Compressor & breaker required?

Page 2 of 2  
and... electric clocks aside, for larger items, like your central air, the circuit and the load are usually matched closely enough to keep the load itself from burning up if there should be a problem.
rhg
CW wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Unfortunately, it's you with the reading comprehension problem. If you didn't suffer this you would have noted my original point. I'm done with this now - you're a waste of time and not at all entertaining.
--

-Mike-
snipped-for-privacy@sprintmail.com
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Maybe what the electrician meant was that a 40 amp breaker wouldn't offer much protection. It would happily deliver enough amps for the motor to fry without tripping.
rhg
CW wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
It's not intended to protect the motor.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I got a new shotgun. I'm only going to shoot at targets that are close until it's broken in so I won't strain it.
DonkeyHody "We should be careful to get out of an experience only the wisdom that is in it - and stop there; lest we be like the cat that sits down on a hot stove-lid. She will never sit down on a hot stove-lid again---and that is well; but also she will never sit down on a cold one anymore." - Mark Twain
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Just got back from sears and HD. Sears had a 5hp which the motor was rated at 22.5FLA. What does FLA mean. HD had a advertised 7hp rated at 17.3amps. When I looked at the HD 2 weeks ago it was $100 less than tonight? So Saturday I'm going to Lowes an see what they have, but online I'm leaning to this one.#20849 for $637 in my area and if I open a new charge I think I can get 10%. Will check the specs and get back to you all.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
FLA=Full Load Amps
17FLA is nominally 3hp motor at 230v 28FLA is 5 HP
per 430.148 in the NEC
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Looks like some _dreadful_ efficiency numbers, or a humongous phase-angle.
3hp == 2237 watts.
17A @ 230v is 3910 VA (or watts at 0 phase-angle.) 17A @ 240V is 4080 VA (or watts at 0 phase-angle.)
2237::3910 equates to a 57.212% efficiency 2237::4080 equates to a 54.828% efficiency.
Postulating 85% mechanical efficiency for the motor, that gets an input power of 2632 watts.
Takes a _substantial_ phase-angle to make 2600 watts equivalent to 3900 VA.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Robert Bonomi wrote:

You're missing a point. He said that that as "per 430.148 in the NEC". That is an electrical code table used for sizing circuits, not the actual rating or current draw of any particular installed motor.
--
--John
Reply to jclarke at ae tee tee global dot net
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Isn't the phase angle supposed to change with load? Near 90 degrees at no load (real power minimum) Near 0 degrees at full load Real power close to apparent power?
rhg
Robert Bonomi wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Well, if you're going to be doing some shopping around then take the time to go out to Campbell Hausfeld's site and look under Hot Buys. They have some great deals on reconditioned compressors. Much less than retail and fully warranted. I don't know who builds Sear's compressors for them, but both Home Depot and Lowes use CH compressors. CH does not build a spec compressor, so what you get from HD is the same compressor that you would get from Lowes, or directly from CH with the possible exception that the private label stuff might have some extras thrown in.
--

-Mike-
snipped-for-privacy@sprintmail.com
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I got 10% off the same model from CH's hot buy($580) for opening up a new account at lowes so the price was 570. It's rated at 4hp and 17.3 amps and so far runs great on a 15amp breaker, but I will upgrade to a 20amp later this weekend. See new post for air line setup.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

least 12 ga. or larger for a long run. If it is on a 15 amp breaker now, I would suspect 14 ga. wire, much too light for a twenty amp breaker. Greg
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I used 8gauge w/g to feed my shop which has a 60 foot run and it's protected by a 40amp breaker.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
FLA = Full Load Amps LRA = Locked Rotor Amps
1 HP = 746 watts so FLA x running voltage / 746 gives a pretty good idea of the real HP. Take advertised HP with a grain of salt. Especially from Sears.
Woodchuck wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

My 5HP motor is 21 amps at 240 volts. That said, the motor is a replacement for a three phase unit and I didn't know about "compressor horsepower". My motor is 5HP continuous duty, not intermittent. It's on a 30 amp breaker.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.