George's Power Supplies

[W9ZSL]

Question.  George has both 230 and 115 volt transformers.  The Gates iron is 230 primary and will provide 1500 DC to the 4-125 or 250 final.  Everything else is 115.  I mentioned early on that I would run 240 to the cabinet and divide it.

After looking at the current-flow possibles in the mains I found balance between both halves of the mains was important.  I plan on plugging into the outlet that leads to our dryer about 10 feet away.  I may tap into that outlet and run 220 to the shack area.  We're talking less than 10 feet so I can keep the rack cord shorter.

Only the RF plate supply will be 220.  RF screen, bias & fils plus the modulator are all 115 iron.  The modulator has a Thordarson plate iron that will give me 1250DC at .3A.  We're looking at 100 watts of audio at a minimum.  The fils for PP 811As are also 115.  All of these have to be balanced on each side of the incoming 220 I assume?  The tap to the dryer is on a solid and little used breaker. 

How critical is it to divide loads from a 220V main into a 300 watt input (max) AM amp and modulator when only the PA plate iron is 220? 

[W3GMS]

George,

You configuration for good design practice requires you to have a 4 wire feed from your service entrance panel.  L1 which we will define as one side of your 240 feed.  L2 which is the other end of your 240V feed.  A neutral and finally a safety ground.  You need that center tap provided by the neutral to assure that you have 120V on each side of that neutral to power your lower voltage 120V primary transformers.  I would distribute the 120V primaries on each side of neutral although that is not absolutely necessary.  Your 240V which is obtained from L1 to L2 will power your larger 240V primary transformer.   Size your breaker back in your service panel for the load current and make sure the wire gauge is adequate for the current level your protecting with the chosen breaker. 

The safety ground should not be carrying any current. 

Hope that helps.

Joe, W3GMS   

[Opcom]

If you have stout wire, balancing won't matter as much. Making the cable as short as possible and making the neutral 2x larger than necessary helps greatly with balance.

I have the same unbalance thing with a rig here where the RF is on one side of the 240V and the modulator is on the other side. Hots are 10 gauge, neutral is two 10 gauges in parallel. With 2000W DC to one side and the other 'off', as would be for CW, it's less than 2V difference in the balance. The safety ground is also a #10. I happened to find a 30FT 'scrap' of 5-conductor cable 8-). would hate to buy that today.

[KA2DZT]

I would follow Joe's advice.  If your dryer line outlet does not have a neutral, you will have a hard time balancing 120v loads across a 240 volt feed.  You need a neutral.

Fred

[The Slab Bacon]

Looking at ur picture and scratching my head leaves me with one design question.

Why are you using plug in replacement rectifiers instead of something more compact like microwave oven diode blocks. (K2AW rectifier diodes, etc)? ? ?

It would give you more room to finagel things around on the chassis, and they are pretty cheap and reasonable. They are also compact and easy to install.
Unless I am going for a "period correct" look, I use them for everything high voltage.

Also, be careful using the dryer feed or dryer socket. Many (most) of them nowadays are wired with 2 hots and a safety ground only. (no neutral)
An easy way to tell is simply to look at the socket. If it has 3 prongs, it has NO neutral, if it has 4, it does.

[N4LTA]

Basically, If you plan to have any 120 volt loads - you must have a neutral. The NEC does not allow any current flowing through the green "ground" or grounding conductor.

As Slab says - many dryers are not supplied with a neutral and have a 3 wire cord. Years ago - the NEC allowed appliances to use the "green" ground to have a few mA of current to run a timer or clock on ranges and dryers. That was stopped and any 120 volt device - no matter how small the current needs a neutral or "grounded conductor"

The neutral may be "reduced" if the load on the 240/120 volt branch circuit has mostly 240 volt load - typically by no more than 50%.

Size your wire for the load using 60 degree C tables for loads under 100 amperes. If the load is "continuous" (operates for 2 hours or more) size the wire for 125% of the load. Size the breaker to the wire size. The breaker does not protect the load - it protects the wire.

A 30 amp breaker will pass 30 amps forever and 60 amps for minutes.



Pat
N4LTA

[KM1H]

The NEC is in business to protect the permanently stupid, keep them employed writing new regs, employ more union electricians and generally cost the consumer money for no added benefit.

