4 post Bradbury liftmaster dol starter

Welshgixxer · Feb 12, 2022

Hi all

From the outset I'm not in an electrician. I am posting here because I'm thinking the subject matter is quite specific and will prob require some historic knowledge/ experience - I'm hoping someone will allow me to benefit from their knowledge.

I am converting a Bradbury 4 post lift (a variation of a liftmaster 735, which I think is a mk1/2) from 3 to single phase - single direction motor.

The issue I have is with the Dol starter. I want to replace the 415v original with a 230v dol starter with overload. The original dols is housed within the oil reservoir and the (dols') on/off buttons are 'pushed' via a mechanical rod & linkage setup connected to the up/down lever on the main post.

I'm thinking I need to either retain the original dol metal enclosure, replacing it's innards OR replace the entire box.

Simplest would appear to be to retain the original enclosure - thus retaining the mechanical on/off linkage - problem would be the successful marriage of the enclosure on/off buttons with the new internals.

Anyone thoughts/ experience/ solutions of/ for this scenario more than gratefully received.

photos attached (hopefully)-

timhoward · Feb 12, 2022

I have a few thoughts, based on a series of assumptions that might quickly collapse like a house of cards! But to get the ball rolling....

I'm first assuming that in original 3 phase mode the Down operation basically opens the hold-on contact to ensure the motor is stopped, and also simultaneously operates the hydraulic recirculation valve mechanically.
So first principles are that you trying to energise the pump for UP, and for DOWN you are trying to mechanically recirculate the hydraulics while ensuring the pump isn't running.

I can't really see from the photo's exactly how it works, but my further assumption is that the UP operation originally manually closed the contactor while energising the coil to hold the contactor there?

If so my thinking would be to leave the original starter in place, using it as a simple two wire "make" switch that closes contacts when the control handle is moved to "UP" and in all other states the contacts would be open.
These could be used to energise a new contactor for the new 230v pump.
You would then be holding the lever in the UP position to ascend, let go and the pump would stop.
Down would be purely mechanical using the existing setup.

Apologies if I've misunderstood how it works. There are finer minds than mine on this forum that in due course I'm sure will have more ideas. ( @pc1966 @Lucien Nunes ).

Welshgixxer · Feb 12, 2022

timhoward said:
I have a few thoughts, based on a series of assumptions that might quickly collapse like a house of cards! But to get the ball rolling....

I'm first assuming that in original 3 phase mode the Down operation basically opens the hold-on contact to ensure the motor is stopped, and also simultaneously operates the hydraulic recirculation valve mechanically.
So first principles are that you trying to energise the pump for UP, and for DOWN you are trying to mechanically recirculate the hydraulics while ensuring the pump isn't running.

I can't really see from the photo's exactly how it works, but my further assumption is that the UP operation originally manually closed the contactor while energising the coil to hold the contactor there?

If so my thinking would be to leave the original starter in place, using it as a simple two wire "make" switch that closes contacts when the control handle is moved to "UP" and in all other states the contacts would be open.
These could be used to energise a new contactor for the new 230v pump.
You would then be holding the lever in the UP position to ascend, let go and the pump would stop.
Down would be purely mechanical using the existing setup.

Apologies if I've misunderstood how it works. There are finer minds than mine on this forum that in due course I'm sure will have more ideas. ( @pc1966 @Lucien Nunes ).

Thanks Tim

You are way ahead of my basic understanding of the existing set up. I think your assumptions are correct. However the existing circuitry is not working.

I purchased the lift 10 years ago - erected it, parked a car on it and then life got in the way. A few weeks ago I cleared the debris, bought a single phase motor & wired it up using existing dols and fused rotary isolation switch (mounted externally to the oil reservoir)

On investigation I found the internals of the rotary isolator to be stripped - it could not have functioned - so replaced.

I have wired the now working isolator to the single phase motor via the existing dols. I have no output (from the dols') to the motor so assumed either fried (like the isolator) or not working due to lack of 230v coil.

I appreciate your time and certainly do not wish to waste it - would any additional photos be of help to you?

