Better is the relay like the RR7 where the coil part sticks out of the box through a 1/2" K/O and the 24v is not exposed to the 120v side. Those relays that have both in the same box are listed as part of a piece of listed equipment, not general premisses wiring.
That is one handy gizmo. How much are they? For anyone who builds or plays around with home equipment, a few of those in the spare parts bin would be terrific.
Of the suggestions, it looks like the one that will work is Daring Dufas's relay in a box suggestion.
easy to mount as it comes in it's own box
15 amps so controlling outlet on 15 amp circuit is OK takes 24V input available online for $21One remaining question. Someone mentioned isolation of the 24V circuit from 120V circuit? I would assume that since an electrical equipment manufacturer is making these relays and they are UL listed they are OK and meet code for my application even though the 24V wires obviously go into the same box as the 120V wires?
Thanks again for the suggestions
If there is not separation between line and low voltage compartments within the enclosure, I would recommend connecting line voltage conductors to the low voltage terminals, then run them outside the enclosure through a knockout, where you can splice them to typical low voltage conductors.
When you have "low voltage" conductors in the same box as line voltage the whole low voltage circuit needs to be treated as "class 1" which means it needs to be treated the same as you would treat the line voltage. Everything needs to be in a box, conduit or in a cable like Romex, end to end. When you have separation you can treat the low voltage side as "class
2" and you can take the liberties we usually have with "low voltage". It is really a little more complicated than that but you see what the general implications are..
I think I may see an out here. Upon closer inspection of the datasheet, the "relay in a box" that I want to use has what appears to be a plastic divider inside the box that seperates the low voltage section from the line voltage. Essentially it's like two seperate sections. Does this make it OK to use as I intended?
Here's a pic and the datasheet:
snipped-for-privacy@optonline.net wrote: ...
...
Yes.
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MR-101 or PAM-1 should do what you need, also I think Air Products sells a similar one that mounts to a knockout of a handy box which might be exactly what you're looking for. Don't remember part number off the top of my head.
You probably won't be able to mount it in the same box as the outlet for box fill reasons. I'd put it up in the attic so you don't have a blank plate showing in your living space.
nate
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I wonder how it is that hvac components don't cause this issue. Inside air handlers and outside units there is both 24vac and
110/220vac circuits. There is no specific separation of the wiring inside the units. Low an dhigh get co-mingled all over the place inside the units. And the 24vac wires go between units and the thermostat without any special treatment. Does the brown jacket on the low voltage wires count as satisfying the "class1" requirement? Is all that is required a 2nd insulation layer like house wiring? Because it would be easy enough to use thermostat wire for the low side of whatever it is he is doing.
"725.136-D Associated systems within enclosures Class 2 and 3 circuit conductors in ...boxes... shall be permitted to be installed with electric light, power... circuits where they are introduced solely to connect the equipment connected to Class 2 and Class 3 circuits, and where (1) OR (2) applies: (1) The electric light, power... circuit conductors are routed to maintain a minimum of 0.25 in. separation from the conductors and cables of Class 2 and Class 3 circuits."
The separation required is 1/4" between conductors. The class 2 conductors can attach to the relay in Dufas's relay box as long as they are kept 1/4" from power wires
Using a barrier is another method (725.136-B).
---------------- There should not be a problem with using a listed relay/contactor in a listed box (where the combination is not listed together).
---------------- The relays that gfretwell and John showed take minimal space in normal boxes, which makes them easy to use in normal wiring (in addition to having the low voltage wires outside the box). It is an advantage if they are installed where exposed (like a basement) to replace the relay in the future. Both are available as 2 wire or latched (momentary) versions.
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Only a 1/4", that makes it pretty easy.
I love their products, they save me a lot of time and money. I keep a few general purpose models in stock. All of the trades, electronic and industrial supply houses around here sell them.
TDD
And that applies to field wiring.
Factor wiring is covered by UL, which can have very different requirements.
This is generally read to say that the entire class 2 system is inside that enclosure. You can't take a wire out of there to another place and still call it class 2.
The handbook commentary on that section says "Power circuit and Class 2 circuit conductors can be permitted in the same motor-starter enclosure, where the Class 2 circuit source is the secondary of a control transformer in the same motor-starter enclosure. In such an installation, the Class 2 conductor insulation is not required to have the same voltage rating as the insulation on the power conductors in the same enclosure."
There is plenty of confusing language in 725. I think the whole thing should be evaluated and parts totally rewritten. You really have to be careful cherry picking out a few lines and believing that applies to your installation. Generally speaking you really need separation between class 2/3 and line power circuits. That is why they have class
Things that go on inside listed equipment do not necessarily apply to things you assemble yourself. Even there, the use of barriers is becoming the norm. The barrier itself may just be a little piece of mylar that the installer throws away but it was there when the product was listed. You also have to remember, cable jackets provide separation, so if the terminations are separated, the jacketed cable can go through the box. That also means you CAN pull a low voltage cable and line voltage cable in the same raceway,as long as you have separation where they terminate.
