Signs Your Make-Up Air Unit Is Failing
Make-up air unit problems show up in the dining room before anyone looks at the roof. The front door takes two hands to open. Hoods backdraft and smoke rolls into the dining room. The kitchen is freezing in January. Customers smell the fryer at their table. Gas appliance pilots blow out.
All of those point to the same thing: the kitchen exhaust is pulling air out of the building faster than the make-up air unit (MUA) is putting it back. The building runs negative, and every door, flue and crack starts pulling outdoor air in the wrong places.
Direct vs Indirect Fired MUA
| Direct-fired MUA | Indirect-fired MUA | |
|---|---|---|
| How it heats | Gas burner in the airstream | Heat exchanger, flue to outdoors |
| Efficiency | Very high | Lower |
| Common uses | Restaurant kitchens, garages, warehouses | Occupancies that need flue-separated heat |
| Typical service | Burner, modulating gas valve, flame safeguard | Heat exchanger, burner, venting |
Our TSSA G1 and G2 techs service both. Brands include Engineered Air, Modine, CaptiveAire and Greenheck.
How We Balance a Kitchen
Balancing is measured, not guessed:
- Measure hood exhaust airflow
- Measure MUA supply airflow
- Check building pressure with a magnehelic gauge
- Adjust MUA fan speed, dampers and controls
- Verify the exhaust hood interlock so supply runs whenever exhaust runs
The goal is a building that runs neutral or slightly positive. Hood interlocks follow NFPA 96 practices and the Ontario Building Code.
The RTU and the MUA are a pair
When the MUA is down, the rooftop unit fights hot or cold infiltration and grease coats its coil. That is why we service both on one visit. See 5-ton rooftop units for restaurant RTU sizing.
How Much Does MUA Service Cost?
MUA work is quoted per site because burner type, airflow and controls vary widely. Our published data point is a Liberty Village restaurant RTU + MUA repair: $1,840 on one visit, tally written before work started. You get a written quote within 24 hours of a site visit. Emergency calls run at standard after-hours rates; see emergency rooftop unit repair.
Where We Service Make-Up Air
Restaurants in Liberty Village, King West and The Queensway, commissaries in the Etobicoke industrial area and Rexdale, light manufacturing in Concord and Vaughan, and parking garages in condo podiums across the GTA, usually on the same roofs as the commercial rooftop units we service. For ventilation that needs dehumidification and energy recovery rather than kitchen replacement air, see DOAS systems.
