Two Motors on Same Branch Circuit

[Little Bill]

I have a setup where there are two motors and a couple of non motor loads on one branch circuit. The largest motor is 2 HP @ 230V = 12A by the table. The other is 1 HP @ 230V = 8A by the table. The non motor loads are 2A, or probably less, combined.

If you take 125% of the largest load, you get 12A * 1.25 = 15A

Add the 2nd motor
15A + 8A = 23A

Add the non motor loads
15A + 8A + 2A = 25A

This is all fed from a 30A 2-pole 240V GFCI breaker on #10 AWG.

The motors are then fed from the load side of a time clock and also within sight of the breaker/panel. The non motor loads are direct line power. All loads are fed by #10 AWG.

Had an inspection and the inspector is concerned about the motors not having individual OCPD. He wasn't sure and said he would look into it.

The motor section in the code is very confusing to me, but I think 430.24,Table 430.28, and 430.53(D) would allow my installation.

Is my install compliant, or do I need individual OCPD for each motor?

Also might help to know that the two motors are pool/spa pump motors and have built in overloads.

Any help on this would be appreciated!

 

[augie47]

A coupe of problems, IMO.
The motor SCGF overcurrent device should be a maximum of 250% (430.52) of the Table FLA. I your case the 30 amp OCP would be too large for the 1 HP motor.
You didn't describe the non-motor loads, but the 30 amp OCP may well be over sized for those loads also.

(also note that 250.53(D) that you quoted refers back to 250.53(C) which is for factory assembled controls)

 

[kwired]

A coupe of problems, IMO.
The motor SCGF overcurrent device should be a maximum of 250% (430.52) of the Table FLA. I your case the 30 amp OCP would be too large for the 1 HP motor.
You didn't describe the non-motor loads, but the 30 amp OCP may well be over sized for those loads also.

(also note that 250.53(D) that you quoted refers back to 250.53(C) which is for factory assembled controls)

I agree. Max size OCP has been exceeded for some of the loads.

 

[Little Bill]

A coupe of problems, IMO.
The motor SCGF overcurrent device should be a maximum of 250% (430.52) of the Table FLA. I your case the 30 amp OCP would be too large for the 1 HP motor.
You didn't describe the non-motor loads, but the 30 amp OCP may well be over sized for those loads also.

(also note that 250.53(D) that you quoted refers back to 250.53(C) which is for factory assembled controls)

I agree. Max size OCP has been exceeded for some of the loads.

Gus, I read the 250.53(C) as also permitting field installations.

I did say the other loads were probably less than 2A. They are for a gas pool heater, which just uses AC for the igniter and control and the other load is a salt cell.

Would a 25A breaker satisfy the requirements and make the install compliant?

 

[kwired]

What do you have for 430.102 disconnecting means? A load center and individual circuits to each load may help facilitate 430.102.

 

[Gregg Harris]

I have a setup where there are two motors and a couple of non motor loads on one branch circuit. The largest motor is 2 HP @ 230V = 12A by the table. The other is 1 HP @ 230V = 8A by the table. The non motor loads are 2A, or probably less, combined.

If you take 125% of the largest load, you get 12A * 1.25 = 15A

Add the 2nd motor
15A + 8A = 23A

Add the non motor loads
15A + 8A + 2A = 25A

This is all fed from a 30A 2-pole 240V GFCI breaker on #10 AWG.

The motors are then fed from the load side of a time clock and also within sight of the breaker/panel. The non motor loads are direct line power. All loads are fed by #10 AWG.

Had an inspection and the inspector is concerned about the motors not having individual OCPD. He wasn't sure and said he would look into it.

The motor section in the code is very confusing to me, but I think 430.24,Table 430.28, and 430.53(D) would allow my installation.

Is my install compliant, or do I need individual OCPD for each motor?

Also might help to know that the two motors are pool/spa pump motors and have built in overloads.

Any help on this would be appreciated!

I believe you set up requires individual protection
430.53 Several Motors or Loads on One Branch Circuit. Two or more motors or one or more motors and other loads shall be permitted to be connected to the same branch circuit under conditions specified in 430.53(D) and in 430.53(A), (B), or (C). The branch-circuit protective device shall be fuses or inverse time circuit breakers.
(A) Not Over 1 Horsepower. Several motors, each not exceeding 1 hp in rating, shall be permitted on a nominal 120-volt branch circuit protected at not over 20 amperes or a branch circuit of 600 volts, nominal, or less, protected at not over 15 amperes, if all of the following conditions are met:

1. The full-load rating of each motor does not exceed 6 amperes.
2. The rating of the branch-circuit short-circuit and ground-fault protective device marked on any of the controllers is not exceeded.
3. Individual overload protection conforms to 430.32.

