Failure/Design issue - Alpha Carette compressor

[PCPhack]

FYI, the Carette compressor runs the water pump off of a 12v switching power supply inside the control box. If this fails open circuit as mine did, then it will not trip the overload protection, and you can run the compressor to death quite easily.

Mine had intermittently tripped the overload some this summer. It sits next to the breaker panel on a dedicated 20 amp circuit, so I attributed it to lower summer voltage (lots of air conditioners running in summer in Texas) and/or a weak overload protector.

I decided to investigate a few days ago and set up a Fluke recording multimeter with clamp on amp meter option right at the breaker panel since it was right there. During that session, I couldn't get it to trip.  Then tonight, I started to top up my tank, but was closely monitoring the compressor, and by shear luck, the power supply fully died, the water pump stopped, and I noted the compressor heads at 200 degrees F. Note that at that point it would run as is fine, not tripping the overload, but no water was circulating and it started overheating. I did not dig into it far enough to see if the high side temperature sensor also runs off the 12v, as it is nicely shrink wrapped up with other harness cables, but I am guessing it does, so that won't save you either.

Suggestions for improvement and I hope Joe over at airtanksforsale can push this with the manufacturer:

-Interlock of the motor AC, only if 12V DC is also working
-12v operational indicator or voltage meter
-Mechanical flow sensor on the coolant line for visual indication of flow
Note that high voltage is immediately present inside of the control box, so do not try your own upgrades unless you are qualified!

I got lucky that I happened to be investigating the intermittent overload trip at the exact time that the 12v supply actually stopped working for good. I can easily see someone overlooking an intermittent trip, or theirs doesn't even intermittently trip, the supply dying, and then they burn up their compressor completely.

[ACHiPo]

Wow sorry to read of the problem.  I've been thinking the Alpha Carettes are high end and not susceptible to the issues us Yong Heng owners deal with.

[PCPhack]

It is a better design, but it just doesn't have a failsafe for this particular mode of failure. It is easily remedied at low cost, so the design ought to be revised.

[cootertwo]

Just for info, I'm not very happy with my Karette. If it had an hour meter, I could say how long it's been run, but not much. Used to pump up to 4500 pretty well, now strains and takes forever to get to 4000, and no way will ever reach 4500. Yes, checked for leaks etc. Never over heated. Just cwappy material I guess. I'm investigating REAL high pressure compressors (scuba) high dollar. Maybe they last longer. In my humble opinion, anything under a couple thousand is just a toy, kinda like buying a moped, then complaining that it won't go over 40 mph.....

[PCPhack]

That's insteresting. Mine does have a cumulative runtime readout. It is about 6 months old and from Joe B.

[AlanMcD]

I'm investigating REAL high pressure compressors (scuba) high dollar. Maybe they last longer. In my humble opinion, anything under a couple thousand is just a toy, kinda like buying a moped, then complaining that it won't go over 40 mph.....

I'll just say a few positive words about the Shoebox compressor here - while slow, they are rock solid.  No worries about them not holding up, and they are easily serviceable for any wear parts, with full support and parts here in the US.  So you don't have to spend thousands for a rock solid pump, unless you want one that is fast.  And honestly I don't see a "need for speed" unless you are shooting big bores - I get air for over 6 shots with my 52 FPE .25 cal Marauder from every minute of run time, so I only need to run it about 50 minutes for every tin of pellets (and much less often for my lower power guns).  And thanks to the cheap Chinese compressors, the cost of the Shoebox has dropped a lot but the robustness is still there.

[PCPhack]

Just a short follow up here. Joe at Airtanksforsale had me in touch with their guys overseas. They are direct shipping me a new power supply and in the meantime, I am just using an external 12v supply that I have. Thanks Joe!

[cobalt327]

I'll just say a few positive words about the Shoebox compressor here - while slow, they are rock solid.  No worries about them not holding up, and they are easily serviceable for any wear parts, with full support and parts here in the US.  So you don't have to spend thousands for a rock solid pump, unless you want one that is fast.  And honestly I don't see a "need for speed" unless you are shooting big bores - I get air for over 6 shots with my 52 FPE .25 cal Marauder from every minute of run time, so I only need to run it about 50 minutes for every tin of pellets (and much less often for my lower power guns).  And thanks to the cheap Chinese compressors, the cost of the Shoebox has dropped a lot but the robustness is still there.

You make some points worth pondering, IMHO. I never understood a fast fill time being a big plus, at least not from the cheaper cost units. Seems like an invitation to rapid wear.

[Taso1000]

I'll just say a few positive words about the Shoebox compressor here - while slow, they are rock solid.  No worries about them not holding up, and they are easily serviceable for any wear parts, with full support and parts here in the US.  So you don't have to spend thousands for a rock solid pump, unless you want one that is fast.  And honestly I don't see a "need for speed" unless you are shooting big bores - I get air for over 6 shots with my 52 FPE .25 cal Marauder from every minute of run time, so I only need to run it about 50 minutes for every tin of pellets (and much less often for my lower power guns).  And thanks to the cheap Chinese compressors, the cost of the Shoebox has dropped a lot but the robustness is still there.

You make some points worth pondering, IMHO. I never understood a fast fill time being a big plus, at least not from the cheaper cost units. Seems like an invitation to rapid wear.

Another thing about filling faster is that, in general, it creates more heat in the compressed air.  When the compressed air cools off you will see the pressure drop on the tank or rifle gauge.  So you're not really getting complete fills.  Sure the slower compressor heats the air too but not as much.

I've never been in a hurry with my Shoebox Max.  I bought two 30 minute scba tanks versus one 60 minute tank.  I figured if I was ever shooting that much I could use one tank while the other fills.  So far I've never had to do that.   

Thanks,

Taso

[PCPhack]

Well, I wasn't so lucky after all. The compressor seemed ok for the first top off after replacing the power supply, but now after I tried it again, it doesn't compress past 3000psi and pops the overload. I did a diagnosis run on it this morning, and sent the information to them. So evidently the over temperature event that I first reported on due to the water pump power supply failure ruined the compression in one or both stages.

[PCPhack]

Update: I have been in contact with Joe and the manufacturer in China. They are really helpful and greenlighted me to do a teardown. So after the 12v supply failed, and the cylinders overheated, it blew out the fiber washer and adjacent oring for the high side. This is why it can't make pressure now. They are sending me the parts to rebuild it the rest of the way.

[PCPhack]

Also, I did pass along the idea to update the design to not allow the pump to run if the 12v supply fails. Only time will tell if they implement something. Even with this situation, I would not want to go to something like the mentioned shoebox. All compressors need some maintenance, and now I know how to fully rebuild the Carette if needed. I will update my own to either alarm or stop if the cooling system is not flowing and it is getting hot.

[PCPhack]

A photo of the failed fiber washer and oring in the compressor high side. I am waiting now for new ones to arrive.

[PCPhack]

The factory sent my rebuild parts via Fedex, and they will already arrive later this week. This has been great support from Joe's contacts there, and I am even a bit shocked. I am not sure if I have ever had such great product support directly from China.

[bandg]

Great to hear of such good support.  Interesting thread.  Keep it going with updates.

[PCPhack]

My parts arrived a day early! The compressor is now fixed, and is currently filling my second of three tanks to 4500 psi.

[cootertwo]

I'm looking for Carette parts....... HELP!

[kendive]

I'm looking for Carette parts....... HELP!

Good lcuk. When I tried to get help fr my alpha filter from Joe B. he sends me this so called kit for $12 and it was one o ring. What a rip. I ened up finding online a complete kit for $19 and repaired the PMV myself. No help from Joe. I will not give him another dime!!!





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