Colin Lindsay Posted January 20, 2019 Report Share Posted January 20, 2019 I have a SIP Airstream 3hp/200 litre compressor and it's been behaving badly for some time now. It no longer gets anywhere near to operating pressure, especially for the sandblast cabinet, and cuts out well before that. The problem is that it's not the pressure relief valve that cuts out, but the circuit breaker. It used to cut out at about 130bar and cut back in about 60, but now it cuts out at about 70 by virtue of the circuit breaker blowing. If I reset it, it'll maybe get to about 80 then go again, and it runs right to empty without ever kicking in again. I replaced both the control box and the circuit breaker a few years back thinking that might cure the problem, which of course it didn't. I can't blast anything any more as there's not enough puff, plus I have to keep going to the compressor and resetting the breaker. It used to blow fuses regularly when cold, and I'm wondering if the oil is at fault - it's proper SIP compressor oil although when I first got it, quite a few years ago, I ran it on car engine oil for a month or two until this was pointed out as harmful, but it ran like a dream. Ever since I used the proper oil it's been sluggish and hard to start when very cold. Any ideas or thoughts to help me get back to blasting rusty bits clean again? I've just removed the circuit breaker to price a replacement which is why the top cover is off. Link to comment Share on other sites More sharing options...
johny Posted January 20, 2019 Report Share Posted January 20, 2019 is the motor getting hot? Sometimes the motors have a thermal switch in the windings that trips if too hot and resets itself automatically when cooled off. It would explain why you dont get a low pressure restart even though the circuit breaker has been reset. If this is the case then theres too much load on the motor which is most likely to be a compressor problem..... Link to comment Share on other sites More sharing options...
Pete Lewis Posted January 20, 2019 Report Share Posted January 20, 2019 silly , but its not overfilled ??? Pete Link to comment Share on other sites More sharing options...
68vitesse Posted January 20, 2019 Report Share Posted January 20, 2019 I have a SIP airmate direct drive V twin 3 hp compressor which is sluggish to start in cold weather and sometimes blows its trip on startup. Once started and its warmed up no problems for rest of the day, currently using macbine mart compresser oil. If the compressors trip is blowing it must be faulty or the motor is faulty and drawing to much current, do you have a meter which will show the amps the motor is drawing?. Presumably you have checked that the motor or pump are not partially siezed, as your compressor seems to be belt drive have you run the motor without the belt to see if it still trips?. Regards Paul Link to comment Share on other sites More sharing options...
NonMember Posted January 20, 2019 Report Share Posted January 20, 2019 What rating is the circuit breaker? My SIP Airmate (twin cylinder direct drive 3HP) needs a 16A circuit, so the two electricians who fitted up my current and previous garages, and the third electrician who did a certification check on the old one when I moved, all fitted a 16A circuit breaker. And all three would trip in normal use. Because it's a heavy duty motor and thus needs a special "motor" rated 16A breaker (I think it's class B rather than class A). Link to comment Share on other sites More sharing options...
Colin Lindsay Posted January 20, 2019 Author Report Share Posted January 20, 2019 I took the breaker out to see the model number and make (to price a replacement) then put it back in again, and the pressure went right up to 110bar but then it blew again; this was with the cover off so I'm wondering if heat is rising from the motor and blowing the circuit when it's all closed up inside the black box, but not when it's open? I've also got the fan against the wall, so it may not be getting enough cooling air. It's usually run from empty and regularly drained. Circuit breaker is 20amp and it's the same rating as the one I removed from the machine a few years back when it started these shenanigans. Link to comment Share on other sites More sharing options...
johny Posted January 20, 2019 Report Share Posted January 20, 2019 modern breakers arent heat operated but use electronics to measure the current. I ask once again, how hot is the motor getting? Link to comment Share on other sites More sharing options...
