The MRGH sits at the top of the Manaras gearhead jackshaft range: a very heavy-duty worm gear operator for large sectional, multi-blade and industrial rolling doors and grilles. Where the MGH covers most heavy industrial doors, the MRGH is what gets specified when the door is genuinely big, think multi-blade industrial rolling steel on a warehouse or works entrance.
What This Operator Suits
Large sectional, multi-blade and industrial rolling doors and grilles that are beyond the standard heavy-duty class. It is a 3-phase machine, the motor is a continuous-duty industrial type, totally enclosed (TEFC or TENV), so the building needs 3-phase supply, and the drive chain steps up to #50, #60 or #80 roller chain with the operator sprocket sized to the application.
Specification
| Item | Detail |
|---|---|
| Motor | 60Hz high starting torque, continuous-duty industrial, 3-phase, totally enclosed (TEFC or TENV) |
| Reduction | 40:1 worm gear in oil bath reducer with air breather and sealed ball bearings |
| Output shaft | 1-3/8″ with 5/16″ keyway, 43 rpm, supported by cast iron flanged pillow block bearings (one support at 2 HP, two at 3 HP and above); base plate included |
| Drive | #50, #60 or #80 roller chain and sprocket on final drive |
| Brake | Electrically activated drum-band solenoid brake (brake motor optional) |
| Manual operation | Emergency chain hoist, floor-level engaging device with electrical cut-out; hoist right standard, field-movable to left |
| Limits | Rotary cam limits with Accu-cam one-hand adjustment |
| Enclosure | Nema 1, simple slide-off cover |
| Control | Monitored control circuit, on-board radio receiver |
Duty rating in plain terms. Very heavy-duty 3-phase gearhead jackshaft, the biggest worm gear unit in the range.
What Fails on This Unit
The same two maintenance points as any worm gear machine, reducer oil and the solenoid brake, but scaled up. The pillow block bearings supporting the output shaft are greaseable service items, and on a unit turning a door this size, a neglected bearing announces itself with a growl long before it seizes. The heavy final drive chain (#60 or #80 on bigger installations) needs tension and wear checks; a stretched chain on a 40:1 gearhead does not slip politely, it wears sprockets. Because the MRGH usually hangs on doors that are themselves heavy and high-tension, most “operator problems” we attend on these turn out to be door problems, springs, bearings, or a door drifting out of balance until the operator is doing work the counterbalance should be doing.
Manufacturer Documents
The MGH is the standard heavy-duty gearhead below it, see the Manaras MGH page. The high-speed equivalent is the Rapido RGH.
Choosing Between Models
If you are unsure which unit you have, the model code is on the data plate on the operator housing. Note the voltage and phase while you are there, and roughly how many cycles a day the door runs, those three facts decide most of what we would bring to a call.
See the full Manaras model reference for the whole range, or Manaras operator repair for service.
Parts and Accessories
Pairs with the full accessory range: photo eyes, light curtains and sensing edges, radio controls, control stations and traffic lights. One point that causes repeated confusion: on a UL 325 monitored circuit, a failed safety device makes the operator refuse to close. That is correct behaviour, not a malfunction. A door that suddenly will not close, with no other symptom, is very often a photo eye or sensing edge that has failed or drifted out of alignment.