Could I get another set of eyes on this schematic? It's a standard bathroom, however I'm adding a whirlpool tub pump, a whirlpool heater, and a macerator unit for waste discharge. I've read the instructions a million times, but I'm a little outdated on code requirements. I'm in Indiana.

The Macerator unit does not specify it need be on a dedicated circuit, but requires a 15A GFCI.

The whirlpool requires 20A GFCI dedicated.

The whirlpool heater requires a 15A GFCI dedicated.

Instructions say to bond the frame lugs of the heater to the whirlpool pump, then back to the electrical panel ground with 8ga. wire. I see the hardware store sells bare copper 8ga bonding wire, so that's what I intend to use.

Have I overlooked anything?

final layout

  • What does the macerator nameplate list for the amperage it draws? That can affect whether it needs a dedicated circuit (even if the instructions don't state that explicitly) or not. If it takes more than 7.5A, (half the circuit capacity) it needs to be dedicated.
    – Ecnerwal
    Commented Feb 2, 2023 at 14:56
  • @Ecnerwal, My thought was worst case a hair dryer (up to 15-16 amps) and the macerator activated at the same time would be right around 20 amps. Although highly unlikely both will be used at the same time, it's still a possibility. Here are the specs on the macerator.. Amperage, 4.5 Amps (Max) ; Motor, 0.5 HP. My initial thought was it would be easy enough to rewire to dedicated if needed since everything that would need changed over would be easily accessible, but I guess it would only cost an extra GFCI outlet and small amount of wire for piece of mind but running low on panel box slots.
    – SlowSL
    Commented Feb 2, 2023 at 15:31
  • If the whirlpool and heater each require a dedicated circuit, shouldn't that mean you need three separate circuits?
    – keshlam
    Commented Feb 2, 2023 at 15:31
  • If the light/vent does not involve a heater-vent, should be all kinds of room on that circuit for a measly 4.5A load. Certainly don't need to dedicate at that amperage.
    – Ecnerwal
    Commented Feb 2, 2023 at 15:51
  • @keshlam each color on my schematic is a separate circuit, so there are (4) separate circuits.
    – SlowSL
    Commented Feb 2, 2023 at 19:59

1 Answer 1


A few rules you need to know about.

A light or fan in the shower needs to have GFCI protection (or be low voltage). That can be tapped off the countertop or other receptacle if that receptacle circuit serves only this bathroom. (210.11(C)(3) exception).

As of NEC 2020, bathroom rules have changed somewhat. Previously, ALL receptacle outlets in a bathroom had to be 20A and follow "only bathroom" rules in NEC 210.11(C)(3). As of NEC 2020, this only applies to receptacles which serve the countertops - other receptacles in other areas can be from circuits that serve other rooms. So for instance, a towel heater receptacle could be on the same circuit with bedroom receptacles. Even if your state is on NEC 2014 or NEC 2017, asking your permit issuer to let you use the 2020 interpretation is perfectly reasonable.

Heaters require a 125% derate. Suppose you have a 960 watt heater (8 amps). You must provision it exactly the same as if it was a 1200 watt (10 amp) heater. And THAT is why the savvy manufacturer made it 20% smaller than a nice round number). This is often incorrectly called the 80% rule (implying it applies to every load; not quite).

Installation instructions must be followed (implied: must be read). NEC 110.3. If the instructions say "dedicated circuit" then that's that.

If you already own (or have to buy) 12 AWG wire, the way spools are priced it's probably cheaper to just buy/use more #12 than buy a separate spool of #14 just for 15A circuits. Use of #12 on a 15A breaker/circuit is allowed.

Fastened-in-place loads are treated as hardwired loads, in the following rule: If fastened-in-place loads take up more than 50% of circuit ampacity, then no receptacles at all are allowed on the circuit. Obviously, for a fastened-in-place plug-in load, the thing is allowed to have one socket for itself... so you need to use a single receptacle there (1-socket, simplex receptacle).

enter image description here src

You may notice a problem. With a simplex receptacle, how do you get GFCI there? You use a GFCI breaker; you use a double box with a GFCI deadfront in the other gang or down at the panel; or you cheat and do this. The switch doesn't need to go to anything; it's just there to prevent a second socket from existing.

enter image description here

You can have 2 or more fastened-in-place devices on a circuit, however in that case you sum their ampacity before applying the "is this 50% of the circuit?" rule. So for instance a 6 amp and 1 amp hardwired load on a 15A circuit is 7 amps, not quite half so it can have receptacles.

