Recommissioning an old Compair Hydrovane air compressor

I've got this unit up and running, it fills my receiver up to the pressure I've adjusted the pressure switch to but the motor continues to run (while not increasing pressure further, which is good!) but I would like the motor to turn off when the max pressure is reached. Its a series 8 hydrovane, probably model 148puas, but the serial/model tag is unreadable and the schematic isnt either. If anyone can direct me on proper operation that would be great. Haven't got a call back yet from messages left with a few service places. There is a drain timer relay DT #6 which from what I can see drains the aftercooler (but after it turned on to open the first time it has not shut off), and a run on time relay IT, #5, and a control relay #4 (in addition to the main contactor) inside and a start switch and a manual/auto switch on the control panel. Haven't tried manual yet as I don't know if that will override the set pressure switch. Anyone have an operations or installation manual for one of these or know how to get the motor to turn off at the pressure limit? Next step is to try manual mode but I'll need to change some plumbing around so as not to risk overpressurizing anything if that bypasses the pressure switch or something, maybe I can avoid the hassle if I can find an installation manual. This is pre 1993 so there are no electronics, just the relays described above. The other solenoid valve I can see other than the drain valve is in some lines to stuff under the air filter that probably unloads as I can hear the compressor end cycling on and off when it reaches set pressure. I'm assuming the drain stays open at that point so as not to continue cycling hot air while not pushing air out to the receiver.

What pressure can you develop?

Have you bench checked the pressure switch for on/off with a pressure source other than the compressor your working on?

Found a few examples of that style on Y o u tube

The machine responds to adjustment of the pressure switch by going in to {motor running but not generating pressure mode} at whatever pressure the switch is adjusted to. it is an allen bradley 836-c7. I have been adjusting the screw with the lettered legend, I have not adjusted the "diff" screw which looks like adjusts the pressure differential between the hi (pressure not being generated but motor still running, adjusted by the screw with the letters) and low (on) pressure being generated, motor still running
https://literature.rockwellautomation.com/idc/groups/literature/documents/td/836-td001_-en-p.pdf

Besides the ground, just 2 wires going to the switch in the pic?

No great mystery about it. Hydrovanes of that era with simple relay controls came configured as standard to either run all the time, usually feeding the attached airlines directly, or in the more usual automatic stop start mode with a reservoir tank and pressure switch.

Yours appears to currently be in continuous run mode with the dump valve opening at regulated pressure to cover temporary air oversupply.

There should be a switch to select the operating mode.

I have an operators manual for the 3 series dated 1986 which almost certainly has the same basic controls.

Book shows an air pressure gauge, hours counter, emergency stop button, rotary control switch and an illuminated start button on the panel.

Book says:-

The control switch has three positions marked 0, 1 and ll.

Position 0 is stop, Position 1 is continuous run, Position ll is automatic stop start running.

To start select operating mode ( Position 1 or ll) and press start button.

For routine stopping turn the control switch back to position 0.

The emergency stop button is for emergencies only, do not use for routine stopping.

The automatic run on time should be set to suit the air system requirements. 30 seconds delay between starts must be regaurded as the minimum setting. If the compressor cycles more than once a minute continuous running will be more economical.

Assuming the wiring hasn't been altered or the switch bypassed its possible that the run on timer is broken or has been twiddled to give a pseudo continuous run when the switch is set to automatic.

In general a Hydrovane runs on for a few seconds after the tank pressure valve has opened to clear the lines. Ones of the same or later vintage than my 502 have a solenoid valve to temporarily open the output line so the comporessor runs up off load. Don't think yours has that.

If need be I can scan the relevant pages and circuit diagrams.

Clive

MJK: I'll need to take another look to see if there are more wires than expected going to that pressure switch...
Clive: Thanks for the info. this one just has a 2 position switch with auto and manual position, a separate stop button, and a stop/reset, which is probably equivalent to your estop. There are two separate timers in the cabinet, one for drain and the other must be for the run on timer for when set to auto (start/stop running) I'll play with the timers as what you say makes sense about the unit having been either set to run for longer than we have tested it for (so it wouldn't have ever timed out & turned off) or the timer is just set permanently on. I'm thinking the feature yours has opening the line to clear is the function of the drain timer & solenoid on mine. If you could scan what you have that would be great.
thanks to all!
tom

Tom

Scanned the English section of the Hydrovane 3 series handbook for you. Send me a PM with your E-Mail and I'll shoot it over tomorrow.

Not a lot of information there but it does have circuit diagrams.

Sounds like yours is another case of "same but different". But having proper stop and sort buttons rather than relying on the rotary switch sounds much safer.

Interestingly I have an old Hydrovane relay type control box obtained from "somewhere" that has a table with instructions for using the rotary switch on the front but no switch, just the remains of two illuminated push buttons on the front and an emergency stop on the top. Actual buttons are long gone and I've never bothered to trace the wires but look to be just stop / start pair. Presumably hard wired to run in one mode or the other. Outside the box cabling is long gone so no help there.

Clive

PS Just found a downloadable copy of the Series 8 manual on Scribd. Control circuits look to be different to yours, more like the 3 series, but it may be useful. Manual Hydrovane 837 PUAS | Nature .