Low voltage wiring bundling conventions

[tmbrown97]

I'm not sure of my options for entering the next wall cavity on either side - I'll have to look. One can is directly above the other - only inches between them (the 20" was existing; I added the 50" above it - well, because I could) - and figured I'd leave the ugly stuff in the 20" can with the solid door (like all the power adapters, UPB CIM, Battery, ETC) and keep the 50" can looking as nice as possible since I sprung for the plexi door. For now I kept the battery directly below the panel as recommended, but I'd like to double the battery size and move it if it makes sense to do so.

My expectation was to use an inline automotive blade fuse holder and put the fuse as close to the battery as possible; I'd also go up a gauge in wire size for good measure (the total run would ube under 5ft)... I've also seen/used the self resetting circuit breakers that'll fit a standard blade fuse pattern - that would seem safer for the self-resetting factor - would it help with the legality? Thx guys.

 

[Sandpiper]

A Class 2 circuit and Power Limited Circuit are NOT the same thing (yes similar). You can not have a circuit be power limited by a fuse. To meet Power Limited you must be Inherently Limited or protected by a PTC or solid state circuit. Additionally a fuse (or PTC or inherently limited transformer etc) can be used to meet Class 2 but NOT a fuse to meet Power Limited requirements.

A fuse has 60 seconds to react to meet Class 2 but Power Limited must be met in 5 seconds with a PTC or inherent limitation. Even if a fuse was to open in 5 seconds or less it would not be considered a Power Limited Circuit.

Additionally the NFPA requires a PTC or solid state circuit to operate within 5 seconds at 0 to 49C. That is why you rarely see PTC in higher power circuits (over a couple of amp etc) of an alarm panel such as a NAC circuit on a FACP. Now most in the industry use current sensing circuits and shut off a FET Transistor to meet the requirements over the temperature range.

You are confusing the means to achieve Class 2 with Power Limited requirements.

I still disagree, but I think the main reason is that we are tripping over definitions. We do need to get to the bottom of this, but in order to keep this thread on topic, I will start a new thread for further discussions of "Class 2" versus "Power Limited".

 

[Photon]

I used tubing in the enclosure and then outside the enclosure I put the wire with the tubing in smurf tubing for mechanical protection up to the battery carrier (way overkill). I placed a fuse within a couple inches of the positive of the battery and that is still inside the battery carrier. My battery leads are not Power Limited but they are protected by the tubing (and an additional smurf tubing outside the enclosure).

Digger, what kind of tubing do you use in the enclosure?

 

[Digger]

I'm not sure of my options for entering the next wall cavity on either side - I'll have to look. One can is directly above the other - only inches between them (the 20" was existing; I added the 50" above it - well, because I could) - and figured I'd leave the ugly stuff in the 20" can with the solid door (like all the power adapters, UPB CIM, Battery, ETC) and keep the 50" can looking as nice as possible since I sprung for the plexi door. For now I kept the battery directly below the panel as recommended, but I'd like to double the battery size and move it if it makes sense to do so.

My expectation was to use an inline automotive blade fuse holder and put the fuse as close to the battery as possible; I'd also go up a gauge in wire size for good measure (the total run would ube under 5ft)... I've also seen/used the self resetting circuit breakers that'll fit a standard blade fuse pattern - that would seem safer for the self-resetting factor - would it help with the legality? Thx guys.

A self resetting fuse is usually a PTC which if appropiately rated would make the battery leads Power Limited. For 0 to 20 Vdc the max value of the PTC is 5A to meet Power Limited.

 

[Digger]

Digger, what kind of tubing do you use in the enclosure?

I used heat shrink tubing 1/2" wide and ran the black and the red in it because I had it handy. You can use other types of tubing.

 

[Digger]

I still disagree, but I think the main reason is that we are tripping over definitions. We do need to get to the bottom of this, but in order to keep this thread on topic, I will start a new thread for further discussions of "Class 2" versus "Power Limited".

