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domwild
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Joined: 16/12/2005
Location: Australia
Posts: 873

Posted: 01:34pm 10 Apr 2016

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Hi,

My Indian pump lists its running Amps at 12.5, but it has an Aussie 10A plug - illegal! But I have a 15A supply with a 20A fuse, is that correct? The next size is probably 30A, which must be too high.

No panic, a licensed electrician will give me a correct supply and will have to cut the supplied illegal cord.

Am driving it from a 10A-rated timer by feeding a USB mobile charger, that output is fed into a 45A (big!) SSR, which then feeds the illegal 10A pump supply, where the socket/plug combination of the extension lead gets warm, I wonder why?

Thanks.

While on this pump topic, has anyone here tried using the cheaper DWV pipes in a lawn irrigation system without them blowing, as they are not pressure rated?

Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up.

Winston Churchill

jeffj
Regular Member

Joined: 04/02/2012
Location: Australia
Posts: 84

Posted: 12:17am 15 Apr 2016

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Just got out my 1986 As3000 wiring rules!
I am assuming you have a single phase motor ? This a big motor for single phase.
4.15.6.1 states that motors over 2.25kw require overload protection ie an overload relay
The reason for this is that a fuse 4*FLC (fulload current )is required for starting current considerations.
If the 15a switch complies with the relevant standard it is ok for 50A fuse
You will need to fit an HRC (high rupture) fuse to take care of short circuit let through current.
You may get away with a 30 amp fuse if you close off the water flow on start up.
This may sound odd (and I assume you are using a centrifugal pump) Put simply you are only accelerating a pump full of water and not the whole pipeline.
If you have trouble starting it, you need a soft starter which will work ok on a centrifugal pump.
To size the fuse you have to calculate the I^2*time and look at curves for the fuse
Assume 6*FLC and say 3 secs and keep below the curve. I have lost mine
good luck Jeff

domwild
Guru

Joined: 16/12/2005
Location: Australia
Posts: 873

Posted: 01:15pm 16 Apr 2016

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Hi Jeff,

Thanks for that. The pump claims to be 2HP single phase. If I remember my figures correctly, that is 2 x 760 or so Watts or 1.5 kW, so below that magic figure of 2.25 kW.

Yes, I have played around with a soft starter and I also am considering a delay circuit to switch the pump on and then open the solenoid, which stops the tank from emptying.

On the other hand, my son has just told me how to get rid of the failure point and restriction of a 1 1/2" solenoid by looping two pipes above the top level of the tank and adding a vacuum breaker to stop the tank from emptying. Ugly. What I need to know from this forum is if the cheaper 2" DVW pipes I have are strong enough for an irrigation system or will they blow?

The relay at the moment is a 45A 240VAC relay (SSR) on a large heat sink and does not get warm. What gets warm is the illegal 10 Amp plug/socket of the extension lead, proving those things are not made for anything higher than 10A.

6xFLC would be 6 x 12.5 or 75A for 3 secs.

Thanks.

Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up.

Winston Churchill

jeffj
Regular Member

Joined: 04/02/2012
Location: Australia
Posts: 84

Posted: 09:38pm 16 Apr 2016

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Hi getting warm is normal hot is not .Try cleaning the oxide coating on the plug and socket connections. You could reduce the load by throttling the pump a bit Jeff

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