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Installation, Pipes, and Wiring Issues Q&A

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Questions & Answers

Resistance Keeping Vacuum On?

We just replaced a 30-year old Nutone CV450 with a Beam Alliance 650SB. We kept our newer Wessel-Werk EBK 360 power head and hose. When the hose end is put into an inlet and the switch is turned on, the vacuum starts up, but doesn't stop when turned off. All the inlets respond the same way. The resistance of the low voltage wire to the canister is a normal 0 ohm. The resistance just through the 30-ft hose, though, is around 16 ohms with the switch turned on, an open circuit with it off. When the unit is turned on at the hose handle, the sound drops a little after 2 seconds. From that point, the power stays on even when the handle switch is turned off. This also happens when I turn the power on at the canister. Is the hose resistance normal or is it somehow fooling the unit into staying on?


The resistance can fool the relay to stay on. It may be chattering your relay which will burn it out in weeks to come. What gauge wire was used in the installation? If anything like a telephone wire, that is trouble. It should be 20 gauge, multithread, insulated wire at the very minimum. If not, you can solve the issue with a Low Voltage Booster Box. The low voltage system is 24 volts. At the wall inlet you need to be about 20 volts to overcome the hose resistance. The longer the hose the more resistance too.

How Do I Wire Multiple Sheaths of Telephone Wire?

Our house was plumbed for central vac by the builder. They used telephone wire for the low voltage wiring. At one of the inlets there are three sets of telephone wires. Is there any reason for this? Do I use one set and ignore the others, or do I need to find a way to use all three?


You will need to use all three sheaths. Be sure at every inlet and at the vacuum unit the pattern is the same. Each wire sheath should have four wires. Put any two together and treat them like one wire (i.e., the red and green), then double up the other two colors. When there is more than one sheath, keep all the red/greens together and the other two together. There are three in that one valve because they run to other valves like a chain. The reason they used telephone wire is they don't know that they are supposed to use 20 gauge wire. Telephone wire is weak and there may be parts of your home the hose will not work properly, or it will work but fry your relay. If it does work it will be a matter of time before it doesn't (most likely). We highly suggest adding a Low Voltage Booster Box. We sell this to homeowners who find out to late that they need it. The product is easy to install right next to the vacuum unit. Please let us know if you have any questions.

Exhausting Outdoors

Hi, We are buying a condo that has an existing Zenex system. It has what appears to be a cloth filter that simply is shaken out and the bottom part replaced back onto the unit w 3 clips. The home inspector said that it is customary for central vacs to have an exterior exhaust, but this unit does not. It is housed in the basement and does not have any exterior exhaust. Is that something that should be repaired/corrected/of concern to us? Thanks.

Central vacuums do not have to be exhausted outdoors. Most all of them can be exhausted into the area they are housed. There will be a vacuum smell and very little to no dust. A few vacuums that have no true filter (such as cloth, bag, pleated, or foam) need to be exhausted outdoors.

Suction Not Starting at Wall Inlets

I just installed my new Kenmore Vac unit and I can only power it on at the unit. When I put the hose in the outlets nothing happens....please let me know what I've done wrong. Thanks, Amie. (Winnipeg, MB)


Please use our Troubleshooting Flowchart and go through the steps to find the issue and solutions.

Low Voltage Connection On Unit

Wherer do I hook up the low voltage wire on the inlet to on the main unit so that the unit turns on when I plug the hose into the outlet? Thanks, John, Winnipeg canada ,. Kenmore type k central vac

It will connect to the back of the unit near the power cord to two small metal wires or posts. Exact locations differ by brand and model.

Motor Turns Off, Shuts Down Intermittently in Main Unit

Hi,Nutone unit works fine some days, other days it will turn on then shut down in a few seconds. Sometimes will run for 15 minutes or more then shut down. Dealer took out unit and bench tested, ran fine. Replaced all outlets. Problem occurs when turning on with hose or at main unit. Thanks. Dave, Phoenix AZ

If a unit motor is unable to run continuously without interruption for at least 15 minutes, it is a good indication that your motors have failed and need to be replaced.

Inlet Shudders When Vacuum Is In Use.

I recently installed a dustpan in an existing central vac system. Now when I use the dustpan (only when the dustpan is used) all the other outlet covers 'shutter' creating a loud noise from the air suction. Any suggestions how to remedy?

The doors on the inlets are not fully closed. Try loosening the screws on the problem inlets about a quarter turn each. When installing the inlets, if the screws are too tight it tends to bend the plastic just enough to open the door for air.

