Wiring for New Vintage Pushbutton Box

[chips&more]

All very helpful info, but kind of all over the map. It would be better if the poster (Susan) could please give a little more detail on the motor. Like: hp, working volts, phases, maybe a pic(s). In that way, the help could be more focused…Dave

Also does this power hacksaw have a coolant pump? Or any other electrical device?

 

[Bi11Hudson]

An addendum to what I said above. It took a while to sketch out a drawing. Something this simple is not a part of my electrical library. Plus, I'm getting old (sleepy) and needed something to keep me awake awhile. Gaahhh.....

To lecture mode: The two vertical lines represent the power leads. Line on the left, neutral on the right. This is based on the assumption that the motor, and hence the relay, are rated for 120 Volts. Since we don't know what the lamp rating is, we are going to keep it disconnected. For the time being..... And, also assuming, the relay is big enough to handle the motor starting current. Read the name plate for current, then multiply by three for the starting current.

Item # 1: A normally closed(NC) pushbutton, the red one.
Item # 2: A normally open(NO) pushbutton, the black one.
Item # 3: An auxiliary NO contact on the relay, a low current one if they are different.
Item # 4: The coil of the relay. Again, assuming the relay and the motor are the same voltage rating.
Item # 5: The (Red) pilot light on the pushbutton station. Shown disconnected with the appropriate
attachment points when sure of the voltage.
Item # M: The motor, powered through a large enough contact on the relay to handle motor current.

The three descending wires to the push buttons are indicative of the name "3 wire" control station. The relay latches in when the start button is pushed. And continues until the stop button is pushed or power is lost.

I am assuming this button assembly to be for aesthetic purposes. There are alternate solutions available through several sources. I use W.W.Grainger out of habit, and they are close to me. They sell a motor switch that, when mounted, appears like a household light switch. However, there is an internal heater that is matched to the motor current. When it trips, it must be manually reset. By switching OFF, then back to ON. For single phase, fractional horsepower motors it is a very elegant solution. I have several on my machines. There are also several switches from Grizzly that I have also used on dangerous woodworking machines. A large paddle to switch off power by "swatting" at the switch. A great improvement on a table saw. Handy on others.

The only issue with them is the ability to handle the current of your motor. Grizzly also has a single phase motor starter at a fairly low price. Your push button station could be used / wired in place of the existing Start-Stop buttons. Perhaps you will find your solution in one of these. I hope these have given enough insight into the situation to help.

http://www.grizzly.com/products/5-HP-Magnetic-Switch-Single-Phase/T20551
http://www.grizzly.com/products/Paddle-Switch-120-230V/D4151
https://www.grainger.com/category/m...switches&sst=subset&nls_boost_words=noContent

Bill Hudson
​

 

[British Steel]

That diagram is for a 220V motor, where you have two HOT lines.

Nope, just following rest-of-the-world practice where anything other than the earth/ground is disconnected - e.g. 240v single phase where both phase and neutral are switched.
Most of Europe requires earth-leakage breakers for safety and the neutral can have sufficient residual voltage on it to trip the breaker if shorted / low resistance to earth so disconnecting the neutral avoids nuisance trips during test and maintenance - and it's a good idea where phase and neutral can be reversed leaving the equipment live...

Dave H. (the other one)

 

[Blackjackjacques]

Nope, just following rest-of-the-world practice where anything other than the earth/ground is disconnected - e.g. 240v single phase where both phase and neutral are switched.
Most of Europe requires earth-leakage breakers for safety and the neutral can have sufficient residual voltage on it to trip the breaker if shorted / low resistance to earth so disconnecting the neutral avoids nuisance trips during test and maintenance - and it's a good idea where phase and neutral can be reversed leaving the equipment live...

Dave H. (the other one)

Switching or breaking the neutral, except in exceptional circumstances, is forbidden here in the US and I'm pretty sure is also the case in both the UK and Europe. In the case of a two pole motor start-stop circuit, the latching circuit described provides a Low-Voltage Protection (LVP) scheme using two pole switches configured in a latching arrangement (a hold-in contactor, etc). I am not sure what you mean by an earth-leakage breaker since in a balanced system, there should be zero current in the neutral. If you mean a system that detects neutral current in a 2-pole or multi-phase system and then trips, that is another issue. If you are referring to a GFCI, then ground fault current is inferred if the return current is less than the pole (send) current.

 

[British Steel]

Actually, no - there's a (rest of the civilised-) worldwide move towards double-pole switching particularly for power outlets serving "portable appliances" and within those appliances, I suggest you read the latest edition of the Wiring Regulations that apply in the UK (17th edition, with a few addenda while we work up to the next*) for a good "grounding" - THIS IS NOT AMERICA.

