HELP!! Pool pump & booster pump wiring sizing

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kc5swi

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I recently looked at a buddies new wiring he had installed and supposedly passed inspection on his pool pump/plus booster pump set up. I am concerned it is unsafe, and of course, my buddy thinks I'm the moron as an "electrician" couldn't be wrong. Please prove me an idiot, or tell me why I'm right before my buddy burns down his house.
:eek:
One double throw 20amp GFI breaker in the breaker box running about 50' of #12 wire to a Intermatic timer mod pf1207 box. From there, power is fed into two timer relays. Exiting one timer to the 240vlt 2hp (10.8amp) main pump on #12 wire about 4' away. The other timer feeds a 3/4 hp, 240vlt, booster pump also on #12 wire. Both pumps often run at the same time.

Shouldn't each pump be individually breakered to ensure each load was protected? Isn't one 20amp breaker too small for both pumps? Isn't #12 wire from the breaker to the split at the pumps too small?

The last issue is this Intermatic box is internally wired with #14. It has a freeze protection relay that essentially routes the total juice through a temperature controlled relay before it gets to the timers. Isn't #14 way too small to operate both pumps simultaneously?
!!Thanks in advance for your input!!
 
Re: HELP!! Pool pump & booster pump wiring sizing

I would not worry about the internal wiring of the timer IF it is part of the timer itself. Wire sizes there are governed by UL requirements and in many cases #14 is quite acceptable for 20 amps.

Its quite possible that the installation is acceptable if the motors have internal thermal overload protection.

The only way you csn tell for sure is to read the manufacturer's literature that came with the stuff. If you are not especially savvy in this type of equipment, what it says may not mean much to you, so if you are really concerned about it, the best answer is to pay someone who actually does know to look over the installation.
 
Re: HELP!! Pool pump & booster pump wiring sizing

Thanks Bob for your input. However, I am looking for a reason to justify my buddy to hire another electrician to look at this. I realize many here are in the biz, but like you, he's not going to be motivated to spend money if he doesn't think there is a problem.

I thought the breaker size was figured as: 2hp pump (10.8amps/240v), 3/4 hp pump (8amp/240v)
10.8x2.5=27 27??+8=35 So I figured a 40 amp breaker was appropriate, not a 20?? :( Right?
 
Re: HELP!! Pool pump & booster pump wiring sizing

maybe. maybe not. it would depend in part on what the instructions from the pump manufacturer's state.

on the face of it, the CB sizing seems small. but there is no safety hazard in undersizing the CB. and if it is not tripping, what difference does it make?
 
Re: HELP!! Pool pump & booster pump wiring sizing

Ok, that does make sense. Thanks.

The motors are individually thermally protected. I guess I always thought sizing the CB to each load provided the best safety margin compared to running two loads in combination on one up sized CB. With inrush, I was suprised both motors would start at one time, but they do, without tripping the CB, so I must be wrong...or just very cautious.
 
Re: HELP!! Pool pump & booster pump wiring sizing

Your friend should, at least, be grateful for your concern. But I suspect that there is no technical or safety reason for concern.

The design process goes in the following order:
</font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">First, look at what the manufacturer says in the instruction manual. If it gives you a breaker size and conductor size, then you can follow that instruction without any concerns.</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">If the book doesn't give you a breaker size and conductor size, then you need to figure out the load. We don't use the nameplate amps. We look it up in a table, add 25% to the largest motor, and then adjust for voltage level, if needed. The 2 hp motor is listed in the table at 12 amps. Adding 25% brings you to 15 amps. Add another 6.9 amps for the 3/4 hp motor. So far, you are at 21.9 amps. But the table shows 230 volts. When you correct for 240 volts, the amps comes down to 21.</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">The next step is to pick a conductor that is good for 21 amps. A #12 is only good for 20 amps, so I would pick a #10.</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">Next, you pick a breaker that will protect the cable. It may not be self-evident, but the purpose of the breaker is not to protect the motor, but to protect the cable. I would pick a 30 amp breaker on this basis.</font>
<font size="2" face="Verdana, Helvetica, sans-serif"></font>
  • <font size="2" face="Verdana, Helvetica, sans-serif">Finally, you think about upsizing the breaker, to allow for the starting inrush current. This is more than a bit complicated, since there is more than one motor. But this is the step in which the factor of 2.5 that you used will come into play. But this step gives you the maximum allowable breaker size. You are free to pick a lower size, but you will run the risk of nuisance tripping.</font>
<font size="2" face="Verdana, Helvetica, sans-serif">I don't expect that your friend's installation is unsafe. If you want to take the next investigative step, then I echo Bob's suggestion that you read the manufacturer's instruction book.

