Alec Pringle Posted March 1, 2016 Report Share Posted March 1, 2016 Most 3hp motors will require their own supply via a switched, fused isolator . . . . . the start-up demand is greater than can be safely handled by a 13amp fused socket or a 30 amp ring main. Cheers Alec Quote Link to post Share on other sites
Eddie Cairns Posted March 1, 2016 Report Share Posted March 1, 2016 Last year I replaced my old compressor with a Clarke SE18C200ND Runs 18CUFM has a 200 ltr. tank and a 4hp motor. Possibly a bit expensive and generally overkill. Even with "soft start" switch gear I always know if I have left it on a night as all the lights in the house dim when it starts! Bought it mainly to run an industrial size blast cabinet but remember a DA air sander uses loads of air. If you are using a DA sander why not think about a smaller compressor and an electric DA. Never runs out of air so no stop/starts. Steve Steve the problem you have is that compressor is an industrial compressor designed to run for long periods. The motor is again made to last for a long time and it likes it power. If you had bought the home unit it would have a softer start motor but would not last as long. Yours will last longer but soon tells you that your overal electricity supply is on the weak side. It realy is at the limit of your home electrical supply as these motors have a power factor that really means they are more like a 4.5kw load as the voltage and the amperage is out of phase and house supplies are not designed for that. The manual for the compressor does suggest a 40 amp supply and it may well be that your own house and any others connected to the grid are on a joint supply that is a bit below par but Ok for normal home use. Quote Link to post Share on other sites
Eddie Cairns Posted March 1, 2016 Report Share Posted March 1, 2016 (edited) Hi Darren, ignoring how your motor starts the nominal current requirement is apprx 9amps (1HP - 740 watts = apprx 3 amps). So with a normal domestic 3 pin plug and a 13 amp fuse you should be OK. Roger Sorry Roger as the motor causes out of phase conditions on the electrical supply it would be much nearer 12 amps running which is too much for a 13 amp supply. If you decide not to bother with the starting current then(head in sand) probably nearer 15 to 25 amps to start the unit. You may just get away with the fuse not blowing but there will be sparking in the electic motor as it stalls for longer than it should before starting due to excessive voltage drop at the motor end of the supply cable that will do nothing for the motor life span. Edited March 1, 2016 by Eddie Cairns Quote Link to post Share on other sites
Stevecross Posted March 1, 2016 Report Share Posted March 1, 2016 Eddie Tell me about it! I am fortunate to live in a lovely area of the countryside but at the end of my local grid. My max supply in is 80amps. I can get away with what I use during the day but at night I start to annoy my neighbours. A few years ago I thought my best course of action was to do the noisy cutting, grinding etc. during the day and my welding at night. Soon realised that my welding was interrupting my neighbours enjoyment of evening TV. They got to count every weld I made by flickering lights & TV reception all through the village. Even without that lights dim when I turn the kettle on! I also have a 4 post lift that the neighbours also know I am using in the evening so tend not to lift cars up at night! Trouble is, we all use so much more power than we did years ago. I have a fairly large house and just counted up that in lighting alone if I have the wall lights on in the lounge & hallway and half the down lighters on in the kitchen there are 40 50w bulbs running that's without all the other stuff. Problem is, as soon as the neighbours in the village get home they are using the energy I need for welding. Wish everyone could get their priorities right. Know the issues but want my toys! Steve Quote Link to post Share on other sites
littlejim Posted March 2, 2016 Report Share Posted March 2, 2016 I went for the largest compressor which would run on single phase 240V. Plenty of pauses during the grit blasting. For painting I eventually found a gun that was specially tuned for low air consumption, few pauses there too. The welder I bought was made to handle higher current inputs, but for the welding on the 4A didn't have to go above what my fuse (circuit breaker) box could cope with. Quote Link to post Share on other sites
DaveN Posted March 2, 2016 Report Share Posted March 2, 2016 I bought a 250 litre 150 psi compressor at a farm auction it cost the grand total of 15 quid. If I'm honest it is a bit noisy and I was thinking of leaving it outside in its own little shed. It runs everything I use. (currently got a dashboard under vacuum renewing the veneer! Quote Link to post Share on other sites
Drewmotty Posted March 2, 2016 Report Share Posted March 2, 2016 You can get around the 13A socket power limit by using a single reservoir with two pumps mounted on it. Quote Link to post Share on other sites
stillp Posted March 2, 2016 Report Share Posted March 2, 2016 if I have the wall lights on in the lounge & hallway and half the down lighters on in the kitchen there are 40 50w bulbs running that's without all the other stuff. Steve, you need to replace all those with LEDs! Pete Quote Link to post Share on other sites
RogerH Posted March 2, 2016 Report Share Posted March 2, 2016 Hi Paul/Ed, I've edited my post after looking at the spec on my 2HP compressor. Roger Quote Link to post Share on other sites
TR5tar Posted March 2, 2016 Report Share Posted March 2, 2016 OK, from what I understand, it seems that at best I might get away with it not blowing fuses all the time (apparently it comes with a 16amp plug), but from what Eddie, Paul, Alec, and Steve say it's risky and I'll soon bu**er the motor. So, I guess if I go ahead I need to get an electrician in, right? What do I need to ask the electrician to do? Cheers, Darren Quote Link to post Share on other sites
Lebro Posted March 2, 2016 Report Share Posted March 2, 2016 FWIW My Sealy 3H/P compressor states "15Amp supply required" The feed to my garage is 13A armoured cable (yes I know, but it's buried under lots on concrete now) I connect the compressor direct to the incoming cable's junction box, via a 15A trip. No 13 A plug or socket used. Been this way for 10+ years, & compressor is always on (uses pressure switch to run when needed) Only problems I have had is a gasket blowing between the air in, & air out section in the cylinder head. (Its a parallel twin type pump) Bob. Quote Link to post Share on other sites
