What the hood does to the refrigeration

01

Negative pressure and a door that drifts

A high-extraction hood removes a great deal of air, and in a house built to a modern airtightness standard that air has to be replaced from somewhere. Where a makeup air provision is absent or not working, the kitchen goes slightly negative while the hood runs. A refrigeration door closed against a gasket that has lost a little grip can then ease back open a few millimetres, and the cabinet spends the evening warming and alarming.

It is an unlikely-sounding fault and it is real. The test costs nothing: run the extraction on its highest setting, close the cabinet door normally, and watch it for half a minute.

02

Grease that gets past the filters

No hood captures everything, particularly in an open-plan room, and the fraction that escapes circulates. Some of it settles on the condenser fins of whatever cooling appliance shares that air. A greasy coil holds dust rather than shedding it, and the resulting deposit insulates far more effectively than dust alone. This is the reason a well-installed cabinet in a kitchen that cooks seriously can lose real capacity in three or four years.

What we check in a heavily ventilated kitchen

• Door closure and gasket contact with the extraction running at full
• Condenser deposit — degreased where needed, not just brushed
• Condenser fan draw, which rises as the coil fouls
• Cabinet temperature logged with the kitchen in real working use
• Clearance between the cooking appliances and the cooling cabinet