110 AC wiring/transfer switch - here we go again!

Tenor · November 19, 2007, 03:57:01 PM

I've been reading old posts for quite a while on this and BNO and my head is spinning. I can't find anything that quite applies to the equipment I have. Here is what I have:
xantrex 4024
7.5kw genset
50 amp shore line
Todd Eng. PS450S transfer switch.

Now, I am aware of the ground lift/neutral lift issues and of the lack of neutral switching in the inverter and I will take the proper precautions. I also know about the delay time needed for the inverter if it is installed after the switching panel. The power switch says it has a 20 to 30 second time delay. So here are the quandaries:

The power switch receives 3 power inputs, genset, shore line and inverter. This power switch says that the genset is the override mode, the shore line is the median mode and the inverter is the default mode. How should I use this based on my inverter selection? Would it be better to put the inverter upstream of the transfer switch instead? The reasons I chose this inverter is that it will automatically turn on the genset when it needs the power and I want to make sure I do not lose that function. As for size, it really is overkill for the little AC we use, EXCEPT that I want to use it to power up to 2 air conditioners while going down the road.

Once I get the transfer switch/order of input figured out, I need to consider my selection of distribution panels. I'd like as few panels as possible. I have read a thread about splitting the bus bar on the panel and using a breaker in the upper section of bar to send power to the lower end of the bar for the inverter loads. It is an interesting idea.

Our electric appliances are a fridge (propane for boondocking), microwave, small flatscreen TV, occasional laptop, roof airs (3, will most likely never run more than 2 at at time), electrical outlets, small bedside fan, nightlight. Maybe the occasional other small appliance (blender for mixed drinks...) So not a huge amount and none of these get used for long except the fan at night. I don't think a huge sub panel will be necessary. My lighting will be 12 volt pulled from my Vanner off of the house batteries as is the furnace and water pump. Hot water is by propane.

Another question about this panel - does it need to have a 50 amp breaker installed in the shore line before the panel input?

Based on this info, please help me with the details! I know enough to get me in trouble, and yet still know when to stop and ask directions! Thanks!

Glenn

NewbeeMC9 · November 19, 2007, 04:18:26 PM

Why are you using a seperate transfer switch when the trace has a 60 amp transfer switch built in and will operate it automatically with shore power etc.

IMHO the extra external transfer switch is complicating things.

You payed the money for the Trace, let it do the work for you.

howver, do it your way

Tenor · November 19, 2007, 04:32:09 PM

Newbee,
As I understand the manual for the inverter, I have to have a separate way to isolate the neutral from ground as the inverter switches from pass through mode to inverter mode, so I think I need to keep the transfer switch in the system. I think I have that right..

Glenn

TomCat · November 19, 2007, 04:49:19 PM

Glenn,

Here is a diagram of the split bus bar method. It is how I wired my system with Iota TS50R, Xantex RS3000, 5500w Onan genny and 50A shore line. http://www.zoto.com/site/#USR.jsbird69::PAG.detail::0a529713bcd40647ecf9ed7746d1f539

Hope that helps.

Jay
87 SaftLiner

gr8njt · November 19, 2007, 05:45:22 PM

Quote from: Tenor on November 19, 2007, 04:32:09 PM
Newbee,
As I understand the manual for the inverter, I have to have a separate way to isolate the neutral from ground as the inverter switches from pass through mode to inverter mode, so I think I need to keep the transfer switch in the system. I think I have that right..

Glenn

As mentioned by NewBeeMC9, you may want to take advantage of the 60 amp auto transfer switch of the Xantrex SW4024. If you connect the Genset directly to the "AC-Gen input" of the 4024, you can also utilize the Genset auto start-stop based on parameters you program. If you use the Todd Eng transfer switch instead, you'll be wasting these "Bells and whistles" you paid for in the SW4024.

