How to Install an Over the Range Microwave with a Metal Cabinet

Installing an over the range microwave oven with a metal cabinet requires some special considerations. The metal can interfere with the microwave’s radio frequency waves, so modifications may be needed. With proper planning and precautions, it is possible to safely install a microwave in this situation. Here is a comprehensive guide on how to install an over the range microwave oven with a metal cabinet.

Safety Considerations with Metal Cabinets

Microwave ovens work by emitting radio frequency waves that cause food molecules to vibrate and generate heat. These waves can reflect off metal surfaces, potentially causing issues:

• Sparking – The waves can arc between the microwave and metal surfaces, creating sparks and a potential fire hazard.
• Overheating – Reflected waves can lead to overheating of the magnetron tube that generates the microwaves. This can shorten its lifespan.
• Uneven cooking – Food may cook unevenly due to hot and cold spots caused by wave interference.

To prevent problems, special care should be taken when installing a microwave near metal:

• Maintain proper clearance between the microwave and cabinet according to manufacturer’s instructions, usually at least 3 inches.
• Use a trim kit designed for metal cabinets that has built-in shields to block reflected waves.
• Position the microwave properly so the door opens away from the cabinet.
• Make sure there is good ventilation to prevent overheating.

Choosing the Right Microwave for a Metal Cabinet

Look for an over-the-range microwave designed to be installed near metal:

• Choose a model that specifically states “for use with metal cabinets” or has a metal cabinet trim kit available.
• Avoid microwaves with exposed antennas, wires, or air vents on the top or sides, as these can arc to metal surfaces.
• Look for models with attractive finishes to match your kitchen. Stainless steel, black, or white finishes are common.
• Consider the microwave’s size, power, and features to meet your cooking needs. Look for sensor cooking, convection, and over-the-range ventilation.
• Measure the microwave space in your kitchen to get the proper width and ensure sufficient overhead space for ventilation. Standard widths are usually 30 inches.

Preparing the Installation Space

Proper preparation of the installation area will ensure a safe microwave placement. Follow these steps:

• Remove existing lower cabinets if present. The microwave must have open space underneath.
• Detach any existing built-in ventilation system. You will need access to run new ductwork.
• Remove any existing countertop work surface below the cabinet.
• Inspect for proper stud placement to secure the microwave. Add reinforcement if needed.
• Install an approved outlet in an accessible location below the microwave per local electrical codes.
• Clean and prep the entire installation area so all surfaces are smooth and free of obstacles.

Ventilation Requirements

Over-the-range microwaves require proper ventilation. Most use a recirculating filter or externally vented duct:

• Recirculating filter – This filters and recirculates air internally, no ducts required. Must be replaced periodically.
• Externally vented – Ductwork vents to the outside. Provides better ventilation than recirculating but requires duct installation.

Check your microwave’s manual for specific duct requirements. Consider hiring an HVAC professional for installation.

Key steps for ventilation:

• Run rigid or flexible metal ductwork from the microwave to the exterior.
• Use proper-sized ducting, avoiding tight bends.
• Connect ducting to an outside vent or roof cap with flapper to prevent backdrafts.
• Use an approved vent hood with grease filters to trap cooking residue.
• Seal all connections thoroughly with aluminum duct tape to prevent leaks.
• Install a duct transition if the duct size differs from the microwave’s ventilation outlet.

Installation Steps for the Microwave

Once you have adequately prepped the installation area, follow these steps:

Attach the Mounting Plate

The mounting plate secures the microwave to the wall.

• Hold the plate centered in the cabinet space and mark the screw hole locations. Drill pilot holes.
• Attach the plate securely using all provided screws and anchors. Make sure it is level.

Attach the Cabinet Trim Kit (For Metal Cabinets)

The trim kit provides clearance and protection between the microwave and metal cabinet.

• Remove packaging and inspect the kit. It should include top and side trim pieces.
• Fasten the rigid metal top trim above the cabinets using provided screws. Leave a 3-inch clearance.
• Attach the side trim pieces, leaving at least 1-inch gap behind the microwave.

Install the Ductwork and Vent Hood

This is the ideal time for proper venting installation before mounting the microwave.

• Run ductwork from the microwave vent location through cabinets and connect to an outside vent.
• Carefully seal all connections with aluminum duct tape.
• Attach the vent hood securely to the cabinets according to directions.