No Wire Vacuum Operation

I installed my own central vac and in a huge mental blank, I forgot to run the wire and the walls are finished now. Fishing through the walls has proven to be virtually impossible. Any suggestions? Is it a really bad idea to run the wire inside the pipe? Is there some way I can bypass having the hose compkeys the circuit to turn it on?

You don't want to run the wires through the inside of the pipe, debris will build up on the wire and form clogs. We have a solution for you! MD carries a radio frequency hose and reciever that will function like the wires are there. Give us call at 1(800) 997-2278 Monday-Thursday 7am-5pm PST to go over what parts you will need to get your system up and running without the headache of fishing wires through the walls.

Self Install Not Working

I have connected all inlets to junction and then to the main unit, the main unit works by manually turning it on, but when I plug in the hose none of them work. any help is appreciated.

You must be sure that all the low voltage wires are connected from the inlets back to the main vacuum unit. Give us a call at 1-800-997-2278 Monday - Thursday 7am-5pm PST to speak to a technician for help.

Low Voltage has Nearly No Voltage

Beam 240 V serenity plus won't start with hose, but works with manual switch. I shorted the low vol. output leads on the front of the canister and it will not start. I tested output voltage from the low voltage connecter on the front of canister and it reads 10.7 volts. When I hook up the leads to the house low voltage wires the meter reads < 1 volt (ie essentially no voltage). Since the manual switch works, I think the circuit board is the culprit as the test of shorting the output does not turn the unit on. My guess is the 24 V. transformer is bad. Do you agree? If so, do you sell the circuit board replacement part. Sincerely, Chris A Dothan, Al

Correct, the transformer is not working. 10 volts at the inlet or at the unit will not close the circuit as you need 20-24 volts. We suggest retrofitting this universal, new circuit board into it. It is made by the same manufacturer, but is likely slightly different than your existing board.

Turns On by Itself

We have a Kenmore Central Vacuum connected to a contractor installed pipe system that has worked great for 5 years. Lately the system tries to start on its own intermittantly almost any time of the day or night. I have checked all outlets and cleaned the power unit. Any Suggestions.


Disconnect the small wire at the unit and see if the same thing happens. If it does, you will need to replace the circuit board in the unit. If it stops, then you have a compromise in the wire somewhere in the home. If you can't locate the compromised wire, then bypass it completely with a RFX Radio Frequency Key Fob & Receiver. It is easy to set up and use.

Install Baseboard Kick Vacuum - ONLY

I am very interested in the automatic dust pan and incorporating it into the building of our new home. I do not prefer vacuuming with central vac, however. How can I get the toe kick without having a full central vac system?

You can enjoy the benefits of the VacPan and even a regular hose valve nearby quite easily. Use the small but powerful M80 or M60 vacuum, a VacPan, and a Stretch Hose. Please see if you have a dealer in your area for sales. If not, please let us know at 1(800) 997-278 Monday-Thursday 7am-5pm PST.

Where is the Main Unit?

We are moving into a new home. It has a central vac system thru out as we see areas in the wall for hose attachments. Our problem is we do not see the main unit anywhere. Is there a way to trace where everything goes to see where the main unit may be found. It is possible that it was taken by the owners, but how do we know where to put a new unit if the old one was taken?

It is very possible the last owners took the vacuum unit. The unit would usually have been in the basement or garage. You'd see a 2 inch PVC pipe and low voltage wire near its location. Rarely is the vacuum in an attic, utility closet, or other closet, but look around for it there as well. You could also contact a local dealer for further assistance.

Repair Low Voltage Wire

I have purchased a house that has a system that installed in 1997. Some of the outlets have had wires break and the wires were not long enough when the system was installed. How is the best way to reconnect the wires?

You can run 20 gauge wires between the breaks and to lengthen them. Use wire nuts to connect the wires. If there is any break that you cannot reach, however, then you'll have to use a remote control unit/clicker to turn the vacuum on and off. Please call us at 1(800) 997-2278 Monday-Thursday 7am-5pm PST and we'll let you know more about it.

Is Humming Sound At Unit Normal?

Hi,I a have an av425a, I recently had to bang it on top to get it going, I replaced the motor after having some of the wires ripped out by mistake but I think that I did not place the wires where they belong. Now I here a hum when I turn it on but the motor does not turn. I got this model 16 years ago. The relay and transformer are seperate but attached to a metal plate that is attached to the vacuum. Is there any way to get a wiring diagram for this model without having to sell my soul.I'm sure there is a wire that is not in it's place.I really do not feel like throwing it into the neighbors pool. Hope you can help. Thank you (Montreal, Canada)


Is the hum you hear there all the time? If so, the sound is normal as it is the hum of the transformer. It is not losing electricity, its rivets are loose. If you don't hear a click when starting the unit then the relay is probably done. You can have an electrician easily replace the electronics with a universal single circuit board. Print the enlarged photo for an installation guide.