JohnD Posted January 20, 2019 Report Share Posted January 20, 2019 I have a Clarke compressor; I think the latest equivalent is this - https://www.machinemart.co.uk/p/clarke-raider-1510000-3hp-100-litre-air-compr/ I used to run it from a three-pin plug socket, but it persistently blew the fuse in the plug. I think it was someone here who explained to me that an electric motor draws more current the slower it runs. At start up, the current can be briefly high enough to blow a domestic 13A fuse. Presumably, this effect could also blow a circuit breaker, but one built into the compressor would be protected, I presume. My solution was to wire the compressor directly, via the sort of wall switch that controls an electric oven. This places the start-up load on the wiring and the circuit breaker in the garage electrical supply, but that hasn't blown, ever. This won't cure, but may explain, the blowing breaker on the compressor. But my compressor had a breaker too, a tiny switch on the side of the control box. That used to blow too, especially after I enclosed my compressor in a sound reducing box, because it was so B!$$%£ loud! Re-setting the breaker took a moment to fip the switch, but I had to dismantle the box to get at it. The compressor got a bit hot in there, so I added an extractor fan, with a delay switch, so that it continues for some time after I turn off the compressor. That stopped the compressor's breaker blowing. So heat, +/- age may the problem. And your plan to replace the breaker may be the cure, as long as you keep the compressor cool. John Link to comment Share on other sites More sharing options...
thescrapman Posted January 21, 2019 Report Share Posted January 21, 2019 I suspect the volts are dropping too low, too much resistance in cabling, upping the amps and tripping the breaker. I lived with that for 19 years with my almost identical to your compressor. Mine was caused by inadequate wiring and distance to the garage. Volts would drop to about 150V at start up. I now have a 10mm feed direct from the incoming fuses (and a 300A 3-phase supply to the fuses) to the garages and a 16A feed to the compressor, starts whatever the weather. What is your cabling Like? Link to comment Share on other sites More sharing options...
Colin Lindsay Posted January 21, 2019 Author Report Share Posted January 21, 2019 16 hours ago, johny said: modern breakers arent heat operated but use electronics to measure the current. I ask once again, how hot is the motor getting? It's not, as far as I can tell. It's definitely not a thermal cutout. There's no burning, and no great heat other than what you would expect, but with the cover removed from the breaker it seems to reach a much higher pressure before cutting out again. This may point to cooler air getting to the unit so it takes longer to overheat, but then it's not heat, as you say, it's current. Re Scrapman's post: the garage is all new, just built and with new wiring. It doesn't trip the circuit breaker box on the wall, just blew 13amp fuses in the plug a lot when cold, and that was in the other garage which was an icebox. This one is a lot warmer so that problem seems to have gone away. The only thing I've done to the compressor that's anyway wiring-related was to fit a longer power cable directly into it, to negate the need for an extension lead. I replaced the original four foot lead with a seven foot lead using cable bought from my local electrical supplies. I think I'll give it a complete service; it gets new filters about every two years, I can replace the oil when I'm at it, and give the motor windings a good clean. I'll also try to improve the air flow over it as it's tight to the wall and may not be getting enough fresh air to the fan. Link to comment Share on other sites More sharing options...
dave.vitesse Posted January 21, 2019 Report Share Posted January 21, 2019 The instantaneous current when the motor starts up is very high. i.e. A very short term current spike. Normally a breaker or fuse will cope with this. But if there is a delay or drag with the motor getting going then this could lengthen the spike, in time, and cause the breaker or fuse to blow. Maybe or maybe not the cause of problem in this case. Dave Link to comment Share on other sites More sharing options...
Clive Posted January 21, 2019 Report Share Posted January 21, 2019 5 hours ago, Colin Lindsay said: . I replaced the original four foot lead with a seven foot lead using cable bought from my local electrical supplies. I presume you used at least 13A rated cable? Higher would be better. Shame you cannot monitor the current draw with a meter. re startup, the reason for the high initial current is that under normal conditions, a motor acts as a dynamo, opposing the electrical supply. Called back EMF. At startup, no back EMF to oppose the current, and it is much bigger than when spinning freely. Explains why power tools burn out if they are worked too hard and motors are slowed down. Anyway, I know of a commercial place where they have a "small" single phase arc welder. For the past 10+ years the 13A fuse has been replaced by a bit of bolt, as the fuse kept blowing when striking the arc. The "lazy" PAT testers don't bother checking inside the plug.... would have a fit if they did! 1 Link to comment Share on other sites More sharing options...
