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File: IMG_2338.jpg (1.72 MB, 3548x2652)
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Starting this thread because I learned a lot the last time we had one of these and I got a compressor to work on and have lots of questions.

I bought this pic related compressor (Emglo 1.5 HP / 6.2 CFM @125 PSI electric compressor, replaced by Jenny K15A-8P) at an auction, and it is missing some parts: Motor run capacitor, pilot valve, relief valve, pressure regulator. It does run and build pressure wired up as shown, with the pressure switch out of the circuit and the 1/4 turn valve between the missing pilot valve and the pressure manifold closed.

Questions:
Motor - is a Century 8-168697-03, any ideas on how to find the right run capacitor for that motor? Google found nothing, I'm planning on calling Jenny dealer, then Jenny and if that fails then Regal-Beloit.

Pilot valve - The manual says this is a 125 PSI pilot valve, I found some on Amazon that are adjustable 95-125 PSI for where it sends the unload signal to the compressor. Would this be okay for 125 PSI or is there a benefit to having a cushion above the rating?

Relief valve - Manual says it's a 165 PSI / 65 SCFM relief valve, can I just buy something rated for 165 PSI, or do you have to worry about the CFM rating?

Pressure regulator - How to pick a regulator? It has 3/8" hose going from the manifold to where the regulator should be so just something with 3/8" pipe thread? They are rated for 80 CFM, sounds like plenty. My experience with regulators is they wander around, especially if you are adjusting them down from a higher pressure vs. up from a lower pressure. Actually, do you even need a regulator?

Should I get a dryer / separator? I will mostly be using this for blowing shit off, filling tires, and occasionally running an impact driver and a nailer.
>>
How the fuck does the pressure switch / unloader valve setup work? I gather from Youtube vids that this is a selectable constant-run / start/stop setup where you would open the valve between the pressure switch and the pilot valve for constant run mode and close it for start-stop mode. with the valve in the open position for constant run mode, both the pilot valve and the pressure switch would see tank pressure, so is the pressure switch just set higher than the pilot valve so the compressor unloads before power is cut to the motor? When the valve is closed, the pilot valve never sees any pressure, so the pressure switch turns off the motor when the tank gets to the cut-out setting of the pressure switch. What is the 1/4" soft copper line going from the pressure switch to the top of the rear tank in the pic? Is that for unloading the 1/2" pressure line when the pressure switch gets to cut-out pressure so the compressor can start without any back pressure, or does it do something else? I ask because that leads to my final question:
How the hell are the two tanks connected together? The only thing I can see that runs from one tank to the other is the two 1/4" soft copper lines, one going from the pilot valve to the compressor, which I'm pretty sure is just for unloading the compressor when it's in constant run mode, and the other going from the pressure switch to the fitting connecting the 1/2" supply line from the compressor to the rear tank in the pic, which I'm pretty sure is just for venting the supply line when the motor turns off in start/stop mode. It does work, in that the pressure gage on the front tank registers pressure and the hose on the front tank blows air, I just can't figure out how the two tanks communicate. Thanks for reading my blog and post all compressor-related questions and advice below!
>>
>>1593129
Im not really sure why you would ever want constant run mode on an electric compressor.
>>
>>1593132
I'm guessing because some motors have a rating of number of start / stops per hour and if you're using a lot of air and it's going to be starting / stopping constantly you should have it in constant run mode. Also I might be retarded - could the handle thing on the left be a hollow pipe connecting the two tanks? I only noticed this as soon as I posted the pic.
>>
first thing is open the drain on the tanks
lots of water and rust not good
>>
>>1593139
They seem okay, there's no water in the tanks and I ran it up to about 40 psi and opened the valves and got clean dry air.
>>
I recently restored my old compressor
take it apart, wire wheel it and paint, change oil in compressor and re seal all joints Be careful as old galvy elbows and shit are hard to loosen. Often the manifolds are cheap pot metal and break easily
>>
Oil free compressors are all shit. Stay away
>>
>>1593179
How do you know if a compressor is oil-free? Does all compressors with an oil sump and recommendations to check oil daily mean its an oil-consuming compressor?
>>
>>1593128

>Motor - is a Century 8-168697-03, any ideas on how to find the right run capacitor for that motor?

