Hi there,

Can 2 x 2.2kw 15A water pumps run on a 4mm cable with around 100m distance?

 

3 hours ago, Tyron- said:

Hi there,

Can 2 x 2.2kw 15A water pumps run on a 4mm cable with around 100m distance?

 

Yes it can. The voltage drop is right on the limit at 5.02% if the power factor is not worse than 0.8.

The cable can draw a lot more current than the 2 pumps. 

12 hours ago, Scorp007 said:

Yes it can. The voltage drop is right on the limit at 5.02% if the power factor is not worse than 0.8.

The cable can draw a lot more current than the 2 pumps. 

Thank you. This is what I thought and proceeded to do. The client sent me the following message after the irrigation guys installed the pumps. Sidenote, the distance is actually only 60m.

"Hi Ty. Sorry for the bad news but the cable is too thin. The voltage drop is too great over the distance and causes a low voltage trip at the pump station. Looks like we’ll have to go to a 10mm cable. The irrigation contractor mentioned that a 10mm SWA cable is normally used"

 

1 hour ago, Tyron- said:

Thank you. This is what I thought and proceeded to do. The client sent me the following message after the irrigation guys installed the pumps. Sidenote, the distance is actually only 60m.

 

I would 1st check if the point of supply is 230V. Then show that the voltage drop is within the SANS 5%.

Then check when 1/2 pumps starting what is the voltage at point of supply and at the pump DB/control box. 

Then only run 1 pump where the current is half and the pump should not trip. 

Then look at the head that the pump must pump to see if the pump size is suitable and the pumps are not overloaded. 

Then with the 4mm² cable installed add a 2nd cable in parallel. 

This only as a 1st check. It could be that one needs to allow for the surge current of the pumps and also if both are started at the same time then one will have to increase the cable even as high as 16mm². Distance is your enemy at these lengths of cable. This is where sizes become application specific. 

Inputs can only be based on the actual measurements of the installation. 

I had a client this week complaining about our PSU which is transformer based giving a too low voltage out to charge his gate motor battery. It turned out that his AC input was only 190V and this 40V lower was the reason the PSU did not output 28.5V for charging the flat battery. 

Edited May 11, 20242 yr by Scorp007

11 minutes ago, Scorp007 said:

I would 1st check if the point of supply is 230V. Then show that the voltage drop is within the SANS 5%.

Then check when 1/2 pumps starting what is the voltage at point of supply and at the pump DB/control box. 

Then only run 1 pump where the current is half and the pump should not trip. 

Then look at the head that the pump must pump to see if the pump size is suitable and the pumps are not overloaded. 

Then with the 4mm² cable installed add a 2nd cable in parallel. 

This only as a 1st check. It could be that one needs to allow for the surge current of the pumps and also if both are started at the same time then one will have to increase the cable even as high as 16mm². Distance is your enemy at these lengths of cable. This is where sizes become application specific. 

Inputs can only be based on the actual measurements of the installation. 

I had a client this week complaining about our PSU which is transformer based giving a too low voltage out to charge his gate motor battery. It turned out that his AC input was only 190V and this 40V lower was the reason the PSU did not output 28.5V for charging the flat battery. 

Eish ok. So if it runs on 1 pump and doesn't trip, can I just run a 2nd 4mm instead of running a 10 or 12? Also, we have it so the main DB is feeding a sub DB, then from the sub it runs to the pump station. We fed the sub DB from the main house with a 4mm as well - obviously that would also need to be upsized?

6 minutes ago, Tyron- said:

Eish ok. So if it runs on 1 pump and doesn't trip, can I just run a 2nd 4mm instead of running a 10 or 12? Also, we have it so the main DB is feeding a sub DB, then from the sub it runs to the pump station. We fed the sub DB from the main house with a 4mm as well - obviously that would also need to be upsized?

Due to a possible short run from main DB to sub DB the 4mm² will not cause much of a voltage drop and the current rating is fine. 

Once again one needs the distances for calculation. 

Next cable size after 10 would be 16.

Edited May 11, 20242 yr by Scorp007