Control question

[paul]

I want to pick the brains of some of you control guys. I have a 20A 480V 3P temp hydraulic pump skid. The owner wants me to add a reversing switch to the skid, because some of the pin and sleeve setups they use are wired backwards. This is a simple on off application with some hi-temp, low pressure type cut-outs in the control system.


Other than wiring up the receptacles correctly, what are some easy fixes for adding a reversing switch and relays? I've thought of just purchasing a reversing contactor or adding in a latching relay to accomplish this.

Thanks,

Paul

 

[xformer]

I want to pick the brains of some of you control guys. I have a 20A 480V 3P temp hydraulic pump skid. The owner wants me to add a reversing switch to the skid, because some of the pin and sleeve setups they use are wired backwards. This is a simple on off application with some hi-temp, low pressure type cut-outs in the control system.


Other than wiring up the receptacles correctly, what are some easy fixes for adding a reversing switch and relays? I've thought of just purchasing a reversing contactor or adding in a latching relay to accomplish this.

Thanks,

Paul

IMO... I would use a reversing contactor and also create an electrical interlock to prevent forward and reverse from happening at the same time.

 

[RichB]

Ditto on the reversing starter--and they generally have the contacts for the interlock factory installed along with a mechanical interlock--then just add a REV button or just change out the current one with a spring return momentary HOA type switch

 

[Smart $]

...Other than wiring up the receptacles correctly...

Nothing like asking for the easiest fix after taking the easiest fix out of the equation :blink:

 

[Smart $]

Ohhh!!! BTW, the second most easiest fix is to use a 3? reversing switch.

 

[paul]

Nothing like asking for the easiest fix after taking the easiest fix out of the equation :blink:

This is how I would do it, but the facility electricians won't have any part of it. So this option is null and void.

 

[paul]

Ohhh!!! BTW, the second most easiest fix is to use a 3? reversing switch.

THANK YOU! I like this method right here. I may even get fancy and get a 3? relay and a green light with interlock to make it semi fool proof.

 

[Smart $]

THANK YOU! I like this method right here. I may even get fancy and get a 3? relay and a green light with interlock to make it semi fool proof.

What you might want to consider is a phase sequence indicator to let the operator know whether the correct rotation is switched before starting anything.

Click here for an example (not an endorsement).

 

[texie]

Assuming you have a magnetic starter, I would do as Smart$ said and add a phase monitor. Wire it in series with the coil ahead of the start switch and sealing contact so that if rotation is wrong the starter won't pull in at all. I would just use a 30 amp 3 pole DT non-fusible safety switch (cross wired on the load ends) ahead of the starter for reversing. This is all pretty inexpensive to do on such a small motor.

 

[Jraef]

Alternative #3, replace the motor starter for the hydraulic pump with a VFD, even though you probably don't need to change the speed. That gives you two things:

1. Soft starting so that if the source is weak, it doesn't trip the feed,
2. The VFD will not care what the incoming phase sequence is because it just rectifies it to DC. So the output phase sequence can always be the same regardless of where it is hooked up.

 

[weressl]

I want to pick the brains of some of you control guys. I have a 20A 480V 3P temp hydraulic pump skid. The owner wants me to add a reversing switch to the skid, because some of the pin and sleeve setups they use are wired backwards. This is a simple on off application with some hi-temp, low pressure type cut-outs in the control system.


Other than wiring up the receptacles correctly, what are some easy fixes for adding a reversing switch and relays? I've thought of just purchasing a reversing contactor or adding in a latching relay to accomplish this.

Thanks,

Paul

If it is a retrofit; a mechanical, rotary pole changing switch may be the most cost effective way to deal with this.

 

[Besoeker]

Other than wiring up the receptacles correctly, what are some easy fixes for adding a reversing switch and relays? I've thought of just purchasing a reversing contactor or adding in a latching relay to accomplish this.

Thanks,

Paul

I'm assuming that the pump motor has has to operating in the one correct direction only and not both.
Surely there must be some connection point, terminal box, where it would be simple to swap a couple of wires?
If you are considering adding a reversing switch that seems to indicate that you can get to the phase conductors otherwise how could you physically connect it?

 

[Jraef]

I have run across this several times. Most were water or wastewater utilities that had pumping stations spread out over a wide geography, maybe serviced by semi-private local entities, that had to occasionally be powered by truck mounted portable generators, i.e. during power outages etc. Over the years people would repair things and reconnect to make the pumps work, but paid no attention to phasing with regard to the pin and sleave connections, so the trucks would connect up and run the pumps backward. They wouldn't know until it was too late.

The one I do with VFDs is for companies that contract with grape growers at crush time to transport juice to the wineries, and they have transfer pumps on portable skids. They tell the growers and wineries that they have to have 208-230V 3 phase available and what type of pin and sleave connector, but no way for them to tell every one they work for to match the phasing on their skids, in fact some of the growers have no permanent power, they bring in gensets for the crush. So they just use the VFD on the skid and don't care. In fact, I recently got them to double the size of the VFD on a few of their skids now because some of the smaller growers don't have 3 phase power, so the VFD takes in 1 phase and still runs the pumps with 3 phase 208V.