1750 RPM Compressor?

[zeug]

Hi guys,

I am in the market for a new compressor- 5hp, 220 VAC, 60-80 gallon tank, and twin stage. I was looking at some of the Qunicy's as I have only heard good things.

However, I noticed most of the 5HP models have a faster spinning motor and my experence from observing other compressors is that the 1750 RPM motors are quite a bit quieter. Do I not have a large enough sample base or can anyone confirm my therory?

That being said, the 1750 RPM Quincy's start at about $2700. Does anyone know if IR or anyone else make a less expensive version? My budget is $1000-1500.

Thanks,

Kent

 

[mayday0017]

From what I researched when shopping for mine is lower RPM motor cost more so most manufactures don't use them. However since they are belt driven they use the pullys to change the speed. So with that said the compressor is not turning at X rpm it is turning at a much lower speed and the noise levels should be the same. And I have heard people say different but this is just what I found while I was reading. Lets see what others have to say....

On side note check out searsoutlet.com and see if there is a compressor there in an area close enough yo are willing to drive. I go to pick mine up tomorrow, only 25 miles away from the house worth paying $770 for a $1300 compressor and driving 25 miles to me!

 

[PT Doc]

Pass on 3450 rpm motor. All the higher end compressors will use low rpm motors and lower rpm pumps as a result. Listen to both if you can but there is a reason that better compressors are quiet.

 

[bsaint]

Yea low speed is better.

 

[BMB]

You might look into:
Bel Aire
Schultz
North Star (Northern Tool)

This site will let you look at a lot of different compressor and compare

http://www.aircompressorsdirect.com/

 

[fordper4mance]

I just ordered an 80 gallon, 5hp Eaton compressor. It runs at 1750 RPM and should fit in at the top end of your budget.

 

[littletoes]

Think about duty-cycle. All compressors (except scroll's), are about 50% duty cycle.
How much cfm do you need?

 

[Jim Johnstone]

Think about duty-cycle. All compressors (except scroll's), are about 50% duty cycle.
How much cfm do you need?

ALL compressors are 50%? I'd like to know what Devilbiss/Quincy/Champion think of that statement.

 

[mayday0017]

hm.... I need to do more research I don't think I agree with people in this thread (I very well can be wrong on this I don't claim to be an expert but I have read a lot on this recently), Is a 1700ish rpm motor hooked to nothing that much quieter then a 3500ish rpm motor hooked to nothing? The pump on both motors are turning at the same speed by using gearing from the pulley's and most all compressors are made by the same hand full of company's and use the same hand full of pumps.... So while there are some out there that break this trend they are really almost all the same with a different label and configuration...

 

[pipsters]

Think about duty-cycle. All compressors (except scroll's), are about 50% duty cycle.
How much cfm do you need?

Typical duty cycles
Oil lubed splash lubricated - 50%
Oil lubed pressure lubricated - 100%
Screw - 100%

One guy in another thread had a great suggestion. He runs two 10 CFM @ 90 psi Kobalt 60 gallon compressors (over 20 CFM). When one isn't keeping up the other run kicks on. Bought both for $800 new.

Best of both worlds as you don't have to fire up a huge 5 or 7.5 hp compressor to do small things but when you need the reserve, it's there. Pretty cost effective.

 

[PT Doc]

Typical duty cycles
Oil lubed splash lubricated - 50%
Oil lubed pressure lubricated - 100%
Screw - 100%

One guy in another thread had a great suggestion. He runs two 10 CFM @ 90 psi Kobalt 60 gallon compressors (over 20 CFM). When one isn't keeping up the other run kicks on. Bought both for $800 new.

Best of both worlds as you don't have to fire up a huge 5 or 7.5 hp compressor to do small things but when you need the reserve, it's there. Pretty cost effective.

Do they come on in some alternating fashion. How would that be done out of curiosty?

 

[Yojinbo]

I looked at the Quincys some time ago but I thought they were less expansive then you describe.
http://www.northerntool.com/shop/tools/product_200350475_200350475

Isn't this 5hp 220v running at 1310 RPM on sale for $1200? Is the above machine a different class then you were looking for?

 

[DekeT]

Typical duty cycles
Oil lubed splash lubricated - 50%
Oil lubed pressure lubricated - 100%
Screw - 100%

One guy in another thread had a great suggestion. He runs two 10 CFM @ 90 psi Kobalt 60 gallon compressors (over 20 CFM). When one isn't keeping up the other run kicks on. Bought both for $800 new.

