# 50 amp generator to a 30 amp transfer switch



## ResLur (Jul 15, 2014)

I have a 17,500 portable generator and have installed a 50 amp transfer switch, which has a 30 amp inlet.  The cord to connect the generator to the transfer switch has a 50 amp male on one  end (generator end) and a 30 amp female on the other.  Is this okay?  My electrician says it is.


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## begreen (Jul 15, 2014)

I don't tink so Lucy. The wire gauge and plug should match the output. At 17,500 watts this sounds like it is designed to be direct wired, not plugged in. I would expect this to be on a 60 amp circuit. Or is the 17,500 watt a surge rating? Moving to the DIY forum to bring in some of the electricians.

What make and model generator?


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## ResLur (Jul 15, 2014)

begreen said:


> I don't tink so Lucy. The wire gauge and plug should match the output. At 17,500 watts this sounds like it is designed to be direct wired, not plugged in. I would expect this to be on a 60 amp circuit. Or is the 17,500 watt a surge rating? Moving to the DIY forum to bring in some of the electricians.
> 
> What make and model generator?


It is a generac generator


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## begreen (Jul 15, 2014)

OK, so if this is the GP17500E portable they have several plugs on the unit for 120V, 120/240 - 30A, & 120/240 50A. Each has its own circuit breaker so you would be ok plugging from the 30 amp generator plug to the 50A transfer panel as long as the connecting cord wire gauge is #10 or higher for the 30A plug. The gauge will depend on the cord length. But that would only be using a small fraction of the power output. Why not connect with a 50A cord and plug?


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## ResLur (Jul 15, 2014)

begreen said:


> OK, so if this is the GP17500E portable they have several plugs on the unit for 120V, 120/240 - 30A, & 120/240 50A. Each has its own circuit breaker so you would be ok plugging from the 30 amp generator plug to the 50A transfer panel as long as the connecting cord wire gauge is #10 or higher for the 30A plug. The gauge will depend on the cord length. But that would only be using a small fraction of the power output. Why not connect with a 50A cord and plug?



The 50amp was difficult to find and I had a 30 amp.  Now let me tell you want happened.  It melted the ground (green) wire in the transfer switch.


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## BrotherBart (Jul 15, 2014)

And that electrician said what about that?


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## BrotherBart (Jul 15, 2014)

Since you are posting this all over the place, hopefully somebody has an answer. This isn't generators.com.


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## begreen (Jul 15, 2014)

ResLur said:


> The 50amp was difficult to find and I had a 30 amp.  Now let me tell you want happened.  It melted the ground (green) wire in the transfer switch.


Agreed. The ground should not be carrying current. Get an electrician onboard before something else melts down.


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## Jags (Jul 16, 2014)

If you are cooking the ground wire, that means you have a wiring mess down the line somewhere.  Get a pro in there before you do permanent damage to something.


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## ResLur (Jul 17, 2014)

BrotherBart said:


> Since you are posting this all over the place, hopefully somebody has an answer. This isn't generators.com.



Yes I posted on three sites.  As you can imagine we are very stressed by this situation and are looking for a resolution as-soon-as-possible.  I think we now have a resolution.  By the way, I would like to thank everyone for their response.  This forum is a wonderful tool and very much appreciated.  Once again, thank you all.
Larry


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## begreen (Jul 17, 2014)

What did you end up doing?


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## ResLur (Jul 18, 2014)

ResLur said:


> Yes I posted on three sites. An you can imagine we are very stressed by this situation and are looking for a resolution as-soon-as-possible. I think we now have a resolution. By the way, I would like to thank everyone for their response. This forum is a wonderful tool an





begreen said:


> What did you end up doing?


Thank for asking.  There may have been an error regarding the wiring of the male 50amp plug, black and red were in the wrong positions.  The diagram is very confusing and contradictory.  We are thinking that the black should be placed on the left, white at the bottom, green at the top and red on the right.  We are also replacing the 30 amp female plug on the cord with a 50 amp.  We are replacing the #10 cord with a #8.  We are replacing the 30amp male plug in the transfer switch with a 50 amp.  We are also testing the generator to make certain it is producing the advertised amps, and not more.  Yes, you guys have guessed it - we are now doing everything that we should have done in the first place.  I think we got lucky here that there was not real damage.  Finally, and once again, I would like to thank you guys for your assistance.  You are wonderful people.

