- Thread starter gasket999
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the snooper
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yes exactly that and the fact you have a 3 phase switch on the compressor already means you can switch both motors and just as if you had 2 compressors just plug both motors into separate sockets
Wendelspanswick
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Ideally have each socket on a separate MCB.
gasket999
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That wouldn't be a problem at all.
The two questions I can't get my head around are these:
The two questions I can't get my head around are these:
- If the motors are started at different times - whether momentarily or a few seconds apart, one of the motors would act as an idler and would be unpowered. Would this cause any damage to either motor?
- In order to keep the pressure switch simple I'd want to switch both motors on and off in line with the pressure in the tank. Would these need to be sequential or could I simply wire the two motors and the pressure switch in series? If wiring in series then would both come on at the same time, creating a heavy start-up load?
the snooper
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you have a three phase switch which will switch motors at exactly the same time and if there was any difference it would be so slight I doubt it would be noticeable
the three phase switch is capable of doing everything you need
you would wire the motors totally separate but the live from each motor would go into the pressure switch which has 3 separate switches in it
the three phase switch is capable of doing everything you need
you would wire the motors totally separate but the live from each motor would go into the pressure switch which has 3 separate switches in it
gasket999
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Ah - thank you very much indeed for your patience. I was a little confused about this earlier. This has been incredibly helpful.
So, just to make sure I've understood it properly (and to help others thinking about the same thing):
Something like this?:
So, just to make sure I've understood it properly (and to help others thinking about the same thing):
- due to the nature of a three phase switch, by using it on a single phase circuit, I could use two of the three inputs/outputs in order to provide two independent power supplies to the two motors, with one input/output unused. However the manual on/off and the pressure on/off switches would control both motors simultaneously - regardless of the fact that they have power supplied from two different MCBs.
- I assume that the 3-phase switch is more than man enough to control the start-up draw of two or three 1-ph 3hp motors.
- Both motors will start and turn off simultaneously using the button on the top of the pressure switch/gauge
- Both motors will start and turn off simultaneously when the pressure switch/gauge detects the pressure in the tank has reached lower/upper levels.
- If the fuse on one motor blows, then the other would keep running but the compressor's performance would drop.
- I would not need to change the pressure switch.
- I would not need to change the pressure gauge.
- I would not need to change the drain/outputs/etc.
- my 3-phase compressor (already got)
- a pair of 3hp motors (which I already have access to - though I might try to get a matching pair)
- The wiring in my garage to be completed, with two 40 amp MCBs dedicated to the compressor (in progress anyway)
- Some wiring to connect the new motors to a plug apiece - run via the single pressure switch.
Something like this?:
the snooper
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looks good to me, in your three phase switch you will have 3 lots of load and supply and as you correctly wrote you will use 2 of the 3 for the live supply to each motor, nothing to be changed apart from the obvious, motors
gasket999
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Fantastic!!!!!
Right - I'll get on with making up the second motor mount and gathering the motors I need. Might take a few weeks but I'll report back with pictures.
I've updated my little diagram to show a pair of plugs for each of the motors (rather than it seeing to be wired straight into the consumer unit) to make it clearer for anyone else who's interested in following this thread.
Right - I'll get on with making up the second motor mount and gathering the motors I need. Might take a few weeks but I'll report back with pictures.
I've updated my little diagram to show a pair of plugs for each of the motors (rather than it seeing to be wired straight into the consumer unit) to make it clearer for anyone else who's interested in following this thread.
the snooper
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good luck with it
gasket999
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Will do thank you. I'm away at the minute so won't get to inspect the compressor for 2 weeks, but will remove the housing and look for any numbers and/or contact the manufacturer.
I haven't seen them yet I'm afraid. but almost certainly no - I know the one from my Dad is quite old. Is having the resettable overload important in this application or would the MCB serve a similar purpose?
the snooper
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Make sure they rotate at the same speed and same size pulleys as well
Wendelspanswick
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Your 3 HP motors are I guess about 2.5kw each so 40amp MCB's are overkill, 20amps should suffice.
2500w / 230v = 10.8 amps
Allowing for inrush current 20amps should be fine.
