# Using Magnetic Contactors in Residential Application

#### BillB3857

Joined Feb 28, 2009
2,543
You're right, Max. That's what I get from just doing a copy from the internet and looking only at the logic and not all the labels.
Thanks for catching that!

#### MisterBill2

Joined Jan 23, 2018
8,440
Doesn't allow any error in order to satisfy the ±10% guaranteed or recommended supply tolerance for residential service standards. When running the higher voltage appliances etc.
This is the standard here, and AFAIK most of N.A.
In the event of a 10% drop you would end up with 187v!
Max.
In those systems, 208 volts is the center voltage. That is what you get with three 120 volt phases. And generally they are able to hold much better than +/- 10%

Joined Jul 18, 2013
22,839
In those systems, 208 volts is the center voltage. That is what you get with three 120 volt phases. And generally they are able to hold much better than +/- 10%
I am fully aware what phase to N is on a 208 3ph. Not sure what you mean by "Centre Voltage"? It is 208 phase to phase. 120v phase to star neutral.!
±10% ????All depends on the service provider? Brown outs etc.
With 208 there is no way to go except up!

Max.

Last edited:

#### GetDeviceInfo

Joined Jun 7, 2009
1,844
The advantage of a relay, when properly set up, is that in the event of a power failure, even wnen power is restored, the load isn't activated until commanded to do so by the push of a button.
How is that an advantage in a residential setting. I can think off some disadvantages.

#### MisterBill2

Joined Jan 23, 2018
8,440
I am fully aware what phase to N is on a 208 3ph. Not sure what you mean by "Centre Voltage"? It is 208 phase to phase. 120v phase to star neutral.!
±10% ????All depends on the service provider? Brown outs etc.
With 208 there is no way to go except up!

Max.
By "center" I meant the middle of the range of voltages. Perhaps "target" would have been better, or maybe the "mean" voltage.

#### Janis59

Joined Aug 21, 2017
1,330
Why You guys are speaking a nonsense about 208 Volts if the 380/220 is a century long Worldwide standard containing both voltages in it name, 380 between phases and 220 (not 208) from any phase to the null-wire.

And there in no ANY need to explore the motors if motor may be built only two ways, or delta or star. One have 380 V coils other 220 Volt coils.

All all all other type of motors are few continent specialisms creating nothing but headache. And if the author have 380/220, it means he is not living in those exemption continents like N-America and may not meet the "full beauties" of 60 Hz 110V.

Ive met, it still stays unused in cellar. No way exempt the frequency invertor plus PWM how to work it up. But all I tried soon was exploded as soon the power may change a bit. I bought this 3 kW angle grinder from US Military Base soldiers near the fence exchanging it against the vodka bottle. That was bad idea to do so, very bad indeed.

Really, WHY the whole world may not unite on the common frequency and voltage standard? Just any. As well the plug standards. Most worst are the variety.

#### Janis59

Joined Aug 21, 2017
1,330
By the way, magnetic launchers are all containing the max amperage written on them, but those figures rather different meaning about. Old soviet series if written 25 A means may sure put the inductive (motor) load for 25 Amps and believe it will work for the century. Old, very large, clumsy, but damn trustful. The Chineese and Polish as well - elegant, small, but if written 25A means even working at 16 A after 100 on/off cases will burn with an open flame. Probably 10A will work rather well. Just be warned, class must be choosen two standard gradations higher if not want a fireworks at cellar. German - much better, but better to take one gradation higher, however if light start regime may believe a figure. Standard gradations are 5-10-16-25-32-63 Amps.

#### MisterBill2

Joined Jan 23, 2018
8,440
Why You guys are speaking a nonsense about 208 Volts if the 380/220 is a century long Worldwide standard containing both voltages in it name, 380 between phases and 220 (not 208) from any phase to the null-wire.

And there in no ANY need to explore the motors if motor may be built only two ways, or delta or star. One have 380 V coils other 220 Volt coils.

All all all other type of motors are few continent specialisms creating nothing but headache. And if the author have 380/220, it means he is not living in those exemption continents like N-America and may not meet the "full beauties" of 60 Hz 110V.

Ive met, it still stays unused in cellar. No way exempt the frequency invertor plus PWM how to work it up. But all I tried soon was exploded as soon the power may change a bit. I bought this 3 kW angle grinder from US Military Base soldiers near the fence exchanging it against the vodka bottle. That was bad idea to do so, very bad indeed.