Larry


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## begreen (Jul 18, 2014)

You should be using #6 stranded for a 50 amp plug. Be sure you know which terminal is for the ground (green) and which is for the neutral (white). Reversing the the red and black is fine. They are both hot legs. Better yet, have someone that understands this make up the cordset. It will be worth it if it saves some serious damage by mis-wiring.


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## ResLur (Jul 18, 2014)

begreen said:


> You should be using #6 stranded for a 50 amp plug. Be sure you know which terminal is for the ground (green) and which is for the neutral (white). Reversing the the red and black is fine. They are both hot legs. Better yet, have someone that understands this make up the cordset. It will be worth it if it saves some serious damage by mis-wiring.



Update, we just tested the generator 50 amp outlet.  From green to hot on one-side 125v, from green to hot on the other 240v.  We think this is the problem.  By the way, the same for the 30 amp outlet.

Larry


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## ResLur (Jul 26, 2014)

ResLur said:


> Update, we just tested the generator 50 amp outlet.  From green to hot on one-side 125v, from green to hot on the other 240v.  We think this is the problem.  By the way, the same for the 30 amp outlet.
> 
> Larry




For me, the original question remains unanswered.  If the generator is producing 120v on X and 240v on Y, why did the ground (green) wire in the transfer switch melt. Some how the additional current must have found it way to the transfer switch box.  The solution becomes important as I move forward with the next attempt at connecting the generator to the main panel box.

Larry


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## CaptSpiff (Jul 29, 2014)

ResLur said:


> Update, we just tested the generator 50 amp outlet.  From green to hot on one-side 125v, from green to hot on the other 240v.


OK, electrical advice without a common diagram to reference is like shooting in the dark. I recommend you make up your own wiring diagram (hand drawn) starting with the generator represented as a "center tapped transformer". Google it for a drawing. Label the top of the winding hot (black), the center tap neutral (white), and the bottom hot (red). Sometimes in industrial generators the center tap neutral is independent of the Ground Lug (green), sometimes they are connected internally (ie white = green).

Now you'll measure 240v hot to hot, 120v each hot to neutral. This is not 3 phase, this is single phase, just like the utility delivers to your service panel in your house.

You measuring "green to hot on the other 240v" is a serious problem. Looking at a picture makes that clear. good luck.


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## ResLur (Jul 29, 2014)

I do give my electrician credit for identifying the defect in the generator, which turned out to be the primary problem.  The ground to Y was producing 240v.  The new setup is as follows:

1. #6-4 cord/wire from generator to transfer switch
2. 50 amp male plug on one end of #6 wire/cord
3. 50 amp female on the other end of #6 wire/cord
4. 50 amp male on the transfer switch (Reliance pb50 plug). Rated for 12,500 watts

The new transfer switch is rated 15,000 watts.  

Remember the primary goal - The 15.5 kw generator will serve as backup power during power outages in our area - which are common. I have a reliance transfer switch rated 15kw watts that will allow me to run various circuits within our home.

The new generator will be here 8/10/14 and the electrician will make all the necessary connections.  I will let you guys know how it works out.

Once again, than you all for your comments. Thank guys are a great source of information.

Larry

Read more: http://www.doityourself.com/forum/e...tor-30-amp-transfer-switch.html#ixzz38tjdS5Rp


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## ResLur (Aug 2, 2014)

Guys, my 50ft #6-4 cord arrive today.  I had no idea it would be this large and heavy.  But I think that I have what I need for the job.  New generator should be here soon.  I am very excited about connecting everything to see if it works.
Larry


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## velvetfoot (Aug 2, 2014)

Excellent!  #6-4, that does have to be heavy.


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## ResLur (Aug 9, 2014)

Update: The 15,500 generator arrived today. I have my electrical permit and the electrician arrives Monday to connect all components. I have a very good feeling about this, why, because I have done my homework and I have a great electrician. (Mostly the research, including help from you guys.) The electrician came by Thursday for a planning meeting. I know what you are thinking, this is a small job - so why the pre-planning meeting? I am a firm believer that many conflicts with contractors could be avoid via pre-planning meetings. It gives you an opportunity to mentally walk through the process and to ensure that both are on the same page. My electrician was not very excited about this approach at first, but indicated afterward that it was time well spent. Based on our meeting, he prepared a materials list and both of us know what to expect. No surprises. (By the way, I fully expect to pay him for the preplanning meeting)

I will let you guys know how it turn out Tuesday.