How the world outside the USA practices electrical installation - we don't split (centre-tap) a single 230-volt phase for two 115-volt services, our distribution is three phases each of 230v to neutral (which is at earth potential, or *should* be), domestic service is normally one of the three phases plus the neutral (which *may* be tied to local earth, called PME in European parlance, and IS ALWAYS earthed at the distribution transformer ("substation" in non-technical terms)), industrial / commercial service takes all three phases plus neutral for 230v (phase-to-neutral) ancillaries (lights, computers, small heaters, kettles ), 415v (phase-to-phase) for heavier loads (machinery, air conditioning, heating etc.).

Earth-leakage breakers aka ELCBs (similar in concept to the USA's GFCI which senses current actually from the ground wire so require adequate ground connectivity) have been overtaken by Residual Current Circuit Breakers or RCCBs, ( AKA Residual Current Devices, RCDs), they don't directly measure earth or neutral current, they measure imbalance in the supply (30mA is typical. they go as low as 5mA for medical applications, up to 100mA for use only to protect cabling, e.g. buried sub-mains) so should any current not flow in and out through the phase and neutral (or the 3 phases and neutral) indicating a current to earth, they trigger and shut down the supply. Hence the name "residual current"- they DO NOT rely on earth cable continuity, and will trip safely without a cabled earth if there's a "dangerous" current imbalance.

Rest-of-the-world wiring is rather different from the USA, e.g. if a neutral wire fails/goes faulty, we don't have appliances dying or catching fire, as there isn't the risk of low-power, low- (115) -voltage equipment finding itself supplied by 230v, ours is 230v all though and a failed neutral just stops everything working (BUT can leave everything potentially live through the other conductor - hence double-pole switching in case of phase-neutral reversals).

Some examples of common-or-garden household electrical fittings:
UK-standard RCD:
https://www.tlc-direct.co.uk/Images/Products/size_3/CPR100.JPG

Dual Pole switched (UK) sockets:
https://www.tlc-direct.co.uk/Products/BG822DP.html

Dual-pole MCB (Magnetic Circuit Breaker - found in consumer electrical supplies)
https://www.tlc-direct.co.uk/Products/CM9810B.html

"Incomer" main supply switch fitted at far end of a consumer unit - note it's double-pole:
https://www.tlc-direct.co.uk/Manufacturers/Contactum_C/CP_Range_Main_Switch/index.html


This is the site for my local electrical supplies house (part of a nationwide chain), no endorsement intended nor association other than as a happy customer! This is all vanilla, standard-fit stuff for homes / premises built since well before the last millennium ended.

Dave H. (the other one - and a qualified electrician for the UK, along with electronic engineer)


* BS 7671: 2008 (Seventeenth Edition) 3rd Amendment - 2015 . British Standards Institute, about $100 US, following it is *compulsory* for any electrical work that attaches to any kind of supply above 12 volts.
https://www.tlc-direct.co.uk/Products/BK1717slash3.html?ad_id=15790937220&source=msn&kw=wiring regulations&matchtype=e&qry=wiring regulations&msclkid=5c061636477a13c0fb064c87f981e464

 

[whitmore]

Actually, no - there's a (rest of the civilised-) worldwide move towards double-pole switching ...

Earth-leakage breakers aka ELCBs (similar in concept to the USA's GFCI which senses current actually from the ground wire so require adequate ground connectivity)....

Just two quibbles: an elderly switch labeled '125V' was the instigation of this thread, so it's probably most relevant to
old practices in the USA. One-pole switching for 125V, two-pole for 220V... If the switch includes a relay, it
would likely be wired for one-pole (Line) switching. The depicted "lamp" gizmo looked like it was more than a bulb in a socket.

And, while a GFCI responds to line/ground or neutral/ground current, it does so by sensing the Line and Neutral currents
in differential mode, and NOT by sensing, or interrupting in any way, the ground wire. The 'test' button is
the important functional use of that ground wire by the GFCI devices I've used.

 

[Blackjackjacques]

Actually, no - there's a (rest of the civilised-) worldwide move towards double-pole switching particularly for power outlets serving "portable appliances" and within those appliances, I suggest you read the latest edition of the Wiring Regulations that apply in the UK (17th edition, with a few addenda while we work up to the next*) for a good "grounding" - THIS IS NOT AMERICA.

