Running Generators in Parallel?

[RNeumann]

This may not answer your question - BUT - most of the easily paralleled generators are under 3KW and inverters and cost a fair bit more.
You might get by with a pair of HF 3.5KW which are on sale for $750, but probably most people will dump on those and tell you to get a pair of Honda EU3000's for $4,000.

The pair should be enough to run your welder.

Now if you need more power there is a 10KW generator that undergoes yo-yo pricing. It's the Duromax 10000 watt dual fuel . Right now it's price is at $1,199 . BUT it often cycles down to below $650, once to $550. I do not understand their pricing schema but I've been following them for 3 years since I bought one based on this thread. The price will drop down to the $650 or less level and they sell out. Several threads here about using them with welders.

A pair of inverter generators can be separated and used at different sites.

/edit -
Of course if you REALLY want to do it right get a pair of Honda EU7000IS's and a parallel kit for about $8K.

2 120v Honda type inverter gens hooked together won’t make 240v. So the 240v welder won’t work. The twist lock on the front is a 30a 120v.

I learned that the hard way!

 

[John_Mc]

Many conventional generators can be synced together. It has nothing to do with inverter types.

Basically you stick a meter in between the two, and when they are in snyc, the voltage goes to zero, you connect them together and if fairly closely matched, they will stay in sync.

That's the easy explanation. But like someone said, things can go wrong. It's more for larger systems.

No way I'd mess with that. Even if you managed to match the frequencies exactly (which is a real longshot), there is no guarantee they will stay that way. Just a slight difference in the way one of the generators responds to a change in load will throw the synchronization off.

 

[newbury]

2 120v Honda type inverter gens hooked together won’t make 240v. So the 240v welder won’t work. The twist lock on the front is a 30a 120v.

I learned that the hard way!

He never wrote 240V. He just wrote Millermatic 211, which also operates at 120, the last I knew.

BUT the Honda EU7000iS Parallel Kit does spec 250V.

 

[RNeumann]

Let’s try this another way......

A 120v gen won’t simply plug into your house (through transfer switch or otherwise) and run all your 120v appliances. The panel has 1/2 the circuits on one phase and the other 1/2 on the other phase.
OP doesn’t have the knowledge (based on the question (which is fine)) of electrical to know about phases, htz etc. So suggesting a 120v gen will work on a tight budget doesn’t paint a very accurate picture. A lot of the money would be eaten up adding or modifying the existing electrical panels at both houses.
If the OP sticks with 240v split phase gens (standard in the USA), he will get what he wants to back feed the house and run his welder. The brand, size etc will depend on the budget and brand recognition.

*as a note- with some modifications and illegal wiring their is a way to energize all 120v circuits in a panel with a single 120v gen. The juice isn’t worth the squeeze in most cases and risk of property loss or injury is real.

 

[Tractor Seabee]

As far as I know the largest "portable emergency" generator that you can manhandle is the Generac 17.5 KW. Has a 50A 240V outlet along with 30s and 20s. I have one using a 100A emergency panel with transfer switch kit. Feeds all my essential circuits + will run my 250A welder that has a 45A input. If I had a gas dryer it would run the whole house. Both Lowes and Home Depot have them on line only, free freight. Price varies throughout the year. Generac's RLP is around $3200. Bought mine 3 years ago on sale at $2400 - my 10% military discount. Not used much since we moved into town but always starts when I want it. Start it monthly to keep the battery up.

Ron

 

[Tractorable]

Gentlemen,

Thanks very much for the advice. It's much appreciated. I've decided to abondon the idea on running two generators in parallel. I might blow myself up. Also, I'm leaning towards getting two generators, one for each house. That will provide redundancy in case one goes down.

Question: since I'll have two generators, if no one is staying in the guest house during a power outage, could I use the extra capacity of the second generator by installing two transfer switches to the panel in the main house, with one generator connected to each?

That would give me the flexibility to have one generator for each house, or have two generators on the main house.

 

[MinnesotaDaveChalmers]

Just my opinion, but I look at generator power a little differently.
I don't really want to run the whole house: just fridge, freezer, well pump, couple fans and lamps.

I have not wired any panels, I just use extention cords.

 

[RalphVa]

I own an 8 acre property. The property has two houses on it, the main house and a guest house. The guest house is operated as an AirBnB so we sometimes have guests staying there.

We recently had a power outage that lasted for three days due to a wind storm. I would like to find a solution to have backup power available to both houses on the property in case of power outages.

There's an electrical panel with a meter at the corner of the property about 75 yards away that feeds power to both houses on the property. Each house has its own electrical panel inside.

