 | Home > Technical > The electrics of a T-Max compressor |
 
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| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971   
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Just in case anyone was curious, like I was, what was inside the little electric box on a T-Max compressor, here is the answer:
 Click image to enlarge The +ve feed comes in, through a 45A thermal overload and to one pole of a 60A changeover relay. A tiddly wire is taken from that terminal to the switch (rated at 15, 16 or 30A at 250V depending on which number you read, usually that's inductive/resistive but it just says 15, 30A: 250V. 16A: 250V) and then to the relay coil. Meanwhile, the -ve feed comes in, goes through a wire nut (eugh) and then disappears in the the bowels of the compressor. Another tiddly wire comes back from the bowels and to the other side of the relay coil. The output of the relay is in a red cable that also disappears. When you switch the switch, the relay energises, switches the power on to the compressors and brzzzzzzzt it goes. Why do I care? Basically, if you want an on board air setup you need to turn the compressor off and on. As the maximum current draw of the compressor is 45A, that's a big ask for a switch and most relays aren't rated at that either. Because this already has a build in relay, to control the compressor all you need to do is run some light cable to a suitable control device (I'll eventually be using a pressure switch) and bob's your uncle. If you are remote switching, it's really important that the little cable is fused right be the compressor. The reason being that even if the compressor is fused at, say, 50A then the little cable will only be protected by that fuse, and it's not up to that sort of fault current. Eventually I'll have this wired in permanently by my battery (there is space), but that will probably be months away 
Edit: Another interesting thing to note is that all the quick disconnects on the air side are on backwards. Normally with an airline, the port is live all the time and under pressure which is contained by a little valve in the connector. When you plug something in to it, the valve is pushed open and air flows (or at least until the next valve). What that means is that when you're done with the windy gun and want to put the inflator on, all you need do is unplug it and the airline won't go whizzing around everywhere. With it this way round, air will always come out of the end. I guess they've done it as there isn't a pressure switch on the compressor so you'd end up pumping against the pressure relief valve all the time. Last edited by Cupboard on 15th Nov 2015 7:44pm. Edited 1 time in total |
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14th Nov 2015 4:25pm |
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| apt100 Member Since: 05 Mar 2015 Location: Derbyshire Posts: 1547 
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An interesting post that could come in useful sometime
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14th Nov 2015 8:29pm |
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| Alien Member Since: 18 Jan 2015 Location: Bacchus Marsh Posts: 230 
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Don't forget you will still need to get big amps to the compressor side of the inbuilt relay.
We don't want people miss reading the post and thinking small wiring is all that is required. The small fussed wire is effectively moving the switch to energize the fitted relay and is a smart way of doing things. I like the idea of what you are doing particularly if mounting it in with the battery. A short heavy wire to the relay will save on voltage drop and make the job simpler. Be aware of air flow though to cool the compressor, mines in the seat box and has cut out on the thermal switch. I would think in a closed battery box it may be a issue on warmer days. I toyed up with mounting my compressor under the bonnet and using a wire from the starter feed to power the relay. I could not find somewhere I was comfortable with to mount the compressor though. Had a few spots but nothing solid to allow for the shake factor when doing our corrugated outback roads. Cheers, Kyle. |
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14th Nov 2015 10:10pm |
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| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971
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Yes, sorry.
Use the already provided cables to go to the battery (preferable with a big fuse but TBH it's all in the same area and it's pretty low risk), then for control and control only you can use light duty cabling, because all you're doing is switching a relay. |
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15th Nov 2015 7:45pm |
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| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971
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I didn't think I'd be able to fit it under the driver's seat because it looked too tall?
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16th Nov 2015 10:00pm |
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| jst Member Since: 14 Jan 2008 Location: Taunton Posts: 8026  
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i took the handle off it Cheers
James 110 2012 XS Utility 130 2011 M57 bespoke Camper 90 2010 Hardtop 90 M57 1988 Hardtop |
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17th Nov 2015 4:03pm |
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| Cupboard Member Since: 21 Mar 2014 Location: Suffolk Posts: 2971
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That's given me an idea actually, I've been thinking about what to use as a receiver and it occurs to me a bit of box section with some plates welded on the end might work well. |
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17th Nov 2015 6:25pm |
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| jst Member Since: 14 Jan 2008 Location: Taunton Posts: 8026
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i used an audo all road air suspension tank initially, cheap on ebay. Cheers
James 110 2012 XS Utility 130 2011 M57 bespoke Camper 90 2010 Hardtop 90 M57 1988 Hardtop |
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17th Nov 2015 8:43pm |
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