The 3 wire 240V with 2 hots and a ground has worked fine for decades in dryers, ovens and similar....no body has been fried by having the 120V devices hung from one hot to ground.

Even several ham products did it including Alpha, Henry, and Johnson.

These days its still OK to hang the 120V fans, etc across one half of a dual 120V winding that is in series for 240V, nothing goes to ground. No overprice wire, conector or outlets required.

In the case where the 240V transformer is only a single winding I suggest seperate 120 and 240V outlets unless you want to rip the house apart to run a 4 wire feed, etc. just to keep your insurance in effect and the building inspector employed.

My HB 2M 1500W amp is still wired the old way for the almost 30 years its been there since it has only a single 240V winding. The feed from the panel is 10-3 and the cord is 12-3. There is no voltage difference between the combined ground/neutral and the copper water pipes overhead which are bonded together there and back at the panel where they are tied to the the ground rods.

If anybody asks its a 1500W heater

[N4LTA]

I am probably one of those idiots that keep themselves employed by the NEC.

Just a little side item - though - the year before the GFI (many say stupidly put into law) was put into law -over 2500 people were killed with 120 volt to ground electricutions.

Last year the number was less than 50

In 20 years time that may add up to as many as 40,000 people that did not die.

If you accidently open that harmless oven ground -feeling safe  because a ground wire has no voltage and can't hurt you - you have 120 volts trying to push that 1/4 amp through your body - likely you won't be killed but if you are under a sink or crammed in a close space - who knows?

The NEC has reasons for every rule. Grounding conductor current is not allowed and in many cases is dangerous. I have witnessed too many injuries and deaths in my career. It's the stuff that seems safe that usually hurts people.
I had a friend from my hometown that went to electrical engineering school at NCSU (same as me) and was a couple of years older. He was killed one summer with a metal Black and Decker drill working under the house when the drill grounded. I am sure that the ground prong was not connected.

Pat
N4LTA

[WD5JKO]

Sometimes the pendulum swings from extreme danger to extreme safety....

I have a Signal 230V/115V Auto transformer here that I'd send George if it were not so dang heavy. Must be good for 15 amps or more. This way with a three wire 230V system (H-H-G) you can make a Neutral in the rack, and any draw from the power line is all 230V with no ground current even though there are 115V loads in the rack referenced to the center tap neutral. Does NEC allow for this option?

I grew up in an old 2 wire 110v system house. I recall my dad straddling two shelves over the basement stairs, house pitch black until the Zippo lighter is lit then looking for the blown screw in fuse. Once found, the pack of spares was always depleted. Then I'd hear, "anyone have a penny"? 

We had a dishwasher in the kitchen, the kind that sat next to the sink, and attached to the sink faucet. The dishwasher had a 3 prong cord in a 2 prong house, so the ground was defeated. Then one day the dishwasher was HOT! Touch the faucet and the dishwasher and it would knock you on your butt. I took a 100 watt lamp and affixed wires to a socket, and put one wire on the dishwasher and one on the faucet. It went full brightness! We used it that way for years!! We knew not to touch it.

These days if someone licks a 9v battery they call a lawyer....

Jim
WD5JKO

[N4LTA]

Yep - That would be perfect - better than a 4 wire feed because the transformer would limit the current.

I grew up with the same system and my "experimenting" sent my father to the service station or curb market late at night looking for a fuse many times.

Pat
N4LTA

[K3YA]

In the case of a ham transmitter there is usually an abundance of ground connections and using a common safety ground and neutral probably isn't such a big deal.  I have been using 3 prong dryer connections for 30 years without issue and have no desire to re do the wiring in my station to correct this.  However, if I was starting with a new installation, I would use 4 wire connection as suggested above.

More of a danger is old transmitters that use fuses on both the hot and neutral side of a 115V primary circuit.  My Collins 30K's do this and sure enough the fuse in the neutral side blew.  Sure enough, I got bit brushing up against something while changing the fuse.  This I need to fix.

[KM1H]

We are talking about a ham install by someone with some smarts, so  trying to spin it doesnt fly Pat.

Most of the morons eliminated from the gene pool prior to GFCI likely had their radio, curling iron, razor, etc fall in the tub or pool with them. Even no coders and CBers are smarter than that.....I think.

