front. Maintain at least 24" (610 mm) clearance in front of the door.
Specifications Summary:
The following tables detail model specifications, including power (KW, BTU), amperage, motor details, and temperature rise at 0.20" W.C. static pressure for both 240V single-phase and 208V three-phase models.
| Model No. | KW | BTU | Amps | Motor HP | Blower | Temp Rise (°C) | Temp Rise (°F) | Speed | RPM |
|---|---|---|---|---|---|---|---|---|---|
| 21B10M | 10 | 34152 | 46 | 1/3 | 10" x 8" (254 mm x 203 mm) | 23 | 41 | LOW | 663 |
| 21B15M | 15 | 51228 | 67 | 1/3 | 24 | 43 | MED-LOW | 814 | |
| 21B18M** | 18 | 61473 | 77 | 1/3 | 27 | 49 | MED-LOW | 814 | |
| 21B20M** | 20 | 68304 | 86 | 1/3 | 33 | 59 | MED-LOW | 814 | |
| 21B25M** | 25 | 85379 | 107 | 1/3 | 37 | 67 | MED-LOW | 814 | |
| 21B27MS*** | 27 | 92210 | 116 | 3/4 | 12" x 8" (304 mm x 203 mm) | 36 | 65 | MED-HIGH | 707 |
| 83B13 | 13.5 | 46105 | 42 | 1/3 | 10" x 8" (254 mm x 203 mm) | 21 | 38 | MED | 960 |
| 83B24 | 24 | 81964 | 70 | 1/3 | 35 | 63 | MED | 960 | |
| 83B27 | 27 | 92210 | 78 | 1/3 | 39 | 70 | MED | 960 |
Airflow and Static Pressure Data:
The following tables provide airflow (CFM and L/s) at various static pressures for the 10" x 8" and 12" x 8" blowers.
10" x 8" (254 mm x 203 mm) Blower
| Speed | Static Pressure (Inches of Water Column) | ||||
|---|---|---|---|---|---|
| 0.2 | 0.3 | 0.4 | 0.5 | 0.6 | |
| LOW | CFM: 756 L/s: 357 | 749 353 | 740 349 | 729 344 | 713 337 |
| MED-LOW | CFM: 1035 L/s: 488 | 1018 480 | 997 470 | 971 458 | 935 441 |
| MED-HIGH | CFM: 1177 L/s: 556 | 1157 546 | 1132 534 | 1102 520 | 1063 502 |
| HIGH | CFM: 1301 L/s: 614 | 1276 602 | 1247 588 | 1207 569 | 1145 540 |
12" x 8" (304 mm x 203 mm) Blower
| Speed | Static Pressure (Inches of Water Column) | ||||
|---|---|---|---|---|---|
| 0.2 | 0.3 | 0.4 | 0.5 | 0.6 | |
| LOW**** | CFM: 727 L/s: 343 | 699 330 | 667 315 | 636 300 | 606 286 |
| MED-LOW**** | CFM: 912 L/s: 431 | 897 423 | 878 414 | 853 402 | 823 388 |
| MED-HIGH | CFM: 1216 L/s: 574 | 1200 566 | 1181 557 | 1157 546 | 1129 533 |
| HIGH | CFM: 1640 L/s: 774 | 1601 755 | 1558 735 | 1513 714 | 1466 692 |
WARNING:
- Models 21B18M, 21B20M, and 21B25M must not be set to run continuously at LOW speed, as this can cause overheating. These models are certified for HIGH, MED-HIGH, and MED-LOW speeds only.
- Model 21B27MS must not be set to run continuously at LOW or MED-LOW speeds, as this can cause overheating. This model is certified for HIGH and MED-HIGH speeds only.
- Speeds marked with **** can only be used with the heater OFF, for cooling/ventilation purposes.
- Model 21B27MS includes additional noise-absorption components for quieter operation.
Specifications are subject to change without notice.
3. Operating Options
The furnace operates in a "Standard Heating Mode" by default, with all switches in the down position. When the thermostat calls for heat, automatic controls activate the furnace.
The blower speed adjusts automatically based on heating element activation via time delay relays. This speed change timing depends on furnace size (10 kW and 13.5 kW models do not change speed) and the SEASON SELECT switch setting (COLD or MILD).
Users can change from the Standard Heating Mode using the furnace controls:
- RECIRCULATION MODE:
- ON: Blower runs continuously on low speed for even air distribution. It automatically adjusts to the necessary heating speed when heating elements are activated.
- OFF: Blower motor operates in standard heating mode, controlled by the thermostat.
- SEASON SELECT:
- MILD (Not included in models 21B10M and 83B13): For spring and fall, approximately half of the heating elements are "off-line" to maintain a comfortable temperature without full capacity.
- COLD: All heating elements are "on-line" and controlled by the thermostat.
NOTE: If using an outdoor or two-stage thermostat, the SEASON SELECT switch MUST be set to MILD.
