Mr. Heater MH175KTR - User Manual

Questions and Answers

J
Jennifer MurphyAug 16, 2025
What to do if my Mr. Heater Heater has no spark?
- M
  Mr. Jacob Gibson Jr.Aug 16, 2025
  If your Mr. Heater Heater is not sparking, verify the extension cord's length and gauge to ensure it provides the correct amperage. Check the wiring to the igniter using the wiring schematic. Ensure the gap between the electrode probes is within the range of 2.3 to 3 mm. If there is still no spark, replace the igniter assembly. As a last resort, consider replacing the oil flame control assembly.
E
Erica PriceAug 20, 2025
What to do if my Mr. Heater Heater is unable to detect flame?
- A
  Aaron DeleonAug 20, 2025
  If your Mr. Heater Heater is unable to detect a flame, begin by checking the wiring to the cad cell, referring to the wiring schematic. Next, clean the cad cell photo cell. If the heater still fails to operate, replace the cad cell. If the issue persists, consider replacing the oil flame control assembly.
K
Kelly LeeAug 27, 2025
What to do if my Mr. Heater Heater has abnormal motor operation?
- B
  Bobby GreeneAug 28, 2025
  If your Mr. Heater Heater's motor is overheating or stopping, it could be due to several reasons. The motor speed might be too low (it should operate at 3450rpm), in which case, replace the motor. With the heater disconnected from the power source, try rotating the fan clockwise to check if the motor is free. Also, remove the air filter housing and inspect the pump rotor for damage, replacing the rotor assembly if needed. If the wiring is correct and the pump rotor is okay, but the motor still isn't rotating freely, you may need to replace the motor or power-pack assembly. If the problem persists, consider replacing the oil flame control assembly.
T
Tracey FisherSep 1, 2025
What to do if my Mr. Heater Heater has a CAD cell failure?
- P
  Patrick TaylorSep 1, 2025
  If your Mr. Heater Heater is experiencing CAD cell failure, first check the wiring to the cad cell using the wiring schematic. Then, clean the cad cell photo cell. If the heater still doesn't operate after these steps, replace the cad cell. As a final measure, consider replacing the oil flame control assembly.
S
Samuel CookSep 4, 2025
What to do if my Mr. Heater Heater has a high limit switch failure?
- A
  Angela WernerSep 5, 2025
  If your Mr. Heater Heater is experiencing a high limit switch failure, ensure the heater has cooled down, then press the reset switch and try again.
L
Lynn Stout DDSSep 8, 2025
What to do if my Mr. Heater Heater has a high limit switch open circuit?
- M
  michellebennettSep 8, 2025
  If your Mr. Heater Heater has a high limit switch open circuit, ensure that the heater is cooled off, toggle the switch to the “OFF” position, wait 5 minutes, and then try again.
J
Joshua BakerNov 12, 2025
What to do if my Mr. Heater Heater has no flame?
- D
  Dana OchoaNov 12, 2025
  If your Mr. Heater Heater has no flame, there are several things you can check: Examine the wiring to the motor according to the wiring schematic. Ensure the pressure gauge is correctly placed and undamaged. Adjust the pressure for proper heater operation as per the manual's instructions. With the heater disconnected from the power source, manually rotate the fan clockwise to ensure the motor spins freely. Inspect the pump rotor for damage after removing the air filter housing from the motor; replace the rotor assembly if needed. If these steps don't resolve the issue, and the wiring is correct but the motor still isn't rotating freely, consider replacing the motor or power-pack assembly. If the problem continues, the oil flame control assembly may need replacing. Also, check for spark arc...
W
william01Nov 23, 2025
Why does my Mr. Heater Heater have sparks but the motor is slow?
- M
  Maria MartinNov 23, 2025
  If your Mr. Heater Heater is sparking but the motor isn't operating correctly, begin by checking the motor's wiring using the wiring schematic. Make sure the pressure gauge is properly in place and undamaged. Adjust the pressure to ensure correct heater operation as detailed in the manual. With the heater unplugged, rotate the fan clockwise by hand to confirm the motor is free. Remove the air filter housing and check the pump rotor for any damage; replace it if necessary. If the wiring is correct, the pump rotor is in good condition, but the motor still doesn't rotate freely, replace the motor or power-pack assembly. If the issue continues, consider replacing the oil flame control assembly. Lastly, inspect for spark arching from the electrode assembly to the combustion cylinder and check t...