I am an engineer, and we tend to oversize things, just for conservatism. If this were my house, I would seriously look into having at least a #10 wire and at least a 30 amp breaker. But that would be a design choice, not necessarily a code requirement. The code only gives the minimum required for safety. It explicitly states that following the code will not always give you an installation that performs to your own satisfaction. It only assures that the installation will be safe.
 
Re: HELP!! Pool pump & booster pump wiring sizing

#12 copper wire is rated for 25 amps, and you can use it at that for motor loads. Normally, #12 wire would be limited to 20A, but motor circuits are one of the exceptions. That being said, I'd still consider upsizing to #10 because of the length and the total load.

Because this is a motor circuit, you can put a 25A or 30A breaker on this #12 wire if you need to.
 
Re: HELP!! Pool pump & booster pump wiring sizing

The code tells we must use the tables rather than the namplate current. On a multimotor load you take the largest motor current and multiply by 1.25 and then add the other motors. Thus you have 12.x 1.25=15. +6.9 =21.9.
. If you are using romex then you cannot use #12. If you use thhn you may use # 12. Then you take the rating of the largest motor of 16 amps and use the table 430.52 for an inverse time bereaker of 250% =40 amps. you then add the rating of the second motor and you come up with 46.9 as the max you may use. I would use 40 and assume that they would never start simulanueosly. This will also allow the 2nd to start after the 1st is running and vice versa.I believe if you had this as a test question on an exam this is what you would do to calculate it.

[ August 21, 2005, 10:58 PM: Message edited by: stew ]
 
Re: HELP!! Pool pump & booster pump wiring sizing

QRZ KC5SWI, nice of you to be concerned. Using THHN wire #12 is fine for this job. Using Romex it would be over the rating of #12. The next factor in wire size would be distance to the load. I'll be QRX for ya. Hi Hi I wonder if the electrician's exam is as hard as getting an Extra? QTH here is CT. 73 Lou W1QJ
 
Re: HELP!! Pool pump & booster pump wiring sizing

Why can't you use 12-2 romex for a 21A motor? The 60C ampacity of #12 copper is 25A and the normal restriction of 20A OCP on a #12 circuit doesn't apply to motor circuits.

Because its a pool motor, I can see why you may not be able to use romex or UF cable (need a raceway method with an insulated neutral unless inside a building at a dwelling).
 
Re: HELP!! Pool pump & booster pump wiring sizing

Thanks to all for the input, it was fantastic. This was my first time here, and I was truly impressed.
73's to all, (thanks!)
kc5swi
Cole
 
Re: HELP!! Pool pump & booster pump wiring sizing

Hi Sue, My understanding of the code is this, I may be wrong though. If the total operating current of two or more motors exceeds 20amps that would disallow #12 Romex which is only rated at 20Amps. It is true that with "motors" you can oversize the OCP above the rating of the wire if the motor trips the breaker at start up BUT the FLA of the motor is within the wire size ampacity. THHN wire though #12 has a higher rating than Romex. However, it seems from the calculations that they want you to add 25% more ampacity than the FLA rating or nameplate. I think this is because as motors age, they tend to draw a bit more current than when they were new. I have seen this happen where an older motor will draw a bit more current than it did when it was new, adding 25% to the calculations in the beginning perhaps allows for this fact, not to mention a "built-ln" safety margin. Ciao
 