Many modern tools and appliances have 2 wire cords

NEC wont even let you enjoy a good tingle these days by limiting line bypass caps to values that are useless for the purpose. Once the nanny state produces rules that protect down to the lowest IQ across the board what will they come up with next? And we will also have a population of breeding morons worse than you can believe.

[N4LTA]

Not trying to spin anything Carl.  Not a thing wrong with a 2 wire cord on a double insulated tool. There is no grounding conductor and no current flowing in it.

I was responding to your review of the NEC:

"The NEC is in business to protect the permanently stupid, keep them employed writing new regs, employ more union electricians and generally cost the consumer money for no added benefit."


We don't agree. I'd bet one hell of a lot of hams don't have a clear understanding of the NEC and the whole idea behind the single point grounding system. Many times have I seen the neutral switched on home made equipment. The AC ground and the antenna ground get confused often. Electrical grounding is not something only idiots don't understand.


I have recently been involved in a very nasty problem with grounding conductor current  - where the grounding conductor was used by a manufacturer of a large piece of equipment as a neutral - 50 amps worth - and they didn't even know this was not allowed.  They stated that a neutral was not required.

The ground was bonded to the water pipe system and the guy removing the valve standing in water had no idea. Imagine how it was holding a 20 pound brass valve with water leaking all over him when the current through the valve was interrupted by his wet self. That's what usually kills people - when you have no ide there is a danger - this guy was not killed thankfully.

Grounds (grounding conductor as defined by the NEC) should not carry current -  That is what the neutral (grounded conductor as defined by the NEC) is for. 

We  agree to disagree - but when someone gets killed  - I don't want to be on your side.
 

Pat
N4LTA

[WD5JKO]

  I once went to change my underwater pool light. The thing was hard wired from a GFCI outlet. So I turned off the breaker, turned off the switch, popped the cover and measured with a DVM to make sure the outlet was dead. So there I was, bare chest wet laying on the concrete with my arms underwater down two feet. When I removed the last screw from the light bezel and pulled the light out of the recessed hole, I was instantly nailed. It was only a few volts, but quite a surprise nevertheless.

 Turns out that the Neutral wire up the power pole was broken loose, so my house was fed 220V with no centertap. The only thing trying to keep things centered was the pool light fixture! If the XYL had turned on something big like the garbage disposal while I removed the light, then I probably wouldn't have survived.

  So the NEC at my house was followed, and I took precautions. I could have been killed just the same. A loose or slippery Ground/Neutral from the power feed connection is very dangerous.

  I guess I'm just a DA.

Jim
WD5JKO

[W2VW]

Safety aside. Save a little copper, make it up in time chasing hummmm.

Those little voltage drops across neutrals tied to ground become large when audio gear is involved.

[K5UJ]

First of all, who is George?

This thing with having to have 4 wire service to ham gear is new to me.  I run a Ten Tec Centurion amp, built about 12 years ago and it runs off two hots and a ground.  There is (or was in my case) a 120 v. fan inside it that runs off one end of the plate iron primary and its center tap. 

I've had a licensed electrician come in a few times over the years to run 240 v. circuits because among other things, I stink at bending conduit, and he always ran two hots and a ground.  I have a gas dryer and stove so that may be why the four wire service is foreign to me. 

If I were uncomfortable with running a combination of 240 and 120 v. loads in a cabinet, I'd just put them on separate circuits i.e. service lines, 240 and ground for the plate supply and 120 hot, neutral and ground for the rest of the rig. 

I dimly recall a dispute on some reflector about not having a neutral return for a RF amplifier that ran off two hots and a ground and it ultimately boiled down to a misinterpretation of the NEC as it applied to out-buildings and sub-panels.  Running a 120 v. load across 1/2 of the plate transformer primary was deemed okay.  It might be interesting to find out if Ten Tec still sells the Centurion amp with a three wire cord--I doubt they'd make and sell it that way if it would get them into trouble.

rob 

[N4LTA]

We are talking about running both 120 and 240 volt loads on a single 240 volt circuit with no neutral.

Using the green grounding conductor as the return for 120 volt current


Pat
N4LTA

[kb3ouk]

First of all, who is George?
 

George is his transmitter.

