MEP 805 Generator 120/208

[Capt.Moondog]

Was going to hook up the generator to my house and my AC electrician says that it needs to be 120/240 not 120/208. Storm blew through last night so this is became high priority. Something I should have done and checked already but here I am. can someone answer the question is it an easy way to step up the 208 to 240. I see you can step it up to 240/416, but that does not work for my set up. The electrician says that it must be 240 not 208 across post for my AC System
Thanks for your advice

 

[DieselAddict]

Take a look at the nameplate for your AC. It likely says 208/240.

I'd be surprised if its a problem.

As far as connecting, you'd use any two of the generator outputs (such as L1 and L2) for the two power phases then connect Neutral and Ground as normal.

 

[Capt.Moondog]

Thanks for the info.. yes I figured out how to connect the wires by the manual but the 120/208 was what the AC tech said not to use

 

[peapvp]

Thanks for the info.. yes I figured out how to connect the wires by the manual but the 120/208 was what the AC tech said not to use

The current is app 10% higher @ 208VAC vs 240VAC

this can cause two issues:
A) overloading the rated wire gauge current which really depends on the length of the wire run

B) overloading the starting capacitor of the motor if the compressor is not rated for 208VAC

 

[2Pbfeet]

You can get "boost" transformers to take the 208 to 240V, if it is really an issue, but the bigger issue is only using two out of three phases on the generator. @peapvp summed up the issues succinctly. Not every AC is capable of operation at 208V, and some of those that are may need to be rewired internally.

All the best,

2Pbfeet

 

[DieselAddict]

Thanks for the info.. yes I figured out how to connect the wires by the manual but the 120/208 was what the AC tech said not to use

Go look at the label. It will clearly state what is acceptable. Below is the label from my heatpump.

Also for emergency, short term power needs, don't worry about running the set on 2 legs. Keep under 2/3rds rated load and do what you have to do. If you need generator power for the long term, this isn't the best machine for your needs.

 

[Capt.Moondog]

Thank you all for your advice and suggestions!!
It has been a busy couple of days dealing with everything and I appreciate the response.
I have concluded that yes this machine is not what I need for I have a mixture of appliances that need the 240. And yes I’ll be running it for several weeks during hurricane season.. At any rate buying this machine and getting it up and running has been a huge learning experience and thanks to you all it does purrr like a kitten!! I already have people wanting it so I’ll probably be shopping for something compatible with my house and shop

Thanks again see ya next project

 

[MatthewWBailey]

Thank you all for your advice and suggestions!!
It has been a busy couple of days dealing with everything and I appreciate the response.
I have concluded that yes this machine is not what I need for I have a mixture of appliances that need the 240. And yes I’ll be running it for several weeks during hurricane season.. At any rate buying this machine and getting it up and running has been a huge learning experience and thanks to you all it does purrr like a kitten!! I already have people wanting it so I’ll probably be shopping for something compatible with my house and shop

Thanks again see ya next project

I just saw this. I'm also looking at a buying local 805a, mainly bc it's local.

You Can use 208 for a house but you need a buck-boost transformer. As a PE, I think I've done this sizing calc about 1000 times. The buck boost trans is relatively small by comparison to the load bc you only need to pass ~14% of the voltage thru the boost up to 240.

As far as #of legs, @DieselAddict is correct, you're only using 2/3 of the gen, so 20kw is avail at 208 single phase. These 805's are a wye config as shown, and with only 2 legs used, it's the same as your service transformer with a center neutral.

some motor-based loads in a house will Eventually trip breakers when ran on 208, well pumps especially, pool pumps etc. Resistor loads (range) will simply be less powerful and draw less amps. 120v loads (fridge, Mwave, toaster, coffee), will run exactly the same since they're still 120. AC compressors need to have the dual voltage rating as said above or they may trip breakers.