Wiring Question

[Jswee]

A question for the experts, I would like to add a wall space heater in my master bathroom. The unit that I like requires a 240V 20 amp circuit. I have a finished ceiling in my basement so running a new circuit for this will be very difficult. Running through the crawl space under the bathroom is a 240V 50 amp line for my air conditioning system. My question is can I run a sub panel off of this 50 amp line and put a 240V 20 amp breaker in it for the new heater? The heater will only be used during the winter when the AC is not in use and it will have a programable thermostast with a seasonal shut off to insure that it is not accidently used while the AC is operating. Also, the heater is hardwired so there is no plug or cord involved. Thanks for your input.

[RB]

If there is a 50 amp breaker in the entrance panel feeding the a/c now you can insert a main lug sub-panel that has two breakers, one 50 amps, and one 20 amps, in that line. The 50 amp breaker will feed the a/c through #8 70 C wire and the 20 amp breaker will feed your heater through #12 wire.

RB

Jswee wrote:

[RB]

Since this is in a bathroom I'd spring for a 20 amp double pole GFI breaker. They're not free but are worth it. I use them to feed my bathroom 240 volt outlets.

RB

RB wrote:

[Toller]

Very creative solution. Does the 50a line have a neutral and a ground; my AC line does not. You will need them for a subpanel even if your heater doesn't need it.

There is also the issue of where to put the subpanel.

[volts500]

IMO, you'd be well advised to leave that AC circuit alone. Panelboards should not be installed in crawl spaces. If you are lucky the floor joists run so that fishing a cable won't be difficult, or use Wiremold. Otherwise, you may be able to run the circuit in conduit on the outside of the house low on the siding or buried, then enter into the crawl space.

[Mark or Sue]

This concept should work. I don't believe you must have a neutral wire in the sub panel, but you must have an equipment grounding bus. If you can find a small panel with feed through lugs (or install double lugs), then you won't have to spring for another 50A breaker for the A/C (assuming this A/C feeder is protected at the source with a 50A breaker). Minimum panel would be two slots to accomodate the 20A breaker.

You thermostat will add complexity to the circuit and is probably not required. Most inspectors should allow an A/C and heater to be considered non-coincident loads. A line voltage thermostat for the wall heater is the most common type. But if you have the contactor to control the heater, that is fine too.

Only issue I can think of is what is the disconnecting means for the heater? If its the 50A feeder breaker, will your inspector accept that?

-- Mark Kent, WA

[zxcvbob]

sub panel, but you

through lugs (or

for the A/C (assuming

would be two slots to

required. Most inspectors

voltage thermostat for

control the heater, that

If its the 50A feeder

He *could* tap into the 50A circuit; install a junction box in the crawlspace. I think the "10 foot tap rule" would let him use #12 wire for the tap conductors. Install a 20A fusable 2-pole switch for the heater. It has to have fuses or a breaker to protect the tap wires.

The only problem I see is having a panel installed in a bathroom. But maybe the switch enclosure is not considered a panel? I've also seen little boxes with room for one 2-pole SWD (switch) rated breaker.

Best regards, Bob

[Tom Horne]

A panel that does not supply line to neutral loads is not required to have the neutral conductor in the feeder. The feeder must, of course, include a properly sized Equipment Grounding Conductor (EGC).

-- Tom H

[Toller]

Can you cite a reference for that? When they sell the house, somebody can stick the wrong load on without knowing there is no neutral; it is hard to believe they would allow that.

[Tom Horne]

What is not forbidden is allowed. The code specifically requires running the neutral conductor from a transformer that is configured to supply one to the service disconnecting means even if it is not used. This is most commonly encountered in fire pump service disconnecting means that are supplied from the same transformer that supplies the regular service to a building. The code has no such requirement for feeder supplied panels. It might be wise to label the panel with a warning that it may not be used to supply line to neutral loads but even that is not required.

-- Tom