All this means, then...

If a 15A circuit will suffice for the fastened-in-place load, then it is legal to use it. You're not forced to a 20A circuit merely because it serves a socket (per NEC 2020 rules).

If two fastened-in-place loads can share a 15A or 20A circuit and still be under the ampacity (after 125% derates applied if applicable), then you can do that.

GFCI receptacles in difficult-to-access places are difficult for people to find when they're having a problem. That is a case where I'd go for a GFCI breaker or deadfront at the panel.

Having all lights on the receptacle GFCI isn't the smartest move. That is the GFCI people are most likely to trip, and you don't want them plunged into total darkness if they do. I think people do this because of misreading 210.11(C)(3). Bathroom wired-in lighting can be on any circuit in the house that isn't restricted by some other rule (e.g. not the furnace, electric dryer or kitchen receptacle circuit).

Putting the shower stall light/fan on one of the bathroom GFCI circuits is reasonable.

Note that GFCI receptacles allow 2 wires on each of the screw terminals, so it's easy to e.g. have a GFCI outlet in the bathroom, power some lights off the LINE terminals and the shower stall light/fan off the LOAD terminals.

GFCI or AFCI deadfronts at the panel

I for one am cheap, and really like Pushmatic. As such, I enjoy GFCI or AFCI deadfront receptacles located right next to the panel.

Here's the secret with those: Install them "2 at a time" in a 4-11/16 (aka 120mm) square steel box. With a domed cover (or mud ring if flush). Why that size and not 4" box? Space. One GFI is an extremely tight fit in a basic box, two GFCIs are an extremely tight fit in a common 4x4 box The tight fi t causes no end of problems - cable and conduit entries can only go in top or bottom, and you must strategize where to position the wire nuts so the GFCI doesn't bottom out on them. It sucks. However with a 4-11/16" box you have elbow room both alongside and behind.

I also like EMT conduit from panel to box, because that takes care of ground for you. 1/2" EMT will easily accommodate the 8 wires you need to bring 2 circuits to the G/AFCIs then 2 circuits back into the panel for connection to their circuits. Remember to tape hot+neutral for each circuit together to identify them as pairs - code requirement. Use #12 THHN black and white wire.

  • Thank you for this. This helps tremendously. I'm at work, but I'll re-read all this in detail and make sure I understand everything before I go any further. I've updated the schematic, adding it to the original post. I've separated a circuit, as well as added a dedicated vent fan circuit for use with a heater. I've changed to simplex recepts where applicable and added dead faced GFCI's located behind the wall, but also include two alternative locations after thinking about ease of access if something goes wrong. One being next to toilet, which seems silly, the other next to panel box.
    – SlowSL
    Commented Feb 3, 2023 at 15:32
  • The heater instructions as well as macerator require a 15A circuit. I'd assume that's a minimum, and 20A would be perfectly fine. I noticed 15A dead faced GFCI's are not available, at least not in stores around here, so I will use 20A for both the heater and whirlpool pump. There is not a problem the way the circuits are laid out since they are 20A, is there? I should be able to use 15A or 20A simplex recepts at their locations, correct?
    – SlowSL
    Commented Feb 3, 2023 at 15:38
  • I'll also add that all wiring will be 12/2, even 15A circuits.
    – SlowSL
    Commented Feb 3, 2023 at 15:39
  • One more thing, I didn't realize a tub skirt was considered a fixed entity. This is a drop in/alcove tub without a skirt, so the front face will have a dummy wall with some type of finishing. The plan was to build in a large access incorporated into that face for service/access. If I go that route, I'm able to use GFCI's under the tub, it looks, correct?
    – SlowSL
    Commented Feb 3, 2023 at 16:08
  • @SlowSL "dead faced GFCI's located behind the wall" I presume you mean that it's facing into another room, not behind drywall. A) buried behind drywall (or other non removable covering) is a code violation for any junction box, and B) How are you going to reset a tripped GFCI if it's behind the drywall? Again, presume you're taking the appropriate action, but just double checking...
    – FreeMan
    Commented Feb 3, 2023 at 18:30

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.