Compressor warning

[JonL]

I managed to procure an old 200l compressor for my workshop, and have plumbed it to the benches in a pretty leak free manner (I've been around with soapy water and can't find any anyway!). When I use it it will pump up to pressure, then stay pressurised when not in use for a very long time indeed.

The downside of this is that when it does kick it, its usually during a fiddly bit of machining, or when I'm peering intently at something delicate, and sooner or later I'm going to need to change my underwear; It makes me jump like crazy. I've tried cladding the machine in soundproofing (with good airflow around it and easily accessed for maintenance), it isn't very loud in use but after 30 minutes of silence the sound of it starting up is apocalyptic in a small space and I don't have room to box it up outside.

I was thinking about fitting a warning buzzer or similar connected to a delay, so instead of just bursting into life when the low pressure is reached it would warn me that its about to start. Even a half second beep or flashing lamp would take the terror out of it a little!

Does anyone have any suggestions on a small 240V ac switch unit that provides a small delay before outputting 240v? I figure if I wire a warning buzzer or lamp into the motor supply feed (after the low pressure switch) but put a short delay in the wiring between the feed and the motor itself it would keep things simple, but I don't know of any small commercially available 240v unit that would enable me to do that, especially with the current draw this motor has. It's a 1500W motor.

To be clear all I'm really looking for is an item (relay or similar) that upon being supplied with 240v waits a second or so before making its output live.

Sorry to ramble, not expressing myself very well today, it's monday!

[JonL]

I may have answered my own question: it would appear a Delay On timer, such as this may be what I need. My only concern is that 8A may be a bit borderline for a 1500w AC motor, but I'll have to check. 

[92220]

You are right. 8 amps is a bit dodgy. While it will handle the running current, it won't handle the starting current which, depending on the load and motor, could reach double the running current. Be careful trying to soundproof the compressor. If you do that you are restricting the air into the soundproofed enclosure and the compressor will be trying to pull a vacuum. It won't, but you will be restricting the air inlet and it could get overheated quite quickly. How much depends on the CFM rating. I was concerned about noise when I bought my compressor so I paid a bit extra and bought a secondhand Hydrovane compressor. They are very quiet.

Bob.

[jackrae]

Or build a small 'lean-to' outside to house the compressor.

[JonL]

Jackrae, as mentioned above there isn't the space outside for a compressor sadly. I measured the current draw and it was peaking at around 10A. Different plan required I think.

Or I could just over my jumpiness!

[RGR 60130]

Why not just leave it switched off until you require it, drain off the water from the bottle then switch it on?

Reg

[Doug]

Dec 17, 2018 14:04:36 GMT JonL said:

I may have answered my own question: it would appear a Delay On timer, such as this may be what I need. My only concern is that 8A may be a bit borderline for a 1500w AC motor, but I'll have to check. 

Just an idea why not use a pressure switch it can be set a little lower than the compressor one so it flashes a led or similar to let you know it will kick in? That way you don’t need to worry about the load and it can be completely isolated from your compressor

[JonL]

Reg, I only turn it on when I use it, but I may be in the workshop for a few hours doing a few different tasks. Normally it's not turned on unless in use.

Dug, thats a grand idea, and more cost effective than the ideas I had, thank you.

[coniston]

Hi, if you use a pressure switch it will need to activate on pressure fall as that is the situation which brings the compressor motor into play. It will need to be set at a higher pressure than the motor cut in pressure. You will need one that closes on pressure drop, and has a hysteresis low enough to open again before the compressor builds pressure to cut off point, otherwise the warning lamp will continue to be illuminated. Alternatively one that closes on pressure rise, opening on fall could be used but a change over relay will need to be in circuit as well (or alternative).

I the existing pressure switch (controlling the motor on/off) actually switch the motor power? or does it switch a motor contactor? if the latter then it shouldn't be expensive to get a delay on relay as you originally thought to interrupt the control feed from pressure switch to motor contactor at the same time illuminating the warning lamp. Just a thought.

Chris D

[JonL]

Thats a good point, I'll investigate.

[jon38r80]

I have my comnpressor plugged in via a socket which is operated by a remote wireless swittch commonly available all over the place, bought mine from CPC because of the good perice not the make. Can turn it on and off from anywhere in the workshop and even outside which isusefull as the compressor is buried under a pile of stuff. Just turn it off when up to pressure.

[chrisb]

You could always use the delay on relay as a pilot relay to operate one that is "man enough for the job"