chemical pump off of controller

[knickelj]

I have 2 motor controllers, and have been assigned the task of adding 1 small chemical pump that would only be energized (cord and plug NEMA 5-15) when any one of the controllers is engaged. These are boiler feed water pumps and the chemical injector only should pump when the feed water pump is running. We have these set-ups in a bunch of our buildings but have not had to look into how they electrically fed the chem. pump. And from what I've seen I wouldn't trust copycatting anyway. Is there anything in the code that would prevent load side taps from the controller to a single receptacle to power the chem. pump. Seems like you should not be able to control a receptacle through a contactor??? For arguments sake lets assume all our other requirements are met (they will be) OCPD, cir ampacity etc. Both motor controllers are fed from the same branch circuit and tapped before the controllers. As an alternate, I know I could use aux contacts off of the controllers but they are not available (would have to replace both). And I thought of adding a separate contactor controlled from the boiler feed water cir. for coil power and add another branch circuit for the line/load side. If any one has seen what is typical set up for these (AND LEGAL) please let me know...

Thank You

 

[hillbilly1]

Thats an easy one, power two relays from the coil voltage powering the feed water pumps. Paralell the contacts to run the chemical pump if the contacts are rated high enough, or drive a contactor that is.

 

[tom baker]

Or a control power transformer large enough for the chem pump, an aux contact and interpoise relay. I would be carefull about have a receptacle that other loads could be plugged into.

 

[JWCELECTRIC]

K,

Depending on the type of chem feed pump you have, LMI type like an independant contact (Interposing relay) off your boilier feed pump when it is running to internal controls of chem feed pump. Plug chem pump into a standard outlet that is energized all the time. Or as Tom has indicated install the interposing relay contact inline with the hot leg to the outlet, it turn on/off with feed pump is called. They usually draw minimal for amperage.

 

[knickelj]

HILLBILLY1

Thats an easy one, power two relays from the coil voltage powering the feed water pumps. Paralell the contacts to run the chemical pump if the contacts are rated high enough, or drive a contactor that is.

This was my first thought, but I still would question the single receptacle fed by a contactor. This just seems wrong... someone could unplug the chem pump and plug in there saw etc. while there looking at there saw to figure out why it doesn't work the feed water pump starts and energizes the recep... off goes a finger. I know this might be a little far fetched but you get the idea. I looked and could not find a code that would prevent a recep from being "auto" controlled.


The chem pump is ul listed and has a factory cord with the 5-15 and no other "control" wiring or dry contacts to tie into. When it's plugged in it runs continuously.

It sounds like you all deduced, even though I forgot to mention, the motor is three phase 208.

 

[don_resqcapt19]

Having a receptacle controlled by a stater or contactor is really the same as having a switched receptacle in a house. I have installed a number of single receptacles that are controlled by starters or relays for use with chemical feed pumps. They will be labeled for chemical feed pump use only.