Air compressor not restarting

[Elektrishun]

Well I tried the compressor again today and it tripped at just over 100 psi with the door wide open. So something is very wrong with the thermal switch.
I tried to pull the end bell and there's no way I can get it off. Can't get a bearing puller in because there's no room for the arms and I'm afraid that cast aluminum end bell is going to break.
Tomorrow I'll pull the motor of the compressor and either take it to a shop or spring for a new one at Princess Auto for $229

I am not entirely certain if your motor design is a little less service friendly than most but here's a YouTube video I found that shows the typical way a single phase AC motor should come apart (2:00 - 7:00 min. portion):

Single Phase AC Motor Disassembly Video

 

[Susquatch]

@David - I've never had any difficulty removing end bells without a puller. At most it required a few love taps at the seal with a plastic or rubber mallet to break the seal.

Nonetheless, I can imagine that this might not always be the case.

If you are contemplating a new motor or a motor rebuild anyway, you have nothing to lose by using a chisel or wedge to break the seal.

 

[David]

I'm off today so I hope to tear compressor apart.
Yesterday was a bit of a bust as my planned one hour motorcycle ride turned into three hours, two of which were sitting in traffic watching the fuel gauge go down and the temperature gauge go up.

 

[Susquatch]

I'm off today so I hope to tear compressor apart.
Yesterday was a bit of a bust as my planned one hour motorcycle ride turned into three hours, two of which were sitting in traffic watching the fuel gauge go down and the temperature gauge go up.

What!!!!

Doesn't that silly bike have automatic start/stop on it?

Btw, the US EPA has officially announced that they are killing that stupid requirement. Only about 30 years too late!

 

[David]

Pulled the motor off the compressor. Thermal switch is a sealed unit so no way to tell if it's burnt or what not inside.
Calling around to see who has one.
Troy Electric to the rescue!

 

[David]

Well blast. They didn't have the switch. Nor can they identify a replacement because the part number off the original switch is meaningless.
Off to Princess Auto.

 

[Elektrishun]

Well blast. They didn't have the switch. Nor can they identify a replacement because the part number off the original switch is meaningless.
Off to Princess Auto.

I posted this link awhile back for trying to size a replacement:

O/L Switch

Pricey but it may help locate a possible replacement and then you could find a better price.

 

[Elektrishun]

One more link. A pdf that gives a lot of info including a sizing chart on page 5:

Klixon Data Sheet

If nothing else the 2 links provide a lot of info about the design and ratings for these devices.

 

[David]

Yeah we tried that at the shop. They had 15 or so examples of the Klixon brand, none had the mounting ears, all were $130+. The sizing worksheet for the Klixon switches is quite involved and specifically says that it is not possible to select a Klixon protector based on horsepower, amperage or nameplate data.
In the end, I decided to just stick a new motor on it. WEG branded motor with warranty.

 

[David]

I do appreciate everyone helping me sort out this problem!

 

[Elektrishun]

Pulled the motor off the compressor. Thermal switch is a sealed unit so no way to tell if it's burnt or what not inside.
Calling around to see who has one.
Troy Electric to the rescue!

Took the above from the first link. Once the switch is out of the motor you could carefully test it's function with a heat gun, thermostat, and meter set to ohms.

Edit: Without knowing the your motor's thermal switch exact ratings but using the ratings above as a rough guide - "120F open and close at 745F (+/- 5-12F)".

 

[Susquatch]

I do appreciate everyone helping me sort out this problem!

Jesus David, does this mean you are gunna start working on other stuff now? Don't you need another bike ride? Maybe down to Mexico or someplace?

 

[David]

Jesus David, does this mean you are gunna start working on other stuff now? Don't you need another bike ride? Maybe down to Mexico or someplace?

Hoping to drop the transmission out of the Vdub this afternoon, put in the new clutch. Won't have time to do the suspension though I'm afraid

 

[Elektrishun]

View attachment 66627

Took the above from the first link. Once the switch is out of the motor you could carefully test it's function with a heat gun, thermostat, and meter set to ohms.

Edit: Without knowing the your motor's thermal switch exact ratings but using the ratings above as a rough guide - "120F open and close at 745F (+/- 5-12F)".

Whoops - I think I see the problem now...



Should be "close at 74F"

 

[slow-poke]

It states 17.x A
On start-up it should pull that many but not more if all is right?

Incorrect, it will pull much higher current for a short time while the motor is coming up to speed, 80A (wild guess). However depending on the response time of the meter you won't see it, you need a C.T. And scope to see that transient current.

I made a little circuit for my 5x6" bandsaw that is supposed to help prevent destruction of the worm gear when the blade jams. When the blade jams, the worm gear can start acting like a knife shaving off the leading edge of the driven gear. My little circuit detects increased current and trips the motor off. When starting, the circuit is disabled while you push the start button. A sensor detecting motion on the saw's motor driven wheel would be a worthwhile improvement.

 

[mbond]

inrush current can easily be 10x the name plate

 

[slow-poke]

This is the start-up current for my little 1/2HP band saw, keep in mind a band saw has minimal load when not actually cutting, unlike a compressor starting with a partially filled tank.

 

[mbond]

So yes? - and we are assuming induction motors right?

Unloaded starts are also an order of magnitude less onerous than loaded starts - any sort of tool versus a pump compressor etc. Which is why those load valves exist