(B) If Smallest Rated Motor Protected. If the branch-circuit short-circuit and ground-fault protective device is selected not to exceed that allowed by 430.52 for the smallest rated motor, two or more motors or one or more motors and other load(s), with each motor having individual overload protection, shall be permitted to be connected to a branch circuit where it can be determined that the branch-circuit short-circuit and ground-fault protective device will not open under the most severe normal conditions of service that might be encountered.
(C) Other Group Installations. Two or more motors of any rating or one or more motors and other load(s), with each motor having individual overload protection, shall be permitted to be connected to one branch circuit where the motor controller(s) and overload device(s) are (1) installed as a listed factory assembly and the motor branch-circuit short-circuit and ground-fault protective device either is provided as part of the assembly or is specified by a marking on the assembly, or (2) the motor branch-circuit short-circuit and ground-fault protective device, the motor controller(s), and overload device(s) are field-installed as separate assemblies listed for such use and provided with manufacturers? instructions for use with each other, and (3) all of the following conditions are complied with:

1. Each motor overload device is either (a) listed for group installation with a specified maximum rating of fuse, inverse time circuit breaker, or both, or (b) selected such that the ampere rating of the motor-branch short-circuit and ground-fault protective device does not exceed that permitted by 430.52 for that individual motor overload device and corresponding motor load.
2. Each motor controller is either (a) listed for group installation with a specified maximum rating of fuse, circuit breaker, or both, or (b) selected such that the ampere rating of the motor-branch short-circuit and ground-fault protective device does not exceed that permitted by 430.52 for that individual controller and corresponding motor load.
3. Each circuit breaker is listed and is of the inverse time type.
4. The branch circuit shall be protected by fuses or inverse time circuit breakers having a rating not exceeding that specified in 430.52 for the highest rated motor connected to the branch circuit plus an amount equal to the sum of the full-load current ratings of all other motors and the ratings of other loads connected to the circuit. Where this calculation results in a rating less than the ampacity of the supply conductors, it shall be permitted to increase the maximum rating of the fuses or circuit breaker to a value not exceeding that permitted by 240.4(B).
5. The branch-circuit fuses or inverse time circuit breakers are not larger than allowed by 430.40 for the overload relay protecting the smallest rated motor of the group.
6. Overcurrent protection for loads other than motor loads shall be in accordance with Parts I through VII of Article 240.

Informational Note: See 110.10 for circuit impedance and other characteristics.
​

(D) Single Motor Taps. For group installations described above, the conductors of any tap supplying a single motor shall not be required to have an individual branch-circuit short-circuit and ground-fault protective device, provided they comply with one of the following:
70-324

1. No conductor to the motor shall have an ampacity less than that of the branch-circuit conductors.
2. No conductor to the motor shall have an ampacity less than one-third that of the branch-circuit conductors, with a minimum in accordance with 430.22, the conductors to the motor overload device being not more than 7.5 m (25 ft) long and being protected from physical damage by being enclosed in an approved raceway or by use of other approved means.
3. Conductors from the branch-circuit short-circuit and ground-fault protective device to a listed manual motor controller additionally marked ?Suitable for Tap Conductor Protection in Group Installations,? or to a branch-circuit protective device, shall be permitted to have an ampacity not less than one-tenth the rating or setting of the branch-circuit short-circuit and ground-fault protective device. The conductors from the controller to the motor shall have an ampacity in accordance with 430.22, The conductors from the branch-circuit short-circuit and ground-fault protective device to the controller shall (1) be suitably protected from physical damage and enclosed either by an enclosed controller or by a raceway and be not more than 3 m (10 ft) long or (2) have an ampacity not less than that of the branch-circuit conductors.

 

[Little Bill]

What do you have for 430.102 disconnecting means? A load center and individual circuits to each load may help facilitate 430.102.

Actually there are two disconnecting means.
One is a timeclock, it is horse power rated.

It is a two timer clock with each side having a manual switch.
One motor is fed off the load side of one of the timers and the other motor is fed off the load side of the other timer.

The better means, IMO, is the panel that feeds the circuit is within sight of the motors/loads.

 

[iwire]

Actually there are two disconnecting means.
One is a timeclock, it is horse power rated.

It is a two timer clock with each side having a manual switch.
One motor is fed off the load side of one of the timers and the other motor is fed off the load side of the other timer.

The better means, IMO, is the panel that feeds the circuit is within sight of the motors/loads.

