Rmoore
I have a new Generac 6437 11 K with a 100 Amp 12 circuit ATS that I am installing. My question is on the breaker size in the main panel to supply the utility power to the ATS:

The Generator itself has a 50 Amp shutoff\breaker. My Generac supplied ATS has a 100 Amp breaker. The Install manual ( for multiple wattage Generators) says for an 11 K use a 70 Amp breaker. The Dealer says 60 Amp is not uncommon. So what size do use? It seems if it pulls more than the 50 amp Generator breaker can take if will pop anyway. Just curious on what anyone is using.

Thanks
Ray
Quote
Skip Douglas SkipD
I'm pretty sure that the size of the breaker to feed your transfer switch with utility power must be married with the wire size you use to make the connection. If the generator has a 50-amp breaker, and assuming that your generator is properly sized for the loads attached to the transfer switch (possibly a huge assumption), you shouldn't need any more than a 50-amp breaker for the utility feed.
Skip Douglas
Quote
Rmoore
Thanks Skip, I did mean ATS ( not sure what I was thinking). I went back and corrected it.
Good point on the wire size. I went back and looked at the labeling on the wire coming from the transfer switch and it does say 240/50 Amp. So looks like 50 amps is the right choice. Confusing how the install manual that came with the generator actually said 70 amp, a dealer recommends 60 amp and the wire label says 50 amp. Then the ATS box is actually a 100 amp box. It seemed logically to me at first it should be 50 Amps as that is what the Generator has in it. But after so many different recommendations I'm questioning what I was thinking.
Quote
Rmoore
Although I did look at the wire size itself and it is AWG 8
Quote
Skip Douglas SkipD
Ray, it would be a very good idea for you to hire a competent electrician who is experienced with residential generator installations. You might use him for the whole job or do like I did and get him to work with you as a "helper" to save money. He will know all the applicable codes as well as who to get involved for the fuel installation and what the location limitations are. There are many codes - some not so easily found - that are involved in a generator installation project. Make sure you pull a permit and have a final inspection by your local authorities.
Skip Douglas
Quote
Rmoore
Thanks Skip. I do have an electrician that will be helping when everything is ready, but I am trying to get everything I think we will need prior to actually doing it. I'll get a 50 amp and if he needs something different the local supply house is 10 minutes away.

Thanks
Ray
Quote
MEC
That combo you mentioned is the 50A 12circuit switch.
The only 100A EZ switch available now is the 16circuit one. Unless there are some old ones still floating around.

You want to use the 50A breaker on the one you have.
Quote
Rmoore
Thanks MEC

Strange, mine came with the 100 Amp version, just got it a few months ago. I just thought it was odd that the ATS was 100 Amp and the Generator has 50 Amp breaker. It seemed like they would have been matched.

From the web site:

Generac 6437 11kW Standby Generator with 12 Circuit 100 Amp Indoor Automatic Transfer Switch **IN STOCK**

Item No. 6437
Quote
ceb58
Rmoore;36793 wrote:
Thanks MEC

Strange, mine came with the 100 Amp version, just got it a few months ago. I just thought it was odd that the ATS was 100 Amp and the Generator has 50 Amp breaker. It seemed like they would have been matched.

From the web site:

Generac 6437 11kW Standby Generator with 12 Circuit 100 Amp Indoor Automatic Transfer Switch **IN STOCK**

Item No. 6437


Don't let the 100 amp throw you. It just means that the ATS is rated for no more than a 100 amp load.
Quote
UPS
Rmoore;36793 wrote:
Thanks MEC

Strange, mine came with the 100 Amp version, just got it a few months ago. I just thought it was odd that the ATS was 100 Amp and the Generator has 50 Amp breaker. It seemed like they would have been matched.

From the web site:

Generac 6437 11kW Standby Generator with 12 Circuit 100 Amp Indoor Automatic Transfer Switch **IN STOCK**

Item No. 6437


The ATS is capable of handling 100 Amps for the loads on it (when the utility power is available) or if used with a larger generator. However an 11K generator can provide only about 45 amps, and is therefore protected by the 50 amp breaker.
Quote
Skip Douglas SkipD
ceb58;36795 wrote:
Don't let the 100 amp throw you. It just means that the ATS is rated for no more than a 100 amp load.
Precisely.

My 5416 generator (rated at a maximum of 75A and provided with an 80A breaker) was bundled with a 200A service-rated automatic transfer switch (ATS). There's a 200A disconnect in the ATS for the generator feed. The limit of the generator is not changed by the rating of the ATS.
Skip Douglas
Quote
MEC
You'll find that was incorrectly advertised.