The confusion is I stated tables 11 and 11A which is Class 2. For Power Limited you need to refer to Tables 12 A and 12 B. Sorry I was going off memory.

If you look at the differences in the tables I think we will probably agree.

 

[paw500]

So leads between a battery and the M1G board or aux power supply boards are considered non-power limited and require separation or isolation.

What about the leads between the AC transformer and the main board / aux supplies, are those power limited? The Elk manual says, "Do not exceed 50 feet between the transformer and the control or run the AC power in a multiconductor with other system circuits." (page 10) Once again, if there is a separation requirement, does this apply to the points of termination? On the M1G or the P212S, the AC terminals are not only right next to the VAux DC terminals, but on the same terminal block where each terminal is spaced less than 1/4" apart from the adjacent one.

In another example, take a look at the ELK-P412 power supply:
http://www.smarthome.com/manuals/72829-ins.pdf

…and compare to, say, an Altronix AL400ULPD supply:
http://www.altronix.com/p_pdf/AL400ULPDseries.pdf (page 3)

Insofar as the proximity of the non-power limited (line voltage or battery) supply terminals are to power-limited DC load terminals, it is interesting to note how each manufacturer implements "separation" in its design.


Just to be clear, it is best to keep the non-power limited AC line-in and battery as close to the power supply as possible and within the same enclosure. However it is fine to run the power limited DC output of the power supply from inside the can at point A, out in bundle with other LV cables, to a remote can at point B and terminate at a power distribution module (with branch protection) in the remote can?

This discussion has been very informative, and I welcome any further tips on best practices for LV wiring and bundling.

 

[Sandpiper]

So leads between a battery and the M1G board or aux power supply boards are considered non-power limited and require separation or isolation.

What about the leads between the AC transformer and the main board / aux supplies, are those power limited? The Elk manual says, "Do not exceed 50 feet between the transformer and the control or run the AC power in a multiconductor with other system circuits." (page 10) Once again, if there is a separation requirement, does this apply to the points of termination? On the M1G or the P212S, the AC terminals are not only right next to the VAux DC terminals, but on the same terminal block where each terminal is spaced less than 1/4" apart from the adjacent one.

In another example, take a look at the ELK-P412 power supply:
http://www.smarthome.com/manuals/72829-ins.pdf

…and compare to, say, an Altronix AL400ULPD supply:
http://www.altronix.com/p_pdf/AL400ULPDseries.pdf (page 3)

Insofar as the proximity of the non-power limited (line voltage or battery) supply terminals are to power-limited DC load terminals, it is interesting to note how each manufacturer implements "separation" in its design.


Just to be clear, it is best to keep the non-power limited AC line-in and battery as close to the power supply as possible and within the same enclosure. However it is fine to run the power limited DC output of the power supply from inside the can at point A, out in bundle with other LV cables, to a remote can at point B and terminate at a power distribution module (with branch protection) in the remote can?

This discussion has been very informative, and I welcome any further tips on best practices for LV wiring and bundling.

Leads between the Ac transformer and the main board- Because the transformer is listed as Class 2, Class 2 wiring can be implemented on the load-side wiring, i.e. the run between the transformer and the panel. So separation from other Class 2 wiring is not required.
Do not Exceed 50 feet- This guideline is not for code purposes but only for voltage drop purposes. Elk recommends 16 to 18 AWG wiring, but if you use larger wire, a longer run is possible.
Do not run the AC power in a multiconductor with other system circuits- I am assuming they mean the 16.5 VAC wiring and not 120VAC wiring. The reason for not recommending the 120VAC with other wiring is obvious, but for 16.5VAC is not so obvious. There is no reason, codewise, that this cannot be done, as they are power-limited conductors which would be placed in a cable with other power-limited conductors. My guess is that cross-talk (or induced voltage) can be an issue. When conductors are in such close proximity, as in a multiconductor cable, even low AC voltages can introduce crosstalk. Remember when we used to use hardwire telephones, and we could faintly hear someone else talking on the same line? That is crosstalk.
the ELK-P412 power supply- This power supply does not claim to be Class 2 power limited. But I don't understand why it couldn't be or wouldn't be. The NEC is clear....to be granted Class 2 status, the board, power supply or other device, must be designed using the rules of Article 725, including the limitations in Tables 11A or 11B, then be "listed" for the purpose. Once it is "listed", which means it has been tested and proven to be safe by a lab such as UL, then it must be labled as such. If it is not labled as Class 2, it cannot be considered Class 2.
the Altronix AL400ULPD supply- This supply does claim to be Class 2, and does also warn of the 1/4" separation requirement for limted and non-limited conductors. It is also interesting to note that the current limitation is obtained by using fuses, or by PTC, depending on which version you want. The manual clearly shows the power limited wiring and how to keep it separated from the non-power limited.

