Swap them round, if the run cap is faulty then what will happen is the motor won't start as the run cap will now be the start cap but if you give it help starting ie start it spinning by hand(obviously watching your fingers) then it will run fine.
- Thread starter gerrymoore
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Swap them round, if the run cap is faulty then what will happen is the motor won't start as the run cap will now be the start cap but if you give it help starting ie start it spinning by hand(obviously watching your fingers) then it will run fine.
gerrymoore
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Sunday is a bad day for messing in the shed (swmbo) so just to answer questions....pump is full of very clean oil. Motor is not laboured when running without the belt...it started running slow and then suddenly went up to full speed. Rev counter shows 2800 - 3000 rpm. Caps are 50uf with 4 connectors and the other is 40uf with just two connectors - not easy to swap them over. Neither of them look particularly new though.
I'm confused in that the pump seems perfect and the motor runs up to full speed unloaded...when belt put back on it's struggling...so is this the sign of a faulty motor.... or a cap that's breaking down??
I'll be back on tomorrow...may take up your offer of a possible cap to swap Norm...
I'm confused in that the pump seems perfect and the motor runs up to full speed unloaded...when belt put back on it's struggling...so is this the sign of a faulty motor.... or a cap that's breaking down??
I'll be back on tomorrow...may take up your offer of a possible cap to swap Norm...
rtbcomp
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The speed of this type of motor is determined by the mains frequency, so with no load it's quite possible for it to run up to speed. However if there's a fault as soon as you put a load on the lack of torque will drag the speed down and lead to overheating.
gerrymoore
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Had another go this morning...managed to get to 30psi !! Motor now starts (without stalling) even at this pressure but it's struggling. I've attached photos of the motor plate which seems to say it uses 40uf and 50uf caps to run. Also posted pics of the caps which have supposedly been replaced but don't look 'new' to me. Have I anything to lose (bar a few quid) in replacing both of them or should I just try a new run cap (which is??).
Just noticed the date on the 40uf cap as 02/11 the compressor is dated 2011 so that is the original...the other one has no date but also seems to be the original cap....
Stop press...I've ordered two new replacements...should be here by Saturday - worth a tenner if it saves me buying a new motor!!
Just noticed the date on the 40uf cap as 02/11 the compressor is dated 2011 so that is the original...the other one has no date but also seems to be the original cap....
Stop press...I've ordered two new replacements...should be here by Saturday - worth a tenner if it saves me buying a new motor!!
gerrymoore
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Been away for a few days. New caps arrived and fitted...it's not the caps
Running the motor without the belt it does get up to 2800 rpm but I can stall it with a piece of wood pressed on the pulley...not easily but I would have thought it should be very hard to stall a 3hp motor!
Loaded, it gets up to around 20psi and then stalls...I can still turn the pump by hand fairly easily so the motor seems to be kaput.
Reading previous posts it doesn't seem to be economical to get the motor rewound...a new one is around the £100 mark.
So, unless anyone can offer any other advice, I'll be ordering a new motor in the new year.
Running the motor without the belt it does get up to 2800 rpm but I can stall it with a piece of wood pressed on the pulley...not easily but I would have thought it should be very hard to stall a 3hp motor!Loaded, it gets up to around 20psi and then stalls...I can still turn the pump by hand fairly easily so the motor seems to be kaput.
Reading previous posts it doesn't seem to be economical to get the motor rewound...a new one is around the £100 mark.
So, unless anyone can offer any other advice, I'll be ordering a new motor in the new year.
carbon
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Worked on one of these wednesday, turned out they were trying to run it from a small generator and motor wouldn’t get it to speed. When connected to the mains supply it ran ok. The original 50uf cap that was in there motor had failed and they had replaced it with a new one, old one had a value of 41uf rather than the 50uf it should have done. Are connections on the pressure switch ok
gerrymoore
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Pressure switch is brand new and connections are tight. It has a 30amp supply and both the caps are new.
I know nothing about these types of motor and can't really understand what's wrong with it as I would have thought if the windings were gone it just wouldn't run??