How the world outside the USA practices electrical installation - we don't split (centre-tap) a single 230-volt phase for two 115-volt services, our distribution is three phases each of 230v to neutral (which is at earth potential, or *should* be), domestic service is normally one of the three phases plus the neutral (which *may* be tied to local earth, called PME in European parlance, and IS ALWAYS earthed at the distribution transformer ("substation" in non-technical terms)), industrial / commercial service takes all three phases plus neutral for 230v (phase-to-neutral) ancillaries (lights, computers, small heaters, kettles ), 415v (phase-to-phase) for heavier loads (machinery, air conditioning, heating etc.).

Earth-leakage breakers aka ELCBs (similar in concept to the USA's GFCI which senses current actually from the ground wire so require adequate ground connectivity) have been overtaken by Residual Current Circuit Breakers or RCCBs, ( AKA Residual Current Devices, RCDs), they don't directly measure earth or neutral current, they measure imbalance in the supply (30mA is typical. they go as low as 5mA for medical applications, up to 100mA for use only to protect cabling, e.g. buried sub-mains) so should any current not flow in and out through the phase and neutral (or the 3 phases and neutral) indicating a current to earth, they trigger and shut down the supply. Hence the name "residual current"- they DO NOT rely on earth cable continuity, and will trip safely without a cabled earth if there's a "dangerous" current imbalance.

Rest-of-the-world wiring is rather different from the USA, e.g. if a neutral wire fails/goes faulty, we don't have appliances dying or catching fire, as there isn't the risk of low-power, low- (115) -voltage equipment finding itself supplied by 230v, ours is 230v all though and a failed neutral just stops everything working (BUT can leave everything potentially live through the other conductor - hence double-pole switching in case of phase-neutral reversals).

Some examples of common-or-garden household electrical fittings:
UK-standard RCD:
https://www.tlc-direct.co.uk/Images/Products/size_3/CPR100.JPG

Dual Pole switched (UK) sockets:
https://www.tlc-direct.co.uk/Products/BG822DP.html

Dual-pole MCB (Magnetic Circuit Breaker - found in consumer electrical supplies)
https://www.tlc-direct.co.uk/Products/CM9810B.html

"Incomer" main supply switch fitted at far end of a consumer unit - note it's double-pole:
https://www.tlc-direct.co.uk/Manufacturers/Contactum_C/CP_Range_Main_Switch/index.html


This is the site for my local electrical supplies house (part of a nationwide chain), no endorsement intended nor association other than as a happy customer! This is all vanilla, standard-fit stuff for homes / premises built since well before the last millennium ended.

Dave H. (the other one - and a qualified electrician for the UK, along with electronic engineer)


* BS 7671: 2008 (Seventeenth Edition) 3rd Amendment - 2015 . British Standards Institute, about $100 US, following it is *compulsory* for any electrical work that attaches to any kind of supply above 12 volts.
https://www.tlc-direct.co.uk/Products/BK1717slash3.html?ad_id=15790937220&source=msn&kw=wiring regulations&matchtype=e&qry=wiring regulations&msclkid=5c061636477a13c0fb064c87f981e464

Thank you for your references - however, I was unable to find in any of them - evidence of the "worldwide" movement for switching of the neutral - however, your devices do look prettier than ours. The relevant breakers you show in your references show what appear to be 2-pole breakers - that open each leg - but not the neutral -- same as ours!

From a distribution standpoint, I also think it an advantage to routinely run 3 phase services to residential customers - however - they don't, and that issue is irrelevant. I am having difficulty understanding your reasoning as to how loss of a neutral (in the US) results in fire. In a 120V (single phase or one leg) installation, loss of neutral results in the appliance to stop working altogether. In a 240V, 2-pole arrangement, the neutral is not connected and not a factor - with the small exception for appliances (such as washing machines for example) where 120V service may be needed for a 120V control circuit servicing the machine - in which case, the neutral is connected but only for the 120V circuitry. In 3-phase circuits, sometimes they bring out the neutral, sometimes they don't. In a 3-phase Delta circuit, as used for higher power equipment for dedicated 3-phase loads - there is no neutral (and please don't identify a corner-grounded Delta as a counterexample). In a 3-phase Wye, the neutral is frequently not used or even "brought out" since in a balanced Wye, there should be zero neutral current - however, in cases with heavy industrial loading, neutral currents are monitored as a means of tripping breakers in the event of an abnormal event.

Here in the US, we like to ground metal enclosures and other relevant metal parts in case a pole should somehow come loose and energize an exposed electrical shock hazard - and to "crowbar" the breaker to OFF. In this regard, solid, effective and continuous grounding is at the core of US electric code architectures as governed by the National Electric Code (NFPA 70). This is also the case in Canada.