4. Breakers
B Series furnaces feature front-panel breakers to protect heating elements from overcurrent. If an overcurrent situation occurs, the breakers will open, cutting power only to the heating elements.
The number of breakers varies by model: 21B10M has none; 21B15M, 21B18M, 21B20M, and 83B13 have two; 21B25M, 21B27MS, 83B24, and 83B27 have three. Refer to Section 8 for Wiring Diagrams.
WARNING: Breakers do not cut power to the entire furnace, only to the heating elements. Do not use breakers to turn off the furnace. Power to the entire unit must be cut from the main electrical panel.
5. Installation Notes
5.1 Cold Air Return
The return air duct can be attached to the side, rear, or bottom of the furnace. For side returns, four 1½" (38 mm) knockouts allow for cutting an 18" x 18" (457 mm x 457 mm) opening. Mount the filter frame over the opening with its open side facing front, then attach the 19" x 19" (483 mm x 483 mm) air duct. For bottom mounting, remove the bottom plate and attach the filter frame to the bottom flanges.
5.2 Electrical Wiring - Power Supply
Furnaces are factory wired. A two-wire plus ground supply wire is required for single-phase units, and a three-wire plus ground for three-phase units. The ground conductor must be firmly attached to the furnace ground lug, and supply wires connected to the terminal block.
NOTE: For single-phase furnaces using an FK120 kit for an air cleaner/humidifier, a third (neutral) conductor must be supplied.
WARNING: Use appropriate gauge copper wire. Electricians are responsible for ensuring wiring and connections comply with the latest Canadian Electrical Code and local codes.
5.3 Connecting and Adjusting the Low Voltage Thermostat
Attach thermostat wires to the low voltage terminal block inside the furnace. Follow the thermostat's diagrams. Generally, R & W terminals control single-stage heating, and R & Y control cooling. Single-stage cooling uses "Y/Y2" as the first stage, while two-stage cooling uses "Y1" for the first and "Y/Y2" for the second. Ensure the thermostat is level and properly located.
CAUTION: Set the heat anticipator in the thermostat correctly before operating the furnace.
To set the anticipator accurately:
- Set the anticipator to its highest setting.
- Disconnect the "W1" thermostat wire from the furnace.
- Connect an AC meter between the "W1" terminal and the loose "W1" wire.
- Turn the thermostat up to start the furnace and let it run with all elements on for 3-4 minutes.
- Read the current draw on the meter and adjust the anticipator to match the reading.
6. Use in Mobile Homes
Models 21B10M, 21B15M, 21B18M, and 21B20M are certified for "L"-shape and "T"-shape shallow duct installations with the FSB-1 sub-base in downflow applications, provided supply air ducts pass through the floor. A recommended floor opening is 14½" x 14½" (362 mm x 362 mm). The duct system must not exceed a maximum external static pressure of 0.50" W.C. (125 Pa).
Shallow Duct Area Requirements:
| Duct Depth | Duct Width |
|---|---|
| 4" (102 mm) | 16" (406 mm) |
| 5" (127 mm) | 13" (330 mm) |
| 6" (152 mm) | 10" (254 mm) |
7. Using Optional Equipment
7.1 Two-Stage or Outdoor Thermostat
These controls are compatible with all models except the 10 kW. Ensure the SEASON SELECT switch is in the MILD position. Follow the thermostat's instructions and the furnace wiring diagram. The chart below shows the heat output stages:
| Model | First Stage (kW) | Second Stage (kW) |
|---|---|---|
| 10 kW | 10 | - |
| 15 kW | 10 | 5 |
| 18 kW | 9 | 9 |
| 20 kW | 10 | 10 |
| 25 kW | 15 | 10 |
| 27 kW | 13.5 | 13.5 |
7.2 Air Conditioning
The furnace is equipped for air conditioning (thermostat not included). The evaporator coil should be installed by a local contractor, centered over the furnace "chimney" 4" to 6" (102 mm to 152 mm) above the furnace top. Prevent air bypass of the cooling coil during operation. A bypass damper may be used for heating if the discharge opening is significantly larger than the coil.
Typical air-conditioning field wiring connections are illustrated in the provided diagram.
7.3 Electronic Air Cleaners and/or Powered Furnace Humidifiers
These units operate at 120V. The 240V furnace can accommodate the Model FK120 adapter kit for the required 120V supply. Instructions are included with the kit. The FK120 kit is not compatible with 83B 208V three-phase models.
7.4 Interlock Connection
When using the electric furnace with another device (e.g., a wood burning furnace), connect as per the wiring diagram. The thermostat of the primary heating device can then automatically activate the electric furnace blower. Nortron also offers a low-speed interlock kit (FIK) to synchronize furnace operation with ventilation fans or HRV units.
8. Wiring Diagrams
This section contains detailed wiring diagrams for each model (21B10M, 21B15M, 21B18M/21B20M, 21B25M, 21B27MS, 83B13, 83B24, 83B27). These diagrams illustrate electrical connections, component layouts, and wiring color codes (BK, BL, O, R, W, Y). They are critical for proper installation and troubleshooting.