From the main Generac site:

[url]http://gens.lccdn.com/generaccorporate/media/library/content/all-products/generators/home-generators/guardian-series/0197980sby-l-8-11kw-hsb.pdf[/url]


The only EZ switch that is rated 100A now is the 16 circuit.
Quote
Peddler
I think the switch itself is the same, the reason the 8KW and 11KW prepacks are rated at 50 amps is the wire size feeding from the main panel and from the switch to the breakers in the switch is down sized and therefore the lower rating. This I am sure is for two purposes, one to save some money and two in the never ending effort to keep people from overloading the generator. Peddler
Quote
MEC
Exactly.

The one thing I can't wrap my head around is they limit its load and do that, but then put in a 2/30A breaker and package it with the 8kW.....

Like someone is going to put an electric dryer or WH on that unit.


I always pull those out and on the 12cir I pull the 2/30A & 2/40A out as well.
Unless there's an existing sub panel with not much of a load on it. It's use is definitely limited.
Quote
Rmoore
Hi MEC

Funny you should mention the 2/30A and 2/240A breakers. I am trying to figure what all I can hook up to the generator in additional to what I have now. Maybe I am already over loaded. I am trying to figure this out myself before asking the electrician to come back. I am posting a new post asking about this and some advice.
Quote
Rmoore
Can I hook all this up to the ATS or how many of these circuits can I power

I may have put the cart in front of the horse so to speak, but we bought the 11 Kw 6437 running on Propane with the 12 circuit ATS thinking that we just needed to protect certain circuits. Now that it has been installed and up and running with only a few circuits on it we are wondering what else we can hook up without overloading the Generator or 50 amp breaker. We went from pumps and refrigerators only to “it would be nice to have this also if the power went out”. I am just trying to understand this myself before asking an electrician to come back and make changes (if it is possible) to add more circuits. I try to do my homework before hand and understand a little but not enough say I want this hooked up for sure. I was wondering if anyone could look this over and tell me if any of the additional circuits sounds feasible to hook up without overloading the Generator.

Background on why we have 4 sumps. We have a house that has a basement in a high ground water area. It did not use to be that way 20 years ago but something changed and now we do. The purpose of the Generator was to power if necessary 2 Sump pumps and if needed 2 back up sump pumps for a total of 4 sumps if the stuff really hit the fan. Also a couple of refrigerators. There have been times where storms come through and we get dumped on months of rain in a few hours and then the power goes out..

So basically we have the 4 pumps and 2 refrigerators hooked up. The Primary and secondary pumps 1 are hooked up to separate 20 amp breakers, The Primary and secondary pumps 2 are hooked up to a single 20 amp breaker. We duplicated the way they are hooked up to the utility power with the same size breakers and they have been that way for 10 years with no problems.

I borrowed a clamp current meter and measured each pump while it was running and at startup with a meter that has a MAX and hold setting. Chances are all 4 pumps will never be on at once but I have to assume it is a possibility. All the pumps are 120 volt and I have 2 on one “leg” of the panel and the other 2 on the other “leg” (excuse my terminology if I am calling them wrong). This is for my own understanding and I may be wrong on this but when figuring all this out hypothetically I thought you would also try the “balance” the load evenly as possible between the “legs” so one “leg does not have 45 amps and the other 5 ( as an example). As of right now I am using 5 120 Volt breakers with 7 spaces free.

Here is what’s hooked up now:
Primary Pump1- Start up 18 amps Running 7 Amp Hooked up to its own 20 amp breaker
Primary Pump 2 - Start up 8.3 Running 4 amps Hooked up to its own 20 amp breaker
Secondary Pump 1- Start up 16 amps Running 11 amps Sharing a 20 amp breaker
Secondary Pump 2-Start up 18 amps Running 10 amps Sharing a 20 amp breaker
Refrigerator1 - When I measured these they only showed less than 1 but I assume compressor was not running, some charts say figure 6 amps, not sure- Hooked up to its own 20 amp breaker
Refrigerator2 - When I measured these they only showed less than 1 I assume the compressor was not running, some charts say figure 6 amps, not sure- Hooked up to its own 20 amp breaker

The additional things we want to add, we would really like to add the first 2. Number 3 and 4 is a wish list. And Well Pump would more important to us then the Microwave (which is a huge current draw it looks like)
1. Kitchen lights ( All LED) and a TV- with everything running 4 amps
2. Bedroom\Bathroom lights ( All LED) and bathroom fans -with everything running 3 amps
3. Microwave- 16 amps –
4. Well Pump 240 volts Pulls 10 amps when running per wire with the Current meter.