Time clocks are typically controllers not disconecting means, but the breakers will meet the needs.

 

[Little Bill]

Time clocks are typically controllers not disconecting means, but the breakers will meet the needs.

I agree somewhat. If using the timer part, that would be a controller.
But if using the manual switch, that to me would be a disconnect. Both ungrounded conductors are switched (open/closed) by the manual switch.

 

[Smart $]

I agree somewhat. If using the timer part, that would be a controller.
But if using the manual switch, that to me would be a disconnect. Both ungrounded conductors are switched (open/closed) by the manual switch.

Is this an OFF-AUTO-ON switch? IOW what prevents the timer contacts from energizing the motor circuits when the manual switch is in the OFF position?

 

[Little Bill]

Is this an OFF-AUTO-ON switch? IOW what prevents the timer contacts from energizing the motor circuits when the manual switch is in the OFF position?

No trippers installed.

 

[Smart $]

Is this an OFF-AUTO-ON switch? IOW what prevents the timer contacts from energizing the motor circuits when the manual switch is in the OFF position?

No trippers installed.

Not sure what you mean by trippers... breakers, fuses??? If so, that has no bearing on my question. What I'm getting at is many clock timers' manual switch is just an override ON, not an override OFF (IOW, bypass ON). In the "not on" position, the timer can energize the load terminals. What you have there may be different, and that's what I'm asking...

 

[Little Bill]

Not sure what you mean by trippers... breakers, fuses??? If so, that has no bearing on my question. What I'm getting at is many clock timers' manual switch is just an override ON, not an override OFF (IOW, bypass ON). In the "not on" position, the timer can energize the load terminals. What you have there may be different, and that's what I'm asking...

Trippers are mechanical trip points that mount to the clock dial. You place one for each on time and one for each off time. Without the trippers, the clock dial just turns and has no control effect on the circuits.

The manual switch can be used in conjunction with the trippers as an override for either on or off, depending on the status of the timer.

But if the trippers aren't installed, the manual switch is the only thing that controls the on/off of the load.

 

[iwire]

Trippers are mechanical trip points that mount to the clock dial. You place one for each on time and one for each off time. Without the trippers, the clock dial just turns and has no control effect on the circuits.

The manual switch can be used in conjunction with the trippers as an override for either on or off, depending on the status of the timer.

But if the trippers aren't installed, the manual switch is the only thing that controls the on/off of the load.

If the manual switch is not capable of holding the contacts open without removal of the trippers it is a controller not a disconnecting means.

 

[Smart $]

If the manual switch is not capable of holding the contacts open without removal of the trippers it is a controller not a disconnecting means.

I agree.

 

[kwired]

Lets not forget 430.102 requires a disconnecting means for the controller as well as motor. Same disconnect can serve both if within sight of one another, and a few other exceptions.

 

[Little Bill]

Guess I'll (reluctantly) concede the timeclock as a disconnect.

Ok, see if this will fly!

If I change the breaker to a 25A and since the breaker/panel is within sight of both the timeclock and the equipment, would this be an acceptable install?

 

[Smart $]

Guess I'll (reluctantly) concede the timeclock as a disconnect.

Ok, see if this will fly!

If I change the breaker to a 25A and since the breaker/panel is within sight of both the timeclock and the equipment, would this be an acceptable install?

Smallest motor protected?

8A ? 250% = 20A
25A > 20A

 

[Little Bill]

Smallest motor protected?

8A ? 250% = 20A
25A > 20A

Yep, and now I'm sure you're the one who called my inspector!:rant:

He's not going to accept the install as is. He is however going to let me set a small panel at the equipment with two breakers, one for each motor. Well, one of the motors will also have the other two small loads.

He's going to let me slide on clearance issues (110.26) because the panel will be just for the equipment at hand. That is the reason I didn't put the panel there to start with, not enough clearance at the equipment area.

The part that really makes me mad is the contractor asked me to do the install the way I did it to save on costs since (as he told me) the HO were over budget already.
I had intended on running individual circuits for each motor, but to try and help out I just ran the one. He said he has this done all the time.:rant:
I had a bad feeling about it, but seemed ok if only the current/conductors/OCPD was considered. I didn't look into grouping the motors the way I should have. I really should have studied more on motor installs years ago as they definitely aren't my strong suit!

Lesson learned-Rant over!:weeping:

 

[kwired]

The part that really makes me mad is the contractor asked me to do the install the way I did it to save on costs since (as he told me) the HO were over budget already.

They were over budget before you were even involved, they always are.

Where does a GC get off telling you what will pass electrical inspection?