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 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.

timhoward · Feb 15, 2022

brianmoooore said:
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.

I take your point - I was also nervous about deviating from an apparent design for similar reasons. But I agree that simpler is safer in this case.

Going back to the 230v coil question -
It looks to me as though the bottom line (A to Grey2) coil resistance of 1.61 ohms is for 230v coil operation. Working out which of the two wires currently joined has the resistance given (1.61 ohms) when measured to Grey2 would be the next step. You should then have a pair of wires that will operate the coil / contact when supplied with 230v. (I trust an RCD protected supply is being used for any testing!)

Welshgixxer · Feb 17, 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

Brian, Lucien, Tim

Sorry for the delay but tonight is the first night I have made it to the shed since.
I'm sure I'll encounter more probs but I rewired the contactor looping N through 2 contacts and isolated 1 coil - it spun the motor - massive thanks to you all.

Ps Tim, yes Rcd

Si

timhoward · Feb 18, 2022

Welshgixxer said:
I rewired the contactor looping N through 2 contacts and isolated 1 coil - it spun the motor - massive thanks to you all.

Well done. You’ll get there. And then I’m driving my car down to Cardiff to look under it ….. ;-)

Welshgixxer · Feb 18, 2022

timhoward said:
Well done. You’ll get there. And then I’m driving my car down to Cardiff to look under it ….. ;-)

Most welcome - at your risk

Welshgixxer · Feb 20, 2022

brianmoooore said:
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.

Bri

Hope you don't mind - electrically lift works fine. All posts are plumb and ramp level.
Without extra load ramp reaches chest level fine but then seems to struggle - not smooth - slow and hesitant I.e. rise/pause/rise/pause - not jumpy but as if needing to build pressure before continuing. It lowers without resistance - so I am thinking pump/ ram seals need replacing - make sense.
Tried attaching vid but too large

Si

4 post Bradbury liftmaster dol starter

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