Volt Free Contact

Yes. You run the hot line to the volt free contact with a voltage and current that the contact is rated for, and the switched-leg to the line side of your starter coil, and when the BMS shuts the contact, the motor starts. Be aware of the ratings on the contact. They may not be adequate to work with large inductive starter coils. Not all contacts are created equal.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

Thanks xnuke,

But our engineer says, volt free contacts are for taking status only. You cant provide command via volt free contacts. Any advise pls.

Your engineer may be correct. Often, low-rated contacts are provided for status only. Without a schematic and bill of material for the control panel, I doubt anyone can advise you. Can you share them?

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

What the supplier might mean is volt free switching where you supply the volts and current that activate a switch on the other side of the relay / switch in the pump panel. it's a bit of a strange way of putting it, but just separates the two systems. Essentially you're powering the solenoid bit of the realy and the pump panel contacts to start / stop are inside the pump panel.

As noted above you need to know what the contacts need in order to make the contact - 12VDc or 240V AC or something else and maximum current the contacts can take.

Simply saying there are a pair of contacts here which start / stop the pump without giving you the voltage and current rating is next to useless.

Also is the relay latched or does the pump stop on loss of volts?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

I just re-read the original post. Are there two control panels - one for the BMS and one for the pump? If so, I was wrong in my previous post. The dry contact would need to be in the BMS panel, and receive and switch a hot leg wire from the pump control panel.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.