Really, WHY the whole world may not unite on the common frequency and voltage standard? Just any. As well the plug standards. Most worst are the variety.
Here in the USA we use 120 v because the shock hazard and insulation requirements are not as demanding. In addition more items use smaller amounts of power and the voltage step down from 120 is cheaper than from 220. also our electrical outlets and plugs can be much smaller. One more thing is that municipal electrical distribution started here, and the higher voltages elsewhere were selected for the benefits of distribution, not use.
And consider that for much of Japan the voltage was, and is, 100 volts.
Sixty hertz was selected as a good frequency based on the speed of steam driven generators, while 50 hertz was what worked with water powered generation. In aircraft 400 and 800 hertz prevail because the transformers can be much lighter. And, in addition, power lines across the ocean are impractical and so there was no need to be compatible. And most 50 Hz equipment will work well on 60Hz.

#### Janis59

Joined Aug 21, 2017
1,330
RE: ""Here in the USA we use 120 v because the shock hazard"" - I know, however even 240 V is considered to be safe enough in the UK, thus the rest of World the 220 V is completely OK. In my 61 years I had been electrocuted from 220 at lest 1000 ocassions and surprize - still alive. I had been electrocuted from 380 couple of times, still alive, I have been electrocuted from DC 600V at lest twice, yes it are dramatic memories but still alive, I ve been elctrocuted from 15 kV capacitor few tiomes, and even that not killed me dead. However I know a 100% sure cases where engineer wife was electrocuted from 4 and half Volt battery to irreversible death, many human had lost a life just from 12 Volts, thus, to live or to die its more about psychology and just a fortune nor a voltage. I would vote for the 120V safety concern is absolutely last rational argument to be mentioned. By the way, according to old soviet standard the safe for slightly electro-dangerous flooring was 36 Volts, and by EU standard it is 42 Volts, what is far less than 120 V. And for hardly unsafe flooring, like wet floors those are 12 V at both standards.

RE:""the voltage step down from 120 is cheaper than from 220"" - wonder if. Transformer core size is dependant only and exclusively from frequency, and I agree that You Americans for this criteria are higher as our 50 Hz, however 50 ir "rounder figure" like 60 . So, even the MASS of copper in trafo is dependant only of power but not voltage. Voltage steers only the turn count and cross section. It is ambiequivalent by mass are there 1000 turns with 1 mm2 or 100 turns by 10 mm2. But there sure IS one factor You forgot, the active loss. As lower the voltage the higher loss in the CABLING, and already the distances so near like a 200-300 meters afar those loss are owewhelming. Therefore as higher the voltage, the less are losses.
3) ""And most 50 Hz equipment will work well on 60Hz."" - Wonder if. About async motors, maybe. But washing machines sure not. Fridges sure not, flex (corner-grinder) machines sure not, radio/TV/PC etc sure not etc etc. Okay, the nichromium heater spirals and "lenin`s lamps" still operates good
4) RE:""In aircraft 400 and 800 hertz prevail because the transformers can be much lighter"" Yes, sure but the price is dramatic - a loss factor. However this moment as the ferrite trafos are invented the 40-200 kHz are more widespread and even 3-6 MHz are obvious at sci pubs. Thus the SMPS technique is strongly take a deal about 1 MW scale projects and even more. The last brick I had deal with was 800 Volt 1200 Amp and that is sure not a most powerful one in the markets.

Last edited:

#### shortbus

Joined Sep 30, 2009
8,468
Here in the USA we use 120 v because the shock hazard and insulation requirements are not as demanding
Then, if that is true, explain why most residential or industrial wire is rated at 600V? Unless a higher voltage is needed.

#### JWHassler

Joined Sep 25, 2013
284
What has not yet been mentioned is that the coil that makes that contactor close the circuit requires a fair amount of power to operate, and so it is going to be getting warm.
And noisy: not a problem in a factory, but you'll notice that hum late at night in a residential situation

Joined Jul 18, 2013
22,839
And noisy: not a problem in a factory, but you'll notice that hum late at night in a residential situation
Not if you use a DC coil!
Also a remote PB station can be used with indicator.
Max.

#### BillB3857

Joined Feb 28, 2009
2,543
How is that an advantage in a residential setting. I can think off some disadvantages.
My wife has a couple of computerized sewing/embroidery machines and a short power interruption (some would call it a major dip, but enough to cause the lights to blink) can result in major damage to the control system. If there is a major dip, the relay drops, does not come back on until reset. This allows the machine system to do a full shutdown without being confused by the power coming back on while it is still shutting down. They don't shut down the instant incoming power is dropped. The internal power supplies keep them up for a short time.
Of course, if you are not home when there is a power failure, if it is only a short one, the power would be off until you returned. Most refrigerators will hold safe temperatures for several hours. What do you do when the utility power fails for a few days? Several years ago, we lost power for 8 days due to an ice storm.

