Mep004

[EnteJager]

I have a opportunity to pick up a 1984 J. Hollingsworth 15 kw gen set that has 171hrs on it since depot overhaul in 2005, the gen is an '84 with the following;
50/ 60 HZ, 208 & 416 LINE TO LINE VOLT, 120 & 240 LINE TO NEUTRAL VOLT, 3 PH
I have seen the gen and it fires right up, the guy bought it for the trailer and has no need for the genny, he doesn't know much about gens this size either.

I have 2 small 5kw (commercial) for the house, they are not big enough to run the whole house. A commercial 15 kw is way to expensive, this seems like a pretty good option.

I know the 15 kw will be big enough, I have analized the requied load for the house, and have a secondary breaker panel with load meters for the left and right side of the breaker panel for load shedding. My current gens plug right into the panel.

The 15 kw will cost me 900.00, does this sound like a good option for home backup power ?

Any comments would be appreciated.

thanks
Dave

 

[Speddmon]

Dave,
It's a great generator in respect to the fact that it's way over built and probably capable of much more than 15KW. However, under it's current configuration you can only run a bunch of 120 volt single phase loads off of it, unless you have some 3 phase motors lying around. Without changing the configuration of the generator output (which shouldn't be too hard to do) you only have 240 volts line to neutral in it's current state. Residential 240 volt appliances require 240 volts line to line with 120 volts from either line to neutral.

Unless your home happens to be powered by 3 phase (unlikely) you'll need to reconnect the generator from a wye "Y" 3 phase configuration to a delta configuration. The problem with using a low voltage (or high voltage) delta set-up is the "high leg". Between any two lines of the three you'll read 240 volts (480 on high voltage). On two of the lines to neutral you'll get 120 volts (240 on high voltage) but on the 3rd line to neutral you'll have 208 volts (415 on high voltage). So in essence, out of the 6 individual coils inside of the generator you'll only be pulling current from two of them

Since it's a 12 lead generator you should be able to reconnect it to a delta configuration but you'll have to watch the loading imbalance as well as not having enough load (wet stacking). I've thought about doing this myself, but I could never find a reliable answer as to the affects this would have on the voltage regulation and metering equipment in the generator itself, so I went with the 10KW MEP-003 gen-sets, they are already configured to run 120/240 single phase.

Don't let this discourage you though. If you have enough information and like to play around with things you can make it work. Just be safe!!!!!

 

[EnteJager]

Thanks for the great information,
i found some info on a zig zag reconnect that will allow a 3 phase gen to produce single phase (only) power at 100% of it's capacity.
Have you ever heard of this?
Thanks
Dave

 

[Speddmon]

i found some info on a zig zag reconnect that will allow a 3 phase gen to produce single phase (only) power at 100% of it's capacity.
Have you ever heard of this?

No I haven't but I certainly would be interested to see the info.

The thing with the military generators is that even reconnected to single phase they are still rated at full power due to the over sized windings used. Even though the MEP-004a doesn't have a single phase reconnect switch or rating for single phase, I personally wouldn't be afraid to load it up to 15KW single phase once it was reconnected.

The MEP-003 10KW is rated at 104 amps 120 volts single phase and 52 amps at 240 volts single phase. If you calculate it out 240 volts X 52 amps = 12480 watts (12.48 KW). Now 12480 watts X 80% = 9948 watts (9.9KW). The 80% used is the power factor rating of the generator.

For the MEP-004a using the same calculations you can assume that set would be rated at 78 Amps at 240 volts. Since it's a military generator, even without that zig zag reconnect you mentioned I wouldn't be afraid to put some single phase load on that baby.

You really should take some time and read up about wet stacking in the link I put in my original post. It's not a good thing for liquid cooled diesels to run with a very light load on them.

On a side note...Rat4spd, if you see any flaws in my thinking please step in and through your into the mix.