Winter Maintenance Checklist: Which Way to Put Air Filter in Furnace (Up or Down), Buddy Heater Safety, and Manitowoc Ice Machine Care

If you're reading this in January, you're probably in one of two situations: your furnace is running warmer than your ice machine, or your ice machine is working better than your furnace. I've been handling refrigeration and HVAC service orders for 8 years. I've personally made (and documented) 13 significant mistakes, totaling roughly $5,200 in wasted budget. This checklist is the one I use now when winter comes.

There are 7 steps here. Follow them in order, or skip to the one that is currently annoying you.

This was accurate as of January 2025. Models change, so verify current instructions for your exact equipment. What was best practice in 2020 may not apply in 2025, especially with new electronics and clean cycles.

Step 1: Clean your Manitowoc ice machine with the right cleaner

From the outside, an ice machine can look perfectly fine. The reality is different: scale, slime, and mineral film hide in the water trough, on evaporator plates, and inside the bin. When the weather turns cold, people tend to ignore the ice machine because they are not thinking about ice. That is exactly when it gets neglected.

I once used the wrong chemical on an evaporator because we ran out of manufacturer-approved cleaner. It stripped the coating. The replacement part alone was about $700 plus the service call. Lesson: use a cleaner made for commercial ice machines, and preferably the one recommended by the brand. For Manitowoc equipment, that means a product like Manitowoc Ice Machine Cleaner, not a generic degreaser.

For most Manitowoc ice machines, the cleaning cycle is built into the control panel. Here is the process:

1. Turn off the ice machine and unplug it. Follow your model's lockout or service mode if it has one.
2. Empty the ice bin. Move the ice to a clean, sealed container or just let it melt.
3. Open the front panel and check for heavy scale or debris. If you see chunks, manually remove loose pieces. Do not force them through the cleaning cycle.
4. Find the clean cycle. Most newer Manitowoc ice machines have a control board with a Clean mode. Follow the instructions in the manual.
5. Mix the cleaner at the exact dilution in your manual. Do not eyeball it.
6. Run the cleaning cycle. Let it complete, then rinse as the manual directs.
7. Sanitize if your manual says to. Cleaning and sanitizing are two separate steps.

I should add that you also need to check the condenser fan. If the fan is loaded with dust, airflow drops, and the machine runs longer. I have seen condenser fans stop completely because someone sprayed a cleaning product directly into them. Keep the area around the fan clear, and use a brush or vacuum, not a pressure sprayer.

Step 2: Which way to put air filter in furnace (up or down)

There is one simple rule: the arrow points in the direction of airflow. That means toward the furnace blower, not automatically up.

The arrow points toward the furnace. Not up. Not the ceiling. Toward the furnace.

People assume the 'up' on the filter arrow means toward the ceiling. It doesn't. It means airflow direction. If the filter is in a ceiling return, the arrow points down into the ceiling opening, not up into the room. If you have a vertical filter slot next to the furnace, the arrow will often point sideways or upward, depending on where the blower is sitting. Look at the blower location and point the arrow at it.

The old 'it does not matter' mindset came from an era when most filters were flat fiberglass panels. Today, many pleated filters are directional, and the arrow is there for a reason. I messed this up in 2019. I put a filter in with the arrow pointing up because I thought 'up is up.' The filter bowed slightly and the return duct whistled every time the fan ran. A tech friend asked me to reverse it. The whistle disappeared.

Step 3: Give your Buddy Heater a second look

A Buddy Heater is a handy emergency heat source. It is also a fuel-burning appliance, not a decoration. If you are going to use one this winter, spend five minutes checking the basics:

• Keep at least 3 feet of clear space on all sides, especially above and in front of the heater.
• Never leave it running unattended or while you sleep.
• Run it in a space with fresh air. Even 'indoor safe' models consume oxygen and produce carbon monoxide.
• Check the oxygen depletion sensor. If the heater has a label about it, do not paint over it or block it with furniture.
• Use the right propane supply. Disposable 1-lb cylinders are easiest, but if you use a hose to a larger tank, use the hose and filter designed for that heater.
• Place the heater on a flat, stable surface. If it tips, shut it off immediately.