The enclosed illustration (Fig 12) is from page 27 of the SW4024 manual depicting the Neutral-to-Ground switching when there is NO GRID power.
They recommend the use of a "Relay" (RY1) to "automatically" perform the switching. If your PS450S transfer switch can do this automatically, then you're set.

gr8njt · November 19, 2007, 06:18:12 PM

Fig 13 from pg 28 of the Xantrex SW4024 manual shows the RY1 relay performing the Neutral-to-Ground switching when the Grid power is available.

Nick Badame Refrig/ACC · November 19, 2007, 07:03:26 PM

Great diagram Ray!

Not only will an external Transfer switch take care of the nutral bonding but, it also serves as an automatic transfer between gen and shore power

before the inverter. Then the inverter transfer switch will switch between incomming shore/gen power and inverter power to your panels.

Nick-

edroelle · November 19, 2007, 07:05:21 PM

The reason to use the Todd Eng. PS450S transfer switch is that it can switch 2 legs where the Xantrex 4024 switches 1.

You could probably run one leg through the inverter and 1 through the transfer switch.

Ed Roelle
Flint, MI

Jerry Liebler · November 19, 2007, 08:49:26 PM

Tenor,
Since your power needs are modest. You can easily use the SW4024's transfer capability. This will be far less likely to DAMAGE the inverter as the transfer switch you have is VERY likely to. You'll need a neutral bonding relay with 50 amp normally closed contacts and 120 volt coil also you'll need to rewire your generator separating it's neutral from ground and making it's output 120 volt only. You'll also need to sell the transfer switch you have now. You'll only be using one side of the shore cord, so on shore power you'll only have 6000 watts (50 amps of 120). Also you'll need to have a 50 amp breaker in the shore cord into the inverter and a 60 amp breaker on the output of the inverter. You'll have 7200 watts (60 amps of 120 volt) of generator power available. The relay can be bought for about $10 and can usually be mounted in the shorecord input breaker's box. The relay coil is across the output of the shore input breaker and it's contacts connect the neutral to ground, all in the box. If it's not clear send me an email with your phone number and I'll give you a call.
Regards
Jerry 4107 1120

Sean · November 19, 2007, 08:54:07 PM

Quote from: NewbeeMC9 on November 19, 2007, 04:18:26 PM
Why are you using a seperate transfer switch when the trace has a 60 amp transfer switch built in and will operate it automatically with shore power etc.

IMHO the extra external transfer switch is complicating things.

You payed the money for the Trace, let it do the work for you.

...and...

Quote from: gr8njt on November 19, 2007, 05:45:22 PM
As mentioned by NewBeeMC9, you may want to take advantage of the 60 amp auto transfer switch of the Xantrex SW4024. If you connect the Genset directly to the "AC-Gen input" of the 4024, you can also utilize the Genset auto start-stop based on parameters you program. If you use the Todd Eng transfer switch instead, you'll be wasting these "Bells and whistles" you paid for in the SW4024.
...

Umm, this advice ignores the problems associated with installing an SW4024 to two separate four wire AC power sources.

The internal 60-amp "transfer switch" does no darn good if you have (A) a generator on board with an internally bonded ground and neutral (the SW4024's internal switch switches only the hot -- all neutrals are ganged), or (B) a pair of inputs with two hots apiece, as the SW4024's internal switch is single-pole only.

So, yes, perhaps you've "paid" for it, but it's nearly useless on a coach. The SW4024 is still a great inverter, but this single-pole transfer switch nonsense is a serious liability, and anyone using the SW series on a coach has a serious challenge to install it properly. And it is a certainty that an external transfer switch of some kind will be needed, unless you have a strictly 120-volt coach with either no generator, or one with the ground-neutral bond removed (which, itself, presents a different set of challenges).

Pardon my being snippy here, but this is the kind of thing that gets people KILLED.