I'm wondering, would it be best to buy one big generator and connect it to the main panel outside to power both homes? or buy two generators, one for each home? If I bought two identical generators, is it possible to run them in parallel to provide double the juice to one home?

Additionally, whatever generator I buy, I'd like it to be powerful enough to run a Millermatic 211 MIG welder. I'm currently considering buying two Westinghouse WGen7500 continuous/9500 surge dual fuel generators.

A standby diesel generator with concrete pad is not in the cards financially.

Absolutely not. Putting 2 120 volt supplies together is how we get 240 volt.

The power supplies would have to be EXACTLY in time. Otherwise, you could have voltage all over the map.

We put in an Isuzu diesel generator, 12.5k, that runs the whole house, even a hot water heater and clothes drier. Uses 2.5 gallons/yr if no power outages, running 15 minutes every 2 weeks. Remarkable diesel. Uses only 0.1 gph of fuel. No smoke. Don't sound like a diesel.

Electrician put replaced one of our 200 amp panels with one from GenTron and put in some little boxes that use smart control on about a half dozen circuit breakers to determine whether they can come on.

Ralph

 

[CobyRupert]

I always thought the danger of paralleling 2 generators was when you switch them together. That is, when you switch one into an energized circuit (be it another generator, or even the utility) when the two different voltage output waveforms are not synchronized (in phase).
The problem being when the energized circuit being switched into has enough power (especially if it's the "grid", or another larger generator) that it will try to bring the new generator into phase instantly. As a rule, mechanical devices usually don't survive anything happening instantaneously. Especially instantly spinning the rotor or the motor's crank 180 degrees (Instantly adding energy is what happens when you hit something with a sledge hammer!)

However, if you can start the two generators together (while connected electrically), or safely switch running generators in together (using a synchro-scope and/or a sophisticated synchronizing relay) then I think most of the danger can be avoided. Then the problem becomes: Are they both generating (or is one motoring), which is a problem of having similar throttle settings, similar governor response, similar motor output etc...
I assume this is why commercially available small generators that can parallel have to be identical brands and have a communication link.

 

[newbury]

Gentlemen,

Thanks very much for the advice. It's much appreciated. I've decided to abondon the idea on running two generators in parallel. I might blow myself up. Also, I'm leaning towards getting two generators, one for each house. That will provide redundancy in case one goes down.

Question: since I'll have two generators, if no one is staying in the guest house during a power outage, could I use the extra capacity of the second generator by installing two transfer switches to the panel in the main house, with one generator connected to each?

That would give me the flexibility to have one generator for
each house, or have two generators on the main house.

Simple answer - Yes, you could move it to the main house.
Transfer switches can be configured to run only select circuits. Get a QUALIFIED LIVE electrician involved, don't bet your houses and lives just on advice from an internet poster.

Just my opinion, but I look at generator power a little differently.
I don't really want to run the whole house: just fridge, freezer, well pump, couple fans and lamps.

I have not wired any panels, I just use extention cords.

That's what I do.

I live just outside the Beltway in Alexandria, Va. 50 miles from the OP. A year or two before Hurricane Isabel back in 2003 our power was cut for while and we suffered through it. Then Hurricane Isabel hit us and we were out for several days. My boss who lived about 10 miles south of us also lost power. We both wanted generators IMMEDIATELY. He added a $15,000 (with installation) whole house generator package. I added a $650 Coleman 8Kw (Honda engine) portable with extension cords ($50). The houses are almost identical in size and power needs.

Since then - in the last 15 years - our power has gone out ONCE for long enough that I've needed to run the generator to ensure the frig, freezer, etc. functioned.
Probably less than 1 hour of usage TOTAL for the "emergency". The same with my boss.

Thus basically I spent about $700 for 1 hour of frig/freezer running, he spent about $15,000 for an hour. Plus there is the "maintenance" running, oil change, etc.

I try to fire up my generator about 4 times a year.

I have actually run the generator and extension cords etc. about 4 times in the 15 years just so I and my family know how to do it.

My point is that in most of Northern Virginia they have been improving the power grid and we suffer very few long term power outages. The OP indicated funds were moderately tight. A package of 2 Duromax 10KW generators (@ < $650), and a couple of 50' 10/3 extension cords ($50@) would get him started with both buildings.

Adding in transfer switches, electricians labor, permitting, etc. etc. will increase cost and I'm sure some TBN'er will help spend more.

/edit -
Looking at the pictures of the houses it looks like it would be simple to build a "dog house/generator shed" for each house to run a generator in silently.

Example here