Manual for SilentMaster, MD, Flo-Master, and AirMaster

Back to Manuals
Central Vacuum Manual

Thank you for purchasing an MD Central Vacuum System!

This manual covers safety, operation, and maintenance of our SilentMaster, Modern Day, Flo-Master, and Air Master Systems. These systems are intended for household use only. For commercial applications, please contact your nearest MD Manufacturing, Inc. dealer.

All information in this publication is based on the latest product information available at the time of approval for printing. M.D. Manufacturing, Inc. reserves the right to make changes at any time without notice and without incurring any obligation.

No part of this publication may be reproduced without written permission.

This manual should be considered a permanent part of your vacuum system and should remain with the vacuum system after purchase and installation.

If any problems should arise, or if you have any questions about your Central Vacuum System, consult your local, independent, authorized MD Manufacturing Dealer, call us direct at (800) 997-2278, visit our comprehensive troubleshooting service guide, or ask a question.

Important Safety Instructions

Read all instructions before using your Central Vacuum System.
WARNING - To reduce the risk of fire, electrical shock or injury:

Important Grounding Instructions

The vacuum unit must be grounded. If it should malfunction or break down, grounding provides a path of least resistance for electric current to reduce the risk of electrical shock. This unit is equipped with a cord having an equipment-grounding conductor and grounding plug. The plug must be plugged into an appropriate outlet that is properly installed and grounded in accordance with all local codes and ordinances.

WARNING - Improper connection of the equipment-grounding conductor can result in a risk of electric shock. Check with a qualified electrician or service person if you are in doubt as to whether the outlet is properly grounded.

Do not modify the plug provided with the appliance. If it will not fit the outlet, have a proper outlet installed by a qualified electrician.

Operation of Power Unit

  1. Simply lift any vacuum inlet lid and insert the short metal hose end into the inlet. The unit will activate automatically. It your vacuum hose has an on/off switch, the power unit will not activate until the switch is turned on and will continue to run until the switch is turned off or the hose is disconnected from the inlet.
  2. If the power unit is equipped with a utility valve, you may vacuum directly from the power unit. Simply insert the short metal hose end into the utility valve and turn the toggle switch on the power unit to the "on" position. Depending on the model of your power unit, the switch will be located either on the lower right side or the upper left side of the unit. CAUTION: This switch is to be used only for vacuuming directly from the power unit.

Installing Tru-Seal Filtration

Video: How to Install Tru-Seal in
New & Old MD Vacuums

Central Vacuum Manual
  1. Install Tru-Seal Support Bag. The shape of the Microfilter Bag and Support Bag complement each other for easy removal. Install the Support Bag with the bottom seam running from the front to the back of the power unit.
  2. Install Tru-Seal Bag Adapter(s). The left and/or right entry ports that are connected to your home’s PVC pipe require a Tru-Seal Snap-in Bag Adapter. If only one entry port is being used, use only one adapter. Slide the PVC pipe off the entry port. Working from inside the tank, push the adapter into the entry port until you hear a slight “click”. If the adapter does not snap into the port’s metal neck, remove the black foam gasket from the adapter to allow for additional depth. Once the adapter is snapped in place, angle the adapter down into the tank and reattach the PVC pipe to the exterior of the entry port. Repeat for the other entry port if in use.
  3. Install Tru-Seal Microfilter Bag. There are three connection seals on the Tru-Seal Microfilter Bag. Each one consists of a plastic structure with membrane and a cap.
    1. Attach to utility valve. The middle connection is for the utility valve and slides onto the metal neck protruding into the can. If your unit doesn’t have a utility valve, cap this connection.
    2. Attach to entry port(s). Simply slide the connection membrane past the ridged end of the Tru-Seal Snap-in Bag Adapter. If only one side of the bag is being used keep the cap attached on the unused side.

Emptying the Power Unit

Tru-Seal Filtration

  1. Lift the lid off the vacuum and set aside. Slide the bag’s left and right connections off the adapters by pulling the plastic rim down. On the utility valve, slide the bag connection straight off. For maximum dust control, attach the caps to each connection opening
  2. Remove the Tru-Seal Microfilter Bag by grabbing the top of the bag with two hands and slowly lifting it up past the bag adapters. Set the bag in an appropriate waste bin. Remove the support bag and shake it out, it is designed to be reused
  3. Install the Tru-Seal Support Bag with the bottom seam running from the front to the back of the power unit for proper alignment and optimal performance.
  4. Install the Tru-Seal Microfilter Bag. The middle connection is for the utility valve and slides onto the metal neck protruding into the can. If your unit doesn’t have a utility valve, cap this connection. For the side connections, simply slide the opening all the way past the ridged end of the bag adapter. If only one side opening is being used keep the cap attached on the unused side.

Open-Top Hyperflow Filtration

  1. Remove the lid from the unit, and turn the vacuum on manually. This will keep the dust completely out of the air. Use a dusting brush to sweep dust down off the edges.
  2. If present, remove the rubber gasket at the top of the filter by pulling gently on its edge.
  3. To remove the filter bag, pull up on the loop of cloth material located along the edge. Both the paper bag and the cloth support come out together. The paper bag is fitted inside the cloth support and wrapped around the edge.
  4. Remove the paper filter bag from the cloth support by pulling the elastic edge over the metal ring of the cloth bag. Discard the paper filter bag. Reuse the cloth support.
  5. Remove the filters at the bottom and beat them out. Older models have three filters and others have one. Green filters must be installed grid side down.
  6. Insert a new paper bag into the cloth support and stretch the elastic edge over the metal ring perimeter of the cloth support.
  7. Replace the cloth/paper assembly into the unit and press it into place at the first level. NOTE: Make certain the entire filter assembly is below the utility valve and vacuum inlet necks and that the pull tab loop on the cloth bag is pointing up.
  8. Lay the rubber gasket over the top of the bag with the top of the gasket flush with the metal unit. There will be a remaining loop that will need to be pushed down into place.
  9. Turn off the vacuum and replace the lid.

