Purchased a 3ph 15 hp frankenstein compressor yesterday need some help

[Kaddo]

Been a while since I was on here last. And as it is I need some information. Yesterday I purchased a huge 3ph air compressor for the right price but there were no general specs on it anywhere so I started researching and it looks as though it was pieced together allbeit with expensive parts. It has a 15 hp reliance 254t electric 3ph motor a 200 psi manchester 120 gallon tank and a laplante 2 stage lp452 compressor. My question stems from the motor andcompressor compatability compressor shows 5 to 10 hp and 590 to 850 rpm motor shows 15 hp and 1760 rpm. It has pulleys on it now and the company I bought it from says it has a problem but noone was there to let me know exactly what the problem was. They gave me a 30 day warranty and said they would have someone call me. So any ideas lol

 

[b-body-bob]

On the RPMs just do the math based on the pulley sizes and figure out how fast the pump will actually turn.

I don't think there would be a problem having too much motor HP for the pump, only if you had too little.

 

[larry_g]

As long as you don't over speed the compressor you will be fine. The HP of the motor spec is the minimum required to spin the pump at the given RPM, anything HP over that and you'll be ok. To drive at the 850rpm your motor pulley should be 1/2 the diameter of the pump pulley.

lg
no neat sig line.

 

[Packard V8]

1. Are you going to be using single or three phase power?

2. Use the largest horsepower motor you can find. It will run cooler, last longer and make more air more quickly.

Back in the bad old days, when I was a Goodyear Service Manager, we were always burning out compressor motors. Without changing the pulleys, I upped the HP from 10hp to 15hp and never had any more trouble. The 10hp were running at their upper limit and the 15hp were loafing.

jack vines

 

[alwaysFlOoReD]

To drive at the 850rpm your motor pulley should be 1/2 the diameter of the pump pulley.

lg
no neat sig line.

I think it would be half the radius edit; radius should read circumference.

Richard

 

[b-body-bob]

The ratio of radius to radius would be the same as the ratio of diameter to diameter.

 

[alwaysFlOoReD]

Sorry, I should have said circumference.

Richard

 

[930dreamer]

Post some pics please.

 

[b-body-bob]

Richard it's the same for circumference (radius * 2 * pi), doing it by diameter makes it easier because it's the simplest way to measure a pulley (IMO).

FWIW I labored over this same question a week or so ago when asked what the pump speed is on my compressor.

For example, assume a 7" pulley and a 14" pulley. both diameter. Circumference for the 7" pulley is 3.5*(2*Pi) ~ 22", for the 14" pulley it's 7*(2*Pi) ~ 44". The ratio is 2:1 anyway you slice it or dice it.

 

[Kaddo]

Here are some pictures

 

[theoldwizard1]

Any place you can test this thing and see if actually works ? The motor could be worth a lot, probably more than the cost of a 7.5hp single phase motor.

The specs I looked at said minimum recommend RPM is 500. Size your motor pulley accordingly.

 

[alwaysFlOoReD]

Richard it's the same for circumference (radius * 2 * pi), doing it by diameter makes it easier because it's the simplest way to measure a pulley (IMO).

FWIW I labored over this same question a week or so ago when asked what the pump speed is on my compressor.

For example, assume a 7" pulley and a 14" pulley. both diameter. Circumference for the 7" pulley is 3.5*(2*Pi) ~ 22", for the 14" pulley it's 7*(2*Pi) ~ 44". The ratio is 2:1 anyway you slice it or dice it.

Thanks for taking the time to spell that out. Now that I've played with the math a bit, it's making sense.
It does make it much simpler to figure out,

Richard

 

[b-body-bob]

A math person would probably lay it out as an equation and say this cancels that, but the older I get the less I remember of my math education

 

[gtermini]

Ratios are the easiest way to figure RPM.

(diameter of drive sheave)
------------------------- X (drive sheave RPM) = driven RPM
(diameter of driven sheave)


Greyson

 

[C96]

As long as your shop is equipped with 3ph power, and the previous owner upgraded the motor starter, the load side wiring to the motor along with setting the overload protection correctly you should be good to go. My guess is they didn’t, and that’s the “problem” with it.

By the way, that thing looks awesome.

Good Luck

 

[Ironhorse]

is it 3 phase 208 or 480? That will make a difference and then yes matching up the proper RPM to your compressor pump. Most of mine are 1700rpm or more at the shop...

 

[larry_g]

is it 3 phase 208 or 480? That will make a difference ....snip.

I'm curious why the voltage has a bearing on the question of HP compatibility?

lg
no neat sig line

 

[Ironhorse]

I'm curious why the voltage has a bearing on the question of HP compatibility?

lg
no neat sig line

If not run with proper voltage it will be less HP it will run, might run for a few years...but it will not run correct...pretty basic...plus I just wanted to ask due to the fact most guys go not have 480v in there garages which would bring a motor swap into play

 

[larry_g]

If not run with proper voltage it will be less HP it will run, might run for a few years...but it will not run correct...pretty basic...plus I just wanted to ask due to the fact most guys go not have 480v in there garages which would bring a motor swap into play

Fair enough.. I just assumed that the OP didn't have a problem with the 3 phase and understood that end of the deal. I should know better than to assume with some of the questions asked and the answers given here over the last few years.

lg
no neat sig line

 

[Fixnair]

Multiply Compressor RPM times flywheel diameter and divide that result by the motor RPM will give you motor pulley diameter.
That looks like a rebranded Kellogg American compressor. Good low speed compressor.

 

[Kaddo]

Hooked it up and it is working well pumps up holds pressure kicks on and off so far so good. I do have 3ph not sure 208 or 480 though. Has 120 on a and c and 239 on b leg. So it is a manchester 120 gallon tank and reliance 3ph 15hp motor and a laplante 2 stage compressor