Cat5 for doorbell?

[hbiss]

I have a PoE injector that outputs 48v.

I think now, those manufacturers also have to state the class of the power source instead of just assuming it will only be used with a CAT cable.

-Hal

 

[gene6]

The listed cable has to be suitable for the purpose per NEC 110.3 . I don't think cat5 is a suitable application unless the doorbell is one of these:

https://catalog.belden.com/techdata/EN/1700A_techdata.pdf

"Suitable Applications: Premise Horizontal Cable, Ethernet 1000BASE-T, Ethernet 100BASE-TX, Ethernet 10BASE-T, PoE++, PoE+, PoE"

When you look at the honeywell data sheet it says doorbells right there.

Also I am told the "ring" brand is the most common and the mfr instructions call for 18 or 16.

 

[jaggedben]

Did you happen to look at Table 725.154(A) Cable Substitutions? Any CM cable can be used as CL2. So, your CMR can be used as CL2 riser.
...

Wasn't aware of that section. Thanks.

725.144 talks about the ampacity of the pins in a RJ-45 connector, not the 23 or 24AWG conductors.

Now it's my turn to ask you if you looked at the table. Table 725.144 most definitely refers to the 'ampacities of each conductor', and ranges from 22 to 26awg. I'm looking at the 2017 NEC at the moment.

 

[Little Bill]

If you're concerned about current and voltage drop, you can always parallel pairs of conductors.

I've run the Cat5E a few times for doorbells. On all these occasions, I chose to parallel the conductors to both the transformer and doorbell. Example:
orange with orange/white for one connection, green and green/white for the other. You also have 4 extra conductors if any fail.

As to the Ring (and similar types), they only need power from the transformer to keep the battery charged. If you are installing one on a house that doesn't have a standard set of chimes, you have to install a transformer and a resistor to limit the current to the Ring. If you have chimes, that acts as the resistor and you don't have to add one.
You can also just install a Ring as stand alone. Problem with that is you have to take it off and charge the battery every so often. This is usually accomplished with a wall wart transformer plugged in to the Ring.

Only thing Wifi related is you have to have an App for your phone to see anyone at the door. There may be a way to hardwire the Ring to a central monitor but I've never heard of doing it.

 

[wwhitney]

I've run the Cat5E a few times for doorbells. On all these occasions, I chose to parallel the conductors to both the transformer and doorbell. Example:
orange with orange/white for one connection, green and green/white for the other. You also have 4 extra conductors if any fail.

Running two pairs of wires in parallel is almost equivalent in cross-sectional area to a single wire of AWG 3 higher. (E.g. parallel 1/0s = single 4/0). So if the Cat5E is AWG 24 (I think there's some variation?), that gets you to AWG 21. If you put 4 together, that gets you to (almost) AWG 18.

Cheers, Wayne

 

[gene6]

Thank you everyone for all your additional input.
Does 725.144(A) say the class 2 power source (in this case 2.4 amp) shall not be larger than the rated current per conductor in the cable?
Or can it be the sum of the parallel conductors?

In this case the cable would be 23 or 24 AWG cat5 60C

Second question:

Just make sure its pure copper and not CCA.

How do I make sure its not copper clad cat5? Does it say so on the box?
Is copper clad allowed at all for class 2??

 

[Sea Nile]

It will say on the box, plus you can tell by weight. CCA is lighter

 

[gene6]

Thanks I had no idea that was even a thing.
I got back to my code book now and I see now 725.144(A) say the class 2 power source (in this case 2.4 amp) shall not be larger than the rated current per conductor not per set of parallel conductors.
The cat5 wires can not carry 2.4 amps.
I am going to conclude that a cat5 off a standard doorbell transformer is a code violation.
Have a great weekend all.

 

[hbiss]

Now it's my turn to ask you if you looked at the table. Table 725.144 most definitely refers to the 'ampacities of each conductor', and ranges from 22 to 26awg. I'm looking at the 2017 NEC at the moment.

I have. Keep in mind that 725.144 is for PoE where power sources are (were) not identified per the standard for other low voltage power sources. I older versions of the Code, Art. 725 too had specifications for CL2 and CL3 but those were eliminated because of the calculations and measurements required. It was replaced by cooperation with power source manufacturers to provide a standard rating according to the voltage and wattage supplied as to what class it will fall into. The manufacturers must state that on the label. CL2, CL3 or if nothing, a Class 1 wiring method must be used.

