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I’ve read on another community forum that on installations of the Onan 5.5kw generator set with one 30A circuit and one 20A circuit, that the 20A circuit is wired “directly to the main living room A/C” as a rule and therefore, not available to any other appliances.This doesn’t seem logical to me.I honestly don’t know.Can anyone confirm this?
It seems more reasonable to me that both generator circuits should go directly to the transfer switch, L1 and L2.This would make the 20A circuit power available to anything on the same leg, or buss as the living room A/C.
You certainly would have to be very careful with only 20A available if it were wired to the transfer switch, but it would be available to anything on that buss.
If the 20A circuit was dedicated to the A/C only, that power would be unusable for part of the year basically.Your 5.5kw generator set would become just a 3.6kw gen set for much of the year and only the appliances on the other buss, or the 30A leg would be useable.
The reason I ask is, I’m in the process of selecting a generator set to install in a new fifth wheel trailer.I’m leaning towards the Onan 7.0kw gen set which has two 30A legs.I’m curious to have an idea if the existing wiring of typical “generator prep” installations simply takes both legs directly to the transfer switch.If it does, the existing wiring can be used and all 58A’s would be usable split with half to each 120VAC buss.
If one leg of generator power is dedicated to the A/C, there is no sense in spending the extra money since there would still only be one 30A leg applied to only one buss.
I know generators have been discussed to some length on this, and other forums.But I have not been able to find any comments from anyone who has actually confirmed the generator wiring in his/her unit.
Dave, I was surprised as well to see a 5.5kW Onan / Cummins wired for 30 / 20 amp output service as you described. However, there are 5.5kW Onan / Cummins wired 30 / 30. We have one and it is wired to feed both "sides" of the 50 amp service. I agree with your comments and if it were me I would go with a 30 / 30.
I would caution, in a 5th wheel, going with the larger one only because of the additional LP usage. Not due to fuel cost, simply due to having to fill the tanks more often. Under lighter load the larger generator will use a lot of fuel for the amps produced. I have a Progressive Industries HW 50C with amp meter to monitor my generator. I find that we're good with the 5.5kW. The only requirement is to not run an AC and the convection microwave at the same time. Other then that limitation we're good with the 5.5kW in a 30 / 30 amp output configuration.
Thanks Bill. I also have seen on the spec sheet that Onan builds the 5.5 with two, 30 amp output circuits. It still only produces about 5.5 kw, or allows about a 45 amp load total in all configurations. But if both circuits go straight to the transfer switch, all of the power from the generator would be available to other appliances. You just have to be careful not to draw more than 45 amps, nor more than 30 amps on either circuit. But you can basically "transfer" loads from one to the other turning something off that's on one circuit in order to turn something on that's on the other circuit. It just gives you more options with the 45 amps. That's a good thing I think.
I intend to buy a gas generator set I think no matter what I decide on the capacity. We'll be buying a fifth wheel toy hauler that has two, 30 gallon tanks, one to fuel the generator and the other to fuel your toys. Since I had to sell my toy, the toy fuel tank can be pumped into the generator fuel tank making 60 gallons available for the generator. With a rated fuel consumption of 1.1 gph at full load, that should be good for about 50 hours of operation at full load. It's rated at 0.7 gph at half load.
Both circuits going straight to the transfer switch would do the same with the 58 amps total from the 7.0 kw gen set. I will have a residential refrigerator and larger battery bank in addition to an already power hungry unit. So I'm guessing there may be times when this upgrade will be worth the extra money.
I have asked factory Reps technical questions in the past. So far, it's been my experience that the Reps available to the public are not from the technical, or build side of the house as much as they are from the sales/customer service/PR side. No surprise there, but it would be nice to run into someone from the other side.
-- Edited by Dave MW on Sunday 21st of October 2018 09:34:12 AM
-- Edited by Dave MW on Sunday 21st of October 2018 09:40:09 AM
-- Edited by Dave MW on Sunday 21st of October 2018 09:51:27 AM
Thanks Bill. I also have seen on the spec sheet that Onan builds the 5.5 with two, 30 amp output circuits. It still only produces about 5.5 kw, or allows about a 45 amp load total in all configurations. But if both circuits go straight to the transfer switch, all of the power from the generator would be available to other appliances. You just have to be careful not to draw more than 45 amps, nor more than 30 amps on either circuit. But you can basically "transfer" loads from one to the other turning something off that's on one circuit in order to turn something on that's on the other circuit. It just gives you more options with the 45 amps. That's a good thing I think.
