SQ-D Thermal overload question

[Spliced]

I have 3 motor contactors with 3 sets of SqD thermal overloads, all are size B45.
Not indicated on the chart or on the packaging, but stamped on each OL under B45, letters LP, FL, HW.
The contactor for pump 1 contains the OL with the FL and it has tripped multiple times, power logger connected and amperage within acceptable limits.
O/L swapped with pump 2 and problem followed.
Anyone know what these sub markings mean?

 

[jim dungar]

Those are likely the date codes of the B45 thermal units.
These items are not available in different versions.

You may have an overload relay that has bad contact surfaces. How old is the relay? The starter contacts may also be an issue.

Is the same starter pole causing the trip?

 

[retirede]

Did you swap just the thermal elements or the entire OL relay?

 

[ptonsparky]

IIRC those use an eutectic alloy. Resetting them before they are cool can ruin them. Especially if done frequently.

 

[jim dungar]

IIRC those use an eutectic alloy. Resetting them before they are cool can ruin them. Especially if done frequently.

the problem was resetting them, turning the ratchet wheel, before they cooled down. They can be restored by heating them up, so the solder melts, and then leaving them to cool down. In the old days we put them on a 100W bulb for a few minutes.

 

[Spliced]

I have 3 motor contactors with 3 sets of SqD thermal overloads, all are size B45.
Not indicated on the chart or on the packaging, but stamped on each OL under B45, letters LP, FL, HW.
The contactor for pump 1 contains the OL with the FL and it has tripped multiple times, power logger connected and amperage within acceptable limits.
O/L swapped with pump 2 and problem followed.
Anyone know what these sub markings mean?

Did you swap just the thermal elements or the entire OL relay?

Those are likely the date codes of the B45 thermal units.
These items are not available in different versions.

You may have an overload relay that has bad contact surfaces. How old is the relay? The starter contacts may also be an issue.

Is the same starter pole causing the trip?

I have not checked contacts. 3 contactors are over 5 years old and used heavily for sewage lift station.
Also have not checked for individual pole trip.
Thanks

 

[Spliced]

Did you swap just the thermal elements or the entire OL relay?

I just swapped the elements.

 

[jim dungar]

I just swapped the elements.

So now you should see if the problem follows a specific thermal unit, or if it stays with a specific relay position.

 

[retirede]

So now you should see if the problem follows a specific thermal unit, or if it stays with a specific relay position.

If the problem followed the heater elements, I’d just replace them with new. Not worth it to troubleshoot further other than to satisfy curiosity.

 

[jim dungar]

If the problem followed the heater elements, I’d just replace them with new. Not worth it to troubleshoot further other than to satisfy curiosity.

You are correct if it follows the thermal unit.

But if not, on the OP's overload relays you can tell which phase trips by looking at the latch-wheel mechanism, before you reset it. The tripped phase(s) will have its latch extended.

 

[retirede]

You are correct if it follows the thermal unit.

That’s how I read post 7.

 

[kwired]

So now you should see if the problem follows a specific thermal unit, or if it stays with a specific relay position.

Still may possibly work to heat up the thermal unit then let it cool down. If it had been reset at some time before cooling off enough it may just have a small portion of solder that is melting when tripping and has basically effected the trip point. This is just about the only thing that can go wrong with these units other than being subject to a fault current level that they can't handle, but that typically blows the heater element and they won't pass any current after that.

 

[jim dungar]

All we know is there is still a problem after the TUs were swapped. Still don't know if the problem is the overload relay, starter contact, or external wiring connection.

Other than being reset, before properly cooling down, the TUs are not likely to fail once they have been put in service. These are not really heaters, which are used in bi-metallic style relays, they are simple with a melting alloy (eutectic solder) pot and an internal heating wire.

 

[kwired]

All we know is there is still a problem after the TUs were swapped. Still don't know if the problem is the overload relay, starter contact, or external wiring connection.

Other than being reset, before properly cooling down, the TUs are not likely to fail once they have been put in service. These are not really heaters, which are used in bi-metallic style relays, they are simple with a melting alloy (eutectic solder) pot and an internal heating wire.

Yes the heater and melting alloy is all inside the replaceable unit. Most other brands you just replaced the heater itself and the melting alloy was more less a fixed part of the overload unit. Some old Allen Bradley units did have removeable melting alloy component but heater component was what you selected in accordance with motor current.

 

[don_resqcapt19]

Yes the heater and melting alloy is all inside the replaceable unit. Most other brands you just replaced the heater itself and the melting alloy was more less a fixed part of the overload unit. Some old Allen Bradley units did have removeable melting alloy component but heater component was what you selected in accordance with motor current.

I thought only the elements that had a gear on them were melting alloy, and the others opened a bi-metallic contact in the overload relay.

 

[Spliced]

I have 3 motor contactors with 3 sets of SqD thermal overloads, all are size B45.
Not indicated on the chart or on the packaging, but stamped on each OL under B45, letters LP, FL, HW.
The contactor for pump 1 contains the OL with the FL and it has tripped multiple times, power logger connected and amperage within acceptable limits.
O/L swapped with pump 2 and problem followed.
Anyone know what these sub markings mean?

If the problem followed the heater elements, I’d just replace them with new. Not worth it to troubleshoot further other than to satisfy curiosity.

New set of OL’s have been installed, we will monitor.
Thanks all!

 

[kwired]

I thought only the elements that had a gear on them were melting alloy, and the others opened a bi-metallic contact in the overload relay.

Pretty certain some the older Allen Bradley's and old Cutler Hammer units maybe even old Furnas units had the gear fixed on the overload relay and you select just a heater unit. Square D possibly about the only one that if not an electronic overload still produces new units with melting alloy and the others are all bi-metal type?