Therefore, I do not understand the basis of your rant.

Cheerio.....

 

[British Steel]

Ummm.... Look closely at the breakers, RCD etc. and you'll see that one pole is marked "N" - for "Neutral", one is marked "L" - for Live. ONLY THE USA USES SPLIT-PHASE 230V. So, you've pretty effectively demonstrated that your "knowledge" doesn't stretch beyond the continent of North America...

The rest of the developed world uses "native" 230v single-phase, no 115v service derived by centre-tapping the final single-phase delivery and calling it neutral (with the exception of 110v Site Transformers for hazardous environments e.g. construction sites - and they're isolating transformers with an earthed centre tap so each "leg" is 55v from earth potential, for safety).

Our 230v service doesn't have a centre-tap neutral, it's between phase and neutral, is that too difficult for you to understand? So there's only one phase connection ("leg" in your terms) in a 230v single-phase circuit, not two, plus the (genuine, earth-potential) Neutral and a two-pole breaker disconnects Phase AND Neutral...

Much of Europe, at least, and some of the UK runs 3-phase to residential buildings, it's more efficient to do so (and cheaper, lighter cables for the same load wattage), sadly in the UK most homes have 230v single phase (one Live phase of the three, the neutral from the transformer's star point), often adjacent houses are on alternate phases for balance (then sods like me run big welders and rotary convertors, and pull the neutral away from earth if it's not adequately connected - hence the possibility of resifual voltages on the Neutral, and the legal requirement (at least since the last few decades of the last millennium) to switch it at the premises incoming connection along with the phase/s).

3-phase in Europe and the UK is ALWAYS delivered with a Neutral connection, allowing single-phase loads at 230v, larger loads use the full 415v (not 208 as per the USA) across two or more phases (e.g. 415v welders, which in the USA would draw more current on a 230v circuit and need heavier cabling unless on a 480v circuit, which won't be in many homes)...

How would loss of the Neutral on US split-phase cause a fire? pretty simple, lose the Neutral, have a high-current device on one side of the split (e.g. 1000W heater or similar), a low-current device on the other, and you're effectively putting 230V with an 11-Ohm series resistor on a device intended to cope with 115v, the current in e.g. its power transformer rises with the increased voltage, it gets hotter and hotter... The user would probably find the rear-panel fuse blown and replace it with a .25 calibre cartridge too, for full Darwin Award status

Dave H. (the other one)

 

[Bi11Hudson]

Well, with all the spitting and posturing, I am reminded of two tom cats squaring off. So, I'll just jump in and throw my two cents worth in too. Not that two cents worth is worth much these days, but then again, neither am I. Retired for the last ten, and into American electrical systems for much of the preceding 40 plus years. Although my degree in EE was earned in an offshore school. And that "offshore" is what I am speaking about now.

Having traveled, and worked, widely since 1969, I feel I must speak up for those third world countries that have been refered to as unindustrialized. Although I have never traveled to Europe, I am decidedly disinclined to now. Not with that sort of attitude anyway. However, on the Pacific side, things are more like the US in their electrical installations.

I can't speak of the now, I was there in the seventies and eighties. But places like Australia, New Zealand, much of Asia (including Japan), and South America would seriously take exception to being called unindustrialized. Now, conceded, most of those places use 50 Hz. Which is decidedly safer than the US's use of 60 Hz. But for the most part, 3 phase is 3 phase. And unless there is a "wye" connected transformation involved, residential service is single phase. Has been since the forties, at least. A ground is a ground, period. And a neutral is a neutral on wye systems. I am sure there was some six phase there, just as there was here. But only in heavy, industrialized locations. It isn't really suited for residential use. Nor was 25 Hz, or 40 Hz, or 2 phase3 wire. But in its' time, it served a valid purpose.

Oh, and by the way, although grounded delta is still grandfathered in, it has been outlawed in the States for a very long time. But it still exists and is in use. I got to taste copper several times on it. Now, I can't speak for Canadians but I am sure they use a similar system there. Else, a lot of appliances would self destruct when connected.

And to the other side of the argument, hospital systems are one of the few places that do not have a neutral as such. And argument it is, two grown men spitting at each other. Over trons, yet. When you get zapped, you get zapped.

 

[Bi11Hudson]

The bottom line here is that we are here to assist a woman in San Francisco (Ms Susan) with an electrical problem. And last I checked, that city was inside the United States. They may do things in the UK the way they want things in the UK. But in this country, we do things the way things are done here. Like it or not, that's the way things are done here for the last couple of hundred years.

Bill Hudson​