3 ton Harrington hoist electrical repair question

cmdevans · Dec 27, 2021

Repairing a 1970s Harrington hoist. Mostly electrical issues left to sort out, the mechanicals have been sorted out.

The current issue is the contactors for the controls. I got new contactors from Harrington via MSC, purportedly direct replacements, but the new ones have one auxiliary set of terminals(21/22), whereas the old ones have two auxiliary sets (15/16 and 21/22) (21/22 set are on sides of contactor housing)

Do I need a different contactor, an add on auxiliary contactor unit, or is there a way to wire this properly as is? I've been unable to get ahold of Harrington directly so far,and would love to get this crane back in service sometime soon.

I've got diagrams and pictures, trying to get them uploaded at the moment.

matt_isserstedt · Jan 1, 2022

In essence you have a 6 pole contactor and are trying to replace with a 5 pole contactor.

Some solutions

- as you mentioned there could be another aux block that adds-on to the replacement contactor. There's likely features which allow it to clip-on or screw-on to the main body.
- to the single aux contact tie that (with an AC control power circuit) to the coil of a little icecube relay, then you easily have 4NO contacts. Downsides are additional packaging, updates to wiring diagrams, wire lengths probably wrong.
- Functionally, you are not required to be tied to OEM Harrington parts, there are plenty of relay manufacturers out there (Sq D, Allen Bradley, etc). Then into issues with parts "outside of engineering" depending on what your compliance level is.
- I'd also revisit why you are replacing a contactor unless you have a known problem with it. I have contactors in lathes which I think are from the 1960s and they seem to work just fine for a very long time. Can't say the class of service this hoist has been in, but if its light and you don't have documented issues I would roll with existing.

Tony Quiring · Jan 2, 2022

It looks like the old one had under-rated contacts and the manufacturer doubled them up, if your drawing is correct.

The drawing shows 4 wires in and 4 wires out with 2 of the wires each using 2 sets of contacts.

So some detective work needed.

Look at nomenclature plate on both units or Google data.

You need to see the current rating or motor HP rating of the contacts.

Also hand is motor size and or current of your controlled device.

It looks like the manufacturer or past owner determined cheaper to use 6 pole contactor with smaller siz than 4 contact of larger size.

If new one rated twice old one good to go.

If just rated bigger than old one maybe...depends on your need.

If manufacturer supplied what you have for your device should be fine.

Just use one wire to each terminal.

Sent from my SM-G781V using Tapatalk

cmdevans · Jan 2, 2022

matt_isserstedt said:
In essence you have a 6 pole contactor and are trying to replace with a 5 pole contactor.

Some solutions

- as you mentioned there could be another aux block that adds-on to the replacement contactor. There's likely features which allow it to clip-on or screw-on to the main body.
- to the single aux contact tie that (with an AC control power circuit) to the coil of a little icecube relay, then you easily have 4NO contacts. Downsides are additional packaging, updates to wiring diagrams, wire lengths probably wrong.
- Functionally, you are not required to be tied to OEM Harrington parts, there are plenty of relay manufacturers out there (Sq D, Allen Bradley, etc). Then into issues with parts "outside of engineering" depending on what your compliance level is.
- I'd also revisit why you are replacing a contactor unless you have a known problem with it. I have contactors in lathes which I think are from the 1960s and they seem to work just fine for a very long time. Can't say the class of service this hoist has been in, but if its light and you don't have documented issues I would roll with existing.

Those are about the same conclusions I've come up with. The hoist is one of 6 in a busy metal fabrication shop, so not light use. The contactors have simply failed (arc burns) after years of daily use. They were apparently getting stuck, and not serviced in time to save the contactor unit. Essentially the plates look like stick weld spatter now.

Tony Quiring said:
It looks like the old one had under-rated contacts and the manufacturer doubled them up, if your drawing is correct.

The drawing shows 4 wires in and 4 wires out with 2 of the wires each using 2 sets of contacts.

So some detective work needed.

Look at nomenclature plate on both units or Google data.

You need to see the current rating or motor HP rating of the contacts.

Also hand is motor size and or current of your controlled device.

It looks like the manufacturer or past owner determined cheaper to use 6 pole contactor with smaller siz than 4 contact of larger size.

If new one rated twice old one good to go.

If just rated bigger than old one maybe...depends on your need.

If manufacturer supplied what you have for your device should be fine.

Just use one wire to each terminal.

Sent from my SM-G781V using Tapatalk

Yeah, they originally ordered a replacement contactor that was 3 time the current rating needed, but was bigger than space in the housing.

I think I'll just order a different contactor tomorrow. If they had sent an updated wiring diagram for the replacement it'd be one thing, but it's either get up there with a multimeter and spend a bunch of time trying to get it all figured out, or try Harrington again. Just replaced one of the cranes, cost was 9-10k. I'd much rather spend a few bucks on extra contactors.

The thoughts are appreciated. Thanks!

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