Paul Down Posted March 2, 2016 Report Share Posted March 2, 2016 A compressor motor starting does not have a significant initial load to overcome unlike a 4 post lift so as Bob says you may well get away with running from a 13A circuit. But strictly as Alec states it should have a separate 30 or 40Amp circuit with a starter /isolator and overcurrent trip. Quote Link to post Share on other sites
stillp Posted March 2, 2016 Report Share Posted March 2, 2016 A compressor motor starting does not have a significant initial load to overcome What about when restarting against stored pressure? Large professional compressors have decompression valves that operate during restarting, smaller ones don't. Pete Quote Link to post Share on other sites
Lebro Posted March 2, 2016 Report Share Posted March 2, 2016 (edited) I don't know whether you would call mine "Professional" but after every charge, it dumps all the air between between the pump, & the tank (which has a non-return valve in the inlet), so on re-start the initial back pressure is zero. Bob. Edited March 2, 2016 by Lebro Quote Link to post Share on other sites
stillp Posted March 2, 2016 Report Share Posted March 2, 2016 (edited) Yes Bob, that's the sort of thing I meant. Mine (cheapo DIY) doesn't. Pete Edited March 2, 2016 by stillp Quote Link to post Share on other sites
RogerH Posted March 2, 2016 Report Share Posted March 2, 2016 Hi Darren, having re-evaluated my compressor (I thought it was a 5HP motor - don;t know where that number came from) My 2HP motor with 100ltr tank works very well and runs off the standard mains plug. https://www.machinemart.co.uk/p/clarke-racer-9100p-2hp-100-litre-belt-driven/ Roger Quote Link to post Share on other sites
SeanF Posted March 2, 2016 Report Share Posted March 2, 2016 Roger, Does your 2Hp machine handle your painting exploits (in your shed) well enough? What size storage tank does it have? I have bought a 3hp 50L Clarke machine https://www.machinemart.co.uk/p/clarke-raider-15500-3hp-50-litre-air-compress/ which in theory puts out 14.5cfm but have not used it in anger yet. I am hoping to spray paint the car using it but must admit to having more and more doubts - not to mention confusion - the more I read. Many thanks, Sean Quote Link to post Share on other sites
RogerH Posted March 2, 2016 Report Share Posted March 2, 2016 Hi Sean, when I bought my compressor back in the 90's it was basically for tools rather than painting. It has worked well very well over the years. It is not used continuously and so can keep pace with my DIY work. My painting consists of doing individual panels one at a time. I only charge the 100ltr tank to 80 psi and do my panel with that charge. It appears to work for me although a professional would probably have kittens. It has a regulator that could be set to 55psi and allow the pump to come into play. Roger Quote Link to post Share on other sites
Alan Cochrane Posted March 2, 2016 Report Share Posted March 2, 2016 (edited) Hi Everyone I also have a 4-post lift which required the breaker in the house consumer unit to be changed from a standard B class to a C class. This is designed for higher starting loads and since then I've had no problems.This might be something to consider if you're having problems with the supply tripping on start-up. It's a legitimate fix by the way and not a bodge that will end up burning everything down. I'm lucky that when I rewired the house I put in a dedicated 6mm twin and earth cable to the garage. This is good for at least 40A. Another thing to consider is making your garage sockets into a ring similar to the house wiring. This will increase the load capacity to 30A, but only if the incoming cable can cope as well. I bought a Cobra air compressor off fleabay and it's been fine. Although it's only limited to supplying my blast cabinet and spray gun so far. Cheers Alan Edited March 2, 2016 by Alan Cochrane Quote Link to post Share on other sites
Nigel A Posted March 2, 2016 Report Share Posted March 2, 2016 When I moved in I wired in a separate 30 amp supply to the garage from the consumer unit I have often operated the MIG and compressor at the same time with no problems. I also have an old worn out compressor that I can connect to the working one and effectively double the tank capacity. Cheers Nigel Quote Link to post Share on other sites
Lebro Posted March 2, 2016 Report Share Posted March 2, 2016 Hi Darren, having re-evaluated my compressor (I thought it was a 5HP motor - don;t know where that number came from) My 2HP motor with 100ltr tank works very well and runs off the standard mains plug. https://www.machinemart.co.uk/p/clarke-racer-9100p-2hp-100-litre-belt-driven/ Roger That looks like the same pump as on mine, only mine is 3H/P. Hi Sean, when I bought my compressor back in the 90's it was basically for tools rather than painting. It has worked well very well over the years. It is not used continuously and so can keep pace with my DIY work. My painting consists of doing individual panels one at a time. I only charge the 100ltr tank to 80 psi and do my panel with that charge. It appears to work for me although a professional would probably have kittens. It has a regulator that could be set to 55psi and allow the pump to come into play. Roger Roger. Why don't you charge the tank right up, then use a regulator to get your 80PSI, that way you will get a bit more time for spraying before you run out of regulation. Bob. Quote Link to post Share on other sites
RogerH Posted March 3, 2016 Report Share Posted March 3, 2016 Hi Bob, I had considered that but I don't do a lot of low pressure work so am happy to bu99er about. Roger Quote Link to post Share on other sites
littlejim Posted March 3, 2016 Report Share Posted March 3, 2016 My compressor has the following specs: Free air delivery 7.24 cu ft/min 2.2 HP tank 58L It works OK on a single phase 240v 10 amp socket. For the painting I tried to find a gun that used the least amount of air; ended up with the Asturo K1/s, that operates at 57psi. Quote Link to post Share on other sites
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