I guess I must ask... Why do you feel you need a contactor or relay in a residential system?

Joined Jul 18, 2013
22,839
If there is a major dip, the relay drops, does not come back on until reset.
I guess I must ask... Why do you feel you need a contactor or relay in a residential system?
As I mentioned, remote control/indication might be one, BTW your comment reminds me of another advantage of using a DC contactor coil/control, with power dips, the DC coil is much less likely to drop out with a brown out, compared to AC version.
Max..

#### MisterBill2

Joined Jan 23, 2018
8,440
Then, if that is true, explain why most residential or industrial wire is rated at 600V? Unless a higher voltage is needed.
Many ratings use a safety factor. And I have had a few extension cords rated at 300 volts. That 600 volt insulation rating allows that wire to be used in areas where 580 volts is also present.
In addition, I happen to like having an adequate safety factor. My tower climbing safety belt is made of webbing rated for at least 5000 pounds working load.

#### KeepItSimpleStupid

Joined Mar 4, 2014
4,633
I once tried to look up voltage ratings of wires. Got nowhere. Dunno if 600 V is AC, DC, 0-peak or what. Units really aren't specified.

#### MisterBill2

Joined Jan 23, 2018
8,440
I once tried to look up voltage ratings of wires. Got nowhere. Dunno if 600 V is AC, DC, 0-peak or what. Units really aren't specified.
The 600 volts is the voltage that an electrician would read on an accurate VOM (Multimeter), just like the 120 volts and the 240 volts. Insulation voltage ratings relate to classes of wiring, as much as anything else. Why is this a big deal???

#### Janis59

Joined Aug 21, 2017
1,330
RE:""Then, if that is true, explain why most residential or industrial wire is rated at 600V?""

I am just sure the reason are 3F 380 V what after full wave rectifier on the capacitors produce the 539-2*0,7=534 Volts. Within margins of tolerance 10% it is 592 V or rounding 600 V.

#### KeepItSimpleStupid

Joined Mar 4, 2014
4,633
The 600 volts is the voltage that an electrician would read on an accurate VOM (Multimeter), just like the 120 volts and the 240 volts. Insulation voltage ratings relate to classes of wiring, as much as anything else. Why is this a big deal???
Makes sense. It's just one of those oddities. Scientifically, I'd figure peak voltage.

So 300/1.4=214 which is 168 V 0-peak+(margin of safety). You would generally use 300 V rated wire for 120 VAC.

Finally: https://sielearning.tafensw.edu.au/toolboxes/Electrotechnology/toolbox/hq/mag1/ratings.htm#voltage

The voltage rating of a cable refers to the maximum voltage to which it may be connected (and have running through it).
If the voltage rating is exceeded, the insulation between cable cores, or between a cable core and earth, may break down and cause a short circuit or a fire.

A typical voltage rating is 0.6/1 kV. This means that a cable with this rating is capable of withstanding a voltage of 0.6 kV (600 volts rms) between the conductor and earth, and 1 kV (1000 V rms) between adjacent conductors.

The voltage rating of a particular cable can usually be found on the cable reel or drum.
This is the first time I saw a reference to RMS.

Even this https://en.wikipedia.org/wiki/Electrical_breakdown isn't good, although there is a VI relationship.

Dielectric strength https://en.wikipedia.org/wiki/Electrical_breakdown is typically in V/m, so it's like confusing.

So just like a 3/4 fitting inplumbing is a 7/8 fitting in HVAC and all optical (eyeglass) screws (purchased from an optical supplier) are specified in Overall length no matter the head type.

So when you take: 300 V hookup wire: https://www.awcwire.com/productspec.aspx?id=ul-1569-hook-up-wire
• Insulation: Polyvinylchloride (PVC), 0.016" nominal insulation thickness
Temperature Range: -40°C to +105°C (-40°C cold bend test)
• Voltage Rating: 300 volts

and apply the PVC values from here: https://omnexus.specialchem.com/polymer-properties/properties/dielectric-strength of 10-30 kV/mm things still don;t work out.

0.016" = 0.4 mm.; 0.4 * 10 kV; 0.4 * 10 = 4 kV?

So, something else is going on.

Another search that was hard to find (nearly impossible) is the differences between tape out and line in levels for consumer equipment.

Last edited: