Electric motor wire size

[acseatsri]

What gauge wire do I need to run a 5HP 230 volt single phase hydraulic pump motor? Motor nameplate says 23 amps and the run is approximately 50 feet. Would 10 gauge wire be sufficient, or do I need to go to 8 gauge? And until I'm able to get a magnetic starter, would plugging it directly into a 50 amp outlet do any harm? This gets very intermittent use on an anchor hauler.

TIA, Acseatsri

 

[ady9250]

Well my friend cable size is simple, just choose one that is able to carry the current of your safety disconnection device (fuse or breaker). So if the fuse is 30amp then cable must take at least that (volt drop calcs are for sparkies, but you will lose a little). The motor nameplate tells only the full load current and if your motor was overloaded you would see the rise in temperature of both motor and cable. I would say that size 10 would be OK for a decent fuse or motor starter breaker. I have probably confused you by now so the next item is much simpler. Please note the recommendation is any motor over 1/2 HP requires a starter (contactor)!

If you plug a motor into the socket without any protection such as fuses, motor overload contactor etc then you may find a flash as you insert it. If the motor turns (it probably would) you run it at a risk of that taken by people from 3rd world countries. That however is a safety issue and possibly a fire hazzard.

Conclusion - Respect electricity, buy the right parts and save yourself the cost of a rewind or health care (yours or others). Good job you asked before acting out your impulses at least.

 

[acseatsri]

Thank you for the thoughtful response. The problem is that we haven't been able to get a marine electrician to come out and wire it before Saturday. We can plug it in and use the circuit breaker (50 amp) to turn it on and off to avoid the flash. Other plus is there are no flammable materials on the boat.
This would just be a temporary setup, maybe for a one-time 15-30 minutes of use or so- definitely not a permanent set-up. The motor is sized correctly for the pump it's driving, so there should be no overload.

I'm just a go-between here. I know just enough about electrical wiring to get myself in trouble, short of electrocution!

 

[advidana]

What do you have a sail boat? The engine fuel is flammable materials on the boat. Temporary setup usually be become permanent ones.

A lot of people take chances but it does not make it safe. There is a lot of thing worst than electrocution such as bad Electrical burns can causing slow death from gangrene. I know of electricians that have died this way. It's not pretty.

Motors can fault at any time. Spend the money and get the right setup. Electrical wiring is something you should leave to the electricians.

 

[acseatsri]

No, it's a 90' aluminum catamaran, and the set-up really will be temporary- probably used once unless we find a marine electrician before Saturday. There are nearly no flammable materials on the boat and is fueled by diesel below decks, the electrical panel is above deck. If you know any marine electricians in the New Jersey area, contact me. Have called several but no one available yet.

 

[rbulsara]

I will advise you the wire size, but more important than that is your safety.

Unless loosing (yours or others) a limb, eye or life or getting a severe burn is not worth waiting (whatever use you may have) or the money you need to spend for the little starter, do not try plugging a 5HP motor with a cord.

Motor branch circuit condutor is sized to 1.25% of its FLA in this case it will be 29A. So a #10, copper is sufficent.

Buy a manual starter (they are HP rated) with a 60A fused disonnect and use 50A fuses (or 35A dual element fuses).

Be safe!

 

[acseatsri]

Marine electrician will be there tonight! Thanks all for the help. If need be, we were going to use the circuit breaker itself as an on-off switch AFTER it was plugged in. As of right now, properly sized magnetic starter being used with remote low-voltage actuation. 100% safe and legal.

 

[jbartos]

Suggestion to the original posting:
acseatsri (Mechanical) Aug 18, 2003
What gauge wire do I need to run a 5HP 230 volt single phase hydraulic pump motor? Motor nameplate says 23 amps and the run is approximately 50 feet.
///If the motor does not have very high inrush current, e.g. the motor is standard or ordinary, the suggested #10AWG copper conductor will suffice. If the motor has some high Locked Rotor Amps (LRA) or inrush current, the conductor may be #8AWG.\\ Would 10 gauge wire be sufficient, or do I need to go to 8 gauge?
///See my comment above.\\ And until I'm able to get a magnetic starter, would plugging it directly into a 50 amp outlet do any harm?
///Assuming, that you pump iron occassionally, there will be no problem. The outlet better be dry and some isolating mat and gloves would improve the safety.\\ This gets very intermittent use on an anchor hauler.

 

[advidana]

Glad you got the electrician. I will give you a tip don't use the circuit breaker as a switch because if you have a short some times the circuit breaker can explode. I know people do it all the time but it better to be safe than sorry. The new electrical installation code is addressing this problem and is starting to have electricians use some protective gear went operating/servicing breakers and other electrical equipment.