Best of both worlds as you don't have to fire up a huge 5 or 7.5 hp compressor to do small things but when you need the reserve, it's there. Pretty cost effective.

I really like this idea. More details on the setup please.

 

[larry_g]

I really like this idea. More details on the setup please.

There are a couple of ways to have two small compressors online at once. You have to basically have to run both outlets into a manifold that you tap off of with your load. You need to have a shutoff or two in the system to allow both or either to be connected to the manifold. The manifold can be as simple as a Tee or you can have a piping system that allows you to connect into the system anywhere that you can. I used to have a ball valve with two quick connect plugs on it. With the ball valve off plug in a wip hose from the compressor to one end and the other end into a QD on the manifold. Open the ball valve and you now have a second compressor online.
You do not need to have the compressors start at the same time. If they are set close to the same cutin and cutout pressures you are good. You could use both a single stage and a two stage though the different operating pressures MAY cause an issue in some cases.

I also apologize to the moderator who had to clean up the pissin contest here.

lg
no neat sig line

 

[pipsters]

Do they come on in some alternating fashion. How would that be done out of curiosty?

I'm not sure and now I can't find the post...but just thinking about it I would probably run one at a lower cut in pressure. Both are 155 psi...run one at 120 psi cut in and one at say 105 psi cut in. That way when you need it, it will kick on.

Also if I were going to do this long term I would probably take the pump and motor off the tank and mount them separately, and sell the tank, no need for 120 gallons of air, 60 would be plenty for a setup putting out 20 CFM I would think.

 

[DekeT]

I'm not sure and now I can't find the post...but just thinking about it I would probably run one at a lower cut in pressure. Both are 155 psi...run one at 120 psi cut in and one at say 105 psi cut in. That way when you need it, it will kick on.

Also if I were going to do this long term I would probably take the pump and motor off the tank and mount them separately, and sell the tank, no need for 120 gallons of air, 60 would be plenty for a setup putting out 20 CFM I would think.

thanks, i see how this could work for me.

 

[BMB]

Isn't this 5hp 220v running at 1310 RPM on sale for $1200? Is the above machine a different class then you were looking for?

FYI
Pretty sure the motor is 3450rpm on that one.
The 1310 is the pump rpm.
That one is rated for 30k pump life according to Quincy not 50k as in the Northern specs.

 

[pipsters]

30,000 hours, run 2 hours a day on average (probably pretty high average for most DIY'ers on this web site) is 41 years....

 

[Yojinbo]

FYI
Pretty sure the motor is 3450rpm on that one.
The 1310 is the pump rpm.
That one is rated for 30k pump life according to Quincy not 50k as in the Northern specs.

OK. Maybe this is the slower one:
http://www.northerntool.com/shop/tools/product_200350476_200350476

It says "Pump RPM: 942". Thanks for the clarification

 

[buening]

FWIW the Belaire 318 compressors have a pump speed of 1250rpm. Motors are likely 3450ish thogh. They aren't the cheapest option but are well made from my experience

 

[Steve_P]

I have a QT 7.5 quincy with a 3450 RPM motor. The Quincy 1725 RPM motor compressor that is also rated at ~7.5 HP is MUCH quieter- i've heard one. The 1725 motor compressor also starts smooth. The 3450 RPM model I have most often starts like you hit it with a 10 lb hammer.

On the positive side the 3450 RPM model I have makes more than enough air for my needs. But if I could do it over, I would spend more $ for a 1725 RPM motor. But, as said, a 1725 RPM motor is significantly more expensive so it will have to depend on your budget.

 

[hicketts]

The Quincy I put together at work use to be a climant control unit with a lead lag controller. It worked great that the second pump would come on when demand was high and then on the next cycle the lead motor and lag motor would switch. As far as rpm goes I would be more concerned about the pump speed not the motor, my are spinning at about 540rpms.

 

[mayday0017]

Good point Hicketts, it is interesting to hear the motor speed battle around this forum. Motor speed has nothing to do with how loud the compressor is but pump speed does. I think the reason this "theory" works is because lower speed motors cost more to make and so they are used on higher end units. Higher end units are also more quiet then cheap ones... Although I will say most 3k rpm motors turn pumps at around 1200ish where 1.7k turn pump close to 1k (9xx) which would make the 3k slightly louder. As for how hard it starts that depends on several other factors.... While a lower RPM motor will have more torque I once again believe it has more to do with they are typically installed on quality compressors and come with hard start setup....

Anyways back to the normal discussion about how 1725rpm compressors are so superior to 3450's