Take care, and again, thank you all for your assistance, Lord knows I needed it.

Larry

Read more: http://www.doityourself.com/forum/e...tor-30-amp-transfer-switch.html#ixzz39vTcT3uf


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## begreen (Aug 10, 2014)

Best wishes for a successful conclusion Larry. I'm glad you are getting a professional to finish the project.


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## maple1 (Aug 10, 2014)

Is this just for house backup? That's a lot of generator. Likely pretty thirsty too?


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## ResLur (Aug 11, 2014)

Today's installation went well.  The electricians did an outstanding job of installing all the components.  When the installation was complete, the electrician used a voltage meter to test the new 15,500 generator.  From 1) hot to hot - approximately 240 volts; 2) from neutral to hot (both) approximately 120 volts each; 3) from ground to hot - approximately 101 volts; 4) from ground to hot - approximately 161 volts.  What are the changes that two different generators from the same company could be defective.  We did not plug the new generator into the transfer switch.  The matter is under discussion with the manufacture.  Of course, Lowes will take the generator back, but I am so frustrated and tired with the process.

Regarding the above question - yes this is backup power for our home.  We loose power often.

I am so disappointed. 

Larry


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## CaptSpiff (Aug 12, 2014)

OK, so a simple voltage test (with a high impedence voltmeter) is not enough. 

Get 2 old 100W incandescent light bulbs, buy 2 construction sockets and connect them in series. Now you've got a 240v tester that can put a load on your voltage sources. Then repeat the same tests as you stated above. The bulbs will be normal bright across the hot-to-hot (240v). They'll be half bright across each hot-to-neutral. Then test each hot-to-ground, and you may get very dim or no light at all. If so then the Ground is not bonded to the Neutral of the Genset. This is not uncommon for industrial units.

If the 101v and 161v remain strong and steady, even with the lamp tester connected, then you've got bigger problems.


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## maple1 (Aug 12, 2014)

Do you really need a genny that big? That would amount to a monthly power bill close to or in the 4 figure range.

Sorry, guess that doesn't do much for the current problem. Hope you get things figured - the frustration must be off the chart. Keep us posted.


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## begreen (Aug 12, 2014)

The GP17500E is going to go through about 16 gallons of gas to run 10 hrs. If your power outages are like ours (up to a week long) then I would consider a backup to the backup that sips fuel. Then run the house like a boat. Only run essential loads. For us this is refrigeration and freezer. Anything else is gravy. Usually we can also run some lights, computer and tv. In comparison our genset goes through about 1.6 gallons in 6 hrs.. During an extended outage it gets run 2 hrs in the morning and 3-4 hrs at night.

Or get a proper whole house propane genset and put it on a big tank. If you have natural gas, even better. This is an 8KW propane or natural gas unit that will cover most loads.
http://www.electricgeneratorsdirect.com/Images/Generac-Guardian-6237-Standby-Generator/i10669.html


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## ResLur (Aug 12, 2014)

Our highest power bill this summer (all electric) was just over $153.  However, once you start adding up the watts, for the devices you want the run, it takes 10kw to 12kw, especially for heating and cooling.  

Concerning the defective 15kw generac, a generac service representative indicated today that it is mostly likely a bad voltage regulator, and that the generator should be returned immediately.  He knew right away, without a lot of explanation.  So it must be a common problem for this machine.  We are thinking about trying the 12,500 Powermate next.  Please keep in mind that a company the size of Generac can encounter faulty parts and workmanship at any time our the company's production history. I just wish it had not happen to us. 


Take care,
Larry


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## ResLur (Aug 12, 2014)

You are correct, about 10 gallons for 10 hours.  It is not uncommon for us to loose power for several days (Hurricane Irene, 7 days, 1/2 hour).  The important devices for us are well pump (lush), heating and lights.  We do not keep a lot of food in the refrigerator due to the unreliable power situation in our area (we are at the very end of the power circuit).  When the power is out, most of the time Karin and I are at work during the day.  So we only require a generator for a few hours each night.  We considered the whole house generator ($9,000-two quotes), but I would not feel comfortable leaving the house with it running.  By the way, propane is not cheap, and could easily cost you several hundred per week.  That is our reasoning, but I certainly understand your reasoning.  Thanks for the comment.  By the way, for our setup, about $3,300 ($2100 for generator, $1,200 installation/parts)

Take care,
Larry


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## begreen (Aug 12, 2014)

All devices don't run simultaneously. There is no need usually to size a generator for the maximum possible load. You can switch off and cycle to conserve power during an outage. For example, don't use the oven and turn off the hot water unless you need it. What is your heating source?

Personally I wouldn't use a contractor generator to run a house. There are too many electronics in today's home that want fairly clean power. Unless you have a serious load, a 6.5kw Honda generator is what I would consider in gas. It will easily handle the well. The whole house propane generators do not have to run on automatic start. That is your option, it can be run in manual mode if preferred. FWIW our propane is exceptionally expensive. But it is a good generator fuel because it doesn't go stale like gasoline can. And during an extended outage it is typical for our gas stations to be without power too. All things to consider for emergency power.


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## ResLur (Aug 12, 2014)

begreen said:


> All devices don't run simultaneously. There is no need usually to size a generator for the maximum possible load. You can switch off and cycle to conserve power during an outage. For example, don't use the oven and turn off the hot water unless you need it. What is your heating source?
> 
> Personally I wouldn't use a contractor generator to run a house. There are too many electronics in today's home that want fairly clean power.




We heat/cool with a 2.5 ton heat pump.  But I recently installed a mini split system that requires 1/2 the wattage.  I will certainly consider your comment. 

Larry


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## ResLur (Aug 12, 2014)

ResLur said:


> We heat/cool with a 2.5 ton heat pump.  But I recently installed a mini split system that requires 1/2 the wattage.  I will certainly consider your comment.
> 
> Larry



Begreen, I just noticed that you are a moderator.  Thank you for the site, and taking the time to moderate.

Larry


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## begreen (Aug 12, 2014)

We heat with a heat pump as well, though once it gets 45 or below we heat mostly with a wood stove. Our 3 ton heat pump can run on a 25 amp service, but that is mostly for starting current. When running it is more like 16 amps. As you noted mini-splits use even less power. In your case to run on a smaller generator of say 6.5KW it would take turning off the heat while raising the well pressure. Once that is done, turn off the well pump and turn on the mini-split. A 10KW system would not need much load management but will use more fuel per hour.

PS: I added a few more thoughts on propane to the previous comment after you had posted.


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## ResLur (Aug 15, 2014)

We have a 5000kw (6250 peak) generac generator that we used for years for the well pump and lights/refrig; however, it will not handle the mini split; which is strange.  It transfers power to the house via a Reliance Transfer Switch.

Lowes pickup the 15kw generator this morning that was defective.  We have decided to go with a 12.5kw Powermate portable generator.  It comes with an automatic voltage regulator, which hopefully, will provide some measure of protection for home loads.

Take care,
Larry


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## fbelec (Aug 17, 2014)

when running heat pumps or air conditioners it's not the running amps you need to worry about it's the start up current. if you look at the specs plate on your compressor outside there will be running load and lock rotor current. the lock rotor current is your start up current. 3 ton might be up into 50 to 75 amp load. that's the hard part of running something that heavy on a generator. once you get it to start your ok it will probably run 15 to 18 amps. i have a customer that wants a propane powered generator but has heat pumps a 5 a 4 a 2.5 and a 3 ton units they are all geothermal. the 5 ton draws 125 amps on start up. they couldn't get a generator big enough to run that house. ductless splits seem to start easier than regular whole house air conditioners. begreen have you run your heat pump on a generator? and if so how many watt gen was it?


frank


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## begreen (Aug 17, 2014)

No I haven't. It looks possible with our 4Kw generator, but I haven't tried. It's a contractor generator so I don't want to risk frying its electronics with dirty power and we have the woodstove as a more practical heating backup.


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## maple1 (Aug 18, 2014)

I can power our house in an outage on a 3kw inverter genny.

