AC Motor and Start Capacitor

Korishan

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I have a pump motor that hada 110VAC 124-148MFD start capacitor. The motor was wired for 110 when I got it. The capacitor was dead. So I replaced it with another 110VAC >140MFD and I had changed the motor config over to 220VAC. I assumed the start windings were 110VAC.

The motor kicked in, ran smooth as butter....

for about 30 seconds when the capacitor decided to become a huge puff of white smoke. (and no, I didn't have the camera on it while this unfolded. I wish I did, tho, the smoke cloud was great)


should I have replaced the capacitor with a 220VAC version instead?

If I replace it with a 230VAC version, what size capacitor should I go with? I had tried a 230VAC of about 64MFD and the motor barely turned and hummed and got hot. It didn't turn fast enough to disengage the capacitor so the start windings stayed engaged. (this motor has a centrifugal switch that has weights. Once the motor gets to speed, the weights fling out disconnecting the contact switch above the shaft)

The motor model is:C48J2PA105A2, 3/4HP, Phase 1, 5.5KW, Code H (what ever that is)

Thanks,
Kori
 
C48J2PA105A2, 3/4HP, Phase 1, 5.5KW << are you sure that's 5.5kW? 3/4hp = ~0.55kW

As you've found the voltage rating on the cap has to be higher for 230VAC use!

Are you sure the cap is a start capacitor? It definitely get disconnected once running?
Could the cap might be a run capacitor instead?

I googled "start capacitor sizing" & there's tables for motor size vs cap size.
Looks like for .55kW at 200V to 250V the cap should be 108 to 140MFD already?
 
Yeah, probably .55kW. The "." could be worn away.

The data I can find with the various sellers of that motor state it is a start capacitor. Altho, there are 3 wires that run to it. Usually a run capacitor stays on the outside of the casing (not sure why this is done) and looks like the motor has a hump, or 2, on the outside. Start capacitors are normally inside the electrical cap on the end.

Found a diagram that shows how the wiring is:
electric-motor-wiring-diagram-110-220-beautiful-single-phase-of-electric-motor-wiring-diagrams-single-phase.jpg


So according to that, the start coil should be 110V as it's only connecting to the one Hot leg.

Tomorrow I'll check with a DMM to see what's connected to what. Maybe there's an internal short allowing 230V to the cap. I hope not. Even though the motor was free, I'd don't wanna have to junk it. ;) Altho, I suppose I could rewind it. Would need to get some wire for that, tho.



Ya know, thinking about it, I realize that maybe this is acting as a start & run capacitor. There's a wire that comes from the thermally protection board, goes into the cap.
Then on the same terminal of the cap there's a red wire that comes off, goes to the centrifugal switch, then comes off the switch and into the motor.
On the other leg of the cap, a wire comes off and goes into the motor.

I suppose it's possible I hooked up the start winding wire to the wrong side. Maybe it needed to be paired with the other wire. But if I remember correctly, if I paired it with that one, the motor didn't turn at all but just buzzed.



Here's the switch that's on the end:

Here's another view of the end. I can't see the wiring paths here. Still looking

image_cyplfu.jpg




Ok, I think I see what I did wrong here.
Is this diagram, it shows the power coming from the thermal switch, to the 1 side of the cap, then continues from 2, the same side, to the motor. The start switch is connected to 3 on the cap and then is disengaged after the motor is spun up.
The reason I think I had it wrong was because when I got the motor, I think it was wired wrong.

image_saczxn.jpg


So I'll see about getting the cap replaced tomorrow and rewire it up and hopefully it'll work without issues :p
 
You're saying two lines (two phases?), but where's neutral?
L1 + L2 + Neutral would make it 3 wire connected & directional depending on phase connection.
If it's only connected to the mains with two wires, it's still a single phase motor, but being run at higher voltage so more power is available.
If it's intended to be 2 wire connected between two phases of 110V system, the motor would see about 208VAC.
Hope that helps?
 
From your diagram if it is 2 coils then the 230V mode would have the coils in series and in 110V mode the coils would be parallel. Usually a 110V to 230V switch requires a coil wiring change or connection but the wiring seems to be just a single coil.

With a smaller than specified capacitor the start coils should not get hot as the smaller capacitor would block more power and with not enough power to the start coils the motor can't get up to speed and the run coils will then heat up.

With the >220V capacitor 140uF you should be fine. Not sure what your maximum line voltage will be as this needs to be taken into acocunt for the working voltage of the capacitor.
 
Update: Got the capacitor wired up correctly and the motor/pump works great! I left it run for like 10mins cycling water around and it did so without a hitch.

