Make-Up Air Unit Start-Up, Service and Replacement for Kitchens, Shops and Garages

It brings tempered outdoor air into a building to replace air that exhaust fans and hoods remove. Without it, the building runs under negative pressure, doors are hard to open, drafts increase and hoods can capture poorly.

It depends on the space, the exhaust load and the code conditions. An indirect-fired unit keeps combustion gases separate and vents them outside, while a direct-fired unit mixes them with the supply air. We explain the trade-offs for your building before quoting.

If the exhaust runs without make-up air, the building goes negative and the hood can lose capture. If make-up air runs without exhaust, the space can be over-pressurized and heat is wasted. An interlock keeps the two in step.

It depends on the environment. A grease-laden kitchen or dusty shop loads filters faster than an office. We check filters at every visit and set a change schedule from what we find.

Usually, yes. We measure airflow, test the interlocks and adjust within the unit's limits. For a kitchen setting, see how this fits with kitchen ventilation support.

It depends on the exhaust equipment, the building design and the code that applies. Large exhaust systems, such as commercial cooking hoods, are normally designed with replacement air. We ask for hood labels, equipment lists and drawings where they exist, then confirm what the building needs before we quote.

Unheated outdoor air would chill the space, drop the room temperature and cause cold drafts. A make-up air unit tempers the incoming air to a set discharge temperature. In an Ontario winter that heating load is large, so burner, gas valve, high-limit and controller checks matter before the cold arrives.

Check that the disconnect is on, the breaker has not tripped, the exhaust switch or interlock is in the right position and the display shows no obvious fault. Look for snow or debris at the intake if you can see it from the ground. If you smell gas, leave the building and call 911 or the gas utility. Otherwise call +1 905-407-7353.

Common signs are doors that are hard to open, whistling at door frames, cold drafts, kitchen odours drifting where they should not and gas appliances that draft poorly. An airflow and pressure check confirms it. If a carbon monoxide alarm sounds, leave the building and call 911. Otherwise, request a balance check.

Often there is a gas permit, and sometimes electrical, mechanical or building permits depending on the work. A direct-fired unit adds code conditions. What applies depends on the municipality and the scope. Rules differ by municipality and change, so we confirm the steps in the written scope before work starts.

It can, but the air has to go where it is needed. The aim is a kitchen that sits slightly negative to the dining room so odours move toward the hood. Supply points, diffusers and the balance between the hoods and the unit decide that. It is a design question, so we review the layout before recommending a setup.

Check them at least each season, and after storms, leaf fall or construction. Snow, leaves, seeds and dust restrict airflow and strain the blower. The right rhythm depends on the site. We look at the intake at every visit and note its condition in the service note.

Cycling can come from a tripped high limit, a dirty filter, a failing airflow switch, an unstable flame signal or a controller set too tight. Repeated lockouts are a sign to stop resetting the unit and book a visit. We test each safety before changing parts. Call +1 905-407-7353 with the display code.