submersible water pumps

[Frostygump68]

We installed a 30A/ 208V/2P circuit for a test bench at a pump testing facility. The controller (provided by the testing facility) we installed can test pumps from 1/2 HP - 5 HP. The pumps are 230V. according to the manufacturer the correct voltage for maximum efficiency should be 230 - 240V and 120V to ground at each leg. We went ahead and installed a buck/ boost transformer to boost the 208V to 240/120V. According to the manufacturer this should be what they are looking for. When they put the pump on the test bench, they are getting an overcurrent of 15A, which is excessive and will burn up the pump. What would cause this overload? Has anyone come across a situation like this? We have tried a variety of different configurations with different sized pumps, all with the same result.

 

[PaulMmn]

Is the pump submerged on the test bench? That wouldn't solve the high current, but would keep the pump from burning up. Maybe.

Is that 15 A total or 15 A above normal??

I'm assuming you've verified the voltage being fed to the pumps!

 

[jim dungar]

We installed a 30A/ 208V/2P circuit for a test bench at a pump testing facility. The controller (provided by the testing facility) we installed can test pumps from 1/2 HP - 5 HP. The pumps are 230V. according to the manufacturer the correct voltage for maximum efficiency should be 230 - 240V and 120V to ground at each leg. We went ahead and installed a buck/ boost transformer to boost the 208V to 240/120V. According to the manufacturer this should be what they are looking for. When they put the pump on the test bench, they are getting an overcurrent of 15A, which is excessive and will burn up the pump. What would cause this overload? Has anyone come across a situation like this? We have tried a variety of different configurations with different sized pumps, all with the same result.

If you use a buck-boost to raise the L-L voltage from 208 to 240V then you will also raise the L-G voltage to roughly 136V.
You most likely need a 208 - 120/240 isolation transformer.

 

[MTW]

You can't use a boost transformer, to go from 208/120V 3W to 240/120V 3W.

The voltages will not be correct or symmetrical.

You need to use a isolation type unit. 208V 2W Primary to 120/240V 3W 1Φ Secondary.

MTW Ω

 

[texie]

If you use a buck-boost to raise the L-L voltage from 208 to 240V then you will also raise the L-G voltage to roughly 136V.
You most likely need a 208 - 120/240 isolation transformer.

I don't understand why the OP needs 120/240 3 wire. It would seem that he just needs 240 volt.

 

[ptonsparky]

Restrict the flow of the pump. Open discharge moves too much water.

 

[Jraef]

Restrict the flow of the pump. Open discharge moves too much water.

Ding ding ding, WINNER!

LOAD on the motor for a centrifugal pump = flow through the pump. If a submersible pump is designed for a specific flow at a specific head pressure (static pipe height above the pump) and you test it with less head pressure, the flow increases and the pump overloads the motor. So to keep the motor from overloading like that, you need to restrict the flow through the pump, i.e. a valve on one side or the other.

If this is a pump testing facility, someone there should have known that. It's not really an electrical issue, its an electrical EFFECT of a mechanical issue.

 

[topgone]

We installed a 30A/ 208V/2P circuit for a test bench at a pump testing facility. The controller (provided by the testing facility) we installed can test pumps from 1/2 HP - 5 HP. The pumps are 230V. according to the manufacturer the correct voltage for maximum efficiency should be 230 - 240V and 120V to ground at each leg. We went ahead and installed a buck/ boost transformer to boost the 208V to 240/120V. According to the manufacturer this should be what they are looking for. When they put the pump on the test bench, they are getting an overcurrent of 15A, which is excessive and will burn up the pump. What would cause this overload? Has anyone come across a situation like this? We have tried a variety of different configurations with different sized pumps, all with the same result.

A 2 HP motor, 230V will have a full load of 12A. A 5 HP motor will have a dull load of 28A. Which is which?

 

[Dzboyce]

Is the facility wanting to test the pumpp ends, the motors under load, or a complete pump/motor combination?

normalky,if I’m installing a pump where they have 208 volt three phase power, that is what kind of motor I’m going to utilize. With Franklin, you have to specifically order a 208 volt motor. A Grundfos motor is dual rated 208/230 volt.

on a somewhat related note, If a VFD were installed on 208 volt three phase input power. Would the output be 208 volt or would it be 230 volt? Would I use a 208 volt motor or a 230volt motor. What I’ve done previously is install a Grundfos motor and not worry about it.