Single Connection Closed Bag Filtration

  1. Remove the lid from the unit.
  2. Pull the cardboard rim down off the bag adapter. Lift the paper bag out from the cloth support and the vacuum unit. Discard appropriately.
  3. Remove the cloth support and filters at the bottom and beat them out. Older models have three filters and others have one. Green filters must be installed grid side down.
  4. Once the cloth support is put back in place, push the new bag’s cardboard connection on the bag adapter and let the bag sit loosely in the support bag

Units with Bottom Bucket

  1. Unlatch the two side clamps and remove the trash receptacle bucket.
  2. If the power unit is utilizing a disposable bag, pull the cardboard off the adapter at a 45 degree angle. Remove the entire disposable bag and replace with a new disposable bag by pushing the cardboard connection on to the adapter. NOTE: The inverted cloth filter remains in the unit at all times.
  3. If the power unit is not utilizing a disposable bag then the filter in use is the “permanent” inverted, center-weighted, cloth filter. To clean it, lift a plastic bag up around the bottom of the tank and firmly grasp the cloth filter shaking it vigorously to remove accumulated dust.
  4. Empty the bucket in a large plastic bag to avoid dust in the air.
  5. Once the filters are cleaned or replaced, align the trash receptacle bucket into position and fasten the latches.

Maintenance of the Power Unit

No maintenance is required for your power unit other than emptying it periodically. All motor bearings are sealed and require no maintenance. It is recommended that the motor brushes be inspected within three (3) years from the date of installation in residential applications and within one (1) year in commercial applications.

CAUTION: Unauthorized service or repair of your power unit may void your warranty.

Troubleshooting Your System

Troubleshooting flowchart and solutions are available here, or you may call your nearest dealer for assistance.

CAUTION: Unauthorized service or repair of your power unit may void your warranty. Please contact your nearest M.D. Manufacturing, Inc. dealer for assistance.

Unit Fails to Activate at the Wall Inlet

  1. Check unit by using the toggle switch on the power unit. If the unit activates, the trouble lies in the wall inlet or the wiring leading to the unit. To check the inlet valve, remove the wall inlet and disconnect the two low voltage wires. Then, connect the two wires together. If the power unit activates, the inlet valve needs to be replaced. If the power unit still fails to activate, the trouble lies in the low voltage wiring from the power unit to the inlet valve.
  2. If the power unit fails to activate from the toggle switch on the power unit, check to see that the power unit is correctly plugged in and then check the household circuit breaker.
  3. It the power unit still fails to activate after all these procedures have been carried out, the trouble a may exist in the vacuum motor or other electrical components.

Insufficient Vacuum Power

  1. Check filter bag in the power unit. Make sure bag is not overfilled or clogged with fine dust.
  2. If vacuum is good at any one inlet but not at others, this indicates the vacuum lines are clogged somewhere.
  3. If the vacuum at all inlets seems insufficient, check the vacuum at the power unit. Insert the hose into the power unit's utility valve and activate the power unit with the toggle switch. If the vacuum seems greatly improved, this indicates the vacuum lines are clogged.
  4. If vacuum still seems insufficient with hose connected directly to the power unit, remove the hose and check the vacuum with your hand placed over the utility valve. If vacuum seems greatly improved. This indicates the vacuum hose is clogged.
  5. If vacuum still seems insufficient when checked with your hand over the utility valve, disconnect the power unit from the vacuum line. With the utility valve closed, check the vacuum directly at the vacuum inlet neck where the vacuum line connects. If vacuum seems greatly improved, this indicates that the vacuum line or an inlet valve(s) is broken somewhere. Inspect all inlet valves and as much vacuum pipe as possible. If unable to find breakage, turn vac on with home completely quiet and listen for a leak behind walls.
  6. If the vacuum still seems insufficient when checked directly at the neck where the vacuum line connects to the power unit, this indicates trouble within the vacuum motor. Your power unit needs to be check.

Preventive Maintenance

Although your system has been designed for maximum performance and service life, there are guidelines you can follow to help prolong its serviceability and life.

  1. When removing hose from inlet valve, hold the inlet lid up for two to four seconds after removing the hose. This lets the pressure decrease and lets in air to cool the motor.
  2. Never vacuum up liquids of any kind. If you do so accidentally, leave the hose plugged into the inlet and allow it to run for approximately five (5) minutes to dry out the hose and vacuum lines.
  3. Empty the power unit periodically.
  4. It is recommended that every three (3) years your central vacuum system should be checked and the motor brushes inspected. To have this done, contact your nearest dealer for assistance.
  5. Never attempt any internal repairs on the power unit. ONLY qualified personnel should do this!

CAUTION: Not all vacuum shops are qualified to work on central vacuums.

Service and Parts

For service and/or parts, check with the dealer where you purchased your central vacuum system. In the event you do not know who installed your system or you are no longer able to contact your dealer, contact the factory direct:

M.D. Manufacturing, Inc.
34970 McMurtrey Avenue
Bakersfield, California 93308
(800) 997-2278

In the event you are out of state, we will endeavor to locate and recommend a reliable central vacuum dealer near you.

CONFORMS TO UL STD 1017;
CERTIFIED TO CSA STD C22.2 NO. 243.