Condensation Drips From Central Vacuum Inlets


You will need to heavily insulate the vacuum pipe in the attic. Please visit a hardware store for options. The pipe should be 2 inch outer diameter. Once insulated, the condensation issue should be resolved. Next summer run a couple of pounds of dry rice through the hose and pipes to clean them.

How Are Low Voltage & Power Lines Run?

wiring diagramm for silent master s2 240v. not clear. do i need to run a sepate power line to each inlet, other then the low volt wires. how do i conect low volt wire to mounting plate and inlet valve. do i splice it or run two sets of wires to each inlet?

The minimum requirements for wiring is to run a 20-gauge multithread, 2 wire with separated-insulation to each vacuum port. The wire connects to the finish plate, not the backing plate, to two screws. Leave 8 inches of slack and then strap or tape the wire to the vacuum PVC and splice it into a wire running down the trunk line PVC all the way to the vacuum unit location. The wire will then be connected to the power unit. This wire provides the ability to turn suction on and off when inserting the hose in the wall port or having an on/off switch on the hose handle. If you also want an electric nozzle for carpet grooming then you have two options. First, buy an electric hose with a pigtail cord. Plug the hose in the inlet and plug the cord into a nearby electrical outlet. Or run 110 volts to inlet ports called SuperValves. The 110V wire can run from the closest electrical box or light switch, it doesn't run from the power unit in the garage or basement. Let us know if you have any more questions by calling 1(800)997-2278 Monday-Thursday 7am-5pm PST.

Installing Vacuum Inlet Valves Into The Floor

do you have a recommended outlet valve and method for installing the outlet in the floor through the carpet? There is nothing but basement below the floor, so it is very accessible, but I wasn't certain if the installation of the outlet in a carpeted floor is even an option. I would plan to install it in a location that wouldn't receive regular foot traffic. Robert


Installing a Metal Basic Inlet Valve in the floor is normal and is often used. Use the Pipe and Backing Plate #517 (cut off the flange with three holes) on our website along with any metal basic inlet valve. There is a raised rim on the #517 that you use as a guide to cut that exact shape out of the wood floor.

Fixing A Hole in A PVC Pipe Run

hi my electrician drilled a small hole in the pvc pipe of my central vaccum by accident. how do i fix he small hole, as it is imposible to take the pipe out and replace it as i had the vaccum installed when i build he house


Take a small piece of central vacuum PVC pipe and put a slit completely down one side. Open it wide and put it over the pipe and over the hole. Use PVC cement liberally, rotating the sleeve in the glue and adding glue all around the edges to be sure there is no leak.

Utility Closet Installation

Duravac Powerhouse (655airwatts) is installed in a utility closet. My wife is concerned that it generates a lot of in do we have to worry about a fire? TX, Eber


To keep the vacuum unit cool, you must open the door to the utility closet whenever the vacuum is in use. Angle the exhaust out of the closet using the PVC installation fittings, if you have the room.

Vacuum Pressure Measurement

If I am checking my system, what should the vacuum pressure be at the wall outlets?

The vacuum pressure (aka waterlift or sealed suction) - when no air is passing into the system and something is completely covering the suction hole, will vary for each vacuum system. We have a sealed suction gauge available for purchase to take these measurements. You will need to look up the motor in the brand pages that goes with your system and find its WaterLift reading, or look up the specifications of your system elsewhere and look for the Waterlift measurement. The reading should be 10-30 marks off the stated specs when measuring it at the inlet, at your hose, or at the unit directly.

Static Build-up & Shock

Jeannie, Mattawa Wa. I have an Imperium vacuum system and it works great until I have to vacuum up fine dust like flour or sand. It seems to have a build up of static electricity that trips the unit off. We flip the breaker and this usually solves the problem until we have more fine dust which seems like all of the time on a farm. Is there a way to bleed off that static?

This is rare, but can happen. Take a dryer sheet and rub down the hose and the exposed pipe near your unit. Then suction a few through your system. For extreme cases, such as outdoor use, you may want to wrap some the exposed pipe in copper wire near the vacuum unit and ground it.

How to Test Low Voltage System

how do I test the low voltage system for my central vacuum,it does not work


Please use our Troubleshooting Flowchart to help determine the low voltage issue with your system. This flowchart is for all central vacuums.