When an 8.4 inch bypass motor quits in a commercial central vacuum or a self-serve car wash vacuum, the machine is down until the right motor arrives. This is the genuine Ametek Lamb 122133-00, a single-stage, 8.4 inch bypass motor with true tangential discharge, double ball bearings and 120 volt power, built on Ametek's 8.4 Premier platform.
Built for
- Commercial and residential central vacuum systems where a power unit has lost suction or burned out.
- Car wash and self-serve vacuum islands running high-airflow bypass power units.
- Machines that must keep working air separate from motor air, which is the reason bypass is specified in debris-heavy and wet-capable equipment.
- OEM and repair-shop builds where the shared 7.2 inch tangential bypass mounting pattern makes this a bolt-in capacity upgrade.
Why bypass is the right design here
A bypass motor uses a separate cooling fan, so the air being vacuumed never travels across the armature. That one difference is what lets these motors survive in commercial service where a thru-flow motor would not. It also changes how you troubleshoot repeat failures. Because the motor keeps cooling itself regardless, a clogged filter or a restricted pipe run starves the work fan without any obvious warning, so techs who are replacing motors repeatedly should look at restrictions and filter condition before blaming the motor.
The other economic point worth knowing is that these motors are meant to be maintained. Ametek's own guidance is that brushes can normally be changed twice, giving roughly 60 percent of original life after the first change and about 40 percent after the second, before the commutator is too worn to continue. Buying the motor buys those rebuild cycles too, which puts the real cost per hour well below the sticker.
Specifications
- Configuration: single stage, bypass, true tangential discharge bracket, universal AC/DC
- Voltage: 120V, 60 Hz
- Maximum sealed vacuum: 110 inches of water
- Peak air watts: 717 per ASTM F2105
- Maximum air flow: 166.2 CFM at a 2.000 inch orifice
- Maximum amps: 15.1 at 120V
- Speed: 26,120 RPM at maximum flow, 34,200 RPM sealed
- Bearings: double ball bearings, 10 mm output shaft
- Diameter: 8.4 inches (213 mm); Height: 6.00 inches; Weight: 9.00 lbs
- Lamination: 3.5 inch high efficiency; rated life 1,500+ hours
- Duty: intermittent; Insulation Class A; maximum ambient 40 C
- Mounting: lug mount, all angle, same pattern as Lamb 7.2 inch tangential bypass
- Replacement brush kit: 8505967-50
- UL recognized, category PRGY2
- Designed to handle clean, dry, filtered air only
Frequently asked questions
What does LB MTR 1 STG 8.4 BP TD BB 120V mean?
It is the catalog shorthand for a Lamb motor, single fan stage, 8.4 inch frame diameter, bypass design, tangential discharge, ball bearings, 120 volt.
What is the difference between bypass and thru-flow?
In a bypass motor a separate fan pulls cooling air over the armature, so the suction air never passes through the motor. That separation is why bypass motors are specified for commercial machines and for equipment that handles heavy debris.
Can I use this motor to pick up water?
Not on its own. Ametek specifies this motor for clean, dry, filtered air, and requires that any machine that contacts liquid or foam be built to keep those substances out of the fan system and motor housing. Follow the machine builder's design.
Which replacement brushes fit it?
Ametek lists brush kit 8505967-50 for this motor.
How do I know the brushes are worn, and how do I seat new ones?
A burning smell and blue sparking around the commutator are the classic signs. After fitting new brushes, run the motor at 50 to 75 percent voltage for about 30 minutes to seat them before applying full voltage, because going straight to full voltage causes arcing and commutator pitting.
Is it the same size as a 7.2 inch Lamb motor?
It uses the same mounting pattern as Lamb's 7.2 inch tangential bypass motor, but the frame is a larger 8.4 inches. Check clearance inside your housing before ordering.
Discount Cleaning Products is an authorized dealer for genuine Ametek Lamb vacuum motors. We stock motors, carbon brushes and gaskets for commercial machines, and our US-based team can help you cross-reference the number on your existing motor before you order.
