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Compressor electrical info at motor and at manual are different

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Forum topic by kyngfish posted 03-17-2020 09:17 PM 801 views 0 times favorited 45 replies Add to Favorites Watch
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kyngfish

115 posts in 898 days


03-17-2020 09:17 PM

Hi all. Just took delivery on a 2 stage 5 hp compressor from puma. the 5040 model. The motor label says voltage is 208-230V and 22-25 amps. I currently have a wire set aside for it that goes to a breaker that is 2 20 amp breakers delivering 115 V each.

The wiring diagram in the manual that came with the compressor (not the motor) is asking for a 40-60 amp breaker. My understanding of those ratings is that they are for EACH breaker, so basically what that says to me is they are asking for 80-120 amps across two breakers, which seems like a lot. I don’t know if this is a generic wiring diagram for multiple versions of the same compressor, which can come with much higher HP, but it feels like a ton.

Just hoping to see if someone can help me clarify….


45 replies so far

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MrUnix

8163 posts in 3007 days


#1 posted 03-17-2020 09:24 PM

Motor data plate wins over manual every time. Manuals are more or less generic, while the motors used can be sourced from many different places and can/do change over the life of the product.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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kyngfish

115 posts in 898 days


#2 posted 03-17-2020 09:26 PM

so does that mean 20 amps on each pole is OK ? or do i need 30 amps on each pole to accomodate that 20 – 25 amp rating?

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tvrgeek

1008 posts in 2458 days


#3 posted 03-17-2020 09:37 PM

5 horse motor: 30A 220. 10 gauge wire.

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kyngfish

115 posts in 898 days


#4 posted 03-17-2020 09:39 PM


5 horse motor: 30A 220. 10 gauge wire.

- tvrgeek

lol – again – 30 A at each pole? Meaning – a total of 60 amps on my board? Sorry for being dense, but just looking for some clarity.

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CaptainKlutz

3374 posts in 2303 days


#5 posted 03-17-2020 09:44 PM

1) A 5HP needs a 30A circuit minimum.
The FLA on 5Hp motor typically runs from 31A at 208v to 28A at 230v. They can draw even more during start up, which is reason the manual suggests a 40A breaker when considering 208v systems. If you attempt to use 20A circuit, the motor will never run, and trip the breaker with every start up.

2) 208-240v circuits use 2 pole breakers. You need a 30A 2 pole breaker for the new compressor on standard 240v household system. You can use (2) 1 pole 30A breakers, but must use proper tie bar to ensure when one phase trips, the other phase is disconnected as well.

3) Your description is scary. It shows you do not really understand electrical power wiring. When discussing 208v-240v 2 pole wiring, the phases are not separated. IE, it is not the sum of current, they both have same current capacity.

Please seek the help of a professional.

Be safe, not sorry!

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

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kyngfish

115 posts in 898 days


#6 posted 03-17-2020 09:49 PM



3) Your description is scary. It shows you do not really understand electrical power wiring. When discussing 208v-240v 2 pole wiring, the phases are not separated. IE, it is not the sum of current, they both have same current capacity.
Please seek the help of a professional.

- CaptainKlutz

“My understanding of those ratings is that they are for EACH breaker,”

Confirming my understanding is not the same as not understanding. This is me trying to be safe. Appreciate the clarity.

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tvrgeek

1008 posts in 2458 days


#7 posted 03-17-2020 10:23 PM

Support your local fire department. Wire it yourself.

Seriously, it should be permitted and inspected. You can actually be liable for a failure in the future from a later owner if it causes a fire. If you don’t understand it well enough to do so, hire an electrician and if he says you don’t need a permit, find another one.

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kyngfish

115 posts in 898 days


#8 posted 03-17-2020 10:27 PM

I had a professional do all of the wiring – the only thing that needs to happen is that breaker needs to change. For which I’m having that same professional come back to fix it. What I was looking for here is to understand what I need because I like to understand the things that I’m asking for.

I really do appreciate all the concern for my safety, but you all are inferring a lot of things that I never stated.

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WhyMe

1300 posts in 2369 days


#9 posted 03-17-2020 10:39 PM

If motor data plate list HP as 5, to be hardwired complaint with the NEC the supply wire needs to be either #8 NM-b or #10 THHN. Breaker should be 40A, but can be higher to handled start up current. This is provided the motor has internal overload protection, which it should. The amperage of a 2 pole breaker is not double. So a 20A 2 pole is just 20A at 240V not 40A. Each leg is 20A at 120V, so you can get 40A of capacity at 120V via 2 120V circuits, but not 40A at 240V on a single circuit. Clear as mud?

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tvrgeek

1008 posts in 2458 days


#10 posted 03-17-2020 11:13 PM

Why,
Are you saying if it is hard wired, the breaker can be larger for the inductive startup load than a traditional load wire size? i.e. [email protected] on 10 ga wire? I only read the paragraphs related to my situation so am not aware of some special cases. Why would Romex be a different size than if in conduit?

Usually 8 gauge/40A would be stranded aluminum and so doubly important for a qualified electrician.

Kyngfish, Sorry, but we are so used to so many folks who do not understand it at all but are trying to do it themselves anyway. Both my current house and my last house were full of extremely dangerous DIY work. Stopped a fire in progress on the last one.

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tvrgeek

1008 posts in 2458 days


#11 posted 03-17-2020 11:23 PM

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tvrgeek

1008 posts in 2458 days


#12 posted 03-17-2020 11:31 PM

Maybe easier to understand.
http://www.wwapump.com/files/ElectricalWireFuseBreakerSizes.pdf

It suggests you need both a fast breaker and a slow blow fuse. If I read it, 8 ga wire. So I had incorrect information above. It says I need the dual protection for a 3 HP. I bet 90% of them are plugged into a 20A outlet and breaker.

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WhyMe

1300 posts in 2369 days


#13 posted 03-17-2020 11:48 PM

The reason a 5HP motor should be hardwired and not cord and plug is standard nema plugs are rated at most 3HP. You could use Pin and Sleeve plugs but are $$$. #8 NM-b is rated 40A, #10 THHN in conduit is 35A. 5HP is 28A X 1.25 = 35A. NEC table 430.248. Larger breaker is allowed on hardwired motor circuit. See NEC section 430.
I need to add if the circuit has a receptacle for cord and plug the breaker is not to be oversized. You are restricted to the normal rules for sizing overcurrent protection to the wire size.

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kyngfish

115 posts in 898 days


#14 posted 03-17-2020 11:52 PM

Took a picture of the motor here. Again. It’s showing significantly lower amps here. What gives?

I looked up the motor and the FLA and the SFA seem to be the same. According to the fuse breaker size sheet above this puts me in the 30A range? So 10 gauge wiring?

Already called my electrician. In the end it’s about 5-6 feet from the panel and it’s a short run.

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tvrgeek

1008 posts in 2458 days


#15 posted 03-18-2020 12:30 AM

From the above chart, you are still @ 40A, 8 ga. It limits [email protected]/10 gauge to a 16A motor.

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