Si

Lucien Nunes · Feb 12, 2022

The starter coil appears to have four leads, which suggests it might be dual voltage. Check any attached labels e.g. inside lid for evidence to that effect. Also check whether the overload relay will adjust to the FLC of the single-phase motor. It probably won't but worth ruling that out before you start modding.

Failing that you can probably use the start and stop contacts in the original starter to control the new one. This will require testing the internal configuration to identify the correct terminals. Are you armed with a multimeter?

timhoward · Feb 12, 2022

Welshgixxer said:
I have wired the now working isolator to the single phase motor via the existing dols. I have no output (from the dols') to the motor so assumed either fried (like the isolator) or not working due to lack of 230v coil.

I'd split this into stages, first check the UP lever manually closes the contactor.
More assumptions.....
You should find that the top row of 3, A B and C are respectively joined to the bottom row of 3 when UP is activated. Check with a multimeter on the continuity setting. So A should show continuity to the one under it, B should show continuity to the one under it etc. You might need to extend wires out of it to test this. (Obviously this is all with power off!)

I suspect the top right hold-on terminal is permanently joined to one of the top 3 internally, most likely the terminal marked C.
Again, check this with a multimeter. As originally configured this would send 400v to the coil once the contactor closed.

Once these principles are confirmed it is possible to wire it for 230v, subject to the coil being dual voltage as Lucien suggested.

Welshgixxer · Feb 12, 2022

timhoward said:
I'd split this into stages, first check the UP lever manually closes the contactor.
More assumptions.....
You should find that the top row of 3, A B and C are respectively joined to the bottom row of 3 when UP is activated. Check with a multimeter on the continuity setting. So A should show continuity to the one under it, B should show continuity to the one under it etc. You might need to extend wires out of it to test this. (Obviously this is all with power off!)

I suspect the top right hold-on terminal is permanently joined to one of the top 3 internally, most likely the terminal marked C.
Again, check this with a multimeter. As originally configured this would send 400v to the coil once the contactor closed.

Once these principles are confirmed it is possible to wire it for 230v, subject to the coil being dual voltage as Lucien suggested.

Tim, Lucien, thank you - I will do as suggested tomorrow & revert.
Si

Welshgixxer · Feb 13, 2022

timhoward said:
I'd split this into stages, first check the UP lever manually closes the contactor.
More assumptions.....
You should find that the top row of 3, A B and C are respectively joined to the bottom row of 3 when UP is activated. Check with a multimeter on the continuity setting. So A should show continuity to the one under it, B should show continuity to the one under it etc. You might need to extend wires out of it to test this. (Obviously this is all with power off!)

I suspect the top right hold-on terminal is permanently joined to one of the top 3 internally, most likely the terminal marked C.
Again, check this with a multimeter. As originally configured this would send 400v to the coil once the contactor closed.

Once these principles are confirmed it is possible to wire it for 230v, subject to the coil being dual voltage as Lucien suggested.

Welshgixxer said:
Tim, Lucien, thank you - I will do as suggested tomorrow & revert.
Si

Tim, Lucien

Welshgixxer said:
Tim, Lucien, thank you - I will do as suggested tomorrow & revert.
Si

Tim, Lucien

I'm attaching numerous photos which may/ may not prove useful.

Mechanical external 'up' mechanism appears to close contact (top right, beneath wheel) - but no continuity across A-L1, B-L2, C-L3 when closed

I have manually closed the coil contact and have continuity across A-L1, B-L2,C-L3.

No continuity between top right terminal (1) and any of A,B or C.

Does this help?

brianmoooore · Feb 13, 2022

Another 4 post Bradbury ramp owner here!
Mine was also 3 phase, now converted to single phase, but I didn't change the motor. It was dual voltage, so reconfigured to the lower voltage, with a capacitor to simulate the missing phases, plus another capacitor and current operated switch to provide starting torque. Mine appears to be a newer model than yours, because the original contactor was a more modern type, which I merely changed for a similar one with a 240 volt coil. Been in use and running fine now for about fourteen years.
Regarding your pics in your last post, if the last pic is the single phase converted final version, the incoming neutral should be connected directly to the isolator, bypassing the fuse. The fuse in the live wire should be retained.

