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Answers to Frequently Asked Questions about Air Conditioners

If your window air conditioner is blowing fuses, icing up or running non-stop, please browse our Air Conditioner FAQ. M G Appliance Services in Ottawa has assembled a list of tips and answers to questions about unusual air conditioner behaviour for your convenience. Contact us if your window unit has stopped functioning and you would like it serviced by a professional.

Air conditioner placement

Where is the best room for placement of an air conditioner? Wherever it gives the most comfort is where it should be installed.

If you only have one air conditioner then we usually suggest the bedroom. Experience has shown that if you can sleep comfortably at night then your next day’s work will be a lot easier, no matter how hot it gets.

Air conditioner won’t cool other rooms

The blower fan in a window air conditioner is not very powerful. It is sized to cool one open area, not a number of interconnected rooms. Therefore a couple of smaller units may be better for your home than one large unit.

Air conditioner sizing chart

Following is a basic sizing chart for calculating the window air conditioner needed for a room. Calculate the size of the room by multiplying the width of the room by the length of the room. Use your room size to determine what BTU’s (air conditioners are sized in British Thermal Units) are required to cool that particular room size.

Room in sq. ft.

  • 100 – 250
  • 250 – 400
  • 400 – 550
  • 550 – 875

Room in sq. m

  • 9 – 23
  • 23 – 37
  • 37 – 51
  • 51 – 81

A/C size in BTUs

  • 5000 – 6000
  • 6000 – 8500
  • 8000 – 11000
  • 11000 – 15000

*Based on a room occupied by two adults, having an average insulation, number of windows, and sun exposure.

Blows fuse or breaker on startup

Check if other appliances are on that same circuit. All refrigeration or air conditioning appliances should be used on an independent electrical circuit. Because window air conditioner uses so much power any other appliances on that circuit can cause fuses or breaker to overload.

Breaker blows when I use microwave or television

Microwave or television is probably on the same electrical circuit as air conditioner. All these items can consume large amounts of electricity and if on the same electrical circuit can cause a circuit overload.

This problem will require the services of an electrician. Under no circumstances increase the size of fuse or circuit breaker. This can lead to a possible fire hazard.

Blows fuse – nothing else on that circuit

Most window air conditioners are meant to operate on a 15 amp fuse or circuit breaker. This is the standard for a household circuit. Never replace with a fuse greater than 15 amps. The fuse is there to protect the wiring inside your walls, not the air conditioner. If too large a fuse is used the wires in the wall can overheat and become a fire hazard.

Replacing with a 15 amp time delay fuse is an acceptable alternative. The DELAY type fuse will allow the air conditioner to start with high amperage while still protecting the household circuitry. Look for a fuse with the letter D stamped onto its top. This is a DELAY type of fuse and usually has a metal cap and a glass body.

If air conditioner continues to blow fuse or breaker then it may have internal problems and you will need a service company.

Filter – how to clean

To clean the filter:
1. Wet filter completely, then lay it flat in the sink
2. Sprinkle surface with powder laundry detergent
3. Add about one inch of hot water to sink. Just enough to cover filter
4. Soak for 15 minutes
5. Remove from water and rinse
6. Hang up to dry or shake water out of filter

Clean every month during cooling season. Clean your filter every week if there are any smokers in the home.

If during cleaning the filter rips or starts to disintegrate, replace with a new one immediately. Never use a filter with a hole in it even for a short period. It is the air conditioners only protection from household dirt and grime.

Never operate air conditioner without a filter. Even for short period of time. Serious damage can result.

Is bigger better?

A larger air conditioner will not always provide more cooling. The size of the cooling system must match that of the room area. A properly sized air conditioner will operate in the manner necessary to maximize the removal of moisture from the air and produce the feeling of cooling. Too large a unit can actually provide less cooling than a smaller, properly sized unit.

An oversized air conditioner will produce a symptom called short-cycling. This is because its run time is too short. Because it’s oversized it cools the air around itself too quickly. It shuts off prematurely, and does not capture enough moisture laden air within the room. Consequently it does not remove enough moisture from the room to produce a feeling of comfort.

Icing up

An air conditioner that constantly ices up will need to be repaired. It can be due to a lack of refrigerant, bad fan motor, or inefficient compressor. Or it may simply need to be dismantled and professionally cleaned to return its efficiency to normal. This involves the use of equipment and tools only your service company will have.

Icing up – only at night

Machine works properly during day, but ices up at night?

This is probably because outside temperature falling below 60 degrees Fahrenheit during night. This allows the air conditioner to produce frost on the inside coil. This problem usually occurs in the fall when days are warm, but the nights are starting to get cool.

If icing occurs when temperature is above 60 degrees Fahrenheit then the air conditioner will need servicing.

Re-circulate lever – what is it

Its purpose is to bring in fresh air from outside.

The re-circulate position can be shown on the control panel as an arrow, or a circle with an arrow attached, or an arrow between two lines. It will allow a small amount (about 5%) of fresh air to enter the room from the outside. It is meant for rooms where people may be smoking, or odours from food may be present.

Warranty – What is covered?

Check your Use and Care Guide that came with the product. Most manufacturers’ warranty all parts and labour for one (1) year from date of sale. Cosmetic parts are usually not covered. These can include the filter, grille, or knobs. Also most manufacturers will only warranty a product used by a single household, for average usage. If a product is used commercially, under extreme usage, or it was abused, the manufacturer may void your warranty.

Previously, manufacturers warranted the compressor and cooling system for up to ten years. This has now been lowered to one year by most manufacturers.

In-home service does not include removing from, or installing into, the window. This is considered the customers responsibility.

Water – leaking

Water leaking from the rear of a window air conditioner is not unusual, especially when humidity levels are high. If water is being dumped outside then the machine is operating properly. Its primary job is to remove moisture from inside the home and dispose of it outside. If in an apartment building then a bucket under the rear of the air conditioner can stop it from leaking onto your downstairs neighbours.

Water – splashing sound

Usually heard when the humidity levels are high. You are probably hearing the water in the base being picked up by the fan blade. The water collected in the base is being used to cool the hot internal sections of the machine. Can usually be heard splashing as the machine starts.

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2413 Junction Ave, Ottawa, ON K1V 8G8


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