 

[Del91574]

the Altronix AL400ULPD supply- This supply does claim to be Class 2, and does also warn of the 1/4" separation requirement for limted and non-limited conductors. It is also interesting to note that the current limitation is obtained by using fuses, or by PTC, depending on which version you want. The manual clearly shows the power limited wiring and how to keep it separated from the non-power limited.

The part I am looking at, in comparison to the Elk and other manufacturers I've installed is the battery leads don't look like they're fused, which I was referring to back in my post. I'm not going to cite a UL issue, NEC, or the NFPA, but many of the manufacturer's panels I install do have fused battery leads, not PTC's. To cite specifics, Honeywell's panels have fuses for the battery connections to the panels, either inline or on the board, and I'm talking about both residential and commercial listed burg/fire panels. Maybe my logic is off, but it appears their products got listed without using any of the means cited for overcurrent protection before, but I'm not a UL or panel engineer

 

[Digger]

The part I am looking at, in comparison to the Elk and other manufacturers I've installed is the battery leads don't look like they're fused, which I was referring to back in my post. I'm not going to cite a UL issue, NEC, or the NFPA, but many of the manufacturer's panels I install do have fused battery leads, not PTC's. To cite specifics, Honeywell's panels have fuses for the battery connections to the panels, either inline or on the board, and I'm talking about both residential and commercial listed burg/fire panels. Maybe my logic is off, but it appears their products got listed without using any of the means cited for overcurrent protection before, but I'm not a UL or panel engineer

The battery leads dont "have" to be Power Limited but if they are not you need to meet the NEC requirements for separetion of circuits (1/4" spacing or barrier etc). A fuse is there in some mfgs for safety reasons not to meet code.

The Power Limited compliance is on the board that the battery connects to. In the case of the ELK M1 there is a PTC connected to the Red lead connection of the terminal block on the PCB. That then makes everything past that on the board Power Limited.

 

[Digger]

Leads between the Ac transformer and the main board- Because the transformer is listed as Class 2, Class 2 wiring can be implemented on the load-side wiring, i.e. the run between the transformer and the panel. So separation from other Class 2 wiring is not required.
Do not Exceed 50 feet- This guideline is not for code purposes but only for voltage drop purposes. Elk recommends 16 to 18 AWG wiring, but if you use larger wire, a longer run is possible.
Do not run the AC power in a multiconductor with other system circuits- I am assuming they mean the 16.5 VAC wiring and not 120VAC wiring. The reason for not recommending the 120VAC with other wiring is obvious, but for 16.5VAC is not so obvious. There is no reason, codewise, that this cannot be done, as they are power-limited conductors which would be placed in a cable with other power-limited conductors. My guess is that cross-talk (or induced voltage) can be an issue. When conductors are in such close proximity, as in a multiconductor cable, even low AC voltages can introduce crosstalk. Remember when we used to use hardwire telephones, and we could faintly hear someone else talking on the same line? That is crosstalk.
the ELK-P412 power supply- This power supply does not claim to be Class 2 power limited. But I don't understand why it couldn't be or wouldn't be. The NEC is clear....to be granted Class 2 status, the board, power supply or other device, must be designed using the rules of Article 725, including the limitations in Tables 11A or 11B, then be "listed" for the purpose. Once it is "listed", which means it has been tested and proven to be safe by a lab such as UL, then it must be labled as such. If it is not labled as Class 2, it cannot be considered Class 2.
the Altronix AL400ULPD supply- This supply does claim to be Class 2, and does also warn of the 1/4" separation requirement for limted and non-limited conductors. It is also interesting to note that the current limitation is obtained by using fuses, or by PTC, depending on which version you want. The manual clearly shows the power limited wiring and how to keep it separated from the non-power limited.

