Broan PM-series power pack hood inserts (PM250 / PM390 / PM400): field service manual

Covers: Broan PM250, PM390/PM390SSP and PM400SS/PM400SSV power pack inserts used inside custom wood or plaster hoods. PM390 is discontinued and was replaced by the PM400SS per one retailer.

Single sourceBrands: Broan6 components

A power pack is the guts of a hood without the shell: blower, filters, lights and controls in a stainless liner that mounts inside a custom hood box. Service problems are usually about the box (air leaks, no liner, poor duct transition) rather than the insert itself.

Safety first

Breaker off before removing filters or covers.
Live voltage tests are caution work.
Support the insert during removal; it is heavy overhead.
For any make-up air or gas range question, follow local code and use a licensed contractor.

How it works

The insert mounts flush in the bottom of a custom hood enclosure. Air enters through the filters, is pulled up by the blower and leaves through the top transition into the duct. Broan sells box liners (for example LB30/LB36 for PM250/PM390) that close the cavity and keep grease off the wood.

PM400SS: 21-3/8 in wide insert, 3-speed rotary control, LED modules, micromesh dishwasher-safe filter, duct 3-1/4 x 10 in (vertical or horizontal) or 6 in round; listings give 120/210/400 CFM steps with 450 max blower CFM. PM390 listings give 390 CFM (440 on one Canadian listing) with a 6 in round duct.

Non-ducted operation needs a recirculation kit sold separately (kit numbers differ by model; one listing names HARKPM21 for the PM400). Without a kit the insert must be ducted outdoors.

Performance depends on the box: a leaky enclosure or a hood box much wider than the insert lets smoke escape around the edges even when the blower works.

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Official manufacturer documentation

Always confirm values against the tech sheet for the exact model.

Broan-NuTone US site (support and manuals)

OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work. © 2026 OnCall Tech. Original content; not a reproduction of any manufacturer document.Generic part photos (not of this brand): Chimney-style range hood with a glass canopy over a cooktop by Bilguun Gantumur, Pexels License

Diagnostic guides for this appliance

Guide · Range Hood

Range hood fan runs only on high, runs slow, or a speed is missing

On simple switch hoods, a missing speed is usually the switch or a failed winding tap; on board-controlled hoods it can be a relay on the control. A fan that is slow on every speed points to grease-dragged bearings, a weak run capacitor on PSC motors, or airflow restriction. Check mechanical drag and airflow before electrical parts.

8 steps ~45 minmoderate

Guide · Range Hood

Cold air, odors or insects coming in through the range hood when it's off

Two dampers should block the duct when the fan is off: one at the hood and one in the wall or roof cap. Grease, bends, missing springs or screws in the path keep them open. Long duct runs and a house under negative pressure make it worse. Fix the dampers first; make-up air questions go to code and an HVAC or licensed contractor.

7 steps ~60 minmoderate

Install · Range Hood

Range hood ducting: duct size, route, termination and makeup air

Hood performance depends more on the duct than the blower. Use the duct size the hood requires (never smaller), smooth metal duct, as few elbows as possible, and a proper wall or roof cap with a damper. Larger hoods can trigger a makeup-air requirement under local code (commonly when the hood can exhaust more than 400 CFM in homes with certain fuel-burning appliances).

6 steps ~240 minadvanced

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Range hoods (under-cabinet, wall chimney, island): ducted vs recirculating field manual

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