Welshgixxer · Feb 13, 2022

brianmoooore said:
Another 4 post Bradbury ramp owner here!
Mine was also 3 phase, now converted to single phase, but I didn't change the motor. It was dual voltage, so reconfigured to the lower voltage, with a capacitor to simulate the missing phases, plus another capacitor and current operated switch to provide starting torque. Mine appears to be a newer model than yours, because the original contactor was a more modern type, which I merely changed for a similar one with a 240 volt coil. Been in use and running fine now for about fourteen years.
Regarding your pics in your last post, if the last pic is the single phase converted final version, the incoming neutral should be connected directly to the isolator, bypassing the fuse. The fuse in the live wire should be retained.

Cheers Bri, thanks - I've been in and out of this for months, sometimes minutes at a time, I can't even explain why I did that when I did it and even more confusing, when I took the photo why I didn't see it.
Si

brianmoooore · Feb 13, 2022

The operating controls on mine are two push buttons and a lever. The ramp, when in use doesn't rely on the hydraulic ram to keep it in position - there is a metal bar alongside the ram housing which has rectangular holes in it about every two inches, you raise the ramp slightly higher than you need, then lower it slightly, and a solenoid operated peg pushes into the hole in the bar that is along side it, taking the entire weight of the ramp bed and whatever is on it.
The LH push button on the control panel starts the motor/pump, retracts the peg, and raises the ramp. You then release the button, pull the lever downwards, and the ramp lowers slightly onto the peg.
To lower the ramp, you push the fist button momentarily to raise the ramp slightly and take the load off of the peg. Next, you push the RH button, which powers the solenoid that retracts the peg. This button is held in, and the lever pulled down, which opens the oil return valve, allowing the ramp to descend. To stop the ramp part way down, you release the RH button, peg goes in, then you release the lever, when the peg reaches the bottom of its 2" hole.
Does yours work the same way?

Welshgixxer · Feb 13, 2022

brianmoooore said:
The operating controls on mine are two push buttons and a lever. The ramp, when in use doesn't rely on the hydraulic ram to keep it in position - there is a metal bar alongside the ram housing which has rectangular holes in it about every two inches, you raise the ramp slightly higher than you need, then lower it slightly, and a solenoid operated peg pushes into the hole in the bar that is along side it, taking the entire weight of the ramp bed and whatever is on it.
The LH push button on the control panel starts the motor/pump, retracts the peg, and raises the ramp. You then release the button, pull the lever downwards, and the ramp lowers slightly onto the peg.
To lower the ramp, you push the fist button momentarily to raise the ramp slightly and take the load off of the peg. Next, you push the RH button, which powers the solenoid that retracts the peg. This button is held in, and the lever pulled down, which opens the oil return valve, allowing the ramp to descend. To stop the ramp part way down, you release the RH button, peg goes in, then you release the lever, when the peg reaches the bottom of its 2" hole.
Does yours work the same way?

Bri

I remember reading how it works (year, maybe years ago) and will have notes somewhere - from memory, simpler than yours - lever up for up, mechanical lock to hold, lever down returns fluid to tank, lowering lift.
Trying to take it one step at a time - getting it to move 1st.
It came in parts - trying not to be too optimistic seeing as the rotary switch internals were literally in bits.

brianmoooore · Feb 13, 2022

When I bought mine, it had been under three feet of floodwater a couple of weeks earlier!

timhoward · Feb 13, 2022

Welshgixxer said:
Mechanical external 'up' mechanism appears to close contact (top right, beneath wheel) - but no continuity across A-L1, B-L2, C-L3 when closed

I have manually closed the coil contact and have continuity across A-L1, B-L2,C-L3.

I haven't been able to understand from photos how the lever moves the contact, but is there any adjustment facility? It sounds as though it is supposed to fully close the contact.

