How do you wire the neutrals and is it safe when running a 240v home appliance (a window air conditioner in my case) from a 120v generator by wiring a 240v breaker that pulls from two of its 120v outlets and outputs to a 240v plug?
2
-
What's the make and model of your generator?– ThreePhaseEelCommented Nov 27, 2016 at 14:58
-
home is 240Vac split phase to get 120V L1 & L2 out of phase from D.T. and grid. Not possible with 2 outlets L1 & L1 from a 120V gen.– Tony Stewart EE75Commented Nov 27, 2016 at 15:21
Add a comment
|
4 Answers
What you describe won't work, and it's not safe for you (or anyone else) to do what you describe.
If you have a single phase 120 volt generator and you need to supply power to a 240 volt split phase load, the safest way is to use a transformer with a 120 volt primary connected to the generator and a 120-0-120 volt secondary connected to the appliance.
-
A similar result could be achieved at higher cost with two 120-volt 1:1 isolation transformers by connecting the primaries to the 120V output of the generator in parallel and the secondaries in series. The common connection of the secondaries would serve as the neutral (N) leg and the free ends of the secondaries would serve as the L1 and L2 legs. You should measure 240 volts between L1 and L2 and 120 volts between L1 and N or L2 and N. If you measure approximately 0 volts between L1 and L2, it means you'll need to reverse the secondary winding of one transformer. Commented Jul 19, 2022 at 22:21
Transformers are your friend!
Easy peasy, if the numbers work.
Start by looking at the air conditioner. You need to know the number of "watts" the air conditioner uses, probably between 1000 and 3000. This number is often called VA instead.
Next, look at the receptacle (outlet) on the generator. If it looks like the totally common AC power outlet, then you can't do it if the A/C unit takes more than 1800 watts.
If it has an extra horizontal bit (like this), then you can't do it if the A/C unit takes more than 2400 watts.
Next, you'll need a 240-120V step-up/down transformer whose watts (or VA) rating is larger than the air conditioner. You set the transformer for 120V input, plug it into the generator, and plug the 240V A/C unit into the 240V receptacle on the transformer.
There's one more hitch: what's the capacity of the generator? (again in watts or VA). If the generator doesn't have enough watts, then it cannot start the air conditioner. That's likely. Generators which are 120V-only tend to be small, and air conditioners which are 240V tend to be large.
(By the way, most 240V window air conditioners are 240V-only, don't need neutral, and use a NEMA 6 connector. I've never seen one that is NEMA 10 or 14 needing neutral.)
answered Nov 28, 2016 at 4:03
Harper - Reinstate MonicaHarper - Reinstate Monica
310k27 gold badges294 silver badges761 bronze badges
To put it simply no the confusion come in that you house is supplied with 220/240 Volts AC. You would be better off just buying a Generator that will supply 220-240 VAC if you have your own engine already you can just buy the generator head Harbor Freight has a 30 amp 240VAC for around $300.
Your best option will be to get a generator with 120/240 output. Now, here is an option if you want to use a 120v generator: It is not cheap, but it will work. Connect the generator to a distribution transformer that have a primary input voltage option for 120v, secondary voltage 120/240v. Like this model: Low Voltage Distribution Transformer - Single Phase, 120/208/240/277 - 120/240V, 10kVA by Acme Electric Catalog ID: T279746S
Consult with a register professional local to you, and size it correctly.