I keep stressing, but you still don't seem to understand, that if you have a CL2 labeled power source you may use any CL2 cable. You don't have to worry about voltage or current other than possible voltage drop.

-Hal

 

[jaggedben]

I have. Keep in mind that 725.144 is for PoE where power sources are (were) not identified per the standard for other low voltage power sources. I older versions of the Code, Art. 725 too had specifications for CL2 and CL3 but those were eliminated because of the calculations and measurements required. It was replaced by cooperation with power source manufacturers to provide a standard rating according to the voltage and wattage supplied as to what class it will fall into. The manufacturers must state that on the label. CL2, CL3 or if nothing, a Class 1 wiring method must be used.

None of that means what you stated in a previous post that the table applies to the connector pins and not the conductors. But thanks for pointing out that this section of the code does not apply to the OP.

I keep stressing, but you still don't seem to understand, that if you have a CL2 labeled power source you may use any CL2 cable. You don't have to worry about voltage or current other than possible voltage drop.

Seems wrong (3+ amps on 26AWG UTP CMR?). And requires reading between the lines of the code. But okay, thanks for the clarifications.

 

[Joethemechanic]

 

[hbiss]

None of that means what you stated in a previous post that the table applies to the connector pins and not the conductors. But thanks for pointing out that this section of the code does not apply to the OP.

There is Article 725.144 which I referred to that talks about the connector pins as being the limiting factor.

Then there is Table 725.144 that lists the Ampacities of Each Conductor in Amperes in 4-Pair Class 2 or Class 3 Data Cables Based on Copper Conductors.

And yes, you are correct that this Article does not apply to the OP anyway.

Seems wrong (3+ amps on 26AWG UTP CMR?). And requires reading between the lines of the code. But okay, thanks for the clarifications.

No lines to read between. All you have to read is Art 725.121. It's the listing that counts.

725.121 Power Sources for Class 2 and Class 3 Circuits.

(1) A listed Class 2 or Class 3 transformer
(2) A listed Class 2 or Class 3 power supply
(3) Other listed equipment marked to identify the Class 2 or
Class 3 power source
(4) Listed audio/video information technology (computer),
communications, and industrial equipment limited-power
circuits. (Apparently AV and IT equipment was not yet required to be labeled in the 2017 Code.)

If it seems wrong, all you have to do is look at audio equipment. There are 700 watt amps that only require CL2 wiring to the 70.7 volt speakers. The manufacturers got their equipment tested and listed as CL2 so who am I to argue. I do like to use at least 18GA conductors though.

-Hal

 

[gene6]

Thanks Hal for your comments.
Do you agree that the T725.144 is saying class 2 power source shall not be larger than the rated current per conductor not per set of parallel conductors?

725.144 just says if the cable transmits power and data I am not seeing the PoE exception?
I interpret data as any kind of signal, such as a button.
Why limit a cables ampacity for one class 2 use but not another?

There are 700 watt amps that only require CL2 wiring to the 70.7 volt speakers. The manufacturers got their equipment tested and listed as CL2 so who am I to argue. I do like to use at least 18GA conductors though.

-Hal

Output Wiring of Amplifiers are in article 640.9 can be treated like class 2 if listed and marked, but are not the same as class2. The amplifier has to be listed and marked for that class, and that listing will specify minimum wire sizes. That is why you can't mix Output Wiring of Amplifiers with other class 2 wiring in the same raceway or cable 725.139(F)

Either way the Ring doorbell manufacturers instructions call for either a 16 or 18 AWG, therefore installing cat5 would be a violation of 110.3(B).

Thanks everyone

 

[hbiss]

725.144 just says if the cable transmits power and data I am not seeing the PoE exception?

THAT'S what PoE is. It should be obvious that's what they are talking about, not plain CL2. PoE is an evolving technology. There are some companies that propose powering whole buildings with it.

Either way the Ring doorbell manufacturers instructions call for either a 16 or 18 AWG, therefore installing cat5 would be a violation of 110.3(B).

I would agree.