Summary

Safety Warnings

General Hazard and Environmental Warnings

Covers fire, explosion, CO, vehicle use, flammable materials, and California warnings.

Operating Precautions

Combustion Products and Ventilation

Explains CO and symptoms of inadequate ventilation.

Heater Operation Procedures

Preparing For Operation

Instructions for checking damage, fueling, and placement.

Heater Start Up and Shut Down

Procedures for starting, stopping, and restarting after safety shutdown.

Maintenance and Storage Schedules

Periodic Maintenance Tasks

Details 500-hour and annual maintenance for filters, dust, cad cell, nozzle, fuel tank, and lines.

Storage and Servicing Guidelines

Guidelines for storing the heater and indicators of normal operation.

Diagnostic Safety and Troubleshooting

LED Indicators and MH125 KTR+ Troubleshooting

Explains LED codes and troubleshooting for MH125KTR+ models.

MH50 KR;MH75 KTR Symptom Troubleshooting

Addresses common issues like no spark, motor problems, and flame control.

Wiring Diagrams

Model-Specific Wiring Schematics

Provides wiring diagrams for different heater models.

Parts List

Component Identification

Lists parts and their corresponding numbers for all models.

Parts Ordering and Service Information

Parts, Service, and Warranty Details

Covers part usage, ordering, service contacts, and warranty details.

This document is an operating instructions and owner's manual for a series of Mr. Heater Kerosene Forced-Air Heaters. The models covered are MH50KR, MH75KTR, MH125KTR, MH175KTR, and MH210KTR.

Function Description

The Mr. Heater Kerosene Forced-Air Heater is a direct-fired, unvented portable heater primarily intended for temporary heating of buildings under construction, alteration, or repair. It operates by drawing air (oxygen) from the surrounding area, mixing it with kerosene fuel, and igniting the mixture to produce heat. A blower or fan pushes the heated air through the heater into the space. The heater is designed for high combustion efficiency, but as a direct-fired unit, all combustion products enter the heated space, necessitating adequate ventilation to prevent the buildup of carbon monoxide (CO).

Important Technical Specifications

The manual provides detailed specifications for each model:

MH50KR:

Burn Rate: 50,000 Btu/hr (14.7 kW)
Fuel Rate: 0.37 gal/hr (1.4 L/hr)
Electrical Input: 115V, 60Hz, 3.5a
Line Protection: 10 amps
Min. Operating Voltage: 110V
Pressure Setting: 3.5 psig (24 kPa)
Max. Outlet Temperature: 1450°F (787°C)
Fuel Tank Capacity: 4 gallons (15.1 L)
Ignition: Direct Spark, Continuous
Spark Generator: Igniter 13 kV, 10ma
Primary Safety Control: Solid State Control
Certification: CSA Certified

MH75KTR:

Burn Rate: 75,000 Btu/hr (22 kW)
Fuel Rate: 0.55 gal/hr (2.1 L/hr)
Electrical Input: 115V, 60Hz, 4a
Line Protection: 10 amps
Min. Operating Voltage: 110V
Pressure Setting: 4.2 psig (29 kPa)
Max. Outlet Temperature: 1450°F (787°C)
Fuel Tank Capacity: 6 gallons (22.7 L)
Ignition: Direct Spark, Continuous
Spark Generator: Igniter 13 kV, 10ma
Primary Safety Control: Solid State Control
Certification: CSA Certified

MH125KTR:

Burn Rate: 125,000 Btu/hr (37 kW)
Fuel Rate: 0.96 gal./hr (3.5 L/hr)
Electrical Input: 115V, 60Hz, 5.5a
Line Protection: 20 amps
Min. Operating Voltage: 110V
Pressure Setting: 5.5 psig (38 kPa)
Max. Outlet Temperature: 1450°F (787°C)
Fuel Tank Capacity: 8.45 gallons (32 L)
Ignition: Direct Spark, Continuous
Spark Generator: Igniter 13 kV, 10ma
Primary Safety Control: Solid State Control
Certification: CSA Certified

MH175KTR:

Burn Rate: 175,000 Btu/hr (51 kW)
Fuel Rate: 1.3 gal/hr (5.0 L/hr)
Electrical Input: 115V, 60Hz, 5.5a
Line Protection: 20 amps
Min. Operating Voltage: 110V
Pressure Setting: 5.8 psig (40 kPa)
Max. Outlet Temperature: 1450°F (787°C)
Fuel Tank Capacity: 13.5 gallons (51 L)
Ignition: Direct Spark, Continuous
Spark Generator: Igniter 13 kV, 10ma
Primary Safety Control: Solid State Control
Certification: CSA Certified

MH210KTR:

Burn Rate: 210,000 Btu/hr (61.5 kW)
Fuel Rate: 1.6 gal/hr (6.0 L/hr)
Electrical Input: 115V, 60Hz, 5.5a
Line Protection: 20 amps
Min. Operating Voltage: 110V
Pressure Setting: 8.5 psig (58.6 kPa)
Max. Outlet Temperature: 1450°F (787°C)
Fuel Tank Capacity: 13.5 gallons (51 L)
Ignition: Direct Spark, Continuous
Spark Generator: Igniter 13 kV, 10ma
Primary Safety Control: Solid State Control
Certification: CSA Certified

All models are CSA certified for use with only No. 1-K kerosene fuel, but are factory tested and can also use No. 2-K kerosene, No. 1 or No. 2 Diesel, No. 1 or No. 2 fuel oil, or JP8 Jet A fuel. The use of gasoline, naphtha, volatile fuels, paint thinners, alcohol, or any other highly flammable fuels is strictly prohibited.

Usage Features

Safety and Precautions:

Ventilation: Crucial for indoor use to prevent carbon monoxide buildup. Requires at least 2 sq. ft. (0.19 sq. m.) of opening near the floor and 2 sq. ft. (0.19 sq. m.) near the ceiling directly to outdoors.
Clearances: Maintain at least 8 ft. (2.4 m) from the heater outlet to combustibles and 3 ft. (1.0 m) from the top, sides, and inlet. For canvas or plastic coverings, a 10 ft. (3.0 m) clearance is required.
Fuel: Only use recommended fuels. Always fill the tank outdoors, away from open flames, and ensure the heater is level. Do not overfill.
Electrical: Requires a properly grounded 3-prong receptacle and extension cord. Electrical connections must comply with National Electrical Code (ANSI/NFPA 70) and CSA C22.1 Canadian Electrical Code, Part 1.
Placement: Operate only on a stable, level surface. MH50KR & MH75KTR models are not suitable for wood floors or other combustible materials unless resting on a suitable insulating material at least 1 inch thick and extending 3 feet or more beyond the heater in all directions.
Operation: Do not move, handle, or service the heater while it is hot or in operation. Do not restrict inlet or exit. Not for home or recreational vehicle use.

Starting the Heater:

MH50KR: Plug into a grounded 115V, 60 Hz, 1 Ø outlet.
MH75KTR, MH125KTR, MH175KTR & MH210KTR: Turn the thermostat to the lowest setting, ensure the "On/Off" switch is "Off," then plug into a grounded 115V, 60 Hz, 1 Ø outlet. Turn the thermostat to the highest setting and push the toggle switch to "On." Adjust the thermostat to the desired setting for automatic cycling.
Cold Weather Start: For temperatures below 10°F, starting may be improved by holding a finger over the vent hole of the pump adjustment screw cap until the heater starts.
Interrupt Circuit: Units are equipped with an interrupt circuit. If the unit does not start, toggle the switch to "Off," wait 5 minutes, and toggle back to "On."

Shutting Down the Heater:

MH50KR: Unplug from the power source.
MH75KTR, MH125KTR, MH175KTR & MH210KTR: Push the "On/Off" switch to "Off." For extended shutdown, unplug the heater.

Restart After Safety Shutdown:

MH50KR: Unplug, wait 5 minutes, then plug back in.
MH75KTR, MH125KTR, MH175KTR & MH210KTR: Toggle switch to "Off," wait 5 minutes, then restart.

Diagnostic Safety Shutdown and Trouble Shooting (MH125KTR, MH175KTR, MH210KTR): These models feature a diagnostic control board with a flashing LED error indicator to signal unit operation status and guide corrective action.

Steady ON: System Check (self-test).
Steady OFF: Operation OK.
2 Flashes: No flame detected (troubleshooting steps include checking wiring, pressure gauge, pump rotor, oil flame control assembly, spark arching, and cad cell).
3 Flashes: High limit switch failure (cool down, press reset switch).
4 Flashes: CAD Cell Failure (check wiring, clean/replace cad cell, replace oil flame control assembly).
Power Light: Power to control (sensing power).

