NVR no volt release what does this mean in USA?

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  #1  
Old 04-12-15, 04:41 AM
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NVR no volt release what does this mean in USA?

I live in Wales and our rules say unless the is a safety issue motors must not auto restart when power is returned after a power cut.

Most of our starters automatically do this be it direct on line, star/delta, Auto transformer, resistor, inverter, or soft start. There are cases where motors have a simple switch and the cheap method is to use an active RCD (GFCI) which auto drops out with a power cut.

However is seems the term NVR is swapped with DOL in some USA Utube videos and out of interest I wonder what you consider is NVR?

I just wonder if it is what we consider as anti-single phase device as in the UK the term NVR is hardly used yet is seems to be used a lot in USA.

Remember I am an electrical engineer so I do know standard systems but it's the language between USA and UK which causes my problem. We all both sides of the pond use words incorrectly so not looking at technical but what it often refers to.

When in UK we say we are going to get a DVD we mean buy or rent a film even though a DVD has many other uses. So what to NVR mean in USA?
 
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Old 04-12-15, 05:00 AM
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Two nations separated by a common language NVR just means what it says, if there is no voltage, then the starting mechanism is released and must be reset or turned on in the event of power failure and restoration.

You use "bonnet", we use "hood". You use "cubby", we use "glove box". You use "dipper", we use "dimmer switch". Believe me, restoring British sports cars will put you in a language learning curve.
 
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Old 04-12-15, 01:16 PM
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Most motors restart here after a power failure and use NVR's if it were a safety issue of the motor restarting.

At least as far as non commercial. Commercial and industrial would be on a case by case basis.
 
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Old 04-12-15, 02:05 PM
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It is my experience that few motors of less than two horsepower, at least in residential usage, will have a motor starter or relay.

In commercial and industrial usage motor starters are far more common and ALL will release on a drop of power. Whether or not they will allow a restart depends mostly upon the pilot device, the means of initiating the motor starter, and the wiring. So-called two-wire pilot devices such as a level or pressure switch WILL cause restart after a power failure has passed. The two-wire pilot device uses a maintained contact that allows power back to the coil of the starter as soon as power is returned.

Three-wire pilot devices, mostly a start/stop combination pushbutton, are momentary contact devices where the stop button is a normally closed switch in series with the power, overload devices and the starter's contactor coil. The start button is a normally open contact that connects the other side of the power source to the other side of the contactor coil. There is an auxiliary contact that is mechanically connected to the main contactor that is wired in parallel with the start button. With this pilot device and arrangement the starter will NOT restart on a resumption of power after an outage.

In the US the former (two-wire pilot) is usually called Low Voltage Release and the latter (three-wire pilot) is called Low Voltage Protection.
 
  #5  
Old 04-12-15, 02:37 PM
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For USA:

OSHA 1910.213 (b)(3) for woodworking machines states, "On applications where injury to the operator might result if motors were to restart after power failures, provision shall be made to prevent machines from automatically restarting upon restoration of power."

It makes common sense to use magnetic starters for motor control for things like conveyors, machine shop tools and others that could cause injury if they experience an uncommanded restart. For things like HVAC motors, not usually necessary.
 
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Old 04-12-15, 02:43 PM
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Thanks I thought it may have the same names. Just wanted to check. As to bonnet and hood correct. But we call it a glove box also, although we dip head lights which means the light is aimed lower to reduce how bright we still say to dim it.

It is a little easier here as films are not voiced over we hear all the USA words. We are told our films have voice over for you.

Where we are lucky is we started after you and learnt from your errors. So we use 230 volt so current is lower and 50 Hz so less losses on power lines. But only because you did it first and we could see your errors.

It would seem you use some old English words correctly like fanny we only use that to describe a hoop for lace with anything else it is rather rude. Some words in the UK have completely swapped meaning decimate did mean get rid of 1 in 10 but now means get rid of near everything.

The small room formed underneath the stairs when boxed in we call a cubby hole but otherwise not seen the word cubby used.

