120V outlet in line to 240V heater?

[borisf]

I'm planning to add a hard-wired infrared patio heater soon. [Infratech SL-30 if anyone has any feedback on this unit].

It's a 3000W 240V heater and I'm going to add a dedicated 20A 240V breaker for it. The heater location is a ways from the panel (~60 ft.) and it would be very convenient to add a standard 120V outlet to the deck as part of the same wiring run.

Is it to code to use one of the 240V legs that runs to the heater for this 120V outlet and share the ground and neutral? See attached diagram.

 

[Reach4]

I don't know if there are rules against what you propose as far as having both on the circuit. It looks OK to me, but I would not be surprised if there was some contrary rule. So somebody else is going to know that

I figured out that the two closely-spaced black lines in your drawings represent a white neutral. I was first thinking that there would be no neutral run to the heater for 240, but then I looked at the brochure that said "May also be installed with duplex/stack switches for effectively a half-power or full-power option". So there may be a neutral involved in that case. I don't know. It also may be that there is a control section that needs the neutral. I would ask the manufacturer about that.

 

[Sponsor]

 

[Stuff]

Not common so your inspector may give you grief. You would need to pigtail the neutral wire at the receptacle as this would be a MWBC. A multi-wire branch circuit requires that the neutral not go through a device.

 

[Standardairconditioner]

This is rather strange and I cannot be sure how the breaker would react to a problem that occurs on the outlet.

An electrician would put a lot of trust into a breaker box, where 120V breakers are for 120V circuits and 240V breakers are for 240V circuits.

There may also be danger for a future worker that would turn off all 120V breakers in a box, only to be shocked (no pun intended) that this outlet was still hot.

I have never seen this setup ever in my life, I am almost certain that this is not legal today.

If this is some sort of auxillary outlet where you will plug in a nite lite or clock, then I'm sure nothing bad will happen in your lifetime. But I would never do this install in my home or a client.

 

[Reach4]

This is rather strange and I cannot be sure how the breaker would react to a problem that occurs on the outlet.

The 240 volt breaker trips both sides if either leg trips.

I have never seen this setup ever in my life, I am almost certain that this is not legal today.

Maybe you have seen this method in action, but did not notice.

 

[Standardairconditioner]

Maybe you have seen this method in action, but did not notice.

Nope, never.

Outdoor heat pumps are 240V installs and on the rare occasion I use an existing breaker, I have to audit the entire home.

I've been combing thru the Canadian Electrical Code and I can't find anything about it.

Someone here should look at the National Electrical Code, and if it allows it, then so be it.

 

[Reach4]

If the 240 VAC heater was 1800 watts instead of 3000 watts, would that change things in your mind?

 

[Stuff]

NEC's section about MWBC's in the handbook has an example of a combination duplex receptacle - both a 240 and 120 on same yoke.

Leviton 5842 - http://www.leviton.com/OA_HTML/ProductDetail.jsp?partnumber=5842-I&section=42416

HVAC equipment normally has the manufacturer requiring dedicated circuits.

Good point about 1800 watt. I forgot about the 50% rule (fastened in place) 20a @240 = 4800 watt / 2 = 2400 watt maximum. So OP's heater would not be allowed to share a circuit with a receptacle unless it was cord-and-plug connected.

 

[Jadnashua]

Outdoor electrical receptacles require GFCI, so, no, I don't think you can do this, while it may work, the combined load is not a good idea anyway.

 

[Reach4]

Outdoor electrical receptacles require GFCI, so, no, I don't think you can do this.

You want to re-think that.

 

[Standardairconditioner]

NEC's section about MWBC's in the handbook has an example of a combination duplex receptacle

That's not what the homeowner wants to do here.

The combo recepticle will still have one flavor on a 240V breaker, with a hot hot neutral ground going into the outlet. What the outlet divides from itself is left to the manufacturer, similiar to 5V usb females on NEMA 5-15 outlets.

Consider this: have any of you ever seen a laundry room controlled by a single breaker, where the 240V was for the dryer, and on the same loop, a hot and neutral was given to an outlet just for the washer? Then builders can save a ton of money by just bringing one wire feed to a new laundry room.

 

[Stuff]

That combo duplex receptacle can be wired two ways and it is up to the installer. One way is with 240 and 120 independent circuits. Other is both from a single 240 circuit. The wiring to configure is external so not the same as a USB device.

It is not done for dryers as the standard there is 30 amp. If you had a 30 amp 120 volt receptacle you would be allowed.

One of the tenets of the NEC is that what is not specifically forbidden is allowed.

 

[Jadnashua]

Given the 80% rule, the 'spare' power available on that 20A circuit is less than 5A, so that could severely limit what you might want to use on that receptacle...it's not that hard to pull two wires verses one and have full use of the receptacle for other things, and if you ran 12/3, you could have two independent 20A circuits for receptacles using a shared neutral and a 240vac breaker. Often, the instruction manual calls for a dedicated circuit for that sort of appliance, but if it's in there, I can't find it.

 

[Cwhyu2]

You cannot share a neutral any more no matter what.

 

[Reach4]

You cannot share a neutral any more no matter what.

What do you mean by that? You are not going to say that multi-wire branch circuits are disallowed in all cases, are you?

 

[Cwhyu2]

According to NEC all circuits must must have the neutral for that one circuit and not combined with 2 or more circuits.

 

[Cwhyu2]

In other words you cannot share one neutral on two seperate hots.

 

[Reach4]

In other words you cannot share one neutral on two seperate hots.

See http://www.ieci.org/newsroom-and-insights/multi-wire-branch-circuits

Maybe you are going to say that breakers that have a handle tie are not separate hots. But it is clear that it OK to have one of the two hots live and the other not as long as the approved means of shutting them both off at the breaker panel exists.

And even if you powered the 120 vac circuits, that are on different legs with a 2-pole breaker, they are still two hots sharing a neutral.

 

[Jadnashua]

IF you choose to use a multiwire branch circuit, there are some functional requirements that make sense if you think about it, but could easily be overlooked. For example, say you are feeding a receptacle and daisy-chaining to others...you cannot use the terminals on the receptacle as a tie point...you must tie the neutrals together and use a pigtail to feed the device so that there will be a continuous circuit if you were to remove that device or there was a local fault. The CB must be rated for 120/240 (or higher) with either an approved handle-tie, or a two-pole device. If it is not obvious, you must tie the neutral and hot leads together (typically tie wraps) where they enter the panel (say you were using conduit and single wires) so that they are identified as being shared. Not all add-on handle ties will work with all CB's, the CB must clearly be labeled for that function. Essentially, if there's a fault in one circuit, it should trip the other. At least that's how I read the latest code cycle information.

 

[Stuff]

Note that a handle tie accomplishes the need for common disconnect but not common trip. This is because when a breaker trips it normally goes to the middle position which would not turn off a connected breaker. You need a two pole common trip breaker if you have a line-to-line (240v) load on a MWBC in the OP's case.