Adding a Pressure switch to a compressor

[pauloliver]

I acquired a compressor with a duff motor last year and have only just had a chance to take a peek at it. After replacing the motor with a spare it pumps a treat but there is a important component missing... the pressure switch! I have whacked on a regulator and it all works fine but I daren't leave it on too long for fear of ending up in pieces.

I'm not sure how it has been used without one, and to be honest I'm not entirely sure how to plumb one in as I'm not sure where I can tsp into so I was hoping you guys could point me in the right direction. The make is C&H who haven't existed for about 30 years it seems however I'm fairly confident something can be retrofitted. I'm not 100% sure of my terminology and what I need so if people could correct me or advise as to what i should be fitting/replacing that would be great.



At the back on the side is this which I'm assuming is a massive drain plug




At the back on the top, tank pressure gauge left, some sort of pressure valve (spring loaded inside) in the middle with a handle welded to it for a reason i'm not entirely sure of, and another pressure valve on the right



At the front on the bottom there is a drain tap that I don't understand how I'm supposed to operate



And at the front side is another drain area with a tap, from what I have gathered this may have been for a certain type of air tool to connect to?



I have been looking at pressure switches online and I'm not sure what is suitable, there seems to be generic cheap ones that vary from £6 to £30 yet seem to be the same unit, I also think I should replace the pressure release valve/s for peace of mind but I'm not sure how many bar they should be rated at?

Any help would be great, it would be nice to get the old thing running safely

[gtviva]

a pressure switch can be fitted anywhere on the tank but some compressors need an unloading type switch so the machine is not trying to start the compressor with pressure in the head, I think that's what the small pipe is coming off that valve with the T handle so the new switch could replace that T handle valve with a new unloading type pressure switch to control the motor, the other little valve next to it is the over pressure relief valve so I would check the rating plate on the tank to see what its maximum working pressure is and fit a new valve with a lower rating, the big valve on the side is just a quick connector for big flexible pipes but I would remove that and fit a modern small quick release type fitting, the drain cock on the bottom looks like its lost its handle but just looks like a quarter turn type thing, again easy enough to replace for something newer and you will need to use it as its surprising how much water you will get in the bottom of the tank

[comfortablynumb]

I'm no expert but isn't that fitting to the right in pic 3 the pressure release valve? The one with the holes in it?
I'd strip and clean that TBH

[Tepper]

You may find that this compressor wasn't designed to run a pressure switch at all - I use an even older compressor that has a similar valve with welded T handle on it. On this one, as it is on yours, there is a pipe running from this valve to the cylinder head of the compressor. What this does is operate some kind of decompression mechanism, I believe by cracking one or both of the valves open, thus preventing the compressor from, well, compressing. The motor is designed to run all the time the compressor is switched on. If this isn't working, you're best off blanking the pipe after the valve on the tank (I think) then just fitting a modern pressure switch to control the motor, which is what we'll be doing with ours soon.