Pages: [1] 2 3   Go Down

Author Topic: Field Operation: generator ground or not?  (Read 10948 times)

DL1MRD

  • Member
  • Posts: 22
Field Operation: generator ground or not?
« on: May 28, 2018, 02:15:20 AM »

As far as I understand, a generator in a typical field scenario does not need to be grounded. But I do see ground used often. So what is common practice?
If not required by code for safety, wouldn't  a ground on a generator have other advantages, as in regard to static, lightning, QRM? Or could it even introduce problems?

73 de Marc DL1MRD

Logged

K7RBW

  • Member
  • Posts: 531
RE: Field Operation: generator ground or not?
« Reply #1 on: May 28, 2018, 03:52:09 AM »

OSHA says you don't need to ground a portable generator: https://www.osha.gov/OshDoc/data_Hurricane_Facts/grounding_port_generator.pdf
Logged

DL1MRD

  • Member
  • Posts: 22
RE: Field Operation: generator ground or not?
« Reply #2 on: May 28, 2018, 04:52:44 AM »

OSHA says you don't need to ground a portable generator
Yes, I know that, but this addresses only electrical safety and no "ham specific" issues. I just want to know what others are doing in a field operation in this regard and why they are doing it.
Logged

W8JX

  • Member
  • Posts: 13268
RE: Field Operation: generator ground or not?
« Reply #3 on: May 28, 2018, 06:01:53 AM »

Yes, I know that, but this addresses only electrical safety and no "ham specific" issues. I just want to know what others are doing in a field operation in this regard and why they are doing it.

I have done several portable and field day ops off generators  and never grounded and never had a issue using bothe old style hybrid rigs that run of 120 and 13.6 volt too running off power supplies. Even have used a SB 200 @ 500 watts a few times too with no problems.
Logged
--------------------------------------
Ham since 1969....  Old School 20wpm REAL Extra Class..

K5LXP

  • Member
  • Posts: 6823
    • homeURL
RE: Field Operation: generator ground or not?
« Reply #4 on: May 29, 2018, 08:12:34 PM »

this addresses only electrical safety and no "ham specific" issues.

What is "ham specific" about a genset and loads?  And why is it "safer"?

When you do see someone using ground rods with a portable generator, you are likely observing the actions of ignorance.  There are specific situations it's warranted, but running a radio and some lights at a Field Day type application isn't one of them.

Mark K5LXP
Albuquerque, NM
Logged

WB6BYU

  • Member
  • Posts: 20896
    • Practical Antennas
RE: Field Operation: generator ground or not?
« Reply #5 on: May 30, 2018, 06:09:06 PM »

I have seen folks drive a ground rod for portable generators, but they didn't put it in deep enough
to get a good low resistance connection because they wouldn't be able to get it out again.

We had one case where the generator was making too much noise:  a ground rod didn't help.
Instead I added a 25m extension cord wound up on a reel right at the generator, and it formed
enough of a common mode choke on the power cord to reduce the noise to a usable level.

W8JX

  • Member
  • Posts: 13268
RE: Field Operation: generator ground or not?
« Reply #6 on: May 31, 2018, 05:30:45 AM »

 Given that a generators "ground" is referenced to itself (unlike commercial power at home) I doubt you gain any safety benefit from grounding it.
Logged
--------------------------------------
Ham since 1969....  Old School 20wpm REAL Extra Class..

KD9FRQ

  • Member
  • Posts: 439
RE: Field Operation: generator ground or not?
« Reply #7 on: June 01, 2018, 10:29:41 AM »

Every time I had to take the twin 50Kw set out to the woods, I had drive 4 20 foot rods and connect them to the rigs.

I had to use the toasters on top because I never used that much power and without the toasters I would burn through 50 gallons of diesel in 10 hours instead of 12.

The spare 30Kw gen set only had three ground rods.

I think the Army has upgraded since then.
Logged

AA4PB

  • Member
  • Posts: 15504
RE: Field Operation: generator ground or not?
« Reply #8 on: June 01, 2018, 11:00:58 AM »

Given that a generators "ground" is referenced to itself (unlike commercial power at home) I doubt you gain any safety benefit from grounding it.

Provided that that no other part of the electrical system is connected to Earth ground then safety is probably improved by NOT grounding the generator. You can safely stand bare foot in a pool of water and hang on to the generator hot lead provided there is no connection between the generator circuits and ground. I wouldn't recommend trying it though because you never know where there might be an unknown leakage path to Earth ground.  ;)


Logged
Bob  AA4PB
Garrisonville, VA

VE3HIX

  • Member
  • Posts: 47
RE: Field Operation: generator ground or not?
« Reply #9 on: June 05, 2018, 07:02:51 PM »

The famous Honda 2000 watt sine wave generators do not have a shielded ignition system, so they will make an ignition noise in field day applications. The cure is to crumple heavy aluminum foil and place it over the spark plug just under the small access door. Don't worry about air cooling problems here as the air goes under this section. I have run the engine for 24 continuous hours without problem.

In addition to the above, a ground rod completely cures the ignition noise problem on these expensive generators.