Mount the Microwave

Now you’re ready to hang the microwave. Be sure you have adequate assistance.

• Carefully lift the microwave and hook slots on the rear onto the mounting plate hooks.
• Rotate the front downward, resting the microwave on the stops.
• Open the door, reach inside and securely tighten all mounting screws. Do not overtighten.

Connect Electrical and Venting

The final steps complete the necessary connections.

• Attach vent ductwork to the microwave’s vent collar and secure with duct tape.
• Plug the power cord into the approved outlet installed earlier. Do not pinch cord.
• Carefully inspect that proper clearance from the cabinets was maintained and venting is properly connected.

Performing a Microwave Safety Check

Always do a safety check after installation:

• Inspect for proper grounding and that all electrical connections are secure.
• Check that door opens and shuts properly against cabinet. Adjust if needed.
• Confirm all venting connections are thoroughly sealed and there are no obstructions.
• Test operate the microwave and verify internal light, cooking, fans, and other functions work correctly.
• Heat a cup of water and check for hot and cold spots that may indicate wave interference issues.
• Break in the microwave by heating moist towels on high for 5 minutes to dissipate manufacturing odors.

Troubleshooting Common Metal Cabinet Installation Issues

If problems arise, check these troubleshooting tips:

Sparking inside the microwave

• Verify trim kit was properly installed with adequate clearance from cabinet.
• Check for microwave door alignment and obstructions.
• Try a trim kit with better RF shielding.

Ventilation fan not working

• Check duct connections for leaks, obstructions or damage.
• Ensure duct size matches microwave requirements.
• Verify electrical connection to outlet and breakers.

Microwave light working but no heat

• Test a low microwave power setting to isolate the problem.
• Ensure door is properly closed and latched. Faulty door switches can prevent cooking.
• Have an authorized service technician evaluate the magnetrons and other components.

Uneven cooking or overheating food

• Check for proper microwave clearance from cabinet and walls.
• Try using microwave-safe cookware, since metal pans can cause issues.
• Have microwave inspected for potential radiation leaks.

FAQ About Installing Over the Range Microwave with Metal Cabinet

Here are answers to some frequently asked questions:

Is it safe to install a microwave with a metal cabinet?

Yes, with proper precautions. Use a microwave designed for metal cabinets and follow installation instructions carefully regarding clearance and venting. The trim kit shields the microwave from the metal to prevent issues.

Should the microwave vent out the back or top?

Venting out the top is preferred. Rear venting can involve sharp turns in ductwork that inhibit airflow. Top venting allows a straighter path outside.

What microwave wattage is best?

900-1000 watts is ideal for most users. It provides sufficient power for cooking while higher wattages can be unnecessary. Lower wattages around 700 watts may have trouble heating larger portions.

How close can a microwave be installed to a range?

30-36 inches is recommended between a microwave and range cooktop for safe operation. Check manufacturer guidelines for required overhead clearance above the cooktop. Proper hood ventilation is also crucial.

Is it better to get a built-in or freestanding microwave?

Built-in over-the-range models maximize space savings. However, freestanding countertop models provide more flexibility if reconfiguring kitchen layouts. Countertop models also avoid concerns with metal cabinets.

What special care is needed when installing ductwork?

Use rigid metal ducts whenever possible, avoid excessively tight turns, make sure to thoroughly seal connections, and ensure the duct size matches the required air flow specs. This optimizes ventilation effectiveness.

Why do microwaves have a metal Faraday cage?

The internal metal shielding prevents microwave leakage while allowing the radio waves to pass through the cooking chamber. The front door mesh screen provides a see-through view while also blocking harmful leakage.

How can you tell if your microwave ventilation is working properly?

Hold a tissue or piece of paper near the hood. Strong suction should hold it in place. Steam from cooking should be drawn into the hood as well. If ventilation seems weak, check for duct obstructions or leaks.

Conclusion

Installing an over-the-range microwave into a metal cabinet raises some challenges due to the potential for reflected radio waves interfering with operation and safety. However, with careful planning and the right materials, the installation can be completed successfully. The key steps are choosing the right microwave, allowing proper clearance, installing effective venting, using a trim kit for metal cabinets, following all directions carefully, and performing thorough safety checks. With attention to detail, your new microwave will provide convenient cooking and valuable kitchen space savings for years to come.