hot water pump VFD Status

[newtohvac13]

Whats up guys, my company is trying to get status off a hot water pump for the front end. We currently have a Current switch hooked up to show us status. The problem is When the VFD ramps down to 15hz we sometimes loose status. This vfd is a SVX9000. by cutler hammer. Today i ramped the vfd down manually to 15 hz and i cant get it to throw an alarm, but our alarm log shows it loosing status when it ramps down, but the pump is really not failing

I was trying to look atcut sheets for the svx9000 to see if there is a " run Status" contact we can hook up our wires to, but had no luck finding anything... Any ideas?

[Elfshadow]

I have seen this with VFD controlled ECWs. Our sollition was simple. Looped the wire through the current sensor several times. The problem is not the vfd but the sensitivity of the current sensor.

[newtohvac13]

yes, we thought about extending it and looping it as well. we installed a real sensitive current sensor on it and it was still throwing the alarm, i think looping it will be our option.

[Gib's Son]

I never use CT's on VFD's, especially if it's belt driven. I use flow sensors.

[Elfshadow]

I'm not familiar with this brand of VFD but does it have a set of status contacts you could wire off of instead of using a current sensor? Its a water pump so I suppose you could use a flow switch instead of a current sensor, of course installing it could be a bit of a pain.

[Elfshadow]

I never use CT's on VFD's, especially if it's belt driven. I use flow sensors.

How would you handle a vfd controlled energy conservation wheel thats driven by a belt? Is there a better way then a current sensor??

[Southern Mech]

I would not reccomend ramping a pump below 18 hz, fans dont go below 20hz.

[chris4]

What about a presure differential switch or a check valve and flow switch

[hvac69]

Do you have relay out RO's? If so use term 22 and 23 NO contacts. RO1 would be defaulted as RUN and RO2 would be defaulted as fault. Though the RO1 RUN status will only tell you that the drive is running. Not a good idea for proof of flow. You could use the AO and set it to motor current in parameter P1.3.2 if you have a way of using the analog output signal and motor current in your system. The best way to prove it though is through a pressure differential switch or flow switch as others have said.