Electrical Question

[slash007]

My old pump stand had 3HP 3 Phase motors and used 20 amp breakers.(6bays total) My new pump stand has 5HP 3 Phase motors and recommends 30 amp breakers. Can I get away with using the 20 amp breakers, or do I have to upgrade? my problem is that the main breaker in the box is only 150amp, so I don't know if upgrading will even be possible. I don't know much about how the motors work or what they will draw, so any suggestions/input is appreciated.

Thanks.

 

[Eric H]

You will have to do a load calculation to see how much capacity you have in the panel. You need to add up the amp draw for every electrical device on the property, lighting, air compressor, vacs etc.
The easier way to do it would be to use a clamp on amp meter and measure the amp load with everything on the property running then estimate the load from the new pumps.

I suspect it won't be a problem unless your panel is maxed out. If you see an electrician at the wash ask him if he will do the measurement for $20.

 

[slash007]

I need to decided before installing the new pumps stand. I am more interested in finding out if the 5hp motors will be fine on 20 amp breakers for now. I will be running the pumps at 1200psi with a 2506 tip. I thought I read somewhere that the load is less based on how the pump is run?

 

[Eric H]

I wouldn't recommend running 5 hp motors on 20 amp breakers. I have not tried it but I am willing to bet that they will trip on startup. The F.L.A (full load amps) may be lower than 20 amps, my FLA is less than 13, but the inrush when the motor starts will be in excess of 40 amps and very likely more than 50 amps. An inrush of 50 amps will very likely trip a 20 amp breaker.
Btw: you ARE going to use 10gauge wire from the breaker to the motor starter, aren't you?

 

[slash007]

I do plan on running 10gauge wire for the motor breakers. Just need to decide on the breaker size. Would the motors have the starting amps listed on them?

 

[Eric H]

Yes, should be on the data plate. I will measure the inrush and FLA on my 5 hp pumps tomorrow. That should give you a good idea of what to expect.

 

[slash007]

Thanks! I will look at my date plate as well tomorrow to compare with what you find out.

 

[MEP001]

FLA (Full Load Amperage) of a 5HP 3PH motor is just over 13 amps. There's no problem running them on a 20A breaker.

 

[slash007]

I just read in the manual that the motors are 13.2 amps at full load, but they say to use a 30 amp breaker for them, and a 20 amp breaker for 3HP 3PH motors. Why is that?

 

[pgrzes]

Why not use your 3 hp motors? They should be the same RPM as the 5hp's.

 

[Stuart]

The main panel will be ok if you do not have an auto bay. Go with the 30 amp breakers, they do not really cost that much and for electrical you should go with the recommendations just like using the proper wire size. about the only way that the 150 panel will trip is every motor in the facility will need to start at the same time.

Do you have any other motors running around 2 hp or above? If you have multiple, things may change.

 

[mjwalsh]

My old pump stand had 3HP 3 Phase motors and used 20 amp breakers.(6bays total) My new pump stand has 5HP 3 Phase motors and recommends 30 amp breakers. Can I get away with using the 20 amp breakers, or do I have to upgrade? my problem is that the main breaker in the box is only 150amp, so I don't know if upgrading will even be possible. I don't know much about how the motors work or what they will draw, so any suggestions/input is appreciated.

Thanks.

slash007,

It is not clear if you have already purchased the 5 HP setup yet??? Eric H. knows exactly what he is talking about ... especially when he shares his to be done clamp on ammeter test on the to be expected starting amps.

You would need to see the overall cost ... especially if you were forced to update your electrical coming from the utility grid & to a larger panel. I am not saying it is the best way but checking into inverter duty motors & adding off the shelf small VFDs could solve the increased draw problem ... especially when it comes to total potential start up amps. We saw the significant amp & KW savings first hand with some laundromat equipment that we custom modified about 4 years ago.

mike walsh www.kingkoin.com

 

[sparkey]

Put the 30 amp breaker in and replace the wire with 10 gauge of course. When a motor starts it can pull 2 -3 times the full load amps on the nameplate. It will probably run on a 20 amp breaker most of the time, but you will eventually have intermittent trips. Who wants their pump stand tripping a breaker when you just sit down for dinner at a restaurant 30 miles from the wash. Your main panel has a 150 amp breaker, if you are pulling to much total load your 150 amp breaker will trip which I doubt is going to happen. You never run everything at your wash at the same time anyways.

 

[Eric H]

11.9 FLA.
my new meter could not detect the inrush/startup amps but if the motor plate says 30 amp you need to use 30 amp breakers and #10 wire

 

[MEP001]

The motor may say to use a 30A breaker, but they're considering that some uses of the motor will involve a slow spin-up which can use up to four times the max rated load. High-pressure bay pumps are almost instantly up to speed and there won't be any measurable start-up peak load. You really don't need 30A breakers, even though you can always change them out to 30A if you have problems with them tripping later on. You also don't need to worry about changing the panel if you have to put in 30A breakers because the panel is rated to peak load use, not the total of the breakers' amperage in it.

 

[slash007]

Thanks for all of the input, I really appreciate it even if the suggestions are all over the place lol I already have the pump stand with the 5HP motors. It is a JC super saver and it came with those motors. I could use my current 3HP motors if I had to, but they are old and I would rather not use them. I would also have to do the work of switching them out which is more work than I want to add to my plate right now. If the 20 amp breakers will work for now, I think that keeping them shouldn't be a big deal as I can easily switch them out if I have tripping issues. I don't have any other 2hp motors running. I would be just the 6 bay motors, 3 small motors to run the procon pumps for TC, TF and FB, and then the spot free delivery and production motors, but those I think are 1HP and shouldn't run often. I agree that the motors do start up basically instantly and the peak shouldn't last long. I will run 10Gauge wiring as I have to run new wires anyway for the new stand.

 

[mac]

Same question as pgrez. Order them with 3 hp motors and be done with it.

 

[slash007]

Same question as pgrez. Order them with 3 hp motors and be done with it.

I already have 5HP motors.... On another note, is there a place online that I can get a good deal on 10gauge wire, or should I just get it from Lowe's?

 

[Greg Pack]

what size tip and pressure will you be running? you can find HP requirements in manufacturers catalogs.

 

[slash007]

2506 tip, 1200 psi