Parallel portable generators

Status
Not open for further replies.
Interesting that (no one says) its not against code or UL rating to supply one panel with two sources. I expected an immediate "no"! :)

I was thinking the same as I was reading this thread.

I understand trying to save money, etc... but I have a hard time wrapping my thoughts around some of the ways people try to save money.
You guys really need to get out of the residential mindset box. THE UTILITY doesn't own all of the generation in the earth. The power sources are not all SERVICES. There is nothing wrong with multiple gensets into one switchboard. One design I have seen had about 10 small (400kw) gen sets. The main PLC automatically step started as many as were needed for rotating reserve. Worked great - kept the fuel consumption way down.

cf
 
You guys really need to get out of the residential mindset box. THE UTILITY doesn't own all of the generation in the earth. The power sources are not all SERVICES. There is nothing wrong with multiple gensets into one switchboard. One design I have seen had about 10 small (400kw) gen sets. The main PLC automatically step started as many as were needed for rotating reserve. Worked great - kept the fuel consumption way down.

cf
As long as you have them in sync as I stated earlier.
 
Well like whats a portable generator its a generator stationary or portable .

Its a GENERATOR!


No chain or belt syncs a generator if you think like that your wrong ?

When they say sync they mean in phase with the other not mechanically linked electrically linked .

Most County or City Buildings in Florida have a generator plus are capable of a large portable hook up in the event of a hurricane .

Most Orange County Schools have two or three parallel generators hooked up with camlocks to building service to emergency supply power .

And yes a power plant all generators in the plant are in parallel to the grid one way or the other its nation wide we all are paralleled with other states we sell them our power they sell us there power .

These run in parallel !http://i611.photobucket.com/albums/tt195/stringking/Mitsubishi005.jpg


Guess were not to the NEC ill tell my boss today that other genset is coming out .
 
Last edited:
Interesting that (no one says) its not against code or UL rating to supply one panel with two sources. I expected an immediate "no"! :)

I see no problem, provided that a single dissconect shuts of all power (or not exceeding 6 branch circuit breakers without a main)
After all the grid consists of a number of generators and no one worries about that!
Of grid homes may have several battery strings in paralel, and again that is permitted.

In practice I would, in most cases, advise against two generators feeding a single panel, but this is due to to various practical diffeculties, not because it is actually prohibited.

Aggreko and probably other hire firms, offer large generators suitable for paralel running, as posted above.
In such cases the paraleling is done at or close to the generating plant, and the panel does not "know" if it is connected to the grid or a generator bank.

There is after all not much difference between a number of diesel generators hired from Agreko, or a similar number permanently installed by a utilty in an isolated area such as an island.

As posted above, when useing multiple generators, the available fault current will increase and a check must be made that this is not in excess of the equipment rating.
In practice however most ultilitiy services have a higher fault current than most generators, even if several are used.

We are however drifting somwhat from the enquiry as to whether two generators each 120 volt could be used one to feed each side of a 120/240 panel.
The answer to that is yes it can be done, but only to feed 120 volt loads, not 240 volt loads, and care must be taken not to overload the neutral bus or wire.

In the case of useing multiple 120/240 volt generaters to feed one panel, the answer is yes it can be done, and is done but only with equipment designed for such use.
MOST small portable generaters are not designed for paralel running.
 
It seems to me that the OP is probably talking about something on the order of pull-start portable generators, not the bigger units so #7 and #16 might be most relevant (and of course #2). Never thought about trying to sync one of the little units. Not sure why you would unless you just happened to have two small ones (probably the case here).
What do you think the utility does nationwide. Multiple generators supplying the loads. Paralleling generators is a a VERY common practice.
But theirs aren't portable
Some utility generators are portable and sync to the grid. Nonetheless, paralleling generators is very common, even for non-utilities. I doubt the little hand-crank units would be good candidates unless you added some tech but, like I said, I can't really see why.
 
Last edited:
Interesting that (no one says) its not against code or UL rating to supply one panel with two sources. I expected an immediate "no"! :)

I was thinking the same as I was reading this thread.

Unless the instructions or labeling of the generators indicates not to be paralleled I see no issue.

Generators are often paralleled, even under NEC applications not just utilities.
 
I'm gonna use that one! It'll be great for management and nosy operators that won't understand your answers any way.



But theirs aren't portable

Why would that make a difference as long as I can control both units.


Several years ago a highly sensitive place (I'd have to kill you if I told you type) had a UPS blow up. It seems you cannot run water through a UPS, who knew. Took them a day to bypass loads restart the data center and get back to running. Anyway they brought in a portable generator and a temporary UPS to be fed from the portable generator as all panels associated with the UPS input were to be replaced. 3-days work 24x7. My job was to get them off utility and back on after repairs.

2-men 2-disconnects and a syncroscope.

We set every thing up and manually paralleled the portable generator to utility for a second to transfer loads, after completion we did this again to get back to normal.

