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Electric Motors/DOERR electric motor on Yale MEL Hoist from 115v to 230v


Hoist Motor Connections
Hoist Motor Connection  
I recently purchased an old crane and hoist currently configured to 115v service.  The hoist has a rocker (reversing) switch and incorporates a Doerr 1hp motor.  I have attached the diagram I found inside the switch cover which seems to indicate I can reconfigure it for 230v service.  

I have marked up the diagram to show the wire markings.  Elsewhere on the web I have seen an MEL hoist diagram that indicates P1-P2 is a thermal motor protection, TA-TB is a winding, TC is one end of a second winding where either J10 or J11 complete the circuit to L1 or L2 depending on desired rotation direction.

The wires connected to the switch have numeric wire markers and also have stamped designations on the wire insulation itself.  The wire with marker 5 is stamped T8, for example.  I show both -- the marker number and then, in parenthesis, the designation on the insulation.

It appears the L2 circuit passes through P1-P2 to the middle left terminal where it is permanently connected to TA and selectively connected to J10 (in which case L1 is connected to TC) or to TC (in which case L1 is connected to J11).

There are two wires connected to the upper-right terminal, one marked "2" and the other without marking (I guess it is T4).

To convert to 230v, the diagram indicates I would disconnect T2 from TB and connect it to TA.  I can do that.  It also removes P2 from the middle left terminal.

I don't understand what I should do with P2.  It seems, without P2, that there is no electrical path for L2.

I would appreciate any help you could provide in defining what changes I need to make to the wiring connections to have my hoist run on 230v.

Thanks in advance,

nice job of explaining things,     these can be confusing,       P leads are protector leads and in this case probably a klixon type n/c  buried in the windings,  when it detects temperatures above it's bi-metal capacity it bends open,      it is a crap device for over temp,   because they are nothing but a bi-metal device that opens by actually bending,  then when it cools   and none are consistent,  as far as time, it slowly bends back  and will start the motor without warning,       I hate these things,     

they are usually in line with a contactor coil  line level of 110 volts  so when it is connected 110 it can go right across line,   in series with a coil or even line,      when the motor is connected 220   the Protector   has to be tapped from the center of the run windings,   so it gets 110 from one 220 line  but the P2 is then connected to the middle of the run,  or where the coils are connected in series,     and at that point the voltage is only half,

The parnens around the T5 or T8 is because they are trying to tell you that T5 and T8 are start leads,    so if the run windings are on line   say  they are 1 and 4   now you have run  put 5 with 1 and you get one direction of rotation,   put T8 with 1 and you get the opposite rotation,   

On a hoist  it is often possible to get it connected and running  but it goes up with the down button on the pendant and up with the down,  and runs fine,    but do not do that,     

It by passes the upper safeties  

P1 is going to be on line whatever the voltage   T1 T2 T3 T4 are run windings,  in parallel for 110 in series for 220    P2 will pick up the series connection when wired for 220 at the T2-T3 series connection,    to keep the thermo on 110 volts as explained above,    

Wire it exactly as it says   the only issue should be if the hoist goes up with down button or vice versa,        if so reverse T5 WITH T8     it shouldn't be a problem but some get marked wrong,       have you tried it just as the diagram shows  and what results did you get?

Don't try to over think the circuit,  these are horrible diagrams but there is a lot going with the windings that is a long complex explanation,        it runs fine on 110 correct?  upper and lower limits function?

You should have it tested at 125%  capacity,  either static or dynamic,  dynamic is better because the chain is moving over the lift wheel  but either test wiil satisfy ANSI  which is what OHSA uses as their parameters,   

My shop is MEAR Services Inc,    in Kansas City,  Missouri,  you can write me there at,  or my personal e-mail,   MEAR Service phone number is 816-650-4030     if you want to chat about it,      but trust the diagram   and connect exactly as it says       P2 should not move only the series connection of the runs should pick it up on high voltage

Also inspect the chain for [I am assuming it is not wire rope]  wear,  each link will wear where it contacts the lift wheel,   if there are sloping indents in the individual links you need to change out the chain and also the lift wheel,

THIS ABOVE IS a free downloadable pdf manual for the older KEL series hoists, both single and three phase should be a big help

This is hoistdirect with many brands and series manuals free to download  :

below is just some other examples because I see you are much more in depth than most,  

There should be enough diagrams to answer any questions in the above links,   but if you are still having problems let me know,   we will get it resolved,    you have to be careful with these old hoists,   I WOULD NEVER USE ONE WITHOUT A FULL 125% load test,  and measuring of the running current,    just too dangerous,  there can be fractures in the lift wheel, shafts, so on,     and if used commercially  it needs an up to date inspection sticker with a follow up test result page on file somewhere,      so be careful,        cheap is not good when it comes to hoists,        

I had a rookie tech I found under a 1000 pound motor  hanging from a 2 ton hoist,   no problem there but he was under the motor    painting the belly,    I told him not even to stick his hand under there and spray up,    we have lifts with openings to do this,     it seemed like not much,    but no kidding,   not a week later,   same tech had another motor on the same hoist using a set of chain slings in the lifting eyes,    it was hanging a foot or two above the floor,  no one around it,   I believe it was drying or waiting to be moved to shipping,   

My office had a glass front and the hoist and motor were right on the rail where I could see it,   it was nothing just a motor hanging,       in a few minutes the damn loudest noise rocked the window,    the chain on on the lifting device  broke,   one link just broke,  

A week prior  he would have been smashed  bad,      it happens,  

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