Output Wiring of Amplifiers are in article 640.9 can be treated like class 2 if listed and marked, but are not the same as class2. The amplifier has to be listed and marked for that class, and that listing will specify minimum wire sizes. That is why you can't mix Output Wiring of Amplifiers with other class 2 wiring in the same raceway or cable 725.139(F)

You really can't say it's not the same as Class2 because we don't know what standards UL uses in either case. Wire sizes are given to reduce line loss (voltage drop), nothing else. I have no idea why they would say CL2 audio output wiring can't be mixed with other CL2. Only thing I can see is AC CL2 in the same conduit inducing a hum on the speaker lines, particularly when the amp is off. That's more of a design issue that the NEC shouldn't get into.

-Hal

 

[tthh]

If I can power survelliance cameras and Ethernet access points and IP phones with PoE, I can light a doorbell LED.

 

[Little Bill]

The way I see it is if the Cat5E is used for a doorbell, you only have the small voltage (14V-16V) for a short duration, less than 5 seconds, while the button is pushed. If you parallel the pairs, that's even better. I don't see any danger there. I would go as far as to say if you held the button in for a long time, the transformer would burn up before the wire would be damaged.

 

[gene6]

The way I see it is if the Cat5E is used for a doorbell, you only have the small voltage (14V-16V) for a short duration, less than 5 seconds, while the button is pushed. If you parallel the pairs, that's even better. I don't see any danger there. I would go as far as to say if you held the button in for a long time, the transformer would burn up before the wire would be damaged.

And if the copper clad 24AWG becomes shorted in the wall and the transformer does not 'burn up'.

If I can power survelliance cameras and Ethernet access points and IP phones with PoE, I can light a doorbell LED.

You could apply the same reasoning to standard 24V HVAC controls people don't use cat5 for that either.
Cat5 is not suitable for the purpose 110.3(A) see post 22.
PoE has more 'smarts' in it to shut off in a fault condition, a simple transformer does not do that level of protection.

I just checked the manufacturers instructions for a more typical Broan/nutone
and it says 18 AWG - 22 AWG

BK125LWH Builder Kit Doorbell with Two Lighted Pushbuttons

Builder Kit Doorbell with Two Lighted Pushbuttons

www.broan-nutone.com

https://www.broan-nutone.com/getmedia/9afc7549-7c7e-4194-9498-ef067252f200/Installation-Guide-BK105-BK110NBWH-BK115LWH-BK120NBWH-BK125LWH-BK131LPB-LRBZ-LSN-LWH-BK144LCL.pdf?ext=.pdf

So 110.3(B) again 22 AWG would be fine, but not copper clad aluminum 24 AWG stuff.
Besides the first thing that new homeowner is going to do is put in one of those "Ring" units that need 18AWG.

 

[Sea Nile]

if the copper clad 24AWG becomes shorted in the wall and the transformer does not 'burn up'.

People shouldn't use cca in walls anyway. From the articles I read, I don't think it's allowed. I was just saying from a general stand point that I don't have a problem 'me personally ' using SOLID copper cat 5/6 cable for doorbells as long as it's solid copper and not cca.

I found a few reference UL 444, CSA 22.2, TIA 568C.2, and ISO/IEC 11801 ed 2.2 and this is a link that I thought may be informative. https://www.flukenetworks.com/createpdf/en/content/application-note-copper-clad-aluminum-cables

Here is an excerpt from the article " “It's very unfortunate that copper clad aluminum products are being marketed as compliant to North America codes and standards for low voltage communications when in fact, they are not. This is particularly concerning if the cable is being used to support power-over-Ethernet devices. These cables should not be called category cable because they do not meet the standards” that require solid copper conductors for multi-conductor communications cables, including the National Electrical Code, UL 444, CSA 22.2, TIA 568C.2, and ISO/IEC 11801 ed 2.2"

 

[Sea Nile]

I just checked the manufacturers instructions for a more typical Broan/nutone
and it says 18 AWG - 22 AWG

As long as the AHJ approves it, it's not something to worry about. I've learned a long time ago to choose my battles and this is not a hill I would choose to die on, or die defending. It's whatever the inspector wants or is acceptable to him. In the realm of things that can do harm, this one is nothing to write home about.

 

[Dennis Alwon]

18/3 T-stat wire was my go to method because I liked the sturdiness of the wire. Sometime they didn't have 18 gauge so I used 20/3. I used 3 wire to have an extra conductor in case something happened to one but also for the chime. I preferred making the splice at the chime which I mounted near the crawl space door.