When the power goes out I shut my main off & hook my gen to the 220 reciptical in my garage to power the house. It's a 6250 watt 10 horse. I have another gen a 5000 watt 10 horse. Can I hook the two together some way to get 11250 watts ? or would it burn them up ?

 

You have a great question there? I don't know how you would get them in phase. This
calls for someone well versed in AC current.

 

You really need a transfer switch to connect the generator to your house to be safe. Big generators have a means of getting them in sync for parallel operation. I would not attempt it with yours.

 

Mike made a valid point - you really should be using a transfer switch to avoid accidentally backfeeding the utility. Not a good thing to do.

Paralleling isn't practical at this level - you're better off building a couple of small distribution panels and feeding the loads separately.

 

Good points all. The two generators will fight each other. Not a good idea...

 

Yes, you would need a special controller to sync the generators' phase rotations. More or less, a phase monitor on both generator outputs will be linked to a throttle control on the secondary generator and adjust the engine speed to keep them in sync. Lot's of PLC programming involved (or you can spend mucho-$ to buy a pre-made control panel) and one generator would need to be fitted with an electronic speed control... As posted above, probably not practical for this application unless you are a computer hardware programmer or have access to someone who can do the programming.

By shutting your MCB off, you are in a sense creating a manual transfer switch which would prevent back-feeding. If you follow your SOP right, you won't have a problem. I've seen similar set-ups in commercial applications (and designed a few of them). Code would require it to be key-interlocked with a proper disconnect switch at the gen-set connection.

More importantly, what size receptacle are you plugging the generator into?

 

50 amp reciptical, 6 gage wire. One gen is 30 amp the other 20 amp.

 

I have to change the plug on my genset cord. Mine is a Generac 7550, 7550 continous running watts, 13,000 surge wattage. At 7550 watts by 240 volts that roughly equalls 33 amps of 240 VAC or 66 amps of 120 VAC. When our power goes out I turn off the main. I use a cord that connects the generator to the dryer outlet. Unfortunatly, the dryer outlet is only rated for 30 amps max. So I am going to buy a new plug to connect the genset to the stove outlet. That one is rated for 50 amps. It pays to be safe with electricity.

Mark, you would need some sort of device to synchonize both gensets. The smallest gensets I have seen that you could paralell are the diesel generators on a 110 foot Coast Guard Cutter. Each genset by itself is rated about 75 - 100 kW. If you do not have the gensets in phase you run a high risk of having one (or both) of your generators turning into the Spark-o-Matic. Not to mention you might fry some of your household devices, especially the electronic ones. I would follow Old Farts suggestion and install a couple of sub panels that would power seperate areas of your house while keeping the generators electrially isolated.

BTW here are some numbers for you on your generators. Calculated by using Ohm's Law.

Your 6250 watt genset :

MAximum genset output
240 Volts AC - 26 amps
120 Volts AC - 52 amps

Your 5000 Watt genset :

Maximum output
240 Volts AC - 20.8 Amps
120 Volts AC - 41.6 Amps

Hope this helps.

 

I assume you're checking wire size?

A 30A receptacle would typically be wired with #10 AWG copper wire. A 50A receptacle would need #6's, although you can get away with #8's in a pinch.

 

Mark a, as jrs_big_ford_f150 indicated above, his genset is double rated (continuous and surge). From all the research I've done regarding engine selection and generator output, you need to have 1 HP for every 500 continuous watts output. Based on this fact, you may actually have two 5000 continuous watt output generators. Often times the manufacturers get over zealous and show the surge rating (similar to air compressor manufacturers). That 6250 watt gen sounds about right for a surge rating for a 10 HP engine.

Fran

 

My mistake, the bigger one is 5250 running & 7350 surge. The other is 5000 running & 6250 surge. However they are both 10 horse. If I isolated them is it ok to run them into the same ground ? I want to be able to run the water heater & I'd use one for that & the other for the house.

 

You actually are _required_ to run them to the same ground.

 

Oh yeah, the wire is 8 guage for the genset cord. If need be I will go buy some thicker cable. I am just getting the plug for now since my genset produces more amps than the current outlet I am using to tie in the genset can handle. The house receptacles are already wired. I am just changing which circuit that will backfeed my main breakers and power the house.

Mark,
The same ground is ideal. But if you can't get them to the same grounding point, remember a ground is better than no ground at all.

 

If you want to run both of your generators at the same time, it would be best to run each one on its own dedicated circuit. Don't try to run them in parallel on the same circuit.

Getting the two generators paralleled initially would be a bear. You need to have phase indicators for the two units and be able to close a breaker when the units are in phase. After paralleling, you would need to figure out how to make them share the AC load. The AC generators running in parallel would need to have almost identical speed and voltage droop characteristics to work well together. Most likely one of them would end up as a load on the other generator. File this one in the "too hard" category.

I'd just run the larger unit on the house and keep the second one as a spare.

Lou Braun

 

File this under "unsafe" at best. Kill a lineman, go to jail.