Cheers,
Bob VE3HIX

Logged

NQ3M

  • Member
  • Posts: 95
RE: Field Operation: generator ground or not?
« Reply #10 on: July 18, 2018, 05:41:32 AM »

If you don't have to use AC for your operation I suggest taking a small engine, an pulley ratio it correctly to a GM single wire DC charging Alternator.
I have a 6.5 HP Honda pulling a 100amp GM alternator that feeds the battery's direct. No hash at all, the engine only turns at 1250-1400 rpm an is very quite, an reliable. Been using it for 5 years now w/o an issue at all, to keep up 2 group 29 deep cycle battery's that power the TS-480sat an a ALS 500. The ALS is rarely used but it's nice to have the switch if needed.
I'd post a photo if I knew how to up load it directly, don't like hosting services at all.
Email an I can send photos of the truck/gear it powers. (good on here an QRZ) Make sure generator photos are in the title so I don't confuse your email for spam. Getting old.
Logged

W8JX

  • Member
  • Posts: 13268
RE: Field Operation: generator ground or not?
« Reply #11 on: July 18, 2018, 08:01:29 AM »

If you don't have to use AC for your operation I suggest taking a small engine, an pulley ratio it correctly to a GM single wire DC charging Alternator.
I have a 6.5 HP Honda pulling a 100amp GM alternator that feeds the battery's direct. No hash at all, the engine only turns at 1250-1400 rpm an is very quite, an reliable. Been using it for 5 years now w/o an issue at all, to keep up 2 group 29 deep cycle battery's that power the TS-480sat an a ALS 500. The ALS is rarely used but it's nice to have the switch if needed.


This is not as good as it sounds. Air cooled engine depend on RPM and fan speed for proper cooling together with internal oil splash too. Running engine loaded at 1250 to 1400 RPM is not good for it. You have been lucky so far. You want at least 2000 to 2200 RPM or more for reliable even cooling with a air cooled. Long ago when they offered 1800 RPM air cooled generators they had special fans on them for proper cooling. This is why low RPM generators are liquid cooled.

Logged
--------------------------------------
Ham since 1969....  Old School 20wpm REAL Extra Class..

NQ3M

  • Member
  • Posts: 95
RE: Field Operation: generator ground or not?
« Reply #12 on: July 18, 2018, 09:58:08 AM »

This is not as good as it sounds. Air cooled engine depend on RPM and fan speed for proper cooling together with internal oil splash too. Running engine loaded at 1250 to 1400 RPM is not good for it. You have been lucky so far. You want at least 2000 to 2200 RPM or more for reliable even cooling with a air cooled. Long ago when they offered 1800 RPM air cooled generators they had special fans on them for proper cooling. This is why low RPM generators are liquid cooled.
Temp is dependent upon load, sport. RTD testing of this unit says your wrong. Been doing Electrical Power Generation (EPG) for over 55 years. 1050 hrs of lucky so far so I'll keep pressing on.
Logged

K5LXP

  • Member
  • Posts: 6823
    • homeURL
RE: Field Operation: generator ground or not?
« Reply #13 on: July 18, 2018, 04:21:03 PM »


I made one too, I call it my Lawnernator.  Mine is direct drive though and as such the alternator doesn't spin fast enough even at wide open throttle for full output, but with the battery picking up the slack it can keep up with most any 12V load you'd put on it (nominal 30A@14.2V).  With the battery serving as a load leveler the throttle can be set fairly low to match the average draw, better than screaming at high throttle whether there's a load or not.  Fun project but not terribly practical, I prefer my inverter generator to it.



http://www.qsl.net/k5lxp/projects/Lawnernator/Lawnernator.html

Mark K5LXP
Albuquerque, NM
 
Logged

NQ3M

  • Member
  • Posts: 95
RE: Field Operation: generator ground or not?
« Reply #14 on: July 18, 2018, 05:58:03 PM »

My alternator is belt drove an is spinning 2.5X engine speed, feeding 2 group 29 deep cycles in the rear of the truck, via 150amp DC plug. Even when the ALS 500 keys up the engine only drops to about 1250 rpm, an as soon as the amp relay drops out she returns to 1400rpm. When I am charging battery's instead of just keeping them topped off I'll spool her to about 2200-2300rpm but with this engine a single 100 amp will never load her up. 100X14.8= 1.48KWe with 82% efficiency thats only 1.804 engine KW or 2.42 Hp at full load. When she is pulling the group 29's the KWe from the engine averages 0.663 or 0.889 hp the alternator efficiency at slow speed is only 67% where as at high speed it's nearly 82%. I tried a few inverter generators but did not like them for one reason or the other an just built my own power supply. The only draw back is when starting. With the pulley ratio I went with you have to disconnect the DC power to the start the engine, because a soon as the engine starts the alt starts producing an over loads the engine at such a slow speed. So I have a 100 amp breaker  I use. Once the engine starts it will idle under load w/o issue but, she will not start under load with a rope. Electric starter might be different.
Logged
Pages: [1] 2 3   Go Up