In domestic wiring we use a cable called twin and earth. There are three wires one brown, one blue and one bare copper inside a grey outer originally that grey outer was lead and there would have been two cores, when the lead was replaced with plastic we added the earth wire often a smaller gauge to other two to replace the lead.

The other big difference is our ring final where we use a 32A supply onto 20 amp cable formed into a ring and take many 13 amp sockets from this and rely on the fuse in plug to stop overload. It was done after second world war and continues to this day.

For lights we daisy chain light to light and then take a switch wire from each light. It means we have power all the time at each lamp so emergency lighting or ceiling fans are easy to install. I think you wire switch to switch.

And we use different colours it was red, yellow and blue plus black for neutral but changed to Brown, Black and Grey with Blue for neutral. We harmonised with Europe and having old wiring with blue as phase and new wiring with blue as neutral has caused problems.

Every now and again we get USA equipment. I look at white and black and would normally use black as neutral but know when there is a white it swaps around.

110 volt stuff is a real problem as in the UK it's either 55 - 0 - 55 volt or 63 - 0 - 63 when from three phase. We call it reduced low voltage and your 0 - 110 is not permitted on our building sites. All 110 volt stuff is always double pole switching which means USA stuff is often not permitted even if it will run on 50 Hz.

We have four earthing systems IT is banned for everything but shaver sockets and is where there is no earth. TT uses an earth rod and TN uses suppliers earth and is split into two. TN-S has a separate neutral and earth all the way back to transformer and TN-C-S has neutral and earth using same wire in the street it separates once in the house. The letters are from the Latin names.

We call 230 volt low voltage and 12 volt extra low voltage. Ulster is the odd one out with 3kV volts rest use 3.3kV and 132kW in the main. Our streets are supplied from buildings with 500A output transformers there are some rural areas with pole mounted transformers but they are rare. In very rural areas we have split phase 230 - 0 - 230 often this just serves one farm.

So how do we compare?
 
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Old 04-12-15, 02:54 PM
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On posting reply found more answers. It would seem it is same as UK. Here also domestic stuff often does not have anything to stop re-start after a power cut but industrial normally it does.

From your answers it would seem U-tube has published some stuff which is far from accurate which is nothing new.
 
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Old 04-12-15, 03:09 PM
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Here the nominal voltages in residential usage are 120 and 240 volts, not the commonly misrepresented "110 and 220" volts. Our 120 volts is derived from center tapped 240 volt secondary transformers with the center tap being grounded (earthed) and called neutral. City distribution voltages may range from a low of about 2300 volts to a high of 26,000 volts. Long range transmission voltages are commonly 115,000 to 230,000 volts and some long transmission lines are in excess of 500,000 volts. We also have some direct current long transmission lines that use rectifiers at the origin and inverters at the receiving end to minimize losses on the line itself.

Three phase is rare in residential usage with the exception of large multi-family complexes and even in these the power at any single residence is only single phase. Three-phase is most common in commercial and industrial usage with voltages ranging from 208 to 480 being the most common. Wye (or star) connections on transformer secondaries is the most common although delta connections used to be common. With the wye connections the common point is grounded-earthed- and called neutral with phase-to-neutral voltages from 120 to 277 being most common. Larger industrial systems will often use voltages of 4,160 and 13,800 for primary distribution and for larger motors.

By code definition any voltage less than 600 is called "line voltage" although we also have a "power limited" voltage designation that is less than 50 volts. Between 600 and about 12,000 volts is referred to as "medium voltage" and anything higher than about 12,000 is called "high voltage". Most lay people know nothing about these designations and call anything 120 volts and above high voltage reserving the term low voltage to around 24 volts or less.
 
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Old 04-13-15, 03:09 AM
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Here in UK it is nearly the same. DC and AC have different demarcation between extra low voltage less than 50 volt AC to earth reduced low voltage that 55 ~ 63 volt to earth our 110 volt system. Low voltage 50 ~ 1000 volt High volts being over 1000 volts AC can't remember after that.