Welshgixxer · Feb 13, 2022

timhoward said:
I haven't been able to understand from photos how the lever moves the contact, but is there any adjustment facility? It sounds as though it is supposed to fully close the contact.

Sorry Tim, I should have provided an explanation to accompany photos. Moving the [post mounted] lever operates (through mechanical linkage) a mechanical spring loaded 'pivot' attached to the Dol starter front cover - which depresses the button (eg green - if lever up) on the Dol starter enclosure. Both buttons have rods attached to their rear - green is the shorter. The green button rod depresses the spring loaded contact plate below the adjustment wheel and completes circuit. I will take a close look to see if I can adjust rod length - if that's what you mean. - I could also wire it up and carefully depress contact manually with cover off - make sense if knew wiring ok first?

brianmoooore · Feb 13, 2022

Looks like you're going to have the problem of either finding a 230V coil for that contactor, or arranging a modern contactor so that it can be operate by the existing mechanical linkage.
Could possibly be solved by a panel mounted pushbutton, as on mine, and two handed operation.

timhoward · Feb 13, 2022

It would be a doddle to start again with a new 230v starter and an auxiliary safety button for the UP operation as Brian said.
The main question in my mind now is how "Down" works....I had imagined the DOWN lever was also operating a mechanical oil return, but now the principle of the lever and the rods has been explained I'm shifting to believing it's an electrically operated return valve?
Maybe annotating the photo of the inside of the DOL would help, showing exactly what UP and DOWN are pressing inside.
I'm thinking that as well as interrupting the coil, DOWN must close two contacts somewhere too.

brianmoooore · Feb 13, 2022

If the OP's ramp uses a solenoid operated latch to lock the ramp in position, like mine, and is single lever operated, then there must be contacts to power that solenoid when the lever is pushed down.
It's unlikely that the oil release valve is electrically operated, because that would make it either fully closed or fully open, and wouldn't allow the descent speed of the ramp to be controlled.

Welshgixxer · Feb 14, 2022

brianmoooore said:
When I bought mine, it had been under three feet of floodwater a couple of weeks earlier!

Brian, Lucien, Tim

I'm not very good at leaving things I don't completely understand so before I move on to resolve the practical issue of incorporating a 230v dols would someone please confirm the correctness of my wiring diagram.

I am attaching an image of the Dols and my basic wiring diagram interpretation of it. I have coloured in live & neutral to distinguish them from hardwiring.

2 things (I am aware of) I don't understand:
1, why 2 of the wires exiting the coil join at a terminal?; and
2, assuming I can use 'L3-C as I have to provide current to the off switch (NC) when on switch (no) released, any idea how I would facilitate the 'orangey '(on diagram) connection to C?

Ps. The purple highlighted circle on the wiring diagram indicates the rocker that opens the off switch (NC) operated by the red button.

Of course I could have it all wrong!

Won't let me add images- to follow hopefully

Thanks again.

Si

Welshgixxer · Feb 14, 2022

Welshgixxer said:
Brian, Lucien, Tim

I'm not very good at leaving things I don't completely understand so before I move on to resolve the practical issue of incorporating a 230v dols would someone please confirm the correctness of my wiring diagram.

I am attaching an image of the Dols and my basic wiring diagram interpretation of it. I have coloured in live & neutral to distinguish them from hardwiring.

2 things (I am aware of) I don't understand:
1, why 2 of the wires exiting the coil join at a terminal?; and
2, assuming I can use 'L3-C as I have to provide current to the off switch (NC) when on switch (no) released, any idea how I would facilitate the 'orangey '(on diagram) connection to C?

Ps. The purple highlighted circle on the wiring diagram indicates the rocker that opens the off switch (NC) operated by the red button.

Of course I could have it all wrong!

Won't let me add images- to follow hopefully

Thanks again.

Si

Welshgixxer · Feb 14, 2022

Please ignore yellow cable - forgot to remove it.
Oil release to reservoir is mechanical, allowing oil return to reservoir.

timhoward · Feb 15, 2022

Welshgixxer said:
I'm not very good at leaving things I don't completely understand so before I move on to resolve the practical issue of incorporating a 230v dols would someone please confirm the correctness of my wiring diagram.