I intend to buy a gas generator set I think no matter what I decide on the capacity. We'll be buying a fifth wheel toy hauler that has two, 30 gallon tanks, one to fuel the generator and the other to fuel your toys. Since I had to sell my toy, the toy fuel tank can be pumped into the generator fuel tank making 60 gallons available for the generator. With a rated fuel consumption of 1.1 gph at full load, that should be good for about 50 hours of operation at full load. It's rated at 0.7 gph at half load.
Both circuits going straight to the transfer switch would do the same with the 58 amps total from the 7.0 kw gen set. I will have a residential refrigerator and larger battery bank in addition to an already power hungry unit. So I'm guessing there may be times when this upgrade will be worth the extra money.
I have asked factory Reps technical questions in the past. So far, it's been my experience that the Reps available to the public are not from the technical, or build side of the house as much as they are from the sales/customer service/PR side. No surprise there, but it would be nice to run into someone from the other side.
-- Edited by Dave MW on Sunday 21st of October 2018 09:34:12 AM
-- Edited by Dave MW on Sunday 21st of October 2018 09:40:09 AM
-- Edited by Dave MW on Sunday 21st of October 2018 09:51:27 AM
Side comment - I "never" assume any sales person has a clue about true "technical" or infrastructure issues. They seldom really know and tend to say, "We've never had an issue with that." Whatever "that" is.
To be sure in my comments, regardless of the "total kW" capacity of the generator, what matters is the ampacity of each side. So one gets to about 26 amps on a 30 amp side that's it. The Generator has 30 amps max per side going to the transfer switch. I think you know that but just making sure.
Absolutely. There are losses of energy everywhere to heat, less than perfect connections that generate resistance to flow, just everywhere. In any discussion on such matters, the use of terms such as "30 amps" is just an approximation and usually higher than reality. But using the published, labeled, rated numbers makes it easy to discuss such matters. You just have to assume they are calculated approximations and keep in mind that in reality, in real world applications, you'll never be able to actually get the rated power from a generator. At least I've never known that to happen on larger generator sets.
I have been reading discussions among the community about generators for some time now and one thing stands out in my mind is comments about voltage drops on line, or park power, and while using generator power. For a constant load demanding 1kw for example, as the voltage goes down the current draw goes up. That's just in the laws of nature. For our purposes, in an RV, this further reduces the list of things we can use at any one time without tripping breakers. So I was sort of surprised to find the continued use of a 5.5 kw gen set in the larger, power hungry units when a better choice, IMHO, is reasonably available in the 7 kw gen set. The Onan 5.5 kw and 7 kw are housed in cabinets that have the exact same dimensions, or did the last time I looked. They probably use the very same housing but with different decals.
Now I can understand the builders installing the 5.5 instead of the 7.0. It saves a little money. Not much at wholesale, but a little perhaps. And it does a respectable job in many situations. They both are fine sets. But in the larger units where the buyer is going to spend $100k to $200k plus, what's a few more bucks for the few more amps. And if the standard "generator prep" is wired straight to the transfer switch with both legs using wire large enough for the rated power on both legs of the 7 kw gen set, installing it should be as simple as "plug and play". Hence my question if anyone has actually confirmed this wiring.
Due to the lack of response to my question, I'm starting to think perhaps not. It really isn't something you would pay much attention to. I know that. And I probably wouldn't either except for the fact that I have to power the addition of a residential refrigerator from a generator or sleep in the loft. And that's what drove me to investigate other options. So if anyone has any thoughts on the matter, please don't hesitate to help educate me and keep me out of the loft. lol.
-- Edited by Dave MW on Thursday 25th of October 2018 10:17:53 AM
-- Edited by Dave MW on Thursday 25th of October 2018 10:19:01 AM
-- Edited by Dave MW on Thursday 25th of October 2018 10:24:57 AM