Re: HELP!! Pool pump & booster pump wiring sizing

#12 Romex which is only rated at 20Amps
Click to expand...
read the thread "wire size" ..some interesting notes on 240.4 which i beleive would apply here too
 
Re: HELP!! Pool pump & booster pump wiring sizing

Originally posted by gudguyham:
QRZ KC5SWI, nice of you to be concerned. Using THHN wire #12 is fine for this job. Using Romex it would be over the rating of #12. The next factor in wire size would be distance to the load. I'll be QRX for ya. Hi Hi I wonder if the electrician's exam is as hard as getting an Extra? QTH here is CT. 73 Lou W1QJ
Click to expand...
would you be allowed to wire a pool pump with romex in the first place?
 
Re: HELP!! Pool pump & booster pump wiring sizing

Take a look at table 310.16 and you will see that #12 copper is rated at 25A @ 60C, 25A @ 75C, and 30A @ 90C. In this wire size, there isn't much of a difference between THHN and NM-B. Both can use the 90C value for thermal derating, but you have to use the 60C ampacity for NM cable and the 75C ampacity could only be used with THHN if the lugs are rated at 75C. But since the 75C and 60C ratings are the same, it makes no difference.

The general rule limiting #12 wire to 20A OCP applies whether you use NM or THHN.
 
Re: HELP!! Pool pump & booster pump wiring sizing

Originally posted by suemarkp:
The general rule limiting #12 wire to 20A OCP applies whether you use NM or THHN.
Click to expand...
Yes on many branch circuits that is correct, but we are talking about motor loads and you can forget about the general rule, 240.4(D).

You are free to use a 50 amp breaker with 14 AWG under the right circumstances. :cool:
 
Re: HELP!! Pool pump & booster pump wiring sizing

bob, you have more patience than I.... I tried :)
 
Re: HELP!! Pool pump & booster pump wiring sizing

I'm bringing this post over here from the "Wire Size" thread.



A Home Inspector inspects a home and cites a violation of #12 THHN conductors connected to a 50 amp breaker in the load center. This branch circuit is feeding a 3 HP 230 V single phase motor; all parts are listed for 75 deg C.

Is the Home Inspector correct in citing this as a violation?

(Hint; articles 240.6, 310.16, 430.22(A), tables 430.52, and 430.148)


Answer: Yes, he is right.

? Table 430.148 gives a 3HP motor an full load current of 17 amps
? 430.22(A) requires conductors be sized at 125% of full load current
? 17 x 125% = 21.25 amps
? Table 310.16, #12 THHN 75 deg C column = 25 amps
? Table 430.52 allows up to 250% for the inverse time breaker
? 17 x 250% = 42.5 amps
? the exception to 430.52(C)(1) allows the next STANDARD size breaker
? Use 240.6
? Answer 45 amp breaker.

Click to expand...
Roger

[ August 23, 2005, 05:52 PM: Message edited by: roger ]
 
Re: HELP!! Pool pump & booster pump wiring sizing

Hi Sue, I see the table you speak of, BUT, isn't that table for a single wire conductor in a raceway? (with less than 3 current carrying conductors) Some will argue that NM cable sheath is a raceway and therefore complies with this table, so then why is it that we only breaker branch circuits using #14 at a max of 15 amps? I agree with you about "copper wire" and is current carrying ability, but this changes with the type of insulation that is on the wire! The insulation that is on Romex cable is not the same as THHN so they carry different current ampacity ratings.
 
Re: HELP!! Pool pump & booster pump wiring sizing

Hi Peter, you ask if it is permissable to run a pool pump motor on Romex? Take the case where a pool pump might be located within 3 feet of a house. You should be able to run #12 Romex to an outlet on the exterior of the house that is GFI protected to a single receptacle that is a twist lock design. Also would be wise to install a "Tay-Mac" type cover. I think this is one condition where you can do that. Normally pool pumps are further than 3 feet and have to go underground to the pool pump in which case the conductors would be in a raceway.
 
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