Power to spare and sipping of gas - but, we only have a shallow well 120v pump. And we don't use the big things like stove & dryer, of course. Even still, we can get by for a few days with very little well pump useage using water from a barrel in the basement that catches condensate from our HRV to flush the toilets. Our heating system uses very little juice, just a couple of circ pumps - and it can deliver heat with no power by convection with closely monitored operation. The main things to keep juice to are the fridge & freezer - everything else is not what I would call essential, and is maybe periodic at best.

Is the mini-split your only heat source?

Here, the things you WANT to run are a lot different that the things you NEED to run when the power goes out - I would have a very hard time keeping anything else in fuel in a extended outage, unless I go to putting in an oil tank and a diesel, or tying to a propane company. Which I am not going to do just for backup power.

But we are all in different circumstances & situations.


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## ResLur (Aug 18, 2014)

Over the weekend I was researching inverter technology, but as with everything connected to alternative power sources, this technology is dependent on batteries (or solar).  The inverters are capable of providing sine wave power.  I do like the fact that Honda has built inverter generators, but only offer them up to 5500 running watts, and I need at least 10kw running watts.  So, it looks like I am going to go with the 12kw Powermate that comes with an AVR.  Maple 1, the mini split is the heating source for the sunroom that I built this spring.  The rest of the house is heated with two 2.5 ton heat pumps.

One thought relative to the inverter, (thinking outside the box, or just plan crazy) - I was thinking if it would be possible to connect a generator directly to an inverter.  The sequence would be as follows:  small generator powering an AC to DC converter that would be connected to an 12kw inverter.  The point, power grind quality electricity.

One final question, is it possible to discharge and charge a battery at the same time.  I am thinking no, as electrons can only travel in one direction at any given moment in time.

Begreen, if you do not mind, where do you live.  Wow it gets really cold there.

Take care,
Larry


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## mustash29 (Aug 19, 2014)

ResLur said:


> small generator powering an AC to DC converter that would be connected to an 12kw inverter. The point, power grind quality electricity


 
The A/C to D/C conversion will waste a bit of power (in heat) and then the inverter process will waste a bit more.



ResLur said:


> is it possible to discharge and charge a battery at the same time


 
Yes, your car does it everytime you run it.  Battery supplies the loads and the alternator is charging it at various rates, based on what the voltage regulator tells it to do.


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## ResLur (Sep 1, 2014)

Success - Finally - The 12,500 Powermate arrive Sunday morning.  My Electrician tested the generator today (before plugging into the transfer switch), and it checked out okay.  Connected the generator to the transfer switch and we turned on the breakers one at a time.  I am able to run the following without placing a lot of stress on the generator (all at once):

Mini Split HVAC
Kitchen Lights
Bedroom Lights
Well Pump
Water Heater
Two TVs
Microwave
Frig.

As you may remember, this was a one month project that turned into 5 months because the first two generators were defective.   I am very, very relieved that it is over.  And I extend a Thank You to each one of you for your ideas and thoughts.  What a nice group of individuals.

Take care friends,
Larry


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## jharkin (Sep 3, 2014)

I know you already bought and installed it... but for the money you likely spent I wonder why you didn't instead buy a smaller inverter generator and spend the rest of hte money to install a wood stove/ insert or even pellet stove to take the heating load? For the same initial investment you would end up with a more robust solution, more flexibility and significantly lower operating cost.  (as it seems the heat was the only thing you needed more than 5kw for).


Oh and expanding on a comment upthread.. in a fixed backup generator the neutral and ground should NOT be bonded at the generator.  By code the generator may have its own ground rod but the only place the neutral and ground would bond are in the service panel.


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## ResLur (Sep 3, 2014)

First of all, we would never install a wood heating system in our current house, as it would not be compatible with the style of house and they tend to be messy.  (No offense intended, please).  Concerning inverter generators - this is a new market and Honda seems to have the best technology at this time.   A 5000 watt Honda would cost approximately $3,600, when we paid approximately $2,100 for the 12,500 watt Powermate.  I have another $1,200 in the 15,000 watt transfer switch and installation costs.

The 12,500 watt Powermate is able to handle all the loads mention above with very little stress on the genny.  This saves gas and wear and tear on the Powermate.

Thank you for your comments and suggestions,
Larry


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