contactors & relays

[bigjer]

I couldn't find a topic comparison so here it is.
i've got a 240 volt heat tape circuit 250' long maxed out on a 20 amp epd controlled by a eti snow sensor. Snow sensor is tied to the coil at 120volts to pull in a contactor 40amps resistive,using a seperate circuit thru the sensor to avoid problems with inrush.

This is a field constructed control one of many ive put togeather some worked well & some not

the problem i have is that the contactor at some point will not stay closed & begin to rattle & make a huge racket. can someone help me with my design problem
the wireing is all in # 12 thhn.

 

[augie47]

My first guess would be that the coil is not sufficeint load for the sensor.
Does the sensor spec indicate a minimum load ?

side note: If "maxed out" means the load is 20 amps, considering 427.4 your 20 amo OCPD and #12 are undersized, IMHO.

 

[S'mise]

Check voltage drop. Also, I've had contactor coils buzz because of dust, particularly metalic dust.

 

[wiigelec]

Snow sensor is tied to the coil at 120volts to pull in a contactor

Can you provide more specifics on the snow sensor, ie is it a dry set of NO contacts, etc...

 

[Jraef]

It appears that there are several different versions of ETI Snow Sensors, some are designed to operate on 120V, others operate in conjunction with their own controller at low voltages. Without knowing which one you are trying to use, it's difficult to offer suggestions.

 

[davidr43229]

My first guess would be that the coil is not sufficeint load for the sen

1. Check the RATED amperage output of the sensor, could be 25ma, VS the amperage necessary to draw in the coil completely
2. Check the voltage output of the sensor.
3. Could be a bad coil.

Options abound here.

Just my $.02

 

[G._S._Ohm]

This is a field constructed control one of many ive put togeather some worked well & some not

the problem i have is that the contactor at some point will not stay closed & begin to rattle & make a huge racket. can someone help me with my design problem
the wireing is all in # 12 thhn.

If any ground wire from the snow sensor is shared by the heat tape supply it can possibly give you the symptoms you describe. You need a single point common return for both the sensor low side and the heat tape supply low side.
If you post your wiring diagram, which is not the same as a schematic, it may help.