http://www.electricmotorwholesale.com/BALDOR-OC3015F12/

this one will be close enough

>Would this be okay for 125 PSI or is there a benefit to having a cushion above the rating?

it would likely be fine. cushion is nice though

>can I just buy something rated for 165 PSI, or do you have to worry about the CFM rating?

as long as the PSV can purge more air than the compressor builds plus a bit of wiggle room. otherwise the PSV is essentially useless

>My experience with regulators is they wander around, especially if you are adjusting them down from a higher pressure vs. up from a lower pressure. Actually, do you even need a regulator?

when practical set regulators using working pressure. no a regulator is not required. they are handy though

>Should I get a dryer / separator? I will mostly be using this for blowing shit off, filling tires, and occasionally running an impact driver and a nailer.

a dryer wouldnt hurt but its not required either. i wouldnt lose sleep over it, just drain it often

be careful what you point your blowgun at, as it will contain some moisture however insignificant it may be
>>
>>1593194
Oil free compressors use a diaphram and sound like huge vibrators
Yours has pistons and a crankshaft thus it need oil
>>
>>1593283
>>1593669
Thank you gentlemen.
>http://www.electricmotorwholesale.com/BALDOR-OC3015F12/
I am leaning towards trying a capacitor about that size (15 MFD), but then I ran across all this literature from modern century 1.5 hp motors and they have much higher capacitance ~40-50 MFD. Are you basing that recommendation on the age of the motor it would be closer to the 'rule of thumb' size of the capacitor at 10-15 MFD?
>>
>>1593704

honestly i did a ton of searching for the proper capacitor but all i could find was the start capacitor.

so i looked up baldors 1.5hp cap start cap run compressor motor (general purpose) that powers compressors with specs very similar to yours, and found the run cap part number.

it will do the trick
>>
>>1593958
Damn dude, thanks for spending the time on it. I found the same thing. Do you know if trying the 3 caps and measuring the total input current and going with the lowest is the correct approach? I got this whole thing for $2, so spending $30 on test caps really isn't an issue.
>>
>>1594345
Sorry I posted that in another thread, what I mean is, can I try a 10 MFD, 15 MFD, and 50 MFD and measure the total current draw and go with the lowest? I saw on one site, and one site only that "If the capacitor value/rating is too low, the phase shift will be higher and the winding current will be too low." but I think this means in the aux. winding, and hopefully the one that gives you lowest amp draw off the mains will be the correct size?
>>
Hey guys lm buying a home and there is a big snap-on air compressor in the garage. That theyre letting me keep.
Could you tell, from this lone picture I have of it. What size it is and its price in the current market if it was maintained well?
>>
>>1594358
Worth about tree fiddy...
>>
>>1594358
looks good, the bigger the radiator, the better. Keep it.
>>1594360
I think itsa 80 gallon 2 stage, so more like seven fiddy.
>>
>>1594369
Its a 5' step ladder...dummy
>>
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>>1593669
>Oil free compressors use a diaphram and sound like huge vibrators
>Yours has pistons and a crankshaft thus it need oil
pic of oil free dewalt compressor
part #80: piston, rod, and cylinder sleeve
>>
>>1594347

yes this would work. also while the units running cheak for heat, it will get warm but if its the wrong cap it will get too warm and you will know somethings up.

too low of MFD will slip hard and heat up.

>I saw on one site, and one site only that "If the capacitor value/rating is too low, the phase shift will be higher and the winding current will be too low." but I think this means in the aux. winding, and hopefully the one that gives you lowest amp draw off the mains will be the correct size?

well youre on the right track

simplified;

excess capacitance (mfd) ---->
more current draw ---->
things get hot

improper phase shift ---->
lower rpm/torque ---->
less cooling ---->
even more heat

too low capacitance ---->
more slip ---->
working harder---->
more heat

>but I think this means in the aux. winding, and hopefully the one that gives you lowest amp draw off the mains will be the correct size?

the aux winding in a cap start/run motor is always in the circuit. the only thing that gets cut by switch is the start cap. not relevant to your motor, but even when an aux winding is cut out of a circuit by a cent switch it still provides a vital role of producing back-emf to keep the motor self regulating. (keep draw and heat down)

tl;dr will work, check for concerning levels of heat during testing



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