Pete Lewis Posted January 21, 2019 Report Share Posted January 21, 2019 as it seemed to work ok on engine oil and played up on compressor oil have you done a reversion test ?? comp oil is funny stuff , can get very gooey if out of life Pete Link to comment Share on other sites More sharing options...
NonMember Posted January 21, 2019 Report Share Posted January 21, 2019 1 hour ago, Pete Lewis said: as it seemed to work ok on engine oil and played up on compressor oil have you done a reversion test ?? Ah, I'd not spotted that note. I'm fairly sure my SIP instruction book said to use engine oil, not compressor oil. At least on mine the oil is only there for lubrication, whereas proper compressor oil is intended for applications where it aids with the pumping in some way. Again, details a bit fuzzy in my forgetory. Link to comment Share on other sites More sharing options...
Colin Lindsay Posted January 21, 2019 Author Report Share Posted January 21, 2019 1 hour ago, Pete Lewis said: as it seemed to work ok on engine oil and played up on compressor oil have you done a reversion test ?? comp oil is funny stuff , can get very gooey if out of life Pete 48 minutes ago, NonMember said: Ah, I'd not spotted that note. I'm fairly sure my SIP instruction book said to use engine oil, not compressor oil. At least on mine the oil is only there for lubrication, whereas proper compressor oil is intended for applications where it aids with the pumping in some way. Again, details a bit fuzzy in my forgetory. I used engine oil when I first got it (serviced it myself the day it arrived) and that is what was recommended to me, and it worked perfectly. THEN someone who 'knows' told me that it was very bad for the piston, so I should use proper compressor oil, and therefore I bought a bottle of SIP's own stuff. Ever since then..... the SIP stuff is a thicker oil, possibly SAE40, but I was using 15/40 before and reckoned that covered everything. There doesn't appear to be any choice with the SIP stuff, it's all one bottle and no oil variation. Maybe I should go back to good old Castrol again and see how it goes then? Link to comment Share on other sites More sharing options...
SpitFire6 Posted January 21, 2019 Report Share Posted January 21, 2019 Hi, You need somebody to check the startup & running current. Voltage off & on load. With these figures, a competent person will determine if the cable, MCCB, MCCB curve & equipment is OK. Let's not forget the most important check; earthing/grounding. It everything was installed correctly by a competent person and the MCCB/breaker trips; Your compressor is the problem. Resetting an MCCB/breaker more than twice in a year would mean to me there is a problem. A problem you need a competent person to fix. BS7671 is what the competent person should "follow". I'm not competent at anything above 24V! So can't help I'm afraid. A "lighter" oil might help? Cheers & good luck, Iain. Link to comment Share on other sites More sharing options...
GT6M Posted January 21, 2019 Report Share Posted January 21, 2019 it could be the ..run capacitor, bigg roundy white thingy inside where thermal cut oot is. or it could be the thermal cut oot strip, its inside the switch bit, tek apart, an look for burning, clean an re assemble it sorted mine oot. https://www.google.com/search?client=firefox-b&q=compressor+problems+and+solutions+pdf&sa=X&ved=2ahUKEwiWy_r-8P_fAhVlTxUIHbrvDBAQ1QIoAHoECAEQAQ&biw=1368&bih=807 M Link to comment Share on other sites More sharing options...
SpitFire6 Posted January 21, 2019 Report Share Posted January 21, 2019 6 minutes ago, GT6M said: it could be the ..run capacitor, bigg roundy white thingy inside where thermal cut oot is. or it could be the thermal cut oot strip, its inside the switch bit, tek apart, an look for burning, clean an re assemble it sorted mine oot. M 9 You da man! Happy to see you. Cheers, Iain. Link to comment Share on other sites More sharing options...
Nick Jones Posted January 22, 2019 Report Share Posted January 22, 2019 Agree on the capacitors. Especially if it used to work and now doesn't as the capacitors age, decrease in value, and may cause motor current to rise as a result. If you are already close to the edge on the breaker, this will tip it over the edge. Equally it is worth checking the various electric connectors along the feed path and seeing if any are getting warm, indicating poor contact and thus volt-drop, which will also cause the current to go up. Nick Link to comment Share on other sites More sharing options...