[ke7trp]

I just went through this fiasco a couple years back when wiring up the big transmitter and a Johnson Tbolt.  The T bolt does exactly what George will do.  It runs the plate off 220 but the LV and fils off 120 volt.  That T bolt has a 3 wire cord.  Two hots and a neutral. No ground. I ended up running the a 4 wire 60 amp 240 volt outlet in the room and running plug that has a four wire and the case of the T bolt to the ground pin.

Here in AZ we have no ground at the house. Thats right, no ground.  No ground at the panel and no ground rods at the panel.  Shocked(pun) I called the power company to make sure this is right.  The man came right out, He said there are no grounds as they do not work in sandy soil and your house uses neutral to the shared power transformer outside at the street.  I said I felt like adding a ground rod and ground buss anyways and he said "My house has one" as he walked away.  We put the ground system in next day. Its also gets wet from sprinklers and seems to have conductivity.

The worst possible case was discovered here. Shared neutral.  Whats shared neutral?  That means that all five homes that run off that Power transformer out in the street SHARE a neutral.  Get RF on that line from your shack and you now sent that RF blasting into the neigbors house. 

Jim. your story scared me.  I bet people have died in your exact situation with the pool.
C

[WD8BIL]

In residential service the white wire is neutral and the bare wire is ground.

Now, look at the service panel and tell me there's a difference when you use 4 wire over 3 wire.

I'm with you Carl. Most regulatory agencies (NEC, IEC, UL, CSA) exist now only to justify their existance. Just look at the 61000-4-2 indirect discharge ESD testing. 

[N4LTA]

OK - I'll tell you there is a big difference

You obviously don't understand the basic concept of AC grounding or the difference would be apparent.

This type of misunderstanding is what causes many grounding problems which can be dangerous and cause transient problems and problems with communication system, as well as safety problems.

The grounding conductor for all NEC power systems is either green in color or bare - usually green. The power company does not supply a ground - they supply a grounded conductor (often called a neutral).
The grounded conductor is bonded at one and only one place - at the service overcurrent device and where the ground system is tied into the system (the grounding electrode).

The grounded conductor (neutral) NEVER is connected to ground downstream. The neutral is a current carrying conductor and so it has voltage drop. The green ground or grounding conductor never carries current except under fault conditions - that is what it is for - to supply a path to trip the overcurrent device. So the neutral condutor is at a different voltage than the grounding conductor. They are not the same and treating them the same causes problems.

I don't really care at all how you wire up your power systems, but the NEC is one of the most important codes for safety that exists. Without it, the safe wiring of power systems would not exist. It is neither brief or simple in concept. I have spent 37 years working with it and am a registered PE in 5 states, and I still learn about it on a regular basis.

I often see the results of ignorance of the NEC and ignorance of proper wiring methods and most of the time it comes from "know it alls" that don't know very much - not ignorant idiots and morons - who for the most part are scared to death of electricity.

Do it anyway you want - there are many ways to make things work - or as a braintrust on here once said "working always beats science". But when the insurance company tells you YOYO ..........

Pat
N4LTA

[The Slab Bacon]

Around here, the code requires that the neutral be "bonded" to the ground buss only at the main panel. But any sub panels the neutral does not get bonded. And that there can only be one ground point per house. Trying to achive an "RF Ground" like this can be a challenging job at best depending on how long the run is, not to mention the "ground loop" issue.  Also all grounds have to be tied together at one central point. This can be a real P.I.T.A. ! ! !  

to me it seems that the safety grounds on anything coming off of a sub panel now have a longer / higher resistance path to ground.

My house is grounded per NEC, but............. I used to have nasty "RF in the shack" issues. I have since put a 8' ground rod with #2 wire on my tower for lightning protection, and I have drilled a hole in the floor of the basement radio room and driven another 8' ground rod into the virgin soil below the floor. It ties into the back of ALL of my gear with very short copper braid or strapping. I have since totally eliminated any and all of the "RF in the shack" issues, tingles when you touch something, etc. But those grounds do not conform to NEC because they are not bonded to the rest of the house's safety grounds and or neutral bus. They do however get it done when it comes to RF! ! ! !

Clark,
        No system ground at all? ? ? ? ? ? Geeze, the electrical inspectors around here would have organisms! I can see the point with very low soil conductivity,
but I still would think they would want it. That may help explain all of the RFI problems you were having a while back. I would definately drive a ground rod anyway. Then put a red plastic fire hydrant above it so the dog would keep the soil as conductive as possible.