I know nothing about these types of motor and can't really understand what's wrong with it as I would have thought if the windings were gone it just wouldn't run??
carbon
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Would be interesting to know what current the motors running at. Come across a three phase one last year idle current was 10 amps and max load on data plate was 12.5 amps which only allowed 2.5 amps for the load. Took it to local rewind place for tests spent some time there while they tested it, couldn’t find any real faults with it just that idle current was high. Wasn’t cost effective to rewind it as new motor was cheaper
8ob
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Looks like the same as the one I run, If the motor kicks into life and pumps with no pressure but struggles when up to pressure to restart it could well be a switch/dump valve issue. The pressure switch when up to pressure should be dumping the air in the small black plastic pipe which in turn activates the dump valve and empties all the air in the compressor pipes ( not the main tank), this allows the compressor to restart under no pressure even though the tank keeps the residual set on the differential. If air is constantly bleeding back there is a problem with the dump valve,
Bob
Mine ran with no problem for yonks then decided to throw the head gasket and then a few weeks later the pressure switch also went .
Bob
Mine ran with no problem for yonks then decided to throw the head gasket and then a few weeks later the pressure switch also went .
normspanners
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As a matter of interest gerry can you hear the centrifical switch make a definite click as it slows they usually make an audible click just before it stops say at 300 rpm ?? take the belt off and listen... one thing you could try is to disconnect the start cap when it gets up to reasonable speed and see if that improves it. You may as well try as it would be a spare motor, if it the cent switch, still worth a go.
Standard asynchronous single-phase motors have a low starting torque and therefore can be difficult to start with loads or voltages lower than the nominal one. The use of a centrifugal switch is a good solution to solve this problem. The aim of this switch is the connection of a starting capacitor to the asynchronous single-phase motor in order to get the required starting torque and to disconnect it in the running condition. E.M.G. has single speed asynchronous single-phase motors with centrifugal switch with high reliability and strength. According to EN 60072-1, standardized powers from 0.25kW (0.33HP) 71 MEC size to 2.2kW (3HP) 100 MEC size are available.
this may help https://www.google.co.uk/search?q=t....13413j0j8&sourceid=chrome&ie=UTF-8#kpvalbx=1
Standard asynchronous single-phase motors have a low starting torque and therefore can be difficult to start with loads or voltages lower than the nominal one. The use of a centrifugal switch is a good solution to solve this problem. The aim of this switch is the connection of a starting capacitor to the asynchronous single-phase motor in order to get the required starting torque and to disconnect it in the running condition. E.M.G. has single speed asynchronous single-phase motors with centrifugal switch with high reliability and strength. According to EN 60072-1, standardized powers from 0.25kW (0.33HP) 71 MEC size to 2.2kW (3HP) 100 MEC size are available.
this may help https://www.google.co.uk/search?q=t....13413j0j8&sourceid=chrome&ie=UTF-8#kpvalbx=1
gerrymoore
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HI Norm...I didn't think this motor had a centrifugal switch...no-one has mentioned it..I though it just had start and run caps (which I've replaced). I must say I've not heard any sort of click from the motor......if it does have one is it easy to check?
normspanners
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I have sent a vid in the edit of last post !!
usually if it has a start cap it has a centrifugal switch.
if you do try disconnecting the cap BE CAREFUL THEY BITE !! best run wires out and do it externally with rubber gloves ON...
your pink marigolds will do
!!
I always wear mine when handling dodgy things
usually if it has a start cap it has a centrifugal switch.
if you do try disconnecting the cap BE CAREFUL THEY BITE !! best run wires out and do it externally with rubber gloves ON...
your pink marigolds will do !!I always wear mine when handling dodgy things
Last edited:
gerrymoore
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Hi Norm...took off the back cover of the motor but no sign of any centrifugal switch...only way to get 'inside' the motor is to take the whole thing apart. I'm buying a new motor in January so I'll wait until then and completely strip this motor and have a good look around inside.
normspanners
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Ok sometimes they are behind the fan in a cover there, but you could still do the cap disconnect test, just run a pair of wires out from one connector on one side of the start cap to some form of connector or a switch, then start the motor let it run for half a second then disconnect the wires or switch the switch off that should do the same job as the motors switch, and see if the motor sounds better.
normspanners
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post 16 start caps are only in circuit for less than 1-2 sec and have total rated, in circuit time of poss 5secs max, so it if the cent switch is TU, so NOW also could be the new start cap !! and the new replacement !!
more info save me typin http://www.capacitorformotor.com/starting_capacitor.html
carbon
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What is surprising to me is that the start cap has a lower value that the run cap as most of the two cap motors I see have a start cap that has a value of at least 200uf. As it’s also the same as the one I looked at last week and the 40uf cap is shown on the motor plate I don’t see that the caps are the issue.