You have the right idea. If there is definitely no continuity between "1" and "A/B/C" with the contactor manually closed that gets interrupted by the Down button, then as you have identified there is a need for the orange wire on your diagram yet nowhere to connect it....
I find myself wondering if the other terminal with the two other coil wires is somehow involved. More testing needed!

Welshgixxer said:
2 things (I am aware of) I don't understand:
1, why 2 of the wires exiting the coil join at a terminal?

The theory that Lucien suggested, which seems likely, is that the coil is either two coils or tapped at various points, enabling the supply voltage to vary. There are two things to do to explore this further...
1 - measure the resistance of the two coil wires that are not joined together, the red and ?grey once. Also measure the resistance of all permutations of the 4 coil wires. Report back on that.
2 - confirm that the terminal that has the two wires joined together has no electrical continuity to any other terminal (with the coil disconnected).

Welshgixxer said:
2, assuming I can use 'L3-C as I have to provide current to the off switch (NC) when on switch (no) released, any idea how I would facilitate the 'orangey '(on diagram) connection to C

That is indeed the question, see above.
Keep at it, you are doing well!

Welshgixxer · Feb 15, 2022

timhoward said:
You have the right idea. If there is definitely no continuity between "1" and "A/B/C" with the contactor manually closed that gets interrupted by the Down button, then as you have identified there is a need for the orange wire on your diagram yet nowhere to connect it....
I find myself wondering if the other terminal with the two other coil wires is somehow involved. More testing needed!

The theory that Lucien suggested, which seems likely, is that the coil is either two coils or tapped at various points, enabling the supply voltage to vary. There are two things to do to explore this further...
1 - measure the resistance of the two coil wires that are not joined together, the red and ?grey once. Also measure the resistance of all permutations of the 4 coil wires. Report back on that.
2 - confirm that the terminal that has the two wires joined together has no electrical continuity to any other terminal (with the coil disconnected).

That is indeed the question, see above.
Keep at it, you are doing well!

Thanks Tim,

More images of contactor and resistance values of coils below

In answer:

• Def no continuity between 1 and A,B or C.

• coil contact terminal (labelled 'A' in resistance value table below and orange dot in image) is plastic and purely a means of connecting coil ends

* I think I have found the missing contact terminal I need for the 'orangey' connection - see image of underside of contactor below (green dot) ** here's the thing - you can see a wire has been/ was intended to be connected to it - problem is the other end of that wire seems to be connected to L3 (see image of top of contactor, blue dot) which would provide a permanent live to the off 'switch'

A) would this configuration work?
B) would a better solution be a connection to C (rather than L3)?

On a practical level - if I rewire contactor as above and provide a 'contactor' live between C and the newfound contact terminal on underside - can I make this dols coil work at 230, considering that max o/l of this dols is 7.2 and the new single phase motor states 8.2?

Sorry to answer your questions with more questions, but sense I am close - although poss not close enough!

Ps really appreciate the positive feedback - my mind doesn't lean to circuitry without a lot of persuasion.

Si

brianmoooore · Feb 15, 2022

Isn't the 'orangey' wire to connect up the auxiliary NO contacts of the contactor and make it into one that holds on?
May be wrong, but I doubt that is required for a hydraulic ramp.

timhoward · Feb 15, 2022

brianmoooore said:
Isn't the 'orangey' wire to connect up the auxiliary NO contacts of the contactor and make it into one that holds on?
May be wrong, but I doubt that is required for a hydraulic ramp.

I agree about the purpose, but my take was that it must have been part of intended original design to hold on, otherwise the "down" operation wouldn't need to open the coil using that little rod.
As you imply it would certainly be possible to proceed without this wire in meantime.

brianmoooore · Feb 15, 2022

The possibility of a ramp moving in any way when the controls are not being operated is extremely dangerous.
It takes about 15 seconds for my ramp to go from down to its highest position, so I can't see what 'hold on' would achieve.