[N4LTA]

Slab

The NEC requires the neutral and ground to be bonded at only one place - At the service - and at that point the green ground is "derived" from the power company neutral (grounded conductor). The service panel should have a ground bus and an insulated neutral bus. The insulated neutral bus is bonded to the ground bus with a strap or bolt and that is the "bonding point"

The power company does not supply a ground - only a grounded conductor (neutral) if the NEC is followed.

The green ground sizes are determined from Table 250.122 and the size is determined by the breaker size ahead of it. Grounding conductors run from #15 for a 15 amp beaker to 800 kcmil for a 6000 amp breaker. The ground is sized to quickly trip the circuit breaker in a fault. The NEC grounding conductor is there for one and only one purpose - to provide a low impedance path for fault current - and so it may not work well at all for RF grounding.

There is nothing at all wrong with supplimenting the ground system - just don't tie it to the neutral except at the service. The ground bus in the service panel is tie to the system "grounding electrode" with a "grounding electrode conductor" which is sized from Table 250.66 and goes from #8 to #3/0 depending on the size of the service. The grounding electrode itself is composed of ground rods, ufer concrete encased grounds, col water main pipe and other specified available ground all bonded together.

The new 2012 code requires a minimum 2 ground rods unless a single one is measured a 25 ohms or less. This requiement is likely to change as it has caused an uproar in the contracting industry.

The local AHD in Spartanburg now requires a UFER concrete encased ground rather than a rod which is probably cheaper and a better ground. They require a minimum of 20 feet of copper wire to be incased in the footing as a UFER ground.

The AHD (Authority Having Jurisdiction) can require pretty much anything they want in addition to the NEC.

Pat
N4LTA

[The Slab Bacon]

Pat,
      What is UFER? ? ?  That is a new one on me.

Also, I knew the ground was a fault path to trip the breaker in the event of a short or failure. But, I was also under the impression that it was also a "bleed off" for any slight leakage (capacitive coupling, resistive leakage, or insulation break down, etc.) to keep everything at ground potential and prevent electric shock / electrocution hazard.

the biggest difference between the ground and the neutral is that in normal operation the neutral leg is a current carrying conductor and the ground isn't.

In just about all cases, the ground conductor in a piece of cable (romex etc) is usually always the same size as the main conductors or 1 or so sizes smaller.

[ke7trp]

The 5 joined neighbors where getting RFI through the Neutral. It was identified here by inspection. Other then that issue, My station passed. Big power contractor style RFI filters for industial equipment solved that.  They have 80DB cut at HF and are available at electrical parts houses.  Its a good idea to install them into transmitters like George here.  Why even chance putting RF into your home?  Those neighbors rarely complained over the years anyays.  But since the inspection found it, I had to fix it.

Around here, the code requires that the neutral be "bonded" to the ground buss only at the main panel. But any sub panels the neutral does not get bonded. And that there can only be one ground point per house. Trying to achive an "RF Ground" like this can be a challenging job at best depending on how long the run is, not to mention the "ground loop" issue.  Also all grounds have to be tied together at one central point. This can be a real P.I.T.A. ! ! !  

to me it seems that the safety grounds on anything coming off of a sub panel now have a longer / higher resistance path to ground.

My house is grounded per NEC, but............. I used to have nasty "RF in the shack" issues. I have since put a 8' ground rod with #2 wire on my tower for lightning protection, and I have drilled a hole in the floor of the basement radio room and driven another 8' ground rod into the virgin soil below the floor. It ties into the back of ALL of my gear with very short copper braid or strapping. I have since totally eliminated any and all of the "RF in the shack" issues, tingles when you touch something, etc. But those grounds do not conform to NEC because they are not bonded to the rest of the house's safety grounds and or neutral bus. They do however get it done when it comes to RF! ! ! !

Clark,
        No system ground at all? ? ? ? ? ? Geeze, the electrical inspectors around here would have organisms! I can see the point with very low soil conductivity,
but I still would think they would want it. That may help explain all of the RFI problems you were having a while back. I would definately drive a ground rod anyway. Then put a red plastic fire hydrant above it so the dog would keep the soil as conductive as possible.