ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat Box
Recent Posts
FPE in Germany
by NORCAL - 10/16/19 08:24 AM
Help with aging employee advice.
by Bill Addiss - 10/15/19 10:58 PM
Fuse blower plug?
by gfretwell - 10/13/19 03:23 PM
Power factor and transformer efficiency
by TeslaEdison - 10/13/19 04:05 AM
Permit Snafus...AHJs and Contractors Jump in
by HotLine1 - 10/10/19 07:35 AM
New in the Gallery:
FPE Breaker panel in germany
What is this for?
Who's Online Now
1 registered members (Scott35), 11 guests, and 8 spiders.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Motor start, motor run capacitors #215217 03/24/15 10:09 AM
Joined: Jun 2004
Posts: 1,273
T
Tesla Offline OP
Member
I've picked up a second hand Gast 'ring compressor' - the kind used to blow air for pneumatic systems at banks and the big box stores -- and the occasional pet store with plenty of fish tanks.

It's wired for 240VAC one-phase... it's a nominal 2.5 hp motor... start cap -- run cap -- and thermal protection via solid state inside the pecker-head.

But the capacitors are all mixed up/ missing.

I don't normally work this side of street... and was hoping that the ECN crew would/ could guess a first approxmation for suitable values.

The internal wiring megs out fine.

Near as I can tell, the motor was either wired Monday morning by a hung over trooper or it was pumped at 120 VAC by a prior owner -- or some such.

I don't have a motor test bench -- no decade boxes. I'd rather not throw every capacitor in the world at this little project.



Tesla
Work Gear for Electricians and the Trades
Re: Motor start, motor run capacitors [Re: Tesla] #215218 03/24/15 01:09 PM
Joined: Jul 2004
Posts: 9,408
G
gfretwell Offline
Member
I would start by looking for the motor specifics on the net, maybe poke around in the Grainger catalog.
They may just tell you what you need and source it for you.

This sounds like what you have but Gast does not make the motor so You are going to have to sort that out somewhere else.
http://www.gastmfg.com/product_detail.aspx?ProductID=215&ProductTypeID=25


Greg Fretwell
Re: Motor start, motor run capacitors [Re: gfretwell] #215221 03/25/15 01:07 AM
Joined: Jul 2007
Posts: 1,335
S
sparkyinak Offline
Member
Hmmm. Didn't Tesla invent the induction motor?.... dunno


"Live Awesome!" - Kevin Carosa
Re: Motor start, motor run capacitors [Re: Tesla] #215222 03/25/15 01:15 AM
Joined: Jun 2004
Posts: 1,273
T
Tesla Offline OP
Member
The Gast nameplate reads: R6125-2

It's an R6 series unit, 1-phase, 2.5 hp with a 2 port.

2.5 hp 1.86kW 215cfm 45in/H2O pressure 56in/H2O vacuum

This is not a high torque machine, though the rotor does have a fare amount of heft.



Tesla
Re: Motor start, motor run capacitors [Re: Tesla] #215223 03/25/15 01:52 AM
Joined: Jul 2004
Posts: 9,408
G
gfretwell Offline
Member
I think I would fire off a message to Gast support. I had no joy searching the documentation online.


Greg Fretwell
Re: Motor start, motor run capacitors [Re: Tesla] #215261 03/30/15 06:24 PM
Joined: Jun 2004
Posts: 1,273
T
Tesla Offline OP
Member
And the answer is:

All field windings check out...

All installed capacitors check out... values and condition

Factory error: the connector from the run cap to the centrifugal switch was flopped over the connector from the start cap -- and vice versa.

The actual internal design of the Emerson motor is NOT shown on the Internet nor in the literature.

Pretty amazing, no?

The way this Emerson motor works:

At start the switch is in position one and the 50mFd start cap is in the circuit to the start windings.

Upon reaching the magic speed, the centrifugal switch shifts to position two and the 50mFd cap is cut out entirely.

However, in position two, the run capacitor (10mFd) drops in to the circuit.

The centrifugal switch is obviously in mass production and is to be expected in all recent motors built. (Forty-years +)

None of litureture ever references this dual connection centrfugal switch... a rotary version of "normally closed" "normally open" logic.

BTW, taking the Gast/ Emerson motor apart was quite a challenge. Fortunately I had a hammer and a temper.




Tesla

Featured:

2020 National Electrical Code
2020 National Electrical
Code (NEC)

* * * * * * *

2017 Master Electrician Exam Preparation Combos
2017 NEC Electrician
Exam Prep Combos:
Master / Journeyman

 

Member Spotlight
HCE727
HCE727
Delaware County, PA, USA
Posts: 186
Joined: November 2005
Show All Member Profiles 
Top Posters(30 Days)
sparky 10
Popular Topics(Views)
259,527 Are you busy
194,919 Re: Forum
184,354 Need opinion
Powered by UBB.threads™ PHP Forum Software 7.7.3