But volts in small factories and homes are the same. So 230 volt +10% -6% supply to homes and factories to earth. So 400 volt phase to phase mines and quarries are special and large factories may have a high voltage supply.

In the premises volt drop permitted 3% lights and 5% power. This is the limit in real terms most homes have 230 ~ 240 volt supply. Solar panels are causing a problem as they are required to switch off at 253 volts and need to stay off for a set time to stop them generating when supply is lost. So just when they are getting the most sun they auto switch off.

So people are fitting them on their homes with a promise of massively reduced bills but for most of the time they are switched off. To start with home owners did not realise as the meters would not measure power out so they were credited with power that size panel should make. But as smart meters are fitted people realise they are not saving what they thought.

How you get on with such low voltages I don't know it must be far worse.
 
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Old 04-13-15, 03:27 AM
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How you get on with such low voltages I don't know it must be far worse.
Not sure if you mean the supply to our homes or the output from solar arrays. For our homes it is simply the way it is. It does mean that we have to use larger conductor sizes and 200 ampere services seem to be the norm for single family residences.

For the photovoltaic panels (solar) it is much more complicated. Small installations usually have a medium to large battery bank that is recharged from the solar array and controlled by a "charge controller" that can vary the voltage within limits to keep from overcharging the battery. Most of the load on these small installations is DC lighting at battery voltage and some items such as refrigerators that are made for the low voltage DC. As the size of the installation grows inverters are added to change the battery DC to line voltage (usually 120 volts) AC for normal usage. Larger installations will often not have the battery at all but use a "line interactive" inverter that is capable of connecting the DC from the solar panels to the utilities AC distribution directly. These line interactive inverters have the ability to adjust their output voltage and overcome the problem of high voltage on the utility side without disconnecting the solar. They will also disconnect completely from the solar if the utility connection is dropped, a feature know as "anti-islanding" which means that in the event of losing the utility power you do NOT have the solar as back-up but are completely without power. As you can imagine, all these special inverters and controls adds significantly to the cost of the installation and were it not for numerous government subsidies the cost of solar would be almost prohibitive.
 
  #11  
Old 04-15-15, 04:11 PM
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You call it a "line interactive" inverter we call it a "grid tie" inverter but it would seem they are nearly the same.

The "anti-islanding" is also required in the UK. In essence the way this works is to measure voltage. If a block of 40 houses have solar panels on say 20 of them then should the supply fail i.e. some one in error has dug up the cable then either the voltage will raise or fall. If each unit disconnects when the voltage exceeds the limit in either direction and does not reconnect for 15 minutes then quickly one by one all the solar panels will close down. Simply looking for power to be present is not good enough as each panel would provide power to panels on the other houses.

Now this has resulted in a major problem as once the panel hits 253 volts it closes down to 15 minutes with one house with panels on this was rare but with a street full of houses with panels it is happening more and more. Some panels are fitted by firms who rent ones roof space so you get the power you use from the panel but they get the government subsidies as long as it's producing power. These companies tend to set their panels slightly high even 1 volt means theirs is the last to drop out. But people who own their own can't access the software so there panel is for ever tripping out on over voltage. Complaining to supplier they will drop the transformer tapping but only so far get all 40 houses with panels and they just can't set transformer low enough as in the evening the power required goes up. Remember we often have 40 houses from one transformer and to keep between 220 ~ 250 volt no load to full load may not be a problem but to keep between 220 ~ 250 - 20% to full load is something else. It will need a whole new bred of transformer which can auto change tapping to match voltage to load.

The suppliers are not willing to do this so unless the government force them people will have paid out for the panels but will get no return.
 
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Old 04-15-15, 04:52 PM
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You call it a "line interactive" inverter we call it a "grid tie" inverter but it would seem they are nearly the same.
Both are used here. The guy I work with on some systems calls them grid tie.

40 houses on one transformer.
Yep... I can see that as an issue to hold voltage constant.
 
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