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Compressor unloader valve help

Xenocide

Well-known member
Joined
May 11, 2010
Messages
61
Location
Wiltshire, UK
Hi everyone.

I've got a compressor which looks decidedly homemade. When the motor starts after the vessel is up to pressure, it stalls and doesn't start.

I have a condor MDR5 switch on it with an EV 5i unloader valve. However it doesn't seem to actually work. I've taken the line out which attaches the unloader to the charge line to the vessel and i can't hear any leaking air so I think the one way valve is ok.

My unloader valve is the EV 5i (page 28 or 3.29 depending which one you look at) here: http://www.fusheng.com.au/download/Condor_Pressure_Switches.pdf which has two ports. One of them is the line from the pump/vessel, the other is blocked off. There's a shaft which goes up into the switch. The valve is held into the switch with a grub screw.

My question is: why isn't it working? :p

The shaft is free to move and it rests on a bar which moves when the switch moves. I assume the air pressure from the line will lift this shaft and the insides of the switch move up allowing the air to slip past the shaft.

Where's the air supposed to vent to? Does having one of the ports affect this? I'm sure i've tried it with it unblocked with no difference.

I'm not really sure what to try next!

Something else to add: The motor is 3phase and it used to have an old vfd which sent it's power through the switch. I've fitted a new vfd which just uses the switch as a 12v start/stop switch - no actual power is transmitted through it. I assume this won't make any difference but thought i'd mention it.
 
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Xenocide

Well-known member
Joined
May 11, 2010
Messages
61
Location
Wiltshire, UK
FYI I've fixed this now. I took the valve out of the body and disassembled it. One of the rubber seals inside was in sideways so the shaft couldn't move unseal. Also this particular valve purges through one of the ports on the side and the input is the other port so having one blocked was 0 help. Thanks previous owner!

Worth mentioning that the shaft should be sprung loaded with, which it wasn't before.
 
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mr-compressor

Member
Joined
Aug 8, 2012
Messages
13
Good to hear it is fixed.

Malfunctioning unloader valves are one of the most common problems with reciprocating air compressors!
 
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