From the outside, a hissing portable heater looks harmless. The reality is that if the room is too sealed, the heater can starve itself of oxygen. I know people who rely on these heaters during power outages. I am not against them, but they are not a substitute for a properly serviced furnace.

Step 4: Set your ceiling fan to winter mode

The word 'fan' has more than one job. In winter, your ceiling fan can push the warm air trapped near the ceiling back down to the floor. That is the whole point of winter mode.

Here is how to do it:

1. Turn the fan off and wait for the blades to stop.
2. Flip the reversing switch on the motor housing.
3. Set the fan to run clockwise as seen from below.
4. Run it at the lowest speed. You should feel a gentle updraft, not a breeze.

Why clockwise? In summer, counterclockwise creates a direct downdraft that cools you. In winter, the clockwise motion pulls cold air up from the floor and pushes the warm ceiling air along the walls and down. It is not a huge effect, but it can make a room feel a degree or two warmer without touching the thermostat.

Step 5: Do not leave the blower fan on 'On' all winter

This one still feels counterintuitive to me. You would think running the fan more would make the house feel more comfortable. It does, sometimes. But in winter, leaving the furnace fan 'On' can cause the blower to keep pushing air after the heat cycle has stopped. That air comes from the ductwork and can feel drafty.

Set your thermostat fan setting to 'Auto' for most of the day. This was not easy for me to accept because I like the air moving. But my electric bill did not like it.

If the blower fan is making a grinding noise or fails to start, check the filter first. A blocked filter can cause the blower to overwork and overheat. If the filter is clean and the noise continues, call a professional.

Step 6: Check the ice machine condensate line and water filter

Actually, I said seven steps and this is step six. You do not need to stop yet.

While you have the Manitowoc ice machine open, look at the condensate line and water filter. In winter, a cold garage or unheated porch can make that line freeze. If the line is blocked, water backs up and can leak onto the floor.

• Check the water filter housing for cracks. If the filter is overdue, replace it.
• Trace the drain line to the floor drain. Make sure it has a downward slope and no sagging loops.
• If the ice machine sits in an unheated space and you haven't winterized it, decide now whether you are going to run it through the winter or shut it down.

This is the place where the 'industry evolution' actually matters. An older ice machine could run for years with a dirty water filter. Newer Manitowoc machines have more sensors and predictable maintenance windows. The fundamentals of clean water and airflow haven't changed, but the service schedule might be different than what you are used to.

Step 7: Write down what you did

I am serious. Grab a paper label, a marker, and a phone photo. Write the date, the cleaning product, and the next service date. If the furnace filter is changed, write the MERV rating on the filter and the date. If you changed the water filter on the ice machine, put the date on the housing with a grease pencil.

This step is the one that made the biggest difference for me. When I started documenting, I stopped guessing whether the cleaner had been run. I also stopped finding old water filters I forgot to replace.

Notes and mistakes I made so you don't have to

Here is a short list of things I have done, regretted, and refused to do again:

• Do not use a generic liquid cleaner in an ice machine just because it says 'food service.' Some cleaners are not nickel-safe and can damage the evaporator coating. Use a known Manitowoc ice machine cleaner or whatever the manual names.
• Do not force a furnace filter into a slot the wrong way. If it bows, the air will find a gap around it, and the filter will not filter anything.
• Do not run a Buddy Heater in a completely closed garage. I did that once in my first year. The oxygen depletion sensor shut the heater down, but the smell and the headache were enough to correct me. If I feel any odor or dizziness, I shut it off and open a door before doing anything else.
• Do not clean the condenser fan with a pressure washer. Yes, I have seen it done. It bends the fins and ruins the motor bearings. Use a soft brush and a shop vacuum.

Bottom line: winter maintenance is repetitive, but it is cheap compared with the emergency calls. A furnace filter is a few dollars. A bottle of manufacturer-approved ice machine cleaner is not a big line item on your maintenance budget. A broken evaporator or a burned-out blower motor is.

By the way, this was accurate as of January 2025. If you own newer equipment, check the manual before trusting a random checklist from the internet. I update mine every year, and you should too.