 

[Mystic Pools]

Ding ding ding, WINNER!

LOAD on the motor for a centrifugal pump = flow through the pump. If a submersible pump is designed for a specific flow at a specific head pressure (static pipe height above the pump) and you test it with less head pressure, the flow increases and the pump overloads the motor. So to keep the motor from overloading like that, you need to restrict the flow through the pump, i.e. a valve on one side or the other.

If this is a pump testing facility, someone there should have known that. It's not really an electrical issue, its an electrical EFFECT of a mechanical issue.

True.
Had a commercial 7.5HP pool pump cook about 25 years ago because of excessive flow-basically a runaway pump overdrawing amps.
We restricted the flow with a butterfly valve (4") to reduce amperage (3 phase) but, it reduced the turnover rate required by the state health code. So, the manufacturer had me swap an impeller from a 5 HP model which solved the problem.

There was a similar post here about a floating pond pump that was having the same issues. The OP reduced the flow with a valve and all was fine.

 

[romex jockey]

Perhaps consider isolating the 'controller' via contactor.....?~RJ~

 

[Besoeker3]

If you use a buck-boost to raise the L-L voltage from 208 to 240V then you will also raise the L-G voltage to roughly 136V.
You most likely need a 208 - 120/240 isolation transformer.

Surely not if you ground the zero of the 120-0-120 ?

 

[Frostygump68]

frostygump68

frostygump68

I'm sorry, we did install an isolation transformer to get 120/240V from 208V.

 

[jim dungar]

Surely not if you ground the zero of the 120-0-120 ?

Please do the math. Remember, you are starting with two legs of a 'star' connected transformer.
If you have 208V L-L and 120VL-G then you increase the L-L voltage by 10% to 240V, the L-G voltage must also increase.

Many people have destroyed equipment by using buck-boost transformers with L-N loads.

 

[jim dungar]

I'm sorry, we did install an isolation transformer to get 120/240V from 208V.

That was the right way to go.

 

[kwired]

I'm sorry, we did install an isolation transformer to get 120/240V from 208V.

Please do the math. Remember, you are starting with two legs of a 'star' connected transformer.
If you have 208V L-L and 120VL-G then you increase the L-L voltage by 10% to 240V, the L-G voltage must also increase.

Many people have destroyed equipment by using buck-boost transformers with L-N loads.

That was the right way to go.

Unless he actually needed a neutral for the load or controls, buck boost would have been fine. Even with buck boost one line is still directly connected to an input line and is still 120 to neutral, you just don't have 120 on both ungrounded conductors.

Depending on testing being done may not even need to increase the 208 volts available. Extensive performance testing - yes get correct voltage. Simple go/no go testing after making repairs - applying 208 volts for no longer than this will run won't hurt it.

 

[Besoeker3]

Please do the math. Remember, you are starting with two legs of a 'star' connected transformer.
If you have 208V L-L and 120VL-G then you increase the L-L voltage by 10% to 240V, the L-G voltage must also increase.

Many people have destroyed equipment by using buck-boost transformers with L-N loads.

I think we have an answer to that now.

 

[ptonsparky]

... Even with buck boost one line is still directly connected to an input line and is still 120 to neutral, you just don't have 120 on both ungrounded conductors....

I've done it that way in the past. Works fine. I don't always worry about 'what if someone doesn't know what they are doing' after I leave scenarios.

 

[kwired]

I've done it that way in the past. Works fine. I don't always worry about 'what if someone doesn't know what they are doing' after I leave scenarios.

You probably seen that a lot on high leg delta where you may have a 120 volt control circuit or other aux 120 volt load on some equipment with all three phases supplied.

 

[jim dungar]

Unless he actually needed a neutral for the load or controls, buck boost would have been fine. Even with buck boost one line is still directly connected to an input line and is still 120 to neutral, you just don't have 120 on both ungrounded conductors.

It depends on how the buck-boost was wired. A single transformer wired 208V to 240V would have the common 'hot' leg which would be 120V to neutral.
However if, as in a previous thread, someone used two transformer each connected to boost the 120V, then neither 'hot' leg would be at 120V to neutral. This is why I mentioned 2 legs of a star, or wye, connection in my post.