# Low voltage wiring for central vac



## leafyme

We just moved into our new home and it's roughed in for central vacuum. We bought a system.

We're installing it ourselves, but the system did not come with very good installation instructions.

My problem is: I'm trying to put on the valve covers and I have to connect the low voltage wires to the connectors on the covers. There are 4 wires and only 2 connectors, I'm assuming 2 wires go to each connector, but which 2 wires go together?

There are red, green black and yellow wires. Which ones go together?


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## chris75

leafyme said:


> We just moved into our new home and it's roughed in for central vacuum. We bought a system.
> 
> We're installing it ourselves, but the system did not come with very good installation instructions.
> 
> My problem is: I'm trying to put on the valve covers and I have to connect the low voltage wires to the connectors on the covers. There are 4 wires and only 2 connectors, I'm assuming 2 wires go to each connector, but which 2 wires go together?
> 
> There are red, green black and yellow wires. Which ones go together?


 
You ran phone wire for the low voltage?  I would parallel the connections, red and black to one screw, yellow and green to the other.


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## leafyme

chris75 said:


> You ran phone wire for the low voltage?  I would parallel the connections, red and black to one screw, yellow and green to the other.


 
We didn't, the house was already roughed in for central vac when we bought it. The builders installed it.

Thanks for the info.


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## 220/221

I am thinking that only two of those wires are being used.

When the vac hose plugs in, it closes the switch and turns on the vac....right?

I've never looked closely.

How many terminals are on the vacuum itself?


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## leafyme

The vac hose doesn't have terminals, there are two knobby terminals coming out of the inlet and when the metal of the hose touches them it completes the circuit and the vac turns on.


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## bob22

I found this site that gives (to me at least) great instructions on how to install a central vac system; it should help:
https://www.centralvacuumstores.com/cvs/install_7.php
Bob


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## chris75

220/221 said:


> I am thinking that only two of those wires are being used.
> 
> When the vac hose plugs in, it closes the switch and turns on the vac....right?
> 
> I've never looked closely.
> 
> How many terminals are on the vacuum itself?


 
Its an end switch, plain and simple... the builders ran phone line instead of 18-2 bell wire.


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## leafyme

Is phone wire sufficient? Should I request that the builders replace the wire?

I was just told by someone else I shouldn't double up the wires.


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## chris75

leafyme said:


> Is phone wire sufficient? Should I request that the builders replace the wire?
> 
> I was just told by someone else I shouldn't double up the wires.


 
Read the vac instructions and see what MIN size AWG your allowed to use.

As far as running the wires in parallel, seems 310.4 Exception #2 would allow it.


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## whirly

Central Vacuum can use ANY type of low voltage wire. Sometimes roughins are done with Phone wire, sometimes much thicker cable. It doesn't matter.

Connecting to the terminals involves two wires, when four are run it is a benefit to you in case there is an issue with one of the two wires.

In these cases, we traditional use Black/Yellow and Green/Red and attached to either screw. It is not specific, just need to complete the cct.

The only thing you have to be aware of is that you HAVE to make sure the same wire pairings are being used throughout the whole installation, right to the machine.

Hope this helps.


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## pwitort

*central vacuum wiring*

Before using *any* wire, find out what the current (amps) requirements are for the vacuum system. If the wire gauge is too fine for the amps (eg. phone wire), the wire could overheat... just like a cheap extension cord on a 1500 watt space heater...and fail. I dont know what the minimum wire size is for your system, but there should be a spec on the current that runs through the sensor line. I have seen 18 ga noted on some systems, but typical phone line is much lighter than that. Doubling an undergauged wire will help the situation, but that kind of approach is certainly not to code specs.

Also, we are all assuming that you wont be running some 120v wire also to power the sweeper... that is a separate calculation of wire size.


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## handyman78

I have installed a central vac in my home and if you are referring to the switch mechanism, there is low voltage wire (zip of 20 ~ 22 gauge or so) that comes with the unit. It is only used as a switch leg for the relay to turn the unit on. Doubling up two smaller wires for each connection should not be a problem in this situation.


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## Billy_Bob

It is common when running low voltage wires to run more wires than what is needed.

All you need is two wires.

The only thing is the same two wires would need to be connected at the main vacuum as at each "valve cover".

So you could decide to use green and red (because it is Christmas), then you would connect green and red at each "valve cover" and at the main vacuum.

Then do not cut off the 2 unused wires, just wrap them back around the jacket of the wire and they will be there if you ever need to use them for any reason.


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## gregzoll

PJW, on LV systems, the current is measured in milliamps, not Amps, so 20-24 is okay as already stated. 18awg is better because it is heavier, and will stand up to wear and tear when you have to replace a Vac cover because your kids or wife tore it up.


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## pwitort

Good, Milliamps should not be a problem. I like the idea of leaving the extra wires in place in case one of the main ones break in the future... the thinner they are , the more apt to flex and break when handling them (attaching them).
I had heard that some systems ran 120 volts to the outlet to run the brush motor... in such cases is there a separate low amp switch wireset, or is it all done on one pair.


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## gregzoll

In that case, there would be 14/2 ran to an outlet nearby, or at the face.


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## Chemist1961

*Central Vac Wiring 101*

If you still have this problem, determine if the system is using 2 pair low voltage phone wire, figure out if there are any joints or any wires eliminated. Because 2 pair is brittle and breaks easily I like two use two strands for each contact, ie black and green vs yellow and red. If doing this be sure to follow the same pattern through out the house. Be sure this pattern is replicated where any pipes branch out to another section of the house. A good installer will have followed the pipe path with the wire and strapped it to the pipe. When you terminate at the machine pair the wires in the same pattern.


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## Yoyizit

Phone wire insulation can stand at least 56vdc, which works out to 40v rms.


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