-Sean
http://ourodyssey.blogspot.com

p.s. Tenor -- I answered your identical question over on the other board.

p.p.s. Jerry squeaked his post in just as I was posting mine -- he is absolutely correct: as I alluded to above, if you go with a 120-volt-only scheme and remove the bond in the generator, then the internal transfer switch can be used. Just bear in mind that you are leaving half the power capability (6 Kw) of your 50-amp shore line on the table. Also, the generator will need to be installed "permanently" and carefully labeled as to being unbonded, and the connection between the generator output and the bonding relay will need to be made with "permanent" means (in other words, there can be no disconnects in the ground and neutral wires such as a plug and receptacle type connection).

niles500 · November 19, 2007, 10:42:33 PM

In addition to what Sean hasd posted - an EXTERNAL transfer swith can provide additional security when hooked to a PP as far as determining polarity and phasing prior to energization - FWIW

Tenor · November 20, 2007, 07:06:52 PM

I'm sorry it took so long to reply back. First, thank you everyone for your help. Ed gave the go ahead to post his diagrams, and I expect he will post to discuss them at length. It is very hard to find people with the exact same plan with the exact same equipment as your own. In several cases in Michigan, Ed helped get this equipment several years ago and helped them with the install. So, here are the diagrams.

Tenor · November 20, 2007, 07:30:33 PM

I think this worked this time!

The second diagram of the transfer switch is a modification to allow 110 ac from the inverter to flow to BOTH legs of the system.

Sean · November 21, 2007, 11:15:03 AM

Glenn,

I've looked over Ed's drawings, and I see some issues for you.

First off, the automatic generator start feature on your SW4024 will not work with the AC1 input as shown in the drawings. At minimum, you will need to use the AC2 input instead. It looks like Ed has a 4024+, which is a completely different unit. The Plus does not include automatic generator start, for example (although there is an optional add-on module to do this.) The Plus, incidentally, is not listed or rated for mobile use, and has not been tested accordingly, FWIW.

Now that you have posted the diagram for it, I can tell you that the Todd Engineering ATS you have is made to work with regular inverters, whereas the SW4024 is an "inverter/charger." One consequence of this difference is that you will be connecting the SW4024 simultaneously to both an input and an output of the ATS. Without studying a more detailed drawing of the ATS, I have to advise caution here.

Another issue here is that the transfer switch does not implement the 100 millisecond transfer delay that is "required" by Xantrex for the SW series inverters. As I have written elsewhere, it is a subject of great debate as to whether this delay is strictly necessary, but you should be aware that the installation documents specify it, and any warranty you have on the inverter may be invalidated by omitting it. Also, if the inverter is operating in "load-support" mode at the time of transfer, you may experience damage to sensitive equipment connected to the output, in addition to any problems with the inverter itself.

I know that some lines may have been omitted for clarity on the drawing, but when you get to actual installation, you need to remember that all hots, neutrals, and grounds for any circuit must run together in the same sheath, conduit, or raceway. So, for example, the lone hot wire shown on the left of the diagram running from the ATS output to the SW4024 input, must be run together with the neutral and ground wires for that circuit. Also, the neutral, ground, and both hots running to the output panelboard will need to run in the same conduit from the ATS. So the inverter output should run direct to the inverter input on the ATS, and then from there to the hot input lug on the panel, not the other way around as shown.

Lastly, remember that any modifications you make to the transfer switch itself (i.e. any connections made other than to the specified input and output lugs on the unit) will invalidate the listing of the switch. Technically, this is a code violation, and you may wish to contemplate the insurance implications of making any such modifications before proceeding.

HTH.

-Sean
http://ourodyssey.blogspot.com

NewbeeMC9 · November 25, 2007, 03:53:58 PM

Quote from: Sean on November 19, 2007, 08:54:07 PM

...Pardon my being snippy here, but this is the kind of thing that gets people KILLED.

-Sean
http://ourodyssey.blogspot.com

OK Sean, I see why your getting Snippy and my feelings have scarred over now

that system is a lot more complicated than mine, I'm all 120. and there is an RV gen with just one wire coming out of it. However I do apreciate your post and I will look thru mine to see whats there since I bought it that way. it has worked so far.

Just out of curiosity, Could he by another 4024 and use the stacked inverer set up and get the 240 he is wanting and have each inverter on each leg? and use the 240 on the gen and the internal transfer switches etc.?