I did make them sign a statement of NO GUARANTEE of service during the transfer..
 
Unless the instructions or labeling of the generators indicates not to be paralleled I see no issue.

Generators are often paralleled, even under NEC applications not just utilities.

Seems a lot of people misunderstand my original question. I'm asking, what if the OP just fed each genset - unsynced - to each leg in the panel. Two unsynced 120V sources, one panel, nothing like the small Honda inverter gensets (which just sync the inverters and not the engines, easy to do). As I pointed out in my original post, obviously you would not be able to run 240V loads with this setup. It would seem to be safe at first blush, and based on other's posts as long as you didn't overload the neutral bus you'd be OK. I would think even this would be hard to do, if for example you were working with a 200A panel. You would need two gensets of more than 12kw each to even possibly overload the neutral, and then only if you had actual total loads above 24kw.

Safe from a practical standpoint, but "legal"?

Edit: the OP was asking about putting both on the same leg, which he was quickly told "no". I'm offering an alternative solution but wondered about the UL/code side of it.
 
Last edited:
Seems a lot of people misunderstand my original question. I'm asking, what if the OP just fed each genset - unsynced - to each leg in the panel. Two unsynced 120V sources, one panel, nothing like the small Honda inverter gensets (which just sync the inverters and not the engines, easy to do). As I pointed out in my original post, obviously you would not be able to run 240V loads with this setup. It would seem to be safe at first blush, and based on other's posts as long as you didn't overload the neutral bus you'd be OK. I would think even this would be hard to do, if for example you were working with a 200A panel. You would need two gensets of more than 12kw each to even possibly overload the neutral, and then only if you had actual total loads above 24kw.

Safe from a practical standpoint, but "legal"?

Edit: the OP was asking about putting both on the same leg, which he was quickly told "no". I'm offering an alternative solution but wondered about the UL/code side of it.
How do you prevent 240v loads.
How do you handle MWBC's?

So I don't think it meets code to do what you are thinking.
 
Last edited:
for example you were working with a 200A panel. You would need two gensets of more than 12kw each to even possibly overload the neutral, and then only if you had actual total loads above 24kw.

How does that help increase the capacity of the system?:-?

I think we can assume a 12 kw generator will be 120/240. That being the case can we get 12 kw from just one line to neutral or do we have to keep it balanced?
 
sierra - MWBC shouldn't be a problem. The shared neutral will just be part of two different electrical paths (I remember building a home-made "Clapper" back in college where a 9V trace was shared with 120V... two different circuits in the same box). The more I think about it even pure 240V circuits wouldn't be an issue even if they were installed - across both "legs" you would always get a 0V reading because they aren't really legs, just two hots of two completely seperate circuits. Appliances that use 120 & 240 might be an issue depending on their design, like a dryer that uses 120 to run a control board. It might appear to be on (lights, LCD screen) but the motor and element will never start. But I still don't think it would be a safety issue. Maybe someone can find fault with my logic - please do!

iwire - I wasn't talking about increasing capacity, just working on how you would overload the shared neutral. Yes, something that large would most likely be 120/240 capable but I'm working on the problem the OP posed - how to use two smaller gensets.
 
Well i found this to be the best example of explaining the mystery behind the parallel generator operation the how and whys ? read the whole article its the best .http://www.basler.com/downloads/VR_parallel.pdf

Very interesting reading, only have time to skim it right now. Looks like this applies to mechanical syncing. The small Honda inverter-gensets just sync up the inverters, much easier. The 60Hz clock signal from one inverter is used to bypass the clock signal on the 2nd unit, but inverted to produce 180-degree output. The engines never need to be synced.
 
sierra - MWBC shouldn't be a problem. The shared neutral will just be part of two different electrical paths

In order to be complaint the Neutral wire of that 3 wire circuit must only carry the unbalanced load. For example in your theory just attach the generators at the panel with two individual breakers one for each leg. OK
You then power up several circuits that are 3 wire. Each of those carry say 16 amps each. The neutral load in your case would be 2X16 = 32 amps on a 20 amp circuit and most likley #12 wire. How is that code?
How is that safe?
Those Gensets need to be sync'd then you're good to go.
 
You guys really need to get out of the residential mindset box. THE UTILITY doesn't own all of the generation in the earth. The power sources are not all SERVICES. There is nothing wrong with multiple gensets into one switchboard. One design I have seen had about 10 small (400kw) gen sets. The main PLC automatically step started as many as were needed for rotating reserve. Worked great - kept the fuel consumption way down.

cf

You would not say that if you saw the size of the residential jobs I am on...
RSB-8220840.jpg


RSB-8220845.jpg


RSB-82208107.jpg





That is all in the basement of this house. ;):grin:


IMG_4160.jpg
 
It's amazing the difference in electrical systems in homes. Sure doesn't look like any residential service that I've ever seen.:wink::grin:
 
Status
Not open for further replies.
Top