WARNING: Always disconnect power before performing any electrical work. Ensure all panels are replaced before operating to prevent electric shock.
Critical Characteristics: Use equivalent wire if replacing original wiring. All wiring must comply with applicable codes, ordinances, and regulations. Use only Class 1 wiring inside furnace compartments. Line voltage wiring specifications are provided for UL and CSA approved wires.
9. Service Parts
A diagram illustrates the location of various components within the furnace, keyed by number. Replacement parts are available, and using genuine Nortron parts is recommended to ensure proper function, safety, and performance. Tables list Time Delay Relays and other replacement parts with their respective key numbers, part numbers, and descriptions.
Optional kits include the FIK (Furnace Interlock Kit) and FK120 (120 Volt Kit).
10. Maintenance
- Motor: Lubricated for life; requires no oiling.
- Filters: Size 20" x 20" x 1" (508 mm x 508 mm x 25 mm). Inspect and replace when dirty, typically twice per heating season, or more if continuous blower operation is used.
Thermal Cut-outs: Each element has an automatic reset thermal cut-out (opens at 160°F / 71°C). Manual reset thermal cut-outs (open at 200°F / 93°C) require front panel removal for resetting.
WARNING: Cut power supply (240 V or 208 V) before removing the front panel.
11. Troubleshooting
Troubleshooting begins by determining if the fault lies with the furnace or the thermostat/wiring. The "Thermostat ON" diagnostic light helps identify if the thermostat is calling for heat.
Diagnostic Guide:
- If the furnace will not start: Turn the thermostat to its highest setting. If the "Thermostat ON" light illuminates, the thermostat is functional, and the issue is with the furnace. If the light remains off, the problem is likely with the thermostat or its wiring.
- If the furnace will not turn off: Turn the thermostat to its lowest setting. If the "Thermostat ON" light turns off and the furnace stops, the thermostat is functioning correctly, and the issue is within the furnace. If the light stays on, the problem is with the thermostat or its wiring.
The following table lists common problems and potential causes:
| Problem | Possible Defective Parts or Components |
|---|---|
| 1. The furnace will not turn on. | • Thermostat • Circuit breaker or fuse is open • RECIRCULATION MODE switch (open contact) • Bottom Sequencer • Transformer |
| 2. Motor runs continuously. | • RECIRCULATION MODE switch is not on OFF position • Thermostat wires incorrectly attached to the furnace • Bottom sequencer (the bottom heating element would also remain on) • 24 V Relay |
| 3. Elements on, but motor does not run. | • Motor or capacitor |
| 4. Motor going on and off in short cycles (or in too long cycles) | • RECIRCULATION MODE switch (open contact) • Bottom sequencer |
| 5. Thermostat setting requires significant adjustment. | • Heat anticipator in thermostat incorrectly set or defective • Thermostat is not leveled or out of calibration |
| 6. Not enough heat | • One or more defective elements or sequencers • SEASON SELECT switch set in MILD position • Safety limits opening due to duct obstruction or dirty filters • Defective or incorrectly wired two-stage or outdoor thermostat • Lack of adequate cold air returns |
| 7. Two-stage or outdoor thermostat not operating properly. | • SEASON SELECT switch not set in MILD position |
| 8. Motor goes off, but one or more elements stay on. | • Sequencer • Top sequencer • 240 V relay |
| 9. Automatic speed change does not occur when furnace heats up. | • Sequencer |
| 10. Thermal cut-out opens. | • Airflow is reduced due to blocked ductwork or very dirty filters. |
| 11. Breaker on front panel trips. | • Overcurrent on heating element. Reset the breaker. If the problem persists, call an electrician. |
12. Warranty
Nortron offers a Sixty-Month Limited Warranty for its products, covering defects in materials or workmanship from the original purchase date. No other warranties, express or implied, including warranties of merchantability or fitness for a particular purpose, are provided.
During the warranty period, Nortron will, at its option, repair or replace defective products or parts free of charge. The customer must ship the product or part prepaid to the company factory or an authorized service center.
This warranty excludes filters, furnace kits, ducts, accessories, normal maintenance, misuse, negligence, accidents, improper maintenance or repair (other than by Nortron), faulty installation, or installation contrary to instructions. Nortron is not responsible for transportation or reinstallation costs.
Implied warranties are limited to the sixty-month period. Some jurisdictions may not allow limitations on implied warranty duration.
Nortron's sole obligation is repair or replacement. Nortron is not liable for incidental, consequential, or special damages. Some jurisdictions may not allow these exclusions.
This warranty grants specific legal rights, which may vary by province. It supersedes all prior warranties and applies only within Canada.
To qualify for warranty service, notify Nortron with the model number and a description of the defect, and provide proof of original purchase date. Contact Nortron at 3400 Boul. Industriel, Sherbrooke, QC J1L 1V8, www.dettson.ca, or 800-567-2733.
