Pool Equipment Sub Panel

[Cleevis]

Currently have 2x 15A, 230V circuits running from main service panel to pool equipment (6 wires total). Existing buried conduit is 1/2 in PVC (90C).
I want to install a sub panel for a fancy new equipment controller and would like to replace the 15A circuits with a single 50A feeder to the sub for distribution to the equipment, lighting, backyard outlets etc.

First questions are on the capacity of 1/2 in conduit:
Have found little information on combined wire gauges in conduit but if i calculate the areas, 3x 8 AWG and 1x 12 AWG conductors (THWN insulated) are below 40% of the internal area of Sch 40 rigid PVC conduit. Am wrong and/or in violation of code to run this?
If I run a bare #12 ground conductor I get a little more room and probably ease in pulling. Is this okay in buried rigid NM conduit?

Second questions are regarding whether i need the 4th wire at all:
If the sub panel gets bonded to the pool ufer ground, and there is no conductive path between the pool, equipment or sub panel and the house other than the feeder conductors, am I in violation if I bond the neutral bar to the ground in the sub panel?
I'm relatively certain i know the answer or at least that regardless of the answer, the best practice would be to keep the lowest resistance ground fault path through the ground to the main but couldn't the ufer ground of the pool structure be lower resistance anyway?

I've found a lot of discussion about bonding/grounding of sub panels but little specifically relating to pool equipment subs so I thought I'd throw this in here.

I appreciate any feedback.

 

[mcclary's electrical]

Currently have 2x 15A, 230V circuits running from main service panel to pool equipment (6 wires total). Existing buried conduit is 1/2 in PVC (90C).
I want to install a sub panel for a fancy new equipment controller and would like to replace the 15A circuits with a single 50A feeder to the sub for distribution to the equipment, lighting, backyard outlets etc.

First questions are on the capacity of 1/2 in conduit:
Have found little information on combined wire gauges in conduit but if i calculate the areas, 3x 8 AWG and 1x 12 AWG conductors (THWN insulated) are below 40% of the internal area of Sch 40 rigid PVC conduit. Am wrong and/or in violation of code to run this?
If I run a bare #12 ground conductor I get a little more room and probably ease in pulling. Is this okay in buried rigid NM conduit?

Second questions are regarding whether i need the 4th wire at all:
If the sub panel gets bonded to the pool ufer ground, and there is no conductive path between the pool, equipment or sub panel and the house other than the feeder conductors, am I in violation if I bond the neutral bar to the ground in the sub panel?
I'm relatively certain i know the answer or at least that regardless of the answer, the best practice would be to keep the lowest resistance ground fault path through the ground to the main but couldn't the ufer ground of the pool structure be lower resistance anyway?

I've found a lot of discussion about bonding/grounding of sub panels but little specifically relating to pool equipment subs so I thought I'd throw this in here.

I appreciate any feedback.

bare ground? you might wanna rethink that. But yes you need 4th wire, and I wouldn't want to try to put all that in a 1/2" conduit. I Didn't check your nuumbers on fill either

 

[Dennis Alwon]

First questions are on the capacity of 1/2 in conduit:
Have found little information on combined wire gauges in conduit but if i calculate the areas, 3x 8 AWG and 1x 12 AWG conductors (THWN insulated) are below 40% of the internal area of Sch 40 rigid PVC conduit. Am wrong and/or in violation of code to run this?

This will not fit in 1/2" conduit.

If I run a bare #12 ground conductor I get a little more room and probably ease in pulling.

You cannot run #12 it must be #10

Is this okay in buried rigid NM conduit?

Buried PVC is fine

Second questions are regarding whether i need the 4th wire at all:
If the sub panel gets bonded to the pool ufer ground, and there is no conductive path between the pool, equipment or sub panel and the house other than the feeder conductors, am I in violation if I bond the neutral bar to the ground in the sub panel?

You must have an insulated ground.

 

[Dennis Alwon]

2 runs of #8 Thwn= .0366
2 run of #10 Thwn= .0211 -- This would be your equipment ground and neutral

.0366*2= .0732
.0211*2= .0422

.0732 + .0422 = .1154

Sched 40 ---1/2 PVC will allow .114 for over 2 wires. This is just barely over. Unfortunately you cannot size the neutral any smaller than the EGC. You may be able to get that okayed but it would be a tough pull.

 

[tom baker]

Are you doing this work yourself?

 

[Cleevis]

Thanks so much for the replies.

To clarify:
1) EGC cannot be 2 sizes reduced from H conductor size. Only one size down is allowed.
2) The N conductor can be reduced one wire size as well as the EGC.
3) Bare EGC not allowed - there is a difference between UF cable directly buried and wires run in buried conduit

Dennis, the 8-8-10-10 suggestion sounds like a great solution.
Two (more) questions:

4) Based on the 40% allowable for more than 2 wires in a conduit, the allowable fill of NM sch 40 rigid should be .1215 in2. The area of 2 #8 and 2 #10 (both stranded according to your numbers) is 37.5%. Are you knocking down the % allowable for multiple wire sizes?

5) Solid #10 N and EGC gets the fill down to 35.7%. I'll test it but this may be an even tougher pull no?

 

[Dennis Alwon]

To clarify:
1) EGC cannot be 2 sizes reduced from H conductor size. Only one size down is allowed.

That is totally incorrect. Table 250.122

2) The N conductor can be reduced one wire size as well as the EGC.

The egc cannot be reduced from T. 250.122 but the neutral can if the calculated load is less the ungrounded conductors. The neutral can never be less than the egc.

3) Bare EGC not allowed - there is a difference between UF cable directly buried and wires run in buried conduit

For sure

Dennis, the 8-8-10-10 suggestion sounds like a great solution.
Two (more) questions:

4) Based on the 40% allowable for more than 2 wires in a conduit, the allowable fill of NM sch 40 rigid should be .1215 in2. The area of 2 #8 and 2 #10 (both stranded according to your numbers) is 37.5%. Are you knocking down the % allowable for multiple wire sizes?

Table 4 schedule 40 PVC --- 1/2" PVC is .114 sq. inches as stated in my other post.

5) Solid #10 N and EGC gets the fill down to 35.7%. I'll test it but this may be an even tougher pull no?

Where did you get that info from?

You have not answered Tom Bakers post. This is not a job for a homeowner as there is much more to pools then this.

 

[roger]

I will ask as Tom did, are you performing this work yourself?

Roger.