Troubleshooting (MH50KR, MH75KTR): These models are not equipped with a diagnostic control board or flashing LED error indicator. Troubleshooting is guided by symptom:

High limit switch Open Circuit: Cool down, toggle switch to "OFF," wait 5 minutes, retry.
Sparks, calling for flame, but no or slow motor operation: Check wiring to motor, pressure gauge, pump rotor, oil flame control assembly, spark arching, and cad cell.
No Spark: Check extension cord, wiring to igniter, electrode gap, replace igniter assembly, replace oil flame control assembly.
Abnormal Motor Operation - Motor overheats or Stops: Check if motor is free, pump rotor, wiring, and replace motor or power-pack assembly.
Unable to Detect Flame: Check wiring to cad cell, clean/replace cad cell, replace oil flame control assembly.
Flame Control Failure: Check wiring in heater, replace oil flame control assembly.

Maintenance Features

Periodic Maintenance (Unplug heater before servicing):

Daily Schedule:
- General: Visual inspection for loose or damaged parts. Check nuts and bolts. Ensure normal operation (flame contained, yellow flame, no strong odor, no smoke/soot, no unplanned shutdowns).
- Filters: Check for dirty air or fuel filters, which can cause an imbalance in the air-fuel mixture, leading to odors or ignition difficulty. Never operate without filters.
500 Hour Schedule:
- Air Intake Filter: Remove, wash with mild detergent, dry thoroughly, and replace. Do not oil. Clean more often in dusty conditions.
- Remove Dust: Clean heater twice a season (more often in dusty conditions). Use compressed air to remove dust from the transformer, burner, motor, and fan blades. Wipe clean and inspect for foreign materials.
- CAD Cell: Clean the glass portion of the cad cell with a soft dry cloth.
- Nozzle: Replace if dirt/carbon accumulation reduces fuel/air flow, causing improper mixture, odor, and smoke.
- Fuel Tank: Clean twice a season (or monthly during frequent use). Drain and flush with clean fuel oil.
Annual Schedule:
- Air Output Filter: Remove and tap to remove contaminants. Do not use compressed air or liquids. Replace if extremely dirty. Ensure gasket is firm and screws are tight to prevent air leaks.
- Fuel Filter: Remove from fuel line and direct compressed air through it in the opposite direction of fuel flow. Wear safety glasses.
- Air and Fuel Lines: Ensure all connections are tight after cleaning.

Adjusting Pump Pressure:

Due to varying fuel viscosities and component wear, pump pressure may need adjustment.
Procedure: Fill tank, start heater, locate the fuel pressure adjustment screw (ref. #29 in exploded parts drawing, located at the rear of the heater in the air filter housing cover), remove the rubber cap. Use a flat-bladed screwdriver to turn the screw clockwise to increase pressure or counter-clockwise to decrease pressure.
Optimal Result: Nose cone in the combustion chamber should be cherry red with no dark spots, and the flame should not extend beyond the nose cone.
Improper Pressure Adjustment:
- Too Low: Heater has a weak flame, smokes, spits raw fuel, nose cone not cherry red. Adjust clockwise to increase pressure.
- Too High: Flame extends beyond the end of the heater. Adjust counter-clockwise to decrease pressure.

Storage:

Store in a dry location free from fumes or dust.
At the end of each heating season, clean the heater as described in the maintenance section.
Drain and flush the fuel tank with clean fuel. The manufacturer recommends completely filling the tank with fuel for extended storage to minimize condensation.

Servicing:

Only use manufacturer's replacement parts. Parts are available directly from the factory and must be installed by a qualified service agency.
Contact Mr. Heater, Inc. at 800-251-0001 or www.mrheater.com for service information. Include model number, date of purchase, and problem description.
A heater that is not working correctly must be repaired by a trained, experienced service person.

Limited Warranty: Mr. Heater, Inc. warrants its heaters and accessories to be free from defects in material and workmanship for a period of 1 year from the date of purchase. The company will repair or replace defective products free of charge if returned at customer expense with proof of purchase within the warranty period. Mr. Heater, Inc. reserves the right to make changes to colors, specifications, accessories, materials, and models without notice.