The only problem, to me anyways, is it's a bit warm on the top of the motor. I'm wondering if not enough air flow is getting around the coils. I'd like to take it apart, but it's got so much weathering to it that the thin bolts that hold it together will break if I try to take them out. I tried to take one the other day, and I could tell it was twisting instead of turning so I left it alone. I suppose I could mount some metal fins on the outside of the casing to help wick the heat away.


As a side note, this is a prototype design for my geothermal setup. I have a 270Gallon IBC multi-liquid tank that I have elevated (to help keep from needing to purge the pump; no need for a flap/ball-valve this way; plus helps with head pressure) and I took the old A/C central air unit cooling coils and going to set up a loop.
The central A/C unit I cut off where the actual A/C unit was housed and left with the air box where the blower fan and cooling coils are located. Took off the smaller (1/4 inch) tubing off the coils that returned to the A/C pump and put standard copper tubing of 3/8 inch and then put a threaded male connector on the two ports. This is so I can circulate water through the coils. Then the blower fan circulates the air from the house, through the coils, back to the house. Here in Florida, the ground temperature at about 7 feet (2.25 meters) is about a constant 72F (22C). The plan is to later on put HDPE piping in the ground at 7-8 feet and about 75 feet (23m) long and 15 feet (4.5m) wide. This should give me ample thermal exchange capacity.

Today I just have the plumbing dry fit as it is the beginning of proof of concept. Not worried about them blowing apart as the pressure is probably around 10psi or so. Later on as I build the next step, I'll take some pictures of the setup and post the progress in a new build thread.
 
It will run warmer if the coils are now running at the voltage/magnetic limits of the design. Additional cooling would help extend the capacitor life at least, rest of the motor will probably be happy even if it burns your hand, well maybe the bearings will run dry...

Another option... depending on the groundwater level..... just dig down 1m diameter hole until you get a well and use the well water as your cold reserve and heat conductor in one.

With a vertical shaft you can then also add a separate vent pipe so that when the air temperature above is below the ground temperature try for a natural cooling convection air circualtion once given a starting airflow. Sort of like a natural free air pump, hot air up the pipe, cold down.. Or just pump some of the water out and pull the colder water from the surrounding area..
 
Vertical shafts would cost too much as we'd need to have a well machine to dig. Too many iron rocks in the ground to try to do it by hand (using the 3 inch PVC pipe method).
Also, using the shaft to cool the air would be a bad idea. The air is to humid and mold will start to grow. I know of a guy who did this and ended up having major mold problem in his house after a couple years of use. The house was nice and cool though.
Now, if we had dryer air, I would agree. Try to use the ground system to cool the air. If I move up north where humidity is <75%, I'll probably try that.

I can dig the horizontal beds myself as we have a tractor with front bucket and backhoe. It just takes a few days to dig the hole for the piping.

Horizontal bed will cost about $200-$300 for the piping
Vertical shaft(s) will cost >$500 per shaft, excluding the other hardware needed
 
Ah, yes, forgot the humidity.The air circulation was to cool the hole/ground and stil use the water piped system to the house not to use the air from the hole. I have managed to cool a point down to 11C over a couple of winters from 17C this way for my battery storage "home" where the batteries will live.

If you have the backhoe that's the game changer, I'd go crazy on one of those and dig the whole garden up :D
 
LOL Yeah, I've gone a bit crazy too. We now have a huuuuuge pond. I haven't measured it's actual size, but it's currently about 75 feet at it's widest and maybe about 30 at the narrowest. It's not done yet, and there's a lot more work to get it right. Problem is, kinda hard to dig dirt out of a hole that rain keeps filling it up with water :p

I'm hoping the geothermal will be cool enough to pull the moisture out of the air in the house. I know the temp needs to be about 20F difference for it to work. If ground temp is only 72F, then it might not do the trick. I might have to employ a freon based cooler to bring the humidity out. Altho, running to remove the humidity is far more efficient than running to cool the place down. So I'll probably still come out ahead.
Or maybe find a natural way to pull it out of the air. Hrmm....
 
Standard cheap freezer unit filled with water -> glycol circulation coil inside -> A/C coils.
Feed the cold water from your trench to cool the radiator on the freezer.
Cold storage battery. Power the freezer via solar main + battery flex.
Just use water in the freezer to get the higher energy difference captured on phase change to freezing.
1m3 of water takes around 93kWh to freeze. Lot cheaper than electric battery for A/C...
 
Ooo, good idea :)
 
Put the water into 2 -5 litre plastic bottles and stack them in the freezer with enough space for expansion and then replace them every 6-12 months if they are showing signs of splitting after a lot of freeze cycles.
 
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