Hold your nose legal ... Pull your CAT5 and Romex through the same conduit, extend the CAT 5 through the box and terminate it in a LV ring next to the box. Some might argue that you need a separation between the place where you split open the RX jacket and the exit of the CAT 5 but if you went in and out in the back of the box with the LV cable, stuffed in a mylar insulator and split the RX jacket on the outside of that you comply. A little dodgier is CAT 5 and THHN in the same pipe. Most AHJs will not let that fly.
Check out X10.com. They have what you need, it's wireless, and requires nothing special but an outlet. You could have as many switches to control it as you wanted. Right now it's $19.99 but prices change often there. I've nothing to gain from them; just love their toys & products.
HTH,
Twayne`
Thanks for the suggestion, but I can't use X10 for two reasons. One is the control signal comes from a controller that already supplies a
24volt output. That also rules out some of the suggestions where the transformer function is already included in the relay. The second problem with X10 is reliability is a concern.I still think Daring Dufas's relay in a box fits all the reqts.
If the wires can't leave the box there is no particular usefulness in being class 2 - they can be class 1.
The section quoted above says class 2 wires are "introduced solely to connect the equipment". Reasonably read, "introduced" can mean to enter the enclosure from the outside.
It is common practice for class 2 thermostat wires to enter a "compartment" in a furnace/boiler where there are exposed insulated power wires. IMHO the section I quoted allows that practice if the class
2 wires are kept separate from the power wires.I dug out an old copy of UL913 which is for intrinsically safe apparatus. As you are no doubt aware, intrinsically safe wiring is a lot touchier than class 2. The standard has several methods to separate field wiring terminals for intrinsically safe circuits from power wiring. One of the methods is to separate the terminals by 2" (and there are requirements for insulation rating and securing the wiring). Intrinsically safe wiring can be in the same enclosure (like a control panel) as the power wiring and terminate in the enclosure. The intrinsically safe wiring is certainly intended to leave the enclosure.
Doesn't say the wires can't leave the box.
Separation? Like the 1/4" specified in the section I quoted?
Cherry picking?
725.136-A says class 2 (and 3) wires can't be in the same box, compartment, raceway, ... with power and light wiring - *except* as permitted by 725.136-B through I.Several of these provisions (B, C, G) allow the combination if class 2 wiring is separated by a physical barrier. The clear intent to me is that the barrier allows the class 2 to remain class 2. IMHO D-1, which I quoted, similarly allows class 2 to remain class 2.
The section I quoted, 725.136-D, essentially has 3 parts (I quoted only the first). Class 2 wires are allowed in an enclosure if it meets any
*one* of the parts- separation of power and class 2 wires by at least 1/4"
- specified class 2 cable jacket and separation or barrier for wires outside the jacket
- else the class 2 circuit becomes a class 1 circuit. Becoming class 1 is a possibility, but only if one of the first 2 provisions is not met.
For listed complete products the instructions from the manufacturer, based on UL requirements, predominate.
If I put a UL listed contactor/relay in an appropriate box, and the installation follows the listing for the contactor/relay, I don't see why the NEC does not apply - specifically 725.136-D-1. What is the violation?
You have posted that previously and it seemed quite reasonable.
When I looked at 725.136, it looks like class 2 and power can be in the same raceway *if* the power (or class 2) is wired in UF (725.136-I). What allows class 2 and Romex? Do the jackets constitute a "barrier" (725.136-B)?
It would allow the use of a class 2 listed transformer.
Again this is a listed assembly and I bet a new one has some kind of plastic barrier when it is shipped. It may not make it through the installation process and electrical inspectors don't really look inside that equipment.
It is an interesting question I will bring up with the IAEI..
You can certainly try it and see what your AHJ says but I doubt it would fly with any inspector I know.
A lot depends on how that part is listed
BTW there are plenty of inspectors who say I am wrong about this "both in the same pipe" thing. They are far more restrictive about how class
2 and line voltages need to be separated.
I'll have to pay more attention next time I have one of my ac's or heat pumps opened up. I've never noticed any plastic separators even in a new unit. On straight AC the only 24vac is to pull the main relay. That starts the whole thing up. On a hneat pump you have that as well as 24vac switching the unit between airconditioning and heat.
IMHO "introduced" clearly allows external class 2 wires to enter a box to connect to "the equipment connected to Class 2 ... circuits".
As I said in my previous post, 725.136-D has 3 options for class 2 wiring entering a box that has power wiring. Separation by at least 1/4" is one option. Only if the first 2 options are not used does 136-D explicitly require the class 2 wiring be class 1.
I agree that it is listed apparatus and should generally be beyond your purview (if wired according to manufacturer instructions). But it is compliant with what I understand is permitted by 725.136-D (class 2 and power wires in the same "compartment").
The AHJ would be arguing with what is explicitly allowed by UL. And, IMHO, what is allowed by 725.136-D.
But inspectors enforce the same code.......
I thought your options sounded reasonable.
IMHO 725.136-I clearly allows THHN power wires in the same raceway with class 2 that is in UF. Now if they would just make #18 UF...
I always liked taping UF with class 2 to the power conduit for installations like external condenser/compressors.
I will bounce this off the Florida inspectors I know. Some are both electrical and mechanical certified
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