I just acquired an old 1 1/2 hp single phase motor. It is set at 220VAC
and I need to run it at 110. The plate with the wiring instructions is
unreadable. The wires are marked "451 through 458". The motor model
number is 5KC184BG205. I can't seem to find much about it on the web.
Can anyone tell me how to connect it to 110 VAC.
Hmm ... *if* it is capable of being run at 110, you should have
three pairs of wires. Two of them are run windings, and they are
connected in parallel for 110 VAC, or in series for 220 VAC. The third
pair are the start winding, and that is only 110 VAC. When the motor is
wired for 220 VAC, one end of the start winding is connected to the
common point where the two run windings are connected together to make
the series connection.
The trick is finding which end of which wires are what. The
start winding will have a capacitor in series with it, so an ohmmeter
will kick up and then drift down. Since it is currently wired for 220,
you will have three wires connected together -- the high end of one run
winding, the low end of the other, and one end of the start winding. So
-- identify which is the start winding, and which are the ends of the
run windings. Disconnect the junction point of the three wires, and
move the end you just disconnected of one run winding to the other
(free) end of the the other run winding. Then join the remaining ends
of the run windings, and finally connect the start windings to the two
ends of the run windings -- and connect the switched power line to
those. If the motor runs backwards, exchange the two ends of the start
winding and it will now run forwards.
You don't say that you need to be able to reverse the motor. If
you do, the wiring of the switch gets a bit more complex, and it is a
bit late to write that up tonight.
But -- beware -- a 1-1/2 HP motor wired for 110 VAC and
connected to a standard power outlet will be more likely to trip the
circuit breaker -- especially when trying to start a lathe with a heavy
chuck and with the belting set for a higher speed. Better to get 220 to
the motor than to rewire the motor for 110. My 12x24 Clausing came
wired for 110, and popped breakers too often, so I rewired it for 220.
The necessary information on that motor was on a sticker on the inside
of the cover over the wiring box on the motor.
To get 220, look at your
circuit breaker box and look for two empty slots side by side. If you
find that, you have enough to get 220 VAC. If you don't know house
wiring, get someone who does to do it for you -- install the 220 circuit
breaker the wire and the 220 VAC outlet -- and if necessary, a matching
plug on the machine's power cord.
As I started looking at the wiring, the previous owner was wrong. The
motor IS wired for 110V. So I don't have to change anything. When I
noticed that the switch only opened and closed one wire, it made sense
that it was 110.
I am going to save your explanation. It will probably come in handy at a
Being wired to a single-pole switch is NOT a reliable test for
whether a single-phase motor is wired for 120V or 240V service. You
have to get the schematic and/or ring out all the windings to see if
they are in series (240V) or parallel (120V).
You are supposed to always switch both energized legs (not at ground
potential) with a double pole switch so the motor windings aren't
energized with the switch off, but people who don't know any better
still do it all the time.
Pool men are the biggest culprits at miswiring a 240V motor like
this, and they're also the ones most likely to knock themselves on
their ass by trying to change out a bad motor with that SP "service
switch" opened and the power still on to the motor.
But older industrial gear by foreign equipment makers meant for
"home market use only" are just as likely - to them, a 240V motor has
one hot that is 240V to ground, and one neutral at ground potential -
to them, if they see any higher voltages it's 240/416V 3-phase.
The 120/240V 1-Ph center-tapped neutral US system didn't even enter
their mind, unless they were deliberately designing for export and
trying to get their designs UL or CSA approvals.
Now I am back to Square One. I can't find the schematic. Any suggestions
on where I would find one? Can you define ring out the windings?
I did plug it into 110v and it seemed to run fine. It didn't seem to
pull a lot of current or make any unusual noises. Of course there was no
Bruce L. Bergman wrote:
Well, you gone and done it anyway, which is sorta okay since it
worked - you applied lower voltage and it started and ran. ;-)
If it had been wired for 240V and you applied 120V it most likely
would have only sat there and hummed, and if you gave it a spin with a
rope it might have gotten moving. No biggie unless you left it
sitting with the power on like that.
On the other hand, if it was wired for 120V and you applied 240V "as
an experiment" you could have had a "Magic Smoke" Release session.
Somewhere further up in the thread you mentioned a model number, and
it sure sounded like a General Electric motor model number. (And they
like stamping the model number in a hidden area of the motor frame in
case the exposed ratings plate gets damaged or removed.) Did you try
Googling the first 5 or 6 characters and see if you get a hit?
Otherwise the "GE Answer Center" is pretty good at stumpers like
that - the company is so old, so big, and has done so many different
things from light bulbs to locomotives, kitchen appliances to the
turbines for Hoover Dam, and motors rated from 2 watts to megawatts -
they need people dedicated to scraping up arcane facts like old
electric motor data sheets with schematics...
They not only found all the information for a 100-year old G.E.
rotary converter (AC-DC rectifier) for a trolley power station, they
still had a division that gave it a full rebuild. Got it back ready
to run, and the whole system is up and running as am operating display
and good for another 50 years of service.
I did Google the motor number and tried the Answer Center. The Answer
Center had nothing. Google lead me back to this thread. 8^(
The kicker now is that the previous owner said that he checked it out at
220 volts. So it seems to run at both 220 and 110 in the current
configuration. Of course this is at no load. I guess I will have to set
it up with a load and then experiment until it runs and doesn't smoke or
buzz. Kinda scary to the electrically challenged.
Bruce L. Bergman wrote:
Can you measure how much current it is drawing? Clip-on amp
meters aren't all that expensive anymore. If it is wired
correctly for 110 the amp reading will be about right. If it
is indeed wired for 220 then it will be low by around half
what it should be for the size motor that it is.