So if someone feels like reading all this stuff and giving me some recommendations I would appreciate it. I just want to know if any more can be added reasonably and that the generator can handle it before asking someone to come out make changes or then tell me I’m out of luck.
Quote
Skip Douglas SkipD
Ray, I moved the post above to your original thread because it all belongs together.

Your generator's maximum rated output is 45.8 Amps at 240VAC. The 50A breaker in the generator is sized for the suggested wire size to be used between the generator and transfer switch. The 50A rating should NOT be considered your target maximum current. If all of your loads are at 120VAC, then you can use a 91.6 Ampere total figure for absolute maximum load on the generator. The starting current values must be considered when adding up your total. Consider that if you had several pumps running when you lost power, they will all try to start at the same time when the generator is connected to them.

Your well pump rating equals 20 Amperes at 120VAC when you're adding it all up.

The loads MUST BE BALANCED across both sides of the generator output if you're anywhere near approaching maximum load. You will have to fully understand how the breakers are wired in order to do this. I suspect that you'll need a qualified electrician for the load calculations and installation of the system to get things right.

It's a very bad idea, in my opinion, to expect a generator to run at 100% of its load capacity for more than very short times. You may want to trade in the generator for a significantly larger one depending on your final load plan.
Skip Douglas
Quote
Peddler
I don't think you would have any problem running those things you mention. The well pump only runs for about one minute at a time as do many appliances. The generator should handle all that with out problem it can surge for a few seconds to cover the starting inrush. What you don't want to add is an electric hot water heater which in most cases is 4500 watts and can be on for hours. Good Luck, Peddler
Quote
Rmoore
Thanks Skip

I appreciate you advice on this. Trying to calculate this out for my own understanding. Putting the current draw figures down on paper and adding them up, And factoring in the bedroom and kitchen circuits. NO Microwave or well pump. If the power went out and all 4 pumps kicked on at the same time and both refrigerators were pulling 6 amps each and all the kitchen lights , bedroom\Bathroom lights and fans were on, I would have a surge of 84 amps for that start up. Then after the startup if all 4 pumps were running and all the other things were on it would go down to 54 amps. That would be everything on at the same time. I also have the breakers configured ( Excluding kitchen and bedroom which are not hooked up yet) so that the running load is 21 on one side and 33 on the other. Start up load is a bit more off balanced 26 and 58. I can probably do more to balance them. I want to try and understand at least the basic concepts on this just so I know what's going on when other people are doing work for me.
Quote
Rmoore
Thanks Peddler

I know you should always factor worst case scenario but my plans are that if we are here and the power goes off I can control things and make sure anything unnecessary if turned off. If I am not here for a long weekend or out of town.I will shut of the breaker to the water pump and the lights will all be off. Then it's just pumps and refrigerators. But I know that you should always assume worst case can happen. The water heater I know is off the list. My wife says "hot water would be nice". I measured that too and said "no".
Quote
Skip Douglas SkipD
Rmoore;36809 wrote:
Thanks Peddler

I know you should always factor worst case scenario but my plans are that if we are here and the power goes off I can control things and make sure anything unnecessary if turned off. If I am not here for a long weekend or out of town.I will shut of the breaker to the water pump and the lights will all be off. Then it's just pumps and refrigerators. But I know that you should always assume worst case can happen. The water heater I know is off the list. My wife says "hot water would be nice". I measured that too and said "no".
Ray, the National Electrical Code requires that a generator be able to handle the ENTIRE load that is set up to be automatically connected to the generator. There's no allowance in the rule for turning off breakers to reduce the load. In other words, you should not even think of wiring load into the ATS that need to be turned off to allow the generator to run properly.

If you need more loads backed up by the generator than the current generator is capable of handling., you may have to trade up to a larger generator.
Skip Douglas
Quote
murphy
A propane fired on demand hot water heater would require minimal current and provide lots of hot water. It's important to keep the wife happy.
Quote
Rmoore
Thanks Skip

That definitely is my plan, To size the load so the Generator can handle it at the proper level and not be required to run anywhere near full load. My comments on the shutting off the breakers on the well pump when we are away are also for other reasons like having a plumbing failure and the water run for days. The by product is I will not have to worry the well pump kicking on while I am away. The other comment on turning off unnecessary things, I meant during a power outage I will be conservative and not have lights or anything not required powered on, being aware I am running off a generator. Not shutting off breakers, Just keeping power consumption to a minimum.
With my current draw that I measured on the circuits that are now hooked up and the ones I am wanting to hook up , my goal is to hook up a few extra things if I can so as to not waste potential of the Generator but keep the load down to an acceptable limit. Right now I have the essentials hooked up, anything else is a plus for me. If I have usable extra potential and stay within best practice I just wanted to see if I can use it.
Quote