Relays

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wmeek

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What symptons would cause a relay to chatter rather than close when pushbutton is pushed.
 
I would go with under voltage to the coil. I've seen control circuits that were so long that the voltage drop at the relay caused it to chatter.
 
Foreign material in the relay, rust on the core, distorted parts, anything that would interfere with full closure of the relay.
 
or an AC relay on DC.. had this happen with a control module in a Carrier air handler hat was feeding and external relay
 
My first guess would depend on whether the installation ever worked or not.

If it never worked, my guess is undersized control transformer, very long control circuit, or too small of a control circuit wire gauge. Each of these causing low voltage at the relay coil.
 
mdshunk said:
My first guess would depend on whether the installation ever worked or not.

If it never worked, my guess is undersized control transformer, very long control circuit, or too small of a control circuit wire gauge. Each of these causing low voltage at the relay coil.
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Marc brings up a good point. A relay that worked for years would have a different reason(s) for a sudden chatter versus one that chattered on the initial startup.
 
Test the relay with a known voltage source. If it pulls in and hold without a problem zero in on the circuit that controls the relay.
 
I have a 50VA transformer with #14 Thhn and a total length of less than 20 Feet. I would not think there would be a problem. What does anyone else think
 
I am using this relay. See Attatchment

Item Details
Electrical > Relays > Relays

Relay,Power
Power Relay, Coil Voltage 240 VAC, Contact Current Rating Inductive 30 Amps, Contact Current Rating Resistive @ 28 VDC 30 Amps, Contact Current Rating Resistive @ 300 VAC 30 Amps, Coil Current Rating 10VA, Power Rating @ 240 VAC 1.5 HP, Power Rating @ 480 VAC 1.5 HP, Contact Form DPDT, Contact Point 8, Length 3.40 Inches, Height 2.50 Inches, Width 2.50 Inches Grainger Item # 5X848
Your Price (ea.) $31.70
Brand DAYTON
Mfr. Model # 5X848

Enlarge Image Qty.
Tech
Specs Additional

Pins 8
Contact Amp Rating (R) 30
Contact Amp Rating (L) 30
Contact Material Silver Cadmium Oxide
HP @ 120V 1.5
Coil Volts 240VAC
Height (In.) 2.50
Width (In.) 2.50
Depth (In.) 3.40
Heavy-Duty Power Relays
Use for switching motor loads in applications such as elevators, machine tools, air handling, and HVAC equipment.
Minimum operating voltage for AC relays is 85% of nominal voltage (75% for Nos. 4JY21 and 4JY22). 0.75 power factor. UL Listed, CSA Certified, and CE Certified.
Screw head terminals
Silver cadmium oxide, self-wiping contacts
Molded thermoset plastic base
There are currently no notes or restrictions for this item.

See Catalog 398 Page for application and/or safety information.
 
I think I'd like to know if it ever worked. If so, I'd like to know what was worked on, related to this, recently. I'd also like to know what else was happening when this trouble started occurring. I'd also like to know what your voltage reading is at the coil. I'd also like to confirm that you have an AC coil in the contactor, or if DC, what the waveform out of your rectifier looks like. Have you done any troubleshooting of this yet?
 
Just saw your relay specs. You say you're using a 50va control transformer, but your specs show the contactor has a 240 volt coil. If that's the case, you either need to get a new coil to match the output of the control transformer, or rearrange the connections to eliminate the control transformer. A 24 volt (presumably) control transformer won't pull in a 240 volt coil. It will just sit there and hum and chatter.
 
It did work. I changed from a 15kva transformer to a 50va control transformer to get my 240V.I am trying to control a contactor to de-energize a 480V panel which feed 4-welders and a 15KVA transformer that feeds a 120/240v Panel. This is all installed on a Tractor powered Generator. I have 240V off of a 50VA transformer rated 480/240 volts.
 
SO... what voltage are you measuring at the coil while it's chattering? Any chance you have your control transformer connections hosed up, and you only have 120 at the secondary?
 
That I haven't checked. Iwill have to do it in the morning when I get to job site. What I have is a generator providing 480 V to a contactor which feeds a 480V panel. I came off of the line side of contactor (And fused) wires to feed a 480v/240v single phase transformer that feeds a frequency monitor rated for 240v. Off of a normally open set of contacts i go to a pushbutton that controls the relay. The relay controls the contactor by a set of normally open contacts.and is operated by a High and Low setting from the frequency monitor
 
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