Need current start relay for unknown compressor...

[Hopefuldave]

OK, I bought it spares-or-repair for not a lot, expected a few problems and someone had Been In There before me...



New start cap (150 uF, under a fiver), checked everything's free, it sat and grumbled rather than starting, blew the fuse.
(It's a cap-start, induction-run motor, so no run cap.)

It has a (manky-looking open-frame) current start relay (coil in series with the feed to the run winding, closes and connects the start cap when the run winding pulls high current on start-up, opens when the current drops once up to speed - or at least it should), which doesn't work despite having continuity through the coil, good contact continuity when wedged closed - wedging it closed when applying power gives a good solid spin-up, no blown fuses, but I'm damned if I'm going to poke a screwdriver in every time it cycles!

The manky relay below the somewhat charred terminal block (already replaced) BEFORE wiring it correctly...




So... can anyone identify the compressor and point me at a parts supplier, or suggest a source for a *current* start relay for what I guess is a 2 - 3 HP 240v motor? If I can't find one I'll play Instrument Maker and try to dismantle and sort the old one, but it's pressed/staked together and may not survive the operation, doctor.

Thanks for any help,
Dave H. (the other one)

 

[angellonewolf]

i cant realy help as dont know much but have seen on the fourm most people ask

can you remove the belt and see if it runs that way you can see if the motor is running and cheak the oil as in this weather it will be thick and harder for the motor to run

im sure someone will be along soon to add more in

 

[Hopefuldave]

Thanks, I've got it to run fine with and without the belt on, but only by monkeying with the faulty relay (screwdriver* pushing the contacts closed) - if I can't find a replacement I'll try to fix the old one and if not see whether I can find a way to put a modern relay in place?

Cheers,
Dave H. (the other one)

*well-insulated!

 

[dobbslc]

I had a motor like that with a knackered current relay and I couldn't find a spare one anywhere! Flogged it on ebad for spares in the end .

 

[WorkshopChris]

Have a look at page 19 you might find something you can use if you can acuratly measure and match the start current.
http://www.rushind.com/WebBroc2002.pdf
http://www.rushind.com/relys.htm

 

[Hopefuldave]

I made a discovery - got the meter out and I've swapped start and run windings so the relay doesn't get enough current to switch - going to try it the right way round tomorrow...

There's also a well-disguised tension adjuster on the watch-spring that holds the armature back, I'll try adjusting it if it's "close but no cigar".

Thanks for the suggestions!
Dave H. (the other one)

 

[Hopefuldave]

It's alive! Had to adjust the watch-spring a quarter-turn to get the relay to drop out, it starts nicely, relay flicks in and out in about 1/4 second and it runs nice and quiet, build pressure fast and doesn't leak (held 100 psi for a few hours, according to the gauge) - drained a bit less than a pint once there was pressure, nice clean un-rusty water

Bit worried that the pressure switch doesn't work, though (the threaded shaft for spring? adjustment seems to be seized in the brass insert in the pressure-cylinder body, which turns with the shaft...) - got to 150 psi and chickened out and pulled the plug! The unloader works when I manually trip it, is it worth taking the switch apart and seeing if it's mendable, or replace with e.g.

https://www.ebay.co.uk/itm/175PSI-A...944845&hash=item1a30d572ec:g:PBIAAOSw70xZ4JCc

winding it back to e.g. 150 psi (regulator downstream) and a few BSP reducers etc.?

Next: manifoldery, it has a 3/8 BSP reducer in the outlet, a 3/8 ball valve, nowt else to connect the filters/regulators/oiler to - I'm thinking I'll tee off and use Euro connectors for oily air (for tools) and UK for clean air (sprayguns, grit blaster, blowgun, air bearings etc.) - worth pulling the 3/8 BSP reducer and going to 1/2? is copper plumbing pipe and brass fittings OK for air?

Any advice, cautions, criticism, gladly received

Dave H. (the other one)

 

[WorkshopChris]

Does it have Pressure relief valve fitted? Just in case the pressure switch fails.
Sound like it should be a nice little compressor.

 

[Hopefuldave]

yep, there's a relief valve, and the tank (when new, Some Decades Ago) was tested to 275 psi according to the plate - as it's stood for at least 6 months without being drained, doesn't leak at 150 psi and the condensate ran clear, it appears to be pretty sound, and so far it's cost me south of £60 - I think I can justify a new switch/unloader, just unsure how much faffing about to match fittings, may be easier to try to fix the original! I suspect the BSP fittings etc. are going to cost more than I expect, to make the manifold up and connect a couple of regulators, filter/dryers and an oiler (most of which I have already, thanks to Aldi and The World's Best Skip).

Dave H. (the other one)