Colin Lindsay Posted January 22, 2019 Author Report Share Posted January 22, 2019 16 hours ago, Spitfire6 said: Hi, You need somebody to check the startup & running current. Voltage off & on load. With these figures, a competent person will determine if the cable, MCCB, MCCB curve & equipment is OK. Let's not forget the most important check; earthing/grounding. It everything was installed correctly by a competent person and the MCCB/breaker trips; Your compressor is the problem. Resetting an MCCB/breaker more than twice in a year would mean to me there is a problem. A problem you need a competent person to fix. BS7671 is what the competent person should "follow". I'm not competent at anything above 24V! So can't help I'm afraid. A "lighter" oil might help? Cheers & good luck, Iain. I'm not big on electrical terms, Iain , but just to clarify - it's NOT the wall-mounted / garage electrical system that trips, just the cut-out on the compressor. Pushing it back in again starts the motor off again. It has done this in at least three garages / sheds in recent years. I'll post a photo of a similar item that shuts off below; I removed it to check the unit number to possibly obtain a replacement if required. It clicks out so that the white band is visible; if I push it back in, the compressor will run for another short while and build up more pressure. A thinner oil is now on the cards by tomorrow latest. Link to comment Share on other sites More sharing options...
SpitFire6 Posted January 22, 2019 Report Share Posted January 22, 2019 (edited) Hi, Colin, That "breaker" looks to be el-cheapo kak. It probably is worn out after several resets. I would buy a more accurate and reliable overload device. A C or D B or C curve rated MCCB of the appropriate amps would be a good choice. it will have to be smaller than your wall mounted one that should be sized to protect the cable to the compressor. A motor starter like a GV2 would be perfect & expensive. It would provide thermal and magnetic tripping & can be used to start and stop the compressor. That's what I would do. But I would borrow one from work as I would not spend 50 quid on one with an IP rated box! The capacitor if it is only there for running and not a start type, can be checked by a competent person by measuring the three-phase currents going to the motor. I know your supply is single phase, but the cap is there to allow a single phase to run a three-phase motor. Crude but works if you do not have a 3 phase supply as in your case. The capacitor value is chosen to balance the amps under load. A bad or wrong uF cap will show as unbalanced phases. If you give me the nameplate data for the compressor I can find you a suitable MCCB of eBay. Cheers, Iain. Edited January 22, 2019 by Spitfire6 Change curve. Link to comment Share on other sites More sharing options...
SpitFire6 Posted January 22, 2019 Report Share Posted January 22, 2019 Hi, Colin, equipment might be a capacitor start motor. "A good example of Capacitor start is an air compressor motor." The 2Kw single phase hi speed motors (2 poles) motors I have seen take around 13.5 Amps. Your main MCCB should be at least 16A or maybe 20A if cable allows. Replace that excuse for a breaker with something better though. Nice compressor. If I could weld I would make & connect a desiccant dryer so my dew-point was -30c. Alas, I also have no garage. Link to comment Share on other sites More sharing options...
Pete Lewis Posted January 22, 2019 Report Share Posted January 22, 2019 We added a truck air brake drier into my old compressor blows all the moisture out to regenerate the cartridge, every time she blows . Pete Link to comment Share on other sites More sharing options...
GT6M Posted January 26, 2019 Report Share Posted January 26, 2019 All ye lot that got a comp, store this in yer favs folders, its link i was gonna bung up, but was on me other comp, so could,nt its a hive of info, by folk woe ev had problemo,s an backed up by the author / owner oft site About Air Compressors https://www.about-air-compressors.com/troubleshooting-your-compressor.html M 1 Link to comment Share on other sites More sharing options...
poppyman Posted January 26, 2019 Report Share Posted January 26, 2019 On 21/01/2019 at 22:16, Spitfire6 said: You da man! Happy to see you. Cheers, Iain. Ditto Tony. 1 Link to comment Share on other sites More sharing options...
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