FYI I just called UL about the Altronix Power Supply to verify what I am writing even though I have done this for years. Unless they have a PTC in series with the battery and the transformer is inherently limited or has a PTC or solid state limitation that meets Table 12 or 13 it can not be considered a Power Limited output on the fused version. The Engineer said he would touch base with them and verify. Off memory of that board I think they have a PTC on the PS Board itself making it Power Limited but I could be wrong. The fused outputs are not what qualify it as Power Limited.

You have to remember that sometimes instruction manuals are written by marketing people and may not be 100% accurate. Or maybe they do comply but not by the means you think.

Again do not mix Power Limited and Class 2 (the Altronix installation instructions are misleading to a degree I agree). In reality is there really a safety difference? Probably not much. But on an installation inspected by an AHJ some will care and some will not.

 

[Sandpiper]

FYI I just called UL about the Altronix Power Supply to verify what I am writing even though I have done this for years. Unless they have a PTC in series with the battery and the transformer is inherently limited or has a PTC or solid state limitation that meets Table 12 or 13 it can not be considered a Power Limited output on the fused version. The Engineer said he would touch base with them and verify. Off memory of that board I think they have a PTC on the PS Board itself making it Power Limited but I could be wrong. The fused outputs are not what qualify it as Power Limited.

You have to remember that sometimes instruction manuals are written by marketing people and may not be 100% accurate. Or maybe they do comply but not by the means you think.

Again do not mix Power Limited and Class 2 (the Altronix installation instructions are misleading to a degree I agree). In reality is there really a safety difference? Probably not much. But on an installation inspected by an AHJ some will care and some will not.

What is the source of the requirement for the PTC? i.e. what standard or code requires it?

Also, I think I'm beating a dead horse, but Class 2 is one of the types of Power Limited Circuits and therefore is power-limited. Repeat.....Class 2 IS power limited, but so is fire alarm power limited (FAPL) and so is Class 1, and so is Class 3 ....

 

[Digger]

What is the source of the requirement for the PTC? i.e. what standard or code requires it?

Also, I think I'm beating a dead horse, but Class 2 is one of the types of Power Limited Circuits and therefore is power-limited. Repeat.....Class 2 IS power limited, but so is fire alarm power limited (FAPL) and so is Class 1, and so is Class 3 ....

I dont want to argue but they are different.

Class 2 is covered by Article 725 and table 11A and 11B as already stated. Power Limited in these applications is covered by Article 760 and table 12A and 12 B (usually B applies).

760-54 desribes using a barrier to seperate Power Limited and Non Power Limited as I previously mentioned. It also describes how Power Limited and Class 2 can be in the same conduit or the same multi conductor cable as long as teh Class 2 conductors have insulation equal to that required by Power Limited circuits.

I dont see how a Class 1 circuit can meet Power Limited as you state (if they did why seperate them?) Class 3 yes Article 760 address's that.

 

[paw500]

Again do not mix Power Limited and Class 2...

Do you mean: do not mix NON-power limited and Class 2?

 

[Digger]

Do you mean: do not mix NON-power limited and Class 2?

I meant dont mix up the two..... sorry I was on break and typing